The choice of devices for protecting medium voltage electrical networks. Qualification groups for electrical safety. General rules for the use of protective equipment

Design of electrical installations of apartments and cottages (Schneider Electric)

4.1. General principles for the selection of protective equipment

Any electrical installation must be protected by automatic shutdown devices in the event of overcurrents or impermissible leakage currents. Overcurrent refers to any current that exceeds the rated current. Basically, overcurrents appear due to overload or short circuit.

Protective devices must be selected taking into account the parameters of the electrical installation, the prospective short-circuit currents, the characteristics of the load, the installation conditions and the thermal characteristics of the conductors.

In accordance with the PUE for electrical installations with voltages up to 1 kV and with a TN grounding system, characterized by a solidly grounded neutral of the power source and the connection of open conductive parts to a solidly grounded neutral of the source by means of zero protective conductors, adopted for residential buildings, in order to ensure electrical safety, the automatic shutdown time should not exceed the values below:

Fuses and circuit breakers are used as protective equipment for automatic shutdown.

Fuse is a switching device which, due to the melting of one or more specially designed and calibrated elements, opens the circuit in which it is connected and cuts off the current when it exceeds a predetermined value for a sufficient time.

Circuit breaker is a mechanical switching device capable of making, passing and breaking currents in a normal circuit condition, as well as making, holding for a specified time and automatically breaking currents in an abnormal circuit condition, such as short-circuit currents.

Given that the electrical installations of high-comfort dwellings and cottages in last years are mainly equipped with circuit breakers, only this type of protective equipment is considered below.

The choice of protective equipment depending on the value of short-circuit currents is based on the fact that the curve of the time-current characteristic corresponding to the permissible thermal load of the protected electrical network should lie above the zone of the time-current characteristic of the protection device for all possible short-circuit currents between the minimum and maximum values.

Under the time-current characteristic is meant a curve that reflects the relationship of time and expected current under certain operating conditions. This principle is illustrated in fig. 4.1.

For the set trip time of the protection, the curve of permissible values I2t (Joule integral) of the protected conductor must lie above the curve I2t protective device, since the I2t characteristic curve of the protective device characterizes the maximum operating I2t values as a function of the prospective short-circuit current. The I2t values of the protective devices are given in the technical data by the manufacturers.

The time to turn off the full short circuit current at any point in the circuit should not exceed the time during which the temperature of the conductors reaches an acceptable limit. This time for the protected conductor can be approximately calculated by the formula

where t - duration, s;

S - conductor cross section, mm2;

I - effective value of short-circuit current, A;

K = 115 or 135 - for copper conductors (115 - with PVC insulation, 135 - with rubber insulation and with XLPE insulation);

K \u003d 74 and 87 - for aluminum conductors (74 - with PVC insulation, 87 - with rubber insulation and XLPE insulation).

K = 115 - for connections by soldering copper conductors.

Ultimately allowed values heating temperatures of conductors are given in the PUE.

Automatic overload protection is designed to disconnect the mains when an overload current flows through the conductors before such a current could cause an increase in the temperature of the conductors, dangerous for insulation, connections, clamps or the environment surrounding the conductors.

Rice. 4.1.

C - characteristic curve of allowable Ft;

D - I2t characteristic of the circuit breaker;

Short circuit - the maximum short circuit current at which protection is provided by the circuit breaker.

The performance of any protective device that protects the cable from overload must meet the conditions:

where Ip is the operating current of the circuit; Id - permissible long-term current of the cable; In - rated current of the protection device (protection devices with adjustable characteristics rated current In is the current of the selected setting); Iz - current that ensures reliable operation of the protection device.

In practice, Iz is taken equal to:

Tripping current at a given tripping time for circuit breakers;

The melting current of the fuse-link at a given operating time for fuses.

To perform protective functions, circuit breakers are equipped with various releases.

AT general view release is a device mechanically connected to (or built into) a circuit breaker that releases a retaining device in the circuit breaker mechanism and causes the circuit breaker to automatically trip.

In domestic circuit breakers, the following are used: overcurrent release, overcurrent release with inverse time delay, direct overcurrent release and overload release.

Overcurrent release - a release that causes the circuit breaker to trip, with or without a time delay, when the current in this release exceeds a predetermined value.

Overcurrent release with inverse time delay - overcurrent release operating after a time delay in inverse relationship from the overcurrent value.

Direct overcurrent release - overcurrent release operating directly from the flowing current in the main circuit of the circuit breaker.

Overload release - overcurrent release designed to protect against overloads.

In accordance with SP31-110-2003, in the internal networks of residential buildings, as a rule, circuit breakers with combined releases should be used.

The rated currents of the combined releases of circuit breakers for protecting group lines and apartment inputs, including lines to electric stoves, must be selected in accordance with the calculated loads.

The settings of protection devices for mutually redundant lines must be selected taking into account their post-accident load.

Circuit breakers are also characterized by making and breaking capacity, ultimate breaking capacity, operating breaking capacity and breaking current.

Since the highest values of overcurrents are determined by the short-circuit currents of the protected circuit, when choosing circuit breakers in the design process, these parameters must be taken into account.

In cases where two circuit breakers are connected in series, the problem of selectivity of their operation arises, which consists in ensuring that the protected circuit is disconnected by the circuit breaker on the load side before the second circuit breaker on the supply side starts the trip.

Selectivity is characterized by the limiting current. The selectivity limit is the current limit:

Below which, in the presence of two series-connected overcurrent protection devices, the device on the load side has time to complete the tripping process before the second device starts it (i.e., selectivity is ensured);

Above which, in the presence of two overcurrent protective devices connected in series, the device on the load side may not have time to complete the tripping process before the second device begins it (i.e., selectivity is not ensured).

The value of the selectivity limit current is determined by the coordinate of the intersection point of the time-current characteristic in the zone of the highest breaking capacity of the protective device on the load side and the time-current characteristic of the release of another device.

In household electrical installations, in order to protect against overcurrents, as a rule, circuit breakers are used, manufactured in accordance with GOST R 50345-99, which is authentic to the international standard IEC 60898-95.

In table. 4.1 shows the preferred values of the rated voltage of circuit breakers manufactured in accordance with the specified GOST.

Table 4.1 Preferred rated voltages

Preferred rated voltages

switches	Circuit breaker power supply	Rated voltage, V
Single pole	Single-phase (phase with neutral)
	Single-phase (phase with neutral ground wire or phase with neutral)
	Single-phase (phase with neutral) or three-phase (three single-pole circuit breakers) (three- or four-wire)
Bipolar	Single-phase (phase with neutral)
	Single phase (phase to phase)
	Single-phase (phase-to-phase, three-wire)
Three-pole	Three-phase (three- or four-wire)
Four-pole	Three-phase (three- or four-wire)

The preferred values of the rated current established by GOST include: 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100 and 125 A.

Standard rated frequencies are 50 and 60 Hz.

Standard values of rated breaking capacity: 1500, 3000, 4500, 6000, 10,000 A. The standard defines three types of instantaneous tripping characteristics: B, C and D. Below are the ranges of instantaneous tripping of the circuit breaker depending on the overcurrent ratio in relation to the rated In:

In electrical installations of residential buildings, circuit breakers with characteristics of types B and C are mainly used. Type B tripping is rationally used to protect socket lines, type C - for lines supplying lamps, heated floors and walls, saunas, etc. When choosing a circuit breaker, it is necessary to take into account the expected ambient temperature at the place of its installation.

The catalogs show the rated current of the circuit breaker for an ambient temperature of 30 0C. An increase in temperature above 30 0С leads to premature operation of the thermal release, since its temperature reaches the operation level at lower current values. Therefore, when installing circuit breakers in places where the ambient temperature exceeds the nominal value, equal to 30 0С, the nominal value of the circuit breaker current decreases:

where In - permissible current at an ambient temperature of 1 ° C, different from the nominal tо.с.н = 30 C;

In.a - rated current of the circuit breaker at rated (calculated) ambient temperature;

Ot - excess of the thermal release operating temperature over the nominal design ambient temperature tac = 30 °C, Ot = tav - t.s.n;

Temperature coefficient that takes into account the decrease (increase) in the permissible current of the circuit breaker, depending on the ambient temperature at the place of its installation.

Here Ot is the excess of the operation temperature tcp of the thermal release over the ambient temperature, Ot = tav - tо.с;

For domestic circuit breakers, the guide values for the Kt value depending on the ambient temperature at the installation site are given below:

toc....20 30 35 40 45 50 55 60

Kt ....1.05 1 0.97 0.95 0.92 0.89 0.87 0.84

In addition, for modular circuit breakers for domestic use installed in cabinets next to each other on rails, a value of 0.8Kt should be used.

The choice of circuit breakers in cases where the ambient temperature is more or less than the standard control, at which its nominal data was determined, is made using the temperature coefficient Kt according to the formula

where In.r - rated current of the release.

1. Maximum rated load current Iras.max = 20 A.

2. Ambient temperature at the place of installation toc = +55 0C while Iras.max=Int The rated current of the circuit breaker under normal conditions should be:

According to the above data, Kt for 55 0С is 0.87.

We accept a circuit breaker with a rated current of 25 A.

If the circuit breaker is installed in a row with other machines, in a metal cabinet, then its rated current is determined by the formula

We accept for installation a circuit breaker with a rated current In.a = 32 A.

4.2. Switching equipment selection principles

Switching devices include a fairly wide range of electrical equipment, with the help of which switching on / off of both the main current circuits and control circuits is carried out.

To switch the main current circuits, along with the circuit breakers discussed above, knife switches, switches, contactors, magnetic starters, etc. are used.

For switching control circuits, various relays are used, both instantaneous and relays with a time delay for closing and opening contacts, buttons and keys (switches), etc.

The control circuit switching apparatus may comprise a control circuit apparatus and associated devices such as indicator lights.

The apparatus for the control circuits may comprise one or more switching elements and a mechanism for transferring the switching force. The switching element can be contact or semiconductor.

When designing devices from the group under consideration, the choice is determined by the following main parameters:

Rated voltage and current consumption of coils;

Switching capacity of contacts or output semiconductor circuits

(rated voltage, rated current of the switched circuit);

For relays with a time delay - the time delay range.

Not less than important factors are the method of installing the device (under the screw, on a DIN rail) and the connection of wires (front, rear).

1.1 Introduction. 3

5.1 General provisions. eighteen

5.3.8 Safety glasses. 25

6. Application. 27

Introduction.

Group	The amount of knowledge required.
I	Persons who do not have special electrical training, but who have a clear idea of the danger of electric current and safety measures when working on a serviced area, electrical equipment, electrical installation, are certified for group 1. Must have practical knowledge of first aid. Training for 1 group is carried out in the form of a briefing followed by a control survey by a specially designated person with an electrical safety group of at least 3.
II	Persons with group 2 must have: 1. elementary familiarity with the electrical installation; 2. a clear understanding of the danger of electric current and approaching live parts; 3. knowledge of basic precautions when working in electrical installations; 4. practical acquaintance with the rules of first aid.
III	Persons with group 3 must have: 1. elementary knowledge of electrical engineering; 2. a clear understanding of the dangers when working in electrical installations; 3. knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures ensuring the safety of work; 4. knowledge of the rules of use protective equipment; 5. knowledge of the structure of the serviced equipment and the rules for its operation; 6. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.
IV	Persons with group 4 must have: 1. clear knowledge of the basics of electrical engineering; 2. knowledge of PTE, PTEEP, MPOT and PUE in terms of fixed electrical installations; 3. a complete understanding of the dangers when working in electrical installations; 4. knowledge of the rules for the use and testing of protective equipment; 5. knowledge of the installation so as to freely understand which elements should be turned off for the production of work, find all these elements in nature and check the implementation necessary activities for security; 6. the ability to organize safe work and supervise them in electrical installations with voltage up to 1000 volts; 7. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.

Checking knowledge of PTE by staff.

Subdivided into:

1. primary;

2. periodical;

3. extraordinary.

Periodic are subject to verification:

personnel involved in the operation of electrical installations, as well as the management and engineering staff organizing their operation - once a year;

management and engineering staff, not related to the previous group, but in charge of electrical installations - 1 time in three years.

Primary called the first of the periodic checks.

Extraordinary knowledge is tested:

Persons who have committed violations of PTE, PTEEP, MPOT, job or operational instructions;

persons who have had a break in work at this electrical installation for more than 6 months;

persons transferred to a new electrical installation;

· persons on the instructions of the management of the enterprise or on the instructions of the inspector of energy supervision.

Shutdown production.

At the place of work, the current-carrying parts on which work is performed, as well as those that can be touched during work, must be disconnected.

Non-insulated current-carrying parts accessible to touch can not be disconnected if they are securely protected by insulating pads made of dry insulating materials.

The disconnection must be carried out in such a way that the parts of the electrical installation or electrical equipment allocated for work are separated on all sides from the current-carrying parts under voltage by switching devices or by removing the fuses, as well as by disconnecting the ends of the cables (wires) through which voltage can be applied to place of work.

Disabling can be done:

1. manually operated switching devices, the position of the contacts of which is visible from the front side or can be established by examining the panels from the rear side, opening the shields, removing the covers. These operations must be carried out in compliance with security measures. If there is full confidence that for switching devices with closed contacts, the position of the handle or pointer corresponds to the position of the contacts, then it is allowed not to remove the covers to check the disconnection;

2. contactors or other switching devices with automatic drive and remote control with contacts accessible for inspection after taking measures to eliminate the possibility of erroneous switching on (removing the auxiliary current fuses, disconnecting the ends of the closing coil).

The procedure for checking the disconnected state of switching devices is established by the person issuing the order or giving the order.

To prevent the supply of voltage to the place of work due to transformation, it is necessary to disconnect all power, instrumentation and various special transformers associated with the electrical equipment being prepared for repair from both the higher and lower voltage sides.

In cases where work is performed without the use of portable grounding, additional measures must be taken to prevent the erroneous supply of voltage to the place of work: mechanical locking of the drives of disconnected devices, additional removal of fuses connected in series with switching devices, the use of insulating plates in knife switches, automatic machines, etc. n. These technical measures must be specified when issuing a work order. If it is impossible to take these additional measures, the ends of the supply or outgoing lines must be disconnected at the switchboard, assembly or directly at the place of work; when disconnecting the cable from the fourth (zero) core, this core must be disconnected from the zero bus.

Grounding overlay.

Grounding locations.

Grounding must be applied to the current-carrying parts of all phases of the section of the electrical installation disconnected for the production of work from all sides, from where voltage can be applied, including due to reverse transformation.

It is sufficient to apply one earth on each side. These grounds can be separated from current-carrying parts or equipment on which work is performed by disconnected disconnectors, switches, circuit breakers or removed fuses.

The imposition of grounding directly on the current-carrying parts on which work is performed is required when these parts may be under induced voltage (potential) or they may be energized from an external source of dangerous magnitude. Places for applying groundings must be chosen so that the groundings are separated by a visible break from live parts under voltage. When using portable grounding, their installation sites must be at such a distance from live parts that remain energized so that grounding is safe.

When working on busbars, at least one ground must be applied to them.

In closed switchgear, portable grounding must be superimposed on live parts in the places designated for this. These places should be cleared of paint and bordered with black stripes.

In all electrical installations, the points of connection of portable grounding to the grounding wiring must be cleaned of paint and adapted for fixing the portable grounding clamp, or there must be clamps (lambs) on this wiring.

In electrical installations, the design of which is such that grounding is dangerous or impossible (for example, in some distribution cells, switchgear of certain types, etc.), when preparing the workplace, additional safety measures must be taken to prevent accidental voltage supply to the place of work. These measures include: locking the disconnector drive, fencing the knives or the upper contacts of these devices with rubber caps or hard plates made of insulating material.

The list of such electrical installations must be determined and approved by the chief power engineer (the person responsible for electrical facilities).

Grounding is not required when working on equipment if tires, wires and cables are disconnected from it on all sides, through which voltage can be applied, if it cannot be energized by reverse transformation or from an external source, and provided that This equipment is not energized. The ends of the disconnected cable must be short-circuited and grounded.

General provisions.

Protective means are devices, devices, portable and transportable devices and devices, as well as individual parts of devices, devices and devices that serve to protect personnel working on electrical installations from damage. electric shock, from the impact of an electric arc, its combustion products, etc.

The protective equipment used in electrical installations includes:

· insulating operational rods, insulating pullers for operations with fuses, voltage indicators to determine the presence of voltage;

· insulating ladders, insulating platforms, insulating rods, grippers and tools with insulated handles;

· rubber dielectric gloves, boots, galoshes, rugs, insulating pads;

· portable grounding;

· temporary fences, warning posters, insulating caps and overlays;

· goggles, canvas gloves, filtering and isolating gas masks, safety belts, safety ropes.

Insulating protective equipment is used to isolate a person from live parts of electrical equipment under voltage, as well as to isolate a person from the ground. Insulating protective equipment is divided into:

on basic protective equipment;

for additional protective equipment.

Main such protective equipment is called, the insulation of which reliably withstands the operating voltage of electrical installations and with the help of which it is allowed to touch live parts that are energized.

The test voltage for the main protective equipment depends on the operating voltage of the installation and must be at least three times the value of the line voltage in electrical installations with an isolated neutral or with a neutral grounded through a compensating device, and at least three times the phase voltage in electrical installations with a solidly grounded neutral.

Additional such protective equipment is called, which by itself cannot provide safety against electric shock at a given voltage and are only an additional measure of protection to fixed assets. They also serve as protection against touch voltage, step voltage and as an additional protective measure against the effects of electric arcs and products.

Additional insulating protective equipment is tested with a voltage independent of the voltage of the electrical installation in which they are to be used.

The main insulating protective equipment used in electrical installations with voltages up to 1000 volts include:

dielectric gloves;

tool with insulated handles;

voltage indicators.

Additional insulating protective equipment used in electrical installations with voltages up to 1000 volts include:

dielectric boots;

dielectric rubber mats;

insulating pads.

The choice of certain isolating protective means for use in operational switching or repair work regulated by safety regulations for the operation of electrical installations and power lines and special instructions for the performance of individual works.

Portable fences, insulating pads, insulating caps, temporary portable grounding and warning posters are designed to temporarily protect live parts, as well as to prevent erroneous operations with switching devices.

Auxiliary protective equipment is intended for individual protection of the worker from light, thermal and mechanical influences. These include goggles, gas masks, gloves, etc.

Requirements for certain types of protective equipment and rules for their use.

Dielectric gloves.

For work in electrical installations, it is allowed to use only dielectric gloves made in accordance with the requirements of GOST or specifications. Gloves intended for other purposes (chemical and others) are not allowed to be used as a protective agent when working in electrical installations.

Dielectric gloves issued for maintenance of electrical installations must be of several sizes. The length of the glove must be at least 350 mm. Gloves should be worn on the hands to their full depth. It is not allowed to wrap the edges of the gloves or lower the sleeves of clothing over them. When working on outdoors in winter time dielectric gloves are worn over woolen ones. Each time before use, the gloves must be checked for tightness by filling them with air.

Dielectric mats.

Dielectric mats are allowed as an additional protective agent in closed electrical installations of any voltage during operations with drives of disconnectors, switches and ballasts. Dielectric mats are insulating only when dry. In damp and dusty rooms, insulating pads should be used instead of mats.

Dielectric mats must be manufactured in accordance with the requirements of GOSTs with a size of at least 50 × 50 cm. The upper surface of the mat must be corrugated.

Control lamps.

The control lamp must be enclosed in a case-fitting made of insulating material with a slot for light signal. The conductors should have a length of no more than 0.5 m and exit the fittings into different holes in order to exclude the possibility of a short circuit when passing them through a common input. The conductors must be reliably insulated, be flexible and have rigid electrodes at their free ends, protected by insulated handles. The length of the bare end of the electrode should not exceed 1–2 cm.

Portable grounding.

Portable grounding in the absence of stationary grounding knives are the most reliable means of protection when working on disconnected sections of equipment or lines in case of erroneous voltage supply to the disconnected section or the appearance of induced voltage on it.

Portable grounding consists of the following parts:

· wires for grounding and for short-circuiting the current-carrying parts of all three phases of the installation. It is allowed to use a separate portable grounding for each phase;

· clamps for connecting grounding wires to the grounding bus and short-circuiting wires to current-carrying parts.

Portable grounding must meet the following conditions:

wires for shorting and grounding must be made of flexible uninsulated copper conductors and have a cross section that meets the requirements for thermal stability in case of short circuits, but not less than 25 mm 2 in electrical installations with voltages above 1000 Volts and not less than 16 mm 2 in electrical installations up to 1000 Volts ; in networks with a grounded neutral, the cross section of the wires must meet the requirements for thermal stability in case of a single-phase short circuit;

· clamps for connecting short-circuit wires to the busbars must be of such a design that during the passage of a short-circuit current, the portable grounding cannot be torn off by electrodynamic forces. Clamps must have a device that allows them to be applied, secured and removed from the busbars using a rod for applying grounding. Flexible copper wire must be connected directly to the clamp without a ferrule;

lug on the wire for grounding must be made in the form of a clamp or correspond to the design of the clamp (lamb) used to connect to the ground wire or structure;

· all connections of portable grounding elements must be made firmly and reliably by pressing, welding or bolting followed by soldering. Soldering alone is prohibited.

Portable earths must be inspected before each installation. Upon detection of destruction contact connections, violations mechanical strength conductors, melting, broken cores, etc. portable grounding should be withdrawn from use.

When grounding is applied, the ground wire is first connected to the "ground", then the absence of voltage is checked on the grounded current-carrying parts, after which the clips of the short-circuiting wires are applied to the current-carrying parts with a rod and fixed there with the same rod or hands in dielectric gloves. Removal of grounding is carried out in reverse order. All operations for applying and removing portable grounding must be performed using dielectric gloves.

Warning posters.

Warning posters should be used to warn of the danger of approaching live parts, to prohibit the operation of switching devices that can be energized at the place reserved for work, to indicate to the working personnel the place prepared for work and to remind the safety measures taken .

Posters are divided into four groups:

1. warning;

3. permissive;

4. reminiscent.

By the nature of the application, posters can be permanent and portable.

Portable warning posters are made of insulating or poorly conductive material (cardboard, plywood, plastic materials).

Permanent posters should be made of tin or plastic materials.

Protective glasses.

Goggles are used for:

1. work without removing voltage near and on live parts under voltage, including when changing fuses;

2. cutting cables and opening sleeves on cable lines in operation;

3. soldering, welding (on wires, tires, cables, etc.), cooking and heating mastic and pouring it into cable boxes, bushings, etc.;

4. turning and grinding rings and manifolds;

5. electrolyte handling and maintenance batteries;

6. tool sharpening and other work associated with the risk of injury to the eyes.

It is allowed to use only glasses made in accordance with the requirements of GOSTs.

Application.

Literature: "Methodology for the selection of conductors and protection equipment when connecting electrical receivers", TOE.

Question number 70. Calculate how much current a 100-watt lamp consumes at mains voltages of 36 and 220 volts. What power will be released on each lamp if two 220 V 100 W lamps are connected in series to a 220 Volt network? Draw a diagram.

Question number 71. Calculate the current consumed by a three-phase electric motor if the data on its nameplate are: U=380 V, P=3 kW, cos j=0.85, h=0.95. What is h?

Question number 72. When a piece of wire PNSV-1´1.2 is turned on, 28 meters long and with a resistance of 3.7 Ohm to the linear voltage of the TP, the current in the wire is 15 Amperes. What should be the length of the wire segments so that you can connect them to a star (three) and the current in the wire remains the same (15 Amperes)?

Question number 73. At a voltage of U = 80 Volts in a piece of wire PNSV-1´1.2 28 meters long and with a resistance of 3.7 Ohm, the current is 15 Amperes. What should be the length of the wire so that the current in it remains the same at a voltage of 36 volts?

Question number 74. Three lamps are connected in a star, the common point is attached to zero. The current in the phases is 3 Amps. How will the current in the phases change if one of the lamps burns out? How will the current change in neutral wire?

Question number 75. To what value should the insulation resistance of a 220 Volt extension cable fall in order for a single-phase 30 mA RCD to be guaranteed to disconnect the line?

Question number 76. Determine how much power is released in an active symmetrical three-phase load at a line voltage of 42 Volts and a line current of 24 Amperes.

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Rules technical operation consumer electrical installations.

Electrical safety rules.

Intersectoral rules on labor protection.

PTB - Safety regulations.

current limiting , in relation to voltage indicators, is a resistor that limits (limits) the maximum current through the device.

Dielectric - non-conductive (poorly conductive) electric current.

1. Basic requirements for the organization of the safe operation of electrical installations. 3

1.1 Introduction. 3

1.2 Requirements for personnel servicing electrical installations. 3

2. Qualification groups for electrical safety. four

2.1 Checking knowledge of PTE by personnel. 5

3. Electrical safety in operating electrical installations up to 1000 volts. Manufacturing jobs. 6

3.1 Technical measures to ensure the safety of work with stress relief. 7

3.1.1 Production of outages. eight

3.1.2 Posting warning posters, fencing the place of work. 9

3.1.3 Checking the absence of voltage. 9

3.1.4 Overlay grounding. ten

3.2 Organizational measures to ensure the safety of work. 12

3.2.1 Order, order, current operation. 12

3.3 Measures to ensure the safety of work without removing voltage near and on live parts under voltage. 13

4. Production of certain types of work. fourteen

4.1 Measurement of insulation resistance with portable megohmmeters. fourteen

4.2 PTE in the performance of work with power tools and portable lamps. fifteen

4.2.1 The choice of the protection class of the power tool depending on the working conditions. fifteen

4.2.2 Connection and rules for performing work with power tools. fifteen

4.2.3 Obligations of the employee issuing the order (instruction) for the performance of work with power tools. 16

5. Rules for the use of protective equipment used in electrical installations. eighteen

5.1 General provisions. eighteen

5.2 General rules use of protective equipment. 19

5.3 Requirements for certain types of protective equipment and rules for their use. twenty

5.3.1 Dielectric gloves. twenty

5.3.2 Dielectric boots and galoshes. twenty

5.3.3 Dielectric mats. 21

5.3.4 Tools with insulated handles. 21

5.3.5 Voltage indicators up to 500 Volts, operating on the principle of active current flow. 22

5.3.6 Portable grounding. 24

5.3.7 Warning posters. 25

5.3.8 Safety glasses. 25

5.3.9 Safety belts, fitter's claws, safety ropes and ladders. 26

6. Application. 27

6.1 Classification of premises (working conditions) according to the degree of danger of electric shock. 27

6.2 Classification of electrical products. 28

6.3 List of examination questions for the 3rd group on electrical safety. 29

6.3.1 Topic: "Knowledge of the structure of the serviced equipment and the rules for its operation - RCD". 29

6.3.2 Topic: "Knowledge of the rules for the use of protective equipment." 29

6.3.3 Topic: "Knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures that ensure the safety of work." thirty

6.3.4 Topic: "Separate types of work - power tools, megohmmeters." thirty

6.3.5 Topic: "Elementary knowledge of electrical engineering." 31

1. Basic requirements for the organization of the safe operation of electrical installations.

Introduction.

The present Toolkit compiled for the training of employees of electrical personnel for the 3rd group in electrical safety (with a tolerance of up to 1000 Volts) on the basis of the existing PTEEP, PTE and MPOT.

Requirements for personnel servicing electrical installations.

Personnel servicing electrical installations, insofar as it concerns them, must know:

Rules for the technical operation of consumer electrical installations (PTEEP);

Rules for the installation of electrical installations (PUE);

Guidelines for the design and operation of electrical installations assigned to it;

job descriptions and operational instructions in relation to the position held and the work performed;

Rules for the release of a person from the action of electric current;

Rules for providing first aid to victims of electric current.

Qualification groups for electrical safety.

drilling machine electric drive automatics

Control devices are designed to turn on, off and switch electrical circuits and electrical receivers, control the speed of rotation and reverse motors, control the parameters of power, lighting, heating and other electrical installations.

Protective devices are designed to turn off electrical circuits when abnormal conditions occur in them (short circuits, significant overloads, sudden voltage drops, etc.)

From right choice protection and automation equipment to a greater extent depend on the reliability of operation and the safety of the equipment as a whole, numerical, qualitative and economic indicators production mechanism and electrical safety of people.

Calculation and selection of switching equipment

We use magnetic starters to control asynchronous motors. Protection of motors against overloads is carried out by thermal relays.

a) Calculation and selection of the KM1 magnetic starter and KK1 thermal relay.

These devices are in the power circuit of the M1 engine with a power of

12 kW.
1) We determine the continuous current in the motor line according to the formula

where I dl - continuous current, A;

R d - engine power, kW;

U n - rated voltage of the electric motor, V;

h e - engine efficiency;

cos - power factor.

2) We select the thermal relay KK1.

The thermal relay is installed in 3 phases of the motor circuit, regardless of the magnetic starter. The thermal relay is selected according to the condition

I tr?1.25 I nd, (10)

where I tr - thermal relay current, A;

I nd - rated motor current, A.

According to the reference book, we select a thermal relay, which is installed regardless of the TRN-40 magnetic starter I nom \u003d 40A, I n.tep.el. =40A

3) Select the wire for the line.

Because line with a thermal relay, then the choice of wire is made taking into account compliance with this protection device, i.e. the condition must be met

I extra? To zshch I tr, (11)

where I additional - allowable current, A;

K ssh - protection factor.

According to the reference book, we select a wire of the PV brand with copper conductors. The wire is laid openly S=2.5 mm 2 ; I dp \u003d 40A

We check the selected wire, taking into account the long-term load current, i.e. the condition must be met

I dp? I extra, (12)

where I dp is the allowable current of the wire, A.

4) We select magnetic starters KM1.

R dv \u003d 12 kW

According to the reference book, we select the closest magnetic starter of the PME-3 brand in terms of power

b) Calculation and selection of magnetic starters KM2-KM3

These devices are in the power circuit of the M2 engine with a power of

1.5 kW.

2) Select the wire for the line.

I additional? 1.25 3.5

S \u003d 0.5 mm 2 I dp \u003d 11A

Since the condition is met, the wire is selected correctly.

3) We select magnetic starters KM2-KM3.

Because magnetic starters KM4-KM5 are designed to control this

engine, then we reduce the calculation to only one, for example, we calculate the KM2 magnetic starter, and take the other of the same brand.

R dv \u003d 1.5 kW

c) Calculation and selection of magnetic starter KM4

These devices are located in the power circuit of the M3 engine with a power of

0.12 kW.
1) We determine the continuous current in the motor line according to the formula (9)

2) Select the wire for the line.

Because line without a thermal relay, then the choice of wire is made taking into account compliance with this protection device, i.e. condition (11) must be satisfied

I additional? 1.25 0.47

According to the reference book, we select the wire of the VRG brand in a PVC sheath with copper conductors. The wire is laid open.

S \u003d 0.5 mm 2 I dp \u003d 11A

We check the selected wire, taking into account the long-term load current, i.e. condition (12) must be satisfied

Since the condition is met, the wire is selected correctly.

3) We select the KM4 magnetic starter.

R dv \u003d 1.5 kW

According to the reference book, we select the closest magnetic starter of the PME-0 brand in terms of power

Electrical appliances and wiring must be protected from possible emergency situations by protection devices, this is a short circuit, connecting an increased load, overvoltage. The main functions of protecting people and electrical wiring in a residential building are performed by VA(automatic switches), RCD (), VD(differential switches), SPD, RPN ().

Automatic switch (VA)

The calculation and selection of protection devices is the basis for designing the power supply of a private house. Their main function is to protect against overcurrent short circuits ( KZ) and when the increased load is switched on. From short circuit provided electromagnetic release, from increased power intended thermal release.

When the consumer chooses VA, he must know that each electrical appliance has starting current. This is an electric current that is greater than the nominal (working) by a certain amount. This value can exceed 3, 5 or 7 times the rated current of the appliance. The inrush current transit time is a few milliseconds. But even this time is enough for the electromagnetic release to work and the VA to turn off the electrical network. For this reason, circuit breakers are divided into several types depending on the magnitude of the starting currents.

Type of AT– (from 3 – 5) In, where In is the rated (working) current of the electrical device.
Type of FROM– (5 – 10) In
Type of D– (10 – 20) In

For example, you need to set VA for an induction motor. For some types, the starting current is 6 In, so we choose VA, and its type is B, and so on.

When choosing machines by type, that is, by starting current, it is necessary to take into account some nuances. So ABB machines are classified according to IEC 60947 - 2 ( international standard), where the class To(8 - 14) In, a class Z(2 – 4) In.

The principle of operation of the thermal and electromagnetic release

Fig.1

Housing VA ( 1 ) are made of a dielectric material, like the handle ( 2 ), which serves to enable it. Retainer ( 3 ) is designed for mounting on a DIN rail with an ordinary screwdriver (you bend it and install or remove the VA). Bimetallic plate (6) is the main element of VA for protection against increased load. Its essence is that it is made of a special alloy and has special physical and technical characteristics, and when a current passes through it, which is greater than the working (rated) current, it bends. As a result of this bending, it acts on the element ( 7 ) and VA disconnects the electrical network. These are actions thermal release.

If over currents (short circuits) appear in the electrical network, then they pass through the solenoid ( 9 ), it draws in the core and the VA is turned off. These are actions electromagnetic release.

The main postulates when choosing VA for a household consumer

When a consumer buys a circuit breaker in a store, first of all he must know the long-term permissible current of the cable that he will protect.
When choosing protection devices (VA) according to the thermal release, it is necessary to take into account the non-shutdown current 1.13 In. Even if the load exceeds the rated current by 1.11 times, the thermal release will not work, and if this current is applied to the wire for a long time, this can lead to undesirable consequences.
Coefficient 1.45 relative to the rated current takes into account when the circuit breaker trips. For VA this time is about 1 hour, but it depends on many factors, external environment, manufacturer, the number of machines that are located. During this time, the cable insulation may melt. Consider this factor when choosing VA on rated current relative to the continuously admissible current of the outgoing cable.

According to the number of poles, VA are divided into one, two, three and four poles. They also choose VA according to the degree of protection, the number of contacts, the type of installation, the presence of current limitation, and so on.

The rated currents of the circuit breakers are at outdoor panel. Main line for household VA 6.3, 10, 16, 20, 25, 32, 40, 63 A there are more.

Personnel servicing electrical installations, insofar as it concerns them, must know:

Rules for the technical operation of consumer electrical installations (PTEEP);

Rules for the installation of electrical installations (PUE);

Guidelines for the design and operation of electrical installations assigned to it;

job descriptions and operational instructions in relation to the position held and the work performed;

Rules for the release of a person from the action of electric current;

Rules for providing first aid to victims of electric current.

2. Qualification groups for electrical safety.

Group	The amount of knowledge required.
	Persons who do not have special electrical training, but who have a clear idea of the danger of electric current and safety measures when working on a serviced area, electrical equipment, electrical installation, are certified for group 1. Must have practical knowledge of first aid. Training for 1 group is carried out in the form of a briefing followed by a control survey by a specially designated person with an electrical safety group of at least 3.
	Persons with group 2 must have: 1. elementary acquaintance with the electrical installation device; 2. a clear understanding of the danger of electric current and approaching live parts; 3. knowledge of basic precautions when working in electrical installations; 4. practical acquaintance with the rules of first aid.
	Persons with group 3 must have: 1. basic knowledge of electrical engineering; 2. a clear understanding of the dangers when working in electrical installations; 3. knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures that ensure the safety of work; 4. knowledge of the rules for the use of protective equipment; 5. knowledge of the structure of the serviced equipment and the rules for its operation; 6. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.
	Persons with group 4 must have: 1. clear knowledge of the basics of electrical engineering; 2. knowledge of PTE, PTEEP, MPOT and PUE in terms of fixed electrical installations; 3. a complete understanding of the dangers when working in electrical installations; 4. knowledge of the rules for the use and testing of protective equipment; 5. knowledge of the installation so as to freely understand which elements must be turned off for the performance of work, find all these elements in nature and check the implementation of the necessary safety measures; 6. the ability to organize safe work and supervise them in electrical installations with voltage up to 1000 volts; 7. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.

2.1 Checking knowledge of PTE by personnel.

Subdivided into:

1. primary;

2. periodical;

3. extraordinary.

Periodic are subject to verification:

personnel involved in the operation of electrical installations, as well as the management and engineering staff organizing their operation - once a year;

management and engineering staff, not related to the previous group, but in charge of electrical installations - 1 time in three years.

Primary called the first of the periodic checks.

Extraordinary knowledge is tested:

Persons who have committed violations of PTE, PTEEP, MPOT, job or operational instructions;

persons who have had a break in work at this electrical installation for more than 6 months;

persons transferred to a new electrical installation;

· persons on the instructions of the management of the enterprise or on the instructions of the inspector of energy supervision.

3. Electrical safety in existing electrical installations up to 1000 volts. Manufacturing jobs.

electrical installations These are the installations in which electricity is produced, converted and consumed. Electrical installations include mobile and stationary sources of electricity, electrical networks, switchgear and connected pantographs.

Operating electrical installations installations are considered to be fully or partially energized or to which voltage can be applied at any time by switching on the switching equipment.

According to the degree of danger of electric shock to personnel, electrical installations are divided into electrical installations up to 1000 Volts and above 1000 volts .

According to the terms of TB, the operation of electrical installations is divided into two parts:

operational maintenance of electrical installations;

· work in electrical installations.

Prompt service includes:

duty in existing electrical installations;

walk-arounds and inspections of electrical installations;

operational switching;

Work performed in the order of current operation.

An employee of management personnel who has an electrical safety group of at least 4th has the right to give an order to perform work in existing electrical installations up to 1000 Volts.

Works in electrical installations in relation to safety measures are divided into those performed:

1. with stress relief;

2. without removing the voltage on current-carrying parts and near them.

To stress relief work includes work performed in an electrical installation (or part of it), in which voltage is removed from current-carrying parts.

To work without removing voltage on current-carrying parts, and near them includes work performed directly on these parts or near them. In installations with voltages above 1000 volts, as well as on overhead lines up to 1000 volts, the same work includes those that are performed at distances from live parts that are less than permissible. Such work must be carried out by at least two persons: the foreman with a group of at least IV, the rest - below III.

3.1 Technical measures to ensure the safety of work with stress relief.

When preparing a workplace for work with stress relief, the operational personnel must perform the following technical measures in the specified order:

1. the necessary shutdowns have been made and measures have been taken to prevent the supply of voltage to the place of work due to erroneous or spontaneous switching on of the switching equipment;

2. Prohibitory posters (“Do not turn on, people work”, “Do not turn on, work on the line”) are hung on the manual drives and remote control keys of the switching equipment and, if necessary, barriers are installed;

3. portable grounds are connected to the "Earth", the absence of voltage on current-carrying parts is checked, on which grounding must be applied to protect people from electric shock;

4. immediately after checking the absence of voltage, grounding must be applied (grounding knives are turned on, and where they are absent, portable grounding devices are installed);

5. warning and prescriptive posters are posted, workplaces and live parts remaining under voltage are fenced, if necessary. Depending on local conditions, current-carrying parts are protected before or after grounding is applied.

The technical measures specified in paragraph 3.1 can be performed by an admissions person with a qualification group of at least 3.

Stress relief work can be carried out either with grounding or without grounding, but with the adoption of technical measures to prevent erroneous voltage supply to the work site.

3.1.1 Production of outages.

At the place of work, the current-carrying parts on which work is performed, as well as those that can be touched during work, must be disconnected.

Non-insulated current-carrying parts accessible to touch can not be disconnected if they are securely protected by insulating pads made of dry insulating materials.

Disabling can be done:

The procedure for checking the disconnected state of switching devices is established by the person issuing the order or giving the order.

3.1.2 Posting warning posters, fencing the place of work.

On the handles, keys and control buttons of all switching devices, as well as on the contact racks (bases) of the fuses, with which voltage can be applied to the place of work, posters “Do not turn on - people work”, “Do not turn on - work on lines".

Non-disconnected current-carrying parts adjacent to the workplace, accessible to accidental contact, must be fenced for the duration of work.

Dry, well-fortified screens, linings made of wood, micanite, getinax, textolite, rubber, etc. can serve as temporary fences. Posters "Stop - life is dangerous" should be hung on temporary fences.

Before installation of protections from them dust has to be carefully wiped off.

The installation of fences applied directly to live parts should be done with caution, wearing dielectric gloves and glasses, in the presence of a second person with IV qualification group.

At all prepared work sites, after grounding is applied, a poster "Work here" is posted.

During the work of the staff of the brigade PROHIBITED rearrange or remove posters and installed temporary fences and enter the territory of fenced areas.

3.1.3 Checking the absence of voltage.

Before starting all work on electrical installations with de-energization, it is necessary to check the absence of voltage in the work area. Checking the absence of voltage is carried out by a voltage indicator with a neon lamp.

Immediately before checking the absence of voltage, it is necessary to make sure that the indicator used is in good condition by checking it on current-carrying parts located nearby and obviously under voltage.

FORBIDDEN use indicators with low input resistance (control lamps, LED voltage indicators, sound "controls", etc.) to check the absence of voltage, since they do not indicate induced voltage dangerous to human life .

The absence of voltage must be checked:

Between three pairs of phases;

Between each phase and PE-conductor ("earth");

between zero working (N) and zero protective conductor(PE).

Stationary devices that signal the disconnected state of the installation are only an auxiliary means, based on the readings of which it is not allowed to draw a conclusion about the absence of voltage.

3.1.4 Overlay grounding.

3.1.4.1 Grounding locations.

When working on busbars, at least one ground must be applied to them.

In closed switchgear, portable grounding must be superimposed on live parts in the places designated for this. These places should be cleared of paint and bordered with black stripes.

The list of such electrical installations must be determined and approved by the chief power engineer (the person responsible for electrical facilities).

3.1.4.2 The procedure for applying and removing grounding.

Grounding should be carried out immediately after checking the absence of voltage. The imposition and removal of portable grounding must be carried out by two persons.

Portable grounds must be connected to the "Earth" terminal before checking for the absence of voltage. Portable ground clamps are superimposed on the grounded current-carrying parts with the help of a rod made of insulating material using dielectric gloves. The fastening of the clamps is carried out by the same rod or directly by hands in dielectric gloves.

It is forbidden to use for grounding any conductors not intended for this purpose, as well as to connect groundings by twisting them.

Portable grounding must be made of bare copper stranded wires and have a cross section of at least 25 mm 2.

Grounding should be removed in reverse order using a rod and dielectric gloves, that is, first remove it from live parts, and
then disconnect from grounding devices.

If the nature of work in electrical circuits requires removal of grounding (for example, when checking transformers, when testing equipment from an external current source, when checking insulation with megohmmeters, etc.), temporary removal of groundings that interfere with work is allowed. At the same time, the place of work must be prepared in full compliance with the above requirements, and only for the duration of the work can those groundings be removed, in the presence of which the work cannot be performed.

Turning on and off grounding knives, applying and removing portable grounding should be taken into account according to the operational scheme, in the operational log and in the order.

3.2 Organizational measures to ensure the safety of work.

Organizational measures that ensure the safety of work in stationary electrical installations are:

1. execution of work by order or order;

2. admission to work;

3. supervision during work;

4. registration of a break in work, transfers to another workplace, end of work.

3.2.1 Order, order, current operation.

Works in electrical installations are carried out:

along with;

by order;

in the order of current operation.

Outfit - this is a written assignment for work in electrical installations, drawn up on a form of the established form and determining the place, time of beginning and end of work, the conditions for its safe conduct, composition of the calculation and persons responsible for the safety of work. According to the order, as a rule, planned work should be carried out.

Disposition - this is a task for work in electrical installations, drawn up in the operational journal by the person who gave the order, or by the person of the operational staff who received the order orally directly or via means of communication from the person who gave the order.

Current operation - this is the performance by the operational (operational and repair) staff at a fixed electrical installation during one shift of work according to the list approved in the established manner, while determining the need and scope of work, as well as preparing the workplace for safe work are carried out directly by the work manufacturer.

3.3 Measures to ensure the safety of work without removing voltage near and on live parts under voltage.

When working without removing the voltage near and on live parts under voltage, measures must be taken to prevent workers in electrical installations with voltages above 1000 volts from approaching these live parts at a distance less than permissible, and in electrical installations with voltages up to 1000 volts - measures that exclude touching live parts. This work should be done in pairs.

These activities include:

1. safe location working persons in relation to live parts under voltage;

2. organization of continuous supervision of workers;

3. the use of basic and additional insulating means that allow you to work directly on live parts.

A person performing work near live parts under voltage must:

Work with the sleeves of clothing lowered and buttoned at the hands and in a headdress;

· be located so that these current-carrying parts are in front of it and only on one side.

PROHIBITED perform work if live parts under voltage are located at the back or on both sides.

PROHIBITED work in a bent position, if, during straightening, contact with live parts under voltage is not excluded.

On electrical installations located in rooms that are especially damp, with conductive dust, caustic fumes, as well as in rooms that are dangerous in relation to fire
or explosion, performance of work on non-disconnected current-carrying parts PROHIBITED .

In rooms with heightened danger if necessary, work can be carried out on non-disconnected current-carrying parts using additional security measures determined by the persons issuing the order or giving the order.

Work on live parts under voltage must be carried out using basic and additional insulating protective equipment.

4. Production of certain types of work.

4.1 Measurement of insulation resistance with portable megohmmeters.

Measurement of insulation resistance in electrical installations is carried out:

· after repair;

· at technical services(regular work);

during conservation;

during technical inspection.

Checking the insulation resistance value of the electrical unit is carried out by persons with a qualification group of at least III using a megohmmeter of the appropriate voltage.

The insulation resistance of individual elements of an electrical installation with a solidly grounded neutral must be at least 0.5 MΩ (500 kΩ).

The insulation resistance must be measured individual elements installation after this item is disabled on all sides. Insulation resistance measurements are made when the voltage is completely removed from the electrical installation and with the implementation of safety measures that exclude accidental voltage supply to the place of work. Before starting measurements, it is necessary to make sure that there are no people on the electrical installation being tested, and take measures to exclude the possibility of accidental contact with live parts.

The wires used to connect the megohmmeter must have good insulation and be terminated with reliable tips. cross section copper wires must be at least 1.5 mm2.

4.2 PTE in the performance of work with power tools and portable lamps.

Here and below, power tools, according to PTE 3.5.1., are understood as portable and mobile power receivers, the design of which provides for the possibility of moving them to the place of use for their intended purpose manually (without the use of vehicles), as well as auxiliary equipment to them. These include: portable lamps; hand power tools; "extenders" of all voltages; vibrators and vibrolaths; portable transformers for power tools; portable electric pumps; welding machines used outside of equipped welding stations.

Persons with the 2nd qualification group for electrical safety are allowed to work with power tools that are not related to the maintenance of its electrical part at JSC DSMU.

4.2.1 The choice of the protection class of the power tool depending on the working conditions.

Use in especially dangerous rooms and especially adverse conditions power tools protection class (against electric shock) 0.01 , 1- ABSOLUTELY FORBIDDEN.

The use of portable lamps with a voltage higher than 42 volts AC without the use of electrical protection equipment in any conditions - ABSOLUTELY FORBIDDEN.

The use of portable lamps with voltages above 12 volts AC in particularly unfavorable conditions - ABSOLUTELY FORBIDDEN;

According to MPOT 10.3, it is allowed to use a power tool of protection class (against electric shock) 2 without the use of means of protection against electric shock in any conditions, except for especially unfavorable ones.

According to the 10.3 MPOT, it is allowed to use a power tool of protection class (against electric shock) 3 without the use of means of protection against electric shock in any conditions.

4.2.2 Connection and rules for performing work with power tools.

The connection of the power tool to the mains supply must be carried out by means of hose flexible wires or cables. The hose wire at one end must be brought into the electrical receiver, the other - into the half-coupling-plug of the plug connection.

PROHIBITED connecting power tools and portable lamps to the mains with a wire or cable without a half-coupling-plug.

Plug connections (plugs, sockets) used for voltages of 42 volts alternating current and below, in their design, must differ from plug connections used for voltages of 220 and 380 volts; the possibility of plugging up to 42 Volt plugs into 220/380 sockets should be technically excluded.

Plug connections (plugs, sockets) used for voltages of 42 volts alternating current and below must have a color that is sharply different from the color of plug connections 220/380 volts.

FORBIDDEN power tool from autotransformers.

FORBIDDEN to turn on and off electric lamps fixtures by screwing them in and out. Burnt out lamps should be replaced after the lamp is disconnected from the mains.

Working with power tools from ladders with a height of more than 2.5 meters PROHIBITED. Use portable metal ladders to work with power tools of protection class below 2 FORBIDDEN .

4.2.3 Obligations of the employee issuing the order (instruction) for the performance of work with power tools.

An employee issuing an order (instruction) to perform work with a power tool must pass a test of knowledge of the norms and rules for working in electrical installations for a group of at least 3rd, have a valid certificate and belong to the management personnel.

4.2.3.1 In the order (instruction), the employee must indicate:

1. the nature of the work;

2. the exact location of the work;

3. a list of protective equipment used in the performance of this work;

4. an exhaustive list of organizational and technical measures that ensure the safety of the prescribed work.

4.2.3.2 The employee issuing the order (instruction) is obliged to ensure:

1. Checking with the work contractor that there is an active electrical safety group required for this type of work;

2. verification of the contractor's access to work with power tools according to age and medical indicators;

3. issuance of serviceable protective equipment to the performer of work in the amount prescribed by the PTE and PTB during the work;

4. issuance to the performer of work of a serviceable tool that meets the conditions and type of work prescribed by the order (order);

5. compliance of the used (specified in the order) power tools and protective equipment with the conditions of the place of work according to the requirements of electrical safety;

6. execution of all organizational and technical measures prescribed in the order (order) to ensure the safety of work;

7. control over compliance by the contractor with PTB, PPB, PTE in the course of work;

8. storage of protective equipment and power tools.

5. Rules for the use of protective equipment used in electrical installations.

5.1 General provisions.

Protective means are devices, devices, portable and transportable devices and devices, as well as individual parts of devices, devices and devices that serve to protect personnel working on electrical installations from electric shock, from the effects of an electric arc, its combustion products, etc. .

The protective equipment used in electrical installations includes:

· insulating operational rods, insulating pullers for operations with fuses, voltage indicators to determine the presence of voltage;

· insulating ladders, insulating platforms, insulating rods, grippers and tools with insulated handles;

· rubber dielectric gloves, boots, galoshes, rugs, insulating pads;

· portable grounding;

· temporary fences, warning posters, insulating caps and overlays;

· goggles, canvas gloves, filtering and isolating gas masks, safety belts, safety ropes.

on basic protective equipment;

for additional protective equipment.

Main such protective equipment is called, the insulation of which reliably withstands the operating voltage of electrical installations and with the help of which it is allowed to touch live parts that are energized.

Additional such protective equipment is called, which by itself cannot provide safety against electric shock at a given voltage and are only an additional measure of protection to fixed assets. They also serve as protection against touch voltage, step voltage and as an additional protective measure against the effects of electric arcs and products.

Additional insulating protective equipment is tested with a voltage independent of the voltage of the electrical installation in which they are to be used.

The main insulating protective equipment used in electrical installations with voltages up to 1000 volts include:

dielectric gloves;

tool with insulated handles;

voltage indicators.

Additional insulating protective equipment used in electrical installations with voltages up to 1000 volts include:

dielectric boots;

dielectric rubber mats;

insulating pads.

The choice of certain insulating protective equipment for use during operational switching or repair work is regulated by safety regulations for the operation of electrical installations and power lines and special instructions for the performance of individual works.

Auxiliary protective equipment is intended for individual protection of the worker from light, thermal and mechanical influences. These include goggles, gas masks, gloves, etc.

5.2 General rules for the use of protective equipment.

The use of insulating protective equipment should be carried out only for their intended purpose in electrical installations with a voltage not higher than that for which the protective equipment is designed. All basic insulating protective equipment is designed for use in open or closed electrical installations only in dry weather. Therefore, the use of these protective equipment outdoors in wet weather (during rain, snow, fog) is prohibited.

Before each use of protective equipment, the electrician must:

Check its serviceability and the absence of external damage, clean and wipe off dust; check rubber gloves, boots, galoshes for the absence of punctures, cracks, bubbles and other foreign inclusions. If a malfunction is detected, the protective agent must be immediately withdrawn from use.

Check on the stamp for which voltage the use of this agent is permissible and whether the validity period of its last test has not expired. It is forbidden to use protective equipment, the test period of which has expired, since such equipment is considered faulty.

5.3 Requirements for certain types of protective equipment and rules for their use.

5.3.1 Dielectric gloves.

For work in electrical installations, it is allowed to use only dielectric gloves made in accordance with the requirements of GOSTs or technical specifications. Gloves intended for other purposes (chemical and others) are not allowed to be used as a protective agent when working in electrical installations.

Dielectric gloves issued for maintenance of electrical installations must be of several sizes. The length of the glove must be at least 350 mm. Gloves should be worn on the hands to their full depth. It is not allowed to wrap the edges of the gloves or lower the sleeves of clothing over them. When working outdoors in winter, dielectric gloves are worn over woolen ones. Each time before use, the gloves must be checked for tightness by filling them with air.

5.3.2 Dielectric boots and galoshes.

Dielectric boots and galoshes, in addition to performing the function of an additional protective agent, are a protective agent against step voltage in electrical installations of any voltage.

For use in electrical installations, only dielectric boots and overshoes made in accordance with the requirements of GOSTs are allowed. They must differ in appearance from boots and galoshes intended for other purposes. Each boot, each galosh must have the following inscriptions: manufacturer, date of issue, OTK mark, test voltage and test date.

Boots and overshoes issued for the maintenance of electrical installations must be of several sizes.

5.3.3 Dielectric mats.

Dielectric mats must be manufactured in accordance with the requirements of GOSTs with a size of at least 50 × 50 cm. The upper surface of the mat must be corrugated.

5.3.4 Tools with insulated handles.

A tool with insulated handles can be used in electrical installations with voltage up to 1000 volts.

Tool handles must be coated with moisture-resistant, non-fragile insulating material. All insulating parts of the tool must have a smooth surface, free of cracks, breaks, and burrs. The insulating coating of the handles must fit snugly against metal parts tool and completely isolate that part of it that is in the hand of the worker during work. Insulated handles must be equipped with stops and have a length of at least 10 cm. For screwdrivers, not only the handle, but also the metal rod must be insulated along its entire length up to the working tip.

When working with a tool with insulated handles on live parts under voltage, the worker must have dielectric galoshes on his feet or stand on an insulating base, in addition, he must be in a headdress with lowered and buttoned sleeves of clothing. Dielectric gloves are not required.

5.3.5 Voltage indicators up to 500 Volts, operating on the principle of active current flow.

Voltage indicators can be of three types:

1. voltage indicators with a neon lamp (current detectors) - used in electrical installations with voltage up to 500 volts;

2. control lamp - allowed in electrical installations with voltage up to 220 volts;

3. other voltage indicators.

5.3.5.1 Neon lamp voltage gauges.

The voltage indicator (current detector) is a portable device operating on the principle of active current flow, and is used to check the presence or absence of voltage only in electrical circuits of alternating current 110 - 500 volts with a frequency of 50 Hz. The current detector is a two-pole device equipped with insulating handles with palm rests.

The resistance of the current-limiting resistor used in the current detector must be at least 500 kΩ when checked with a megger for a voltage of 500 volts.

5.3.5.2 Pilot lamps.

The control lamp must be enclosed in a case-fitting made of insulating material with a slot for a light signal. The conductors should have a length of no more than 0.5 m and exit the fittings into different holes in order to exclude the possibility of a short circuit when passing them through a common input. The conductors must be reliably insulated, be flexible and have rigid electrodes at their free ends, protected by insulated handles. The length of the bare end of the electrode should not exceed 1–2 cm.

5.3.5.3 Other voltage indicators.

These include portable voltmeters and two-pole voltage indicators, in which LEDs, liquid crystal indicators, and audible alarms are used for indication. To be used as a voltage indicator, they must have a housing made of dielectric material. The conductors of the device must be reliably insulated, flexible and have rigid electrodes at their free ends, protected by insulated handles. The length of the bare end of the electrode should not exceed 1–2 cm.

5.3.5.4 Use of voltage indicators.

To check the presence of voltage, you need to touch two opposite phases or poles with the contacts of the voltage indicator. FORBIDDEN touch the electrodes of the voltage indicator at a time when at least one of the electrodes is connected to parts that may be energized.

The threshold for a distinct glow of the current detector lamp should be no higher than 90 volts, and for a control lamp - no more than 50% of the operating voltage. The current detector is designed for intermittent operation. The use of the current detector is carried out without the use of other protective equipment.

Use single-pole devices as a voltage indicator (various “indicator screwdrivers”), in which the operating current of the device flows through the human body, FORBIDDEN. If such devices are used in 220/380 Volt electrical installations for other purposes, for example, as a pointer electromagnetic field(EMF), as "continuity", etc., then the resistance of the current-limiting resistor of the device should be checked. The check is made with a 500 volt megger, the resistance of the resistor must be at least 500 kOhm.

5.3.6 Portable grounding.

Portable grounding consists of the following parts:

· wires for grounding and for short-circuiting the current-carrying parts of all three phases of the installation. It is allowed to use a separate portable grounding for each phase;

· clamps for connecting grounding wires to the grounding bus and short-circuiting wires to current-carrying parts.

Portable grounding must meet the following conditions:

· clamps for connecting short-circuit wires to the busbars must be of such a design that during the passage of a short-circuit current, the portable grounding cannot be torn off by electrodynamic forces. Clamps must have a device that allows them to be applied, secured and removed from the busbars using a rod for applying grounding. The flexible copper wire must be connected directly to the terminal without a ferrule;

lug on the wire for grounding must be made in the form of a clamp or correspond to the design of the clamp (lamb) used to connect to the ground wire or structure;

· all connections of portable grounding elements must be made firmly and reliably by pressing, welding or bolting followed by soldering. Soldering alone is prohibited.

Portable earths must be inspected before each installation. Upon detection of destruction of contact connections, violation of the mechanical strength of conductors, melting, breakage of cores, etc., portable grounding should be withdrawn from use.

When grounding is applied, the ground wire is first connected to the "ground", then the absence of voltage is checked on the grounded current-carrying parts, after which the clips of the short-circuiting wires are applied to the current-carrying parts with a rod and fixed there with the same rod or hands in dielectric gloves. Grounding is removed in reverse order. All operations for applying and removing portable grounding must be performed using dielectric gloves.

5.3.7 Warning posters.

Posters are divided into four groups:

1. warning;

3. permissive;

4. reminiscent.

By the nature of the application, posters can be permanent and portable.

Portable warning posters are made of insulating or poorly conductive material (cardboard, plywood, plastic materials).

Permanent posters should be made of tin or plastic materials.

5.3.8 Safety glasses.

Goggles are used for:

1. work without removing voltage near and on live parts under voltage, including when changing fuses;

2. cutting cables and opening couplings on cable lines that are in operation;

3. soldering, welding (on wires, tires, cables, etc.), cooking and heating mastic and pouring it into cable boxes, bushings, etc.;

4. turning and grinding rings and manifolds;

5. work with electrolyte and maintenance of storage batteries;

6. tool sharpening and other work associated with the risk of injury to the eyes.

It is allowed to use only glasses made in accordance with the requirements of GOSTs.

5.3.9 Safety belts, fitter's claws, safety ropes and ladders.

Safety belts are designed to protect against falls from a height when working on supports or wires of power lines and on structures or switchgear equipment.

The belts are made of durable, non-stretch material. The width of the belts must be at least 100 mm, the length - from 900 to 1000 mm. Three rings are fixed on the belt: one for fastening the belt sling, the other for fastening the carabiner of the sling and the third for attaching the safety rope.

The belt sling, designed to be grabbed by supports or structures, is made of a belt, chain or nylon halyard in accordance with the requirements of GOSTs and is tightly attached to the right ring, and a carabiner is tightly attached to the other end of the sling.

The carabiner, in addition to the lock with a spring, must have an additional latch to prevent spontaneous opening.

When working near live parts under voltage, on power lines or in switchgear, a belt with a sling made of a belt, nylon halyard or cotton rope should be used. For work performed on disconnected power lines or switchgears, as well as away from voltage, belts with a chain are allowed.

If during operation the safety belt was subjected to a dynamic load (during a jerk in the event of a fall of the worker), the belt should be removed from service and should not be used until a test with a static load in order to check its integrity. The belt, the parts of which have received any damage from dynamic loading, must be destroyed.

The safety rope is used as additional measure security. It is mandatory to use it in cases where the place of work is at a distance that does not allow the safety belt to be secured to a support or structure.

Mounter's claws are designed for lifting and lowering smooth wooden poles and power line poles. Mounter's claws should be inspected before use, and attention should be paid to the serviceability of belts, buckles, spikes, the absence of cracks, etc.

When servicing electrical equipment located at a height of up to 5 m, fitter's ladders and stepladders. The height of the stairs should not exceed 4.5 m. When working at a height of more than 5 m, scaffolding and scaffolding should be used.

6. Application.

6.1 Classification of premises (working conditions) according to the degree of danger of electric shock.

significant impact on electrical safety environment industrial premises. With regard to the danger of electric shock to personnel, the PUE distinguish:

Premises without increased danger in which there are no conditions that create an increased or special danger;

Premises with increased danger , characterized by the presence of one of the following signs that create an increased danger:

Dampness (relative air humidity exceeds 75% for a long time) or the presence of conductive dust (depositing on wires, penetrating inside machines, devices, etc.);

conductive floors (metal, earthen, reinforced concrete, brick, etc.);
heat(exceeds +35 ◦С for a long time);
the possibility of a person simultaneously touching the metal structures of buildings connected to the ground, technological apparatus, etc., on the one hand, and to the metal cases of electrical equipment, on the other;

Particularly dangerous premises , characterized by the presence of the following conditions that create a particular danger:

special dampness ( relative humidity close to 100% - ceiling, walls, floor, objects are covered with moisture);

chemically active or organic environment (aggressive vapors, gases, liquids are contained for a long time, deposits or mold are formed that destroy insulation and current-carrying parts);

Two or more high-risk conditions at the same time.

Territories for placement of outdoor electrical installations (in the open air, under a canopy, outside mesh fences) - are equated to especially dangerous premises.

In a number normative documents allocated to a separate group of work in especially adverse conditions (in vessels, apparatuses, boilers, etc.) metal containers with limited ability to move and exit the operator). The danger of electric shock, and hence the safety requirements in these conditions, is higher than in especially dangerous rooms.

The conditions for the production of work impose certain requirements on the power supply of such consumers as power tools, local lighting lamps, portable lamps.

In rooms with increased danger and especially dangerous, they should be powered by a voltage of no more than 42 volts alternating current, in especially unfavorable conditions - no more than 12 volts.

6.2 Classification of electrical products.

According to the method of protecting a person from electric shock, electrical products are divided into 5 protection classes:

Protection class.	Characteristics of the protection method.
	Products with working insulation and no elements for grounding.
0 I	Products with working insulation, a grounding element and a wire without a grounding core for connection to a power source.
	Products in which a working insulation is provided, a grounding element and a wire with a grounding conductor and a plug with a grounding contact.
	Products with double or reinforced insulation, without earthing elements.
	Products in which there are no internal and external electrical circuits with a voltage of more than 42 volts. Products powered by an external source may be classified in class 3 only if they are intended to be connected directly to a power source with a voltage not exceeding 42 volts. When used as a power source for a transformer, its input and output windings must not be electrically connected and there must be double or reinforced insulation between them.

6.3 List of examination questions for the 3rd group on electrical safety.

6.3.1 Topic:"Knowledge of the device of the serviced equipment and the rules of its operation - RCD."

Question number 30. Explain the principle of the RCD. What types of RCDs do you know?

Question number 31. Name the most common cause of RCD operation in your electrical installation. How do you deal with it?

Question number 32. What is the difference between electromechanical and electronic RCDs? How can they be distinguished without supporting documentation?

Question number 33. What is the purpose of RCDs? In what parts of electrical installations is the use of RCDs mandatory?

Question number 34. What checks should electromechanical RCDs be subjected to? With what frequency?

Question number 35. draw typical scheme turning on a three-phase electric motor through an RCD. Sign the conductors according to the PUE.

6.3.2 Topic: "Knowledge of the rules for the use of protective equipment."

Literature: “Electrical safety. Methodical materials… for the 3rd group”, PTE.

Question number 40. State the general rules for the use of protective equipment.

Question number 41. State the rules for using a tool with insulated handles ("electrician's tool") and the requirements for it.

Question number 42. Outline the rules of use and requirements for voltage indicators.

Question number 43. Why is it forbidden to use pilot lamps if the voltage of the electrical installation exceeds 220 volts? What are the advantages of test lamps over other voltage indicators, what are the disadvantages?

Question number 44. State the rules for use and requirements for dielectric gloves.

Question number 45. Outline the rules for use and requirements for dielectric boots and galoshes.

Question number 46. State the rules of use and requirements for dielectric mats.

Question number 47. Outline the rules of use and requirements for warning posters.

Question number 48. State the rules for use and requirements for protective glasses.

Question number 49. Outline the rules for use and requirements for safety belts, fitter's claws, safety ropes and ladders.

6.3.3 Topic: "Knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures that ensure the safety of work."

Literature: “Electrical safety. Methodological materials ... for the 3rd group”, PTE, PTEEP, MPOT.

Question number 50. State the requirements for personnel servicing electrical installations.

Question number 51. List what an electrician with the 3rd qualification group should know (amount of necessary knowledge).

Question number 52. What types of PTE knowledge tests do you know? Who is subject to each type of PTE knowledge test?

Question number 53. How is the operation of electrical installations divided according to safety conditions? What is included in operational maintenance, how are works in electrical installations divided?

Question number 54. What safety measures should be taken if stress relief work is carried out without the use of portable earths?

Question number 55. How exactly should warning posters be hung out, temporary fences should be applied during work with complete stress relief?

Question number 56. List the organizational measures that ensure the safety of work in electrical installations.

Question number 57. Explain the difference between work along side, by order and in the order of current operation.

Question number 58. List the measures that ensure the safety of work without stress relief. What rules must be followed by a worker directly performing work under voltage?

Question number 59. State the classification of premises according to the degree of danger of electric shock to personnel.

Question number 60. State the classification of electrical products according to the method of protecting a person from electric shock.

6.3.4 Topic: "Separate types of work - power tools, megohmmeters."

Literature: “Electrical safety. Methodological materials ... for the 3rd group”, PTE, PTEEP.

Question number 61. How is the protection class of power tools selected depending on the working conditions?

Question number 62. State the rules for connecting a power tool to the mains.

Question number 63. List what must be indicated in the order (order) for the performance of work with power tools. Who has the right to issue such an order (order)?

Question number 64. What is the employee who gave the order to work with a power tool obliged to provide?

Question number 65. List PTB when working with portable megohmmeters? What is the lowest value of insulation resistance at which it is possible to continue the operation of electrical equipment of stationary electrical installations?

6.3.5 Topic: "Elementary knowledge of electrical engineering."

Literature: "Methodology for the selection of conductors and protection equipment when connecting electrical receivers", TOE.