By the way, Dear experts, here is another comment on my original question, only from the ElectroAS website:
my question was like this -
How many conductors can be connected under one bolt?
Can you enlighten me on a question that is very difficult in my opinion: when in the construction of industrial enterprises and in housing construction, electricians connect 2 wires under one ground bolt, coming, for example, from two adjacent shields, are they right? I believe that they are wrong, because. in the PUE there is a requirement (1.7.119 - PUE 7th) for the main grounding bus - “The bus design must provide for the possibility of individually disconnecting the conductors connected to it. Disconnection must only be possible with the use of a tool." Does this mean that in general, absolutely everywhere and not only on the GZSH, ONLY one ground wire should be clamped under one bolt? This opinion or understanding breaks the work of one scientist - R.N.KARYAKIN Doctor of Engineering. Sci., professor of GROUNDING NETWORK STANDARDS, MOSCOW, Energoservice, 2002. There he writes as follows (by the way, he interprets GOST R 50571 (IEC364) as well): “10.5.4. It is forbidden to connect more than two cable tips. On the grounding (zero) bus, bolted connections of the required number of grounding, zero protective and zero working conductors must be provided.
10.5.5. It is not required to deliberately ground the cases of electrical equipment and apparatus installed on zeroed metal structures, switchgear, switchboards, cabinets, shields, machine beds, machines and mechanisms, provided that reliable electrical contact with zeroed bases is ensured. That is, the author states that no more than two tips can be put under the bolt. But he described this about shields, obviously for a bolt inside the shields, and not for wires with lugs that sit on the bolts of the ground loop, which usually runs nearby. GOST 10434-82 also states that it is allowed to put 2 ground wires under one bolt (Excerpt from GOST: (Changed edition, Rev. No. 1, 2).
2.1.12. It is recommended to connect no more than two conductors to each bolt (screw) of a flat terminal or to a pin terminal, unless otherwise specified in the standards or technical specifications for specific types of electrical devices.), but this GOST seems to be general technical and the following is written at the beginning of its text: “The requirements of the standard in terms of the permissible value of electrical resistance and resistance of contact connections at through currents also apply to contact connections in circuits of grounding and protective conductors made of steel.
The standard does not apply to electrical contact connections of electrical devices for special purposes. Here the confusion of opinions and all as one documents bypass the exact indication - one or two wires (tip) must be put under one bolt. Why is it that in PUE 7 it is exactly about the GZSH that is accurately described, but nothing is written about the rest of the grounding and, in particular, about my question that was voiced? Please help me figure out how to understand all this and come to any one correct understanding."
answer:
Message from FAQ
when in the construction of industrial enterprises and in residential construction, electricians connect 2 wires under one ground bolt, coming, for example, from two adjacent shields, are they right?
The ban applies to connecting more than two conductors, but up to two is always welcome. Although I personally think that it is necessary to tighten and prescribe - no more than one conductor.
Message from FAQ
I believe that they are wrong, because. in the PUE there is a requirement (1.7.119 - PUE 7th) for the main grounding bus - “The bus design must provide for the possibility of individually disconnecting the conductors connected to it.
And where did you find in paragraph 1.7.119 a ban on connecting 2 conductors? The connection of two lugs in the bolt does not lead to the impossibility of individual disconnection of the connected conductors. I unscrewed the nut, removed the corresponding tip and wrapped the nut back. What is the problem?
Message from FAQ
Does this mean that in general, absolutely everywhere and not only on the GZSH, ONLY one ground wire should be clamped under one bolt?
Where did you find the restrictions?
Message from FAQ
The standard does not apply to electrical contact connections of electrical devices for special purposes.
For a complete understanding, you need to familiarize yourself with the terms and definitions of the basic concepts.
GOST 18311-80
This standard establishes terms and definitions of concepts in the field of electrical products
Types of electrical products, electrical devices, electrical equipment
15. An electrical product (electrotechnical device, electrical equipment) of general purpose - an electrical product (electrotechnical device, electrical equipment) that meets a set of technical requirements common to most applications.
16. An electrical product (electrotechnical device, electrical equipment) for special purposes - an electrical product (electrotechnical device, electrical equipment) made to meet the requirements specific to a particular purpose or for certain operating conditions and (or) having special performance characteristics and (or) a special design .
17. An electrical product (electrotechnical device, electrical equipment) of a specialized purpose - an electrical product (an electrical device, electrical equipment) of a special purpose, adapted for use with only one specific object.
Message from FAQ
Here the confusion of opinions and all as one documents bypass the exact indication - one or two wires (tip) must be put under one bolt.
On one bolt no more than 2 conductors (tips).
Message from FAQ
Why is it that in PUE 7 it is exactly about the GZSH that is accurately described, but nothing is written about the rest of the grounding and, in particular, about my question that was voiced?
You have confused the number of conductors with individual disconnection.
In general, comrade FAQ indicates that 2 conductors under the bolt are NOT FORBIDDEN !!! Well, about one conductor for one bolt on the GZSH - this only concerns the GZSH! Well, yes, most likely he is right ... and Volk is right !!! I hope our dialogue has now fully revealed the understanding of the topic raised by me! Let it become useful for all doubters))) I am also for tightening the requirements - one wire for one bolt! This is correct and easy to remember.
ELECTRICAL CONTACT CONNECTIONS CLASSIFICATION. GENERAL TECHNICAL REQUIREMENTS GOST 10434-82
STATE STANDARD OF THE UNION OF THE SSR
CONNECTIONS CONTACT ELECTRIC
Classification. General technical requirements
Electrical contact connections. classification.
General technical requirements
GOST 10434-82
Date of maintenance 01.01.83
This standard applies to demountable and non-separable electrical contact connections of tires, wires or cables (hereinafter referred to as conductors) made of copper, aluminum and its alloys, steel, aluminum-copper wires with leads of electrical devices, as well as to contact connections of conductors to each other for currents from 2, 5 A. For contact connections of electrical devices for currents less than 2.5 A, the requirements of the standard are recommended. The requirements of the standard in terms of the permissible value of electrical resistance and resistance of contact connections with through currents also apply to contact connections in circuits of grounding and protective conductors made of steel.
The standard does not apply to electrical contact connections of electrical devices for special purposes.
The terms used in the standard correspond to GOST 14312-79, GOST 18311-80.
1. CLASSIFICATION
1.1. Depending on the field of application, electrical contact connections (hereinafter referred to as contact connections) are divided into classes in accordance with Table. one.
Table 1
| Scope of contact connection | Contact connection class |
|---|---|
| 1. Contact connections of circuits, the sections of the conductors of which are selected according to the permissible long-term current loads (power electrical circuits, power lines, etc.) | 1 |
| 2. Contact connections of circuits, the sections of conductors of which are selected for resistance to through currents, voltage loss and deviation, mechanical strength, overload protection. Contact connections in circuits of grounding and protective conductors made of steel | 2 |
| 3. Contact connections of circuits with electrical devices, the operation of which is associated with the release of a large amount of heat (heating elements, resistors, etc.) | 3 |
Note. Classes 2 and 3 should be indicated in standards and specifications for specific types of electrical devices, class 1 is not indicated.
1.2. Depending on the climatic version and the category of placement of electrical devices in accordance with GOST 15150-69, contact connections are divided into groups in accordance with Table. 2.
1.3. By design, contact connections are divided into non-separable and collapsible.
1.4. Depending on the material of the connected conductors and the group of contact connections according to clause 1.2, collapsible contact connections are divided into:
- - not requiring the use of means for stabilizing electrical resistance - see paragraphs. 2.1.6 and 2.1.8;
- requiring the use of means for stabilizing electrical resistance - see paragraphs. 2.1.7 and 2.1.8.
table 2
| Climatic version and placement category of the electrical device | |
|---|---|
| 1. All climatic versions for location category 4.1 with atmosphere types II and I. Climatic modifications U, UHL, TS for placement category 3 and climatic modifications UHL, TS for placement category 4 with atmosphere types II and I |
BUT |
| 2. Any combination of climate version and location category, other than those indicated above, with atmosphere types II and I. Any combination of climate version and placement category with atmosphere types III and IV |
B |
2. TECHNICAL REQUIREMENTS
2.1. Design requirements
2.1.1. Contact connections must be made in accordance with the requirements of this standard, standards and specifications for specific types of electrical devices according to working drawings approved in the prescribed manner.
2.1.2. The conclusions of electrical devices must comply with the requirements of GOST 24753-81.
2.1.3. Contact screw clamps must comply with the requirements of GOST 25034-85, terminal clamps must comply with the requirements of GOST 19132-86.
2.1.4. Linear fittings must comply with the requirements of GOST 13276-79.
2.1.5. Non-separable contact connections must be made by welding, soldering or crimping. It is allowed to use other methods specified in the standards or specifications for specific types of electrical devices.
Examples of making non-separable contact connections are given in Appendix 1.
2.1.6. Collapsible contact connections that do not require the use of electrical resistance stabilization means must be made using steel fasteners protected from corrosion in accordance with the requirements of GOST 9.303-84, GOST 9.005-72.
2.1.7. Detachable contact connections requiring the use of means for stabilizing electrical resistance must be made using the following means either individually or in combination:
- 1) fasteners made of non-ferrous metals with a linear expansion coefficient from 18 10 -6 to 21 10 -6 1/°C;
2) Belleville springs in accordance with GOST 3057-90 or specifications for specific types of springs;
3) protective metal coatings of working surfaces, selected in accordance with GOST 9.303-84, taking into account the requirements of GOST 9.005-72.
It is allowed to use other types of protective coatings specified in the standards or specifications for specific types of electrical devices;
4) transition parts in the form of copper-aluminum plates according to GOST 19357-81, copper-aluminum lugs according to GOST 9581-80 and hardware clamps made of clad aluminum according to TU 34-13-11438-89;
5) transition parts in the form of plates and tips made of aluminum alloy with a tensile strength of at least 130 MPa (hereinafter referred to as hard aluminum alloy);
6) pin tips according to GOST 23598-79 made of hard aluminum alloy;
7) pin tips according to GOST 23598-79, copper-aluminum;
8) electrically conductive lubricants or other electrically conductive materials, if the possibility of their use is confirmed by the test results in accordance with GOST 17441-84 and is indicated in the standards or specifications for specific types of electrical devices.
When using means 2)-8), contact connections, as a rule, should be made using steel fasteners protected from corrosion in accordance with the requirements of GOST 9.303-84, GOST 9.005-72.
Note. The need to apply a protective metal coating on the working surfaces of copper conductors should be specified in the standards or specifications for specific types of electrical devices.
(Changed edition, Rev. No. 1, 2, 3).
2.1.8. Collapsible contact connections, depending on the group according to clause 1.2 and the material of the connected conductors and terminals of electrical devices, must be made in accordance with the requirements of the standard specified:
- - for contact connections of conductors with flat leads, as well as contact connections of conductors to each other - in table. 3;
- for contact connections of conductors with pin terminals - in table. four;
- for contact connections of conductors with socket terminals - in table. 5.
Table 3
| Contact connection group | Conductor material | Standard item number depending on the material of the output or the second conductor | |||
|---|---|---|---|---|---|
| copper and its alloys | solid aluminum alloy | aluminum | steel | ||
| BUT | Copper, aluminum copper | 2.1.6 | 2.1.6 | ||
| Solid aluminum alloy | |||||
| Aluminum | 2.1.7 1) or 2) or 3) or 4) or 5) or 8) | ||||
| B | Copper, aluminum copper | 2.1.6 | 2.1.6 | ||
| Solid aluminum alloy | 2.1.7* 3) or 4) or 5) and 3) | 2.1.6 | 2.1.7 4) or 5) and 3) | ||
| Aluminum | 2.1.7 4) or 5) and 3) or 1) and 3) or 2) and 3) | 2.1.7 1) or 2) or 3) or 4) or 5) | |||
Contact connections in accordance with the climatic version and category of placement of electrical devices, determined in accordance with GOST 15150-69 and GOST 15543-70, must withstand the effects of climatic environmental factors specified in GOST 15150-69, GOST 15543-70, GOST 15963-79, GOST 16350-80, GOST 17412-72 or in standards and specifications for specific types of electrical devices.
Table 4
| Contact connection group | Conductor material | Standard item number depending on the material of the pin | ||
|---|---|---|---|---|
| copper or brass for rated current | steel for rated current up to 40 A | |||
| up to 630 A | above 630 A | |||
| BUT | Copper, aluminum copper | 2.1.6 | ||
| Solid aluminum alloy | ||||
| Aluminum | 2.1.7 1) | 2.1.7 3) or 4) or 5) | 2.1.7 2) or 3) or 4) or 5) | |
| B | Copper, aluminum copper | 2.1.6 | ||
| Solid aluminum alloy | 2.1.7 4) or 5) and 3) | 2.1.7* 4) or 5) and 3) | 2.1.7 4) or 5) and 3) | |
| Aluminum | 2.1.7 4) or 5) and 3) | |||
* Contact connections of electrical devices of climatic modifications U, UHL of placement categories 1 and 2 are allowed to be made according to clause 2.1.6.
Note. In all cases, for pin terminals with a rated current above 40 A, thrust nuts made of copper or brass must be used.
Table 5
| Contact connection group | Conductor material | Standard item number depending on the type of core | |
|---|---|---|---|
| single-wire | stranded | ||
| BUT | Copper | direct connection | |
| Aluminum copper | - | ||
| Aluminum | Direct connection* or 2.1.7 6) or 7)** | ||
| B | Copper | Direct connection* or 2.1.6*** | 2.1.6*** |
| Aluminum copper | - | ||
| Aluminum | 2.1.7 7) or 6) and 3) | ||
* The possibility of direct connection must be specified in the standards or specifications for a specific type of electrical device.
** It is allowed to connect aluminum conductors fused into a monolith with the addition of alloying additives from a hard aluminum alloy.
*** The contact connection is made by terminating with copper pin tips according to GOST 22002.5-76, GOST 22002.12-76, GOST 22002.13-76, GOST 23598-79 or by tinning the cores with tin-lead solders according to GOST 21931-76.
It is allowed, in agreement with the consumer, to use contact connections that differ from those indicated in Table. 3-5.
Examples of collapsible contact connections are given in Appendix 2.
(Changed edition, Rev. No. 1, 3).
2.1.9. Contact connections of hard aluminum alloy plates and the aluminum part of copper-aluminum plates with aluminum conductors (leads) must be made by welding or soldering, and the connections of hard aluminum alloy lugs and the aluminum part of copper-aluminum lugs with aluminum conductors of wires and cables must be made by welding or crimping.
2.1.10. Collapsible contact connections of single-wire conductors of wires and cables with flat or pin terminals must be carried out:
- - lived with a cross section of up to 16 mm 2 - after termination with lugs according to GOST 7386-80 or directly: by forming into a ring or without it, with protection in both cases from extrusion with shaped washers or other methods;
- core with a cross section of 25 mm 2 or more - after termination with lugs in accordance with GOST 7386-80, GOST 7387-82, GOST 9581-80 or by forming the end of the core into a flat clamping part with a bolt hole.
2.1.11. Collapsible contact connections of stranded conductors of wires and cables with flat or pin terminals must be carried out:
- - lived with a cross section of up to 10 mm 2 - after termination with lugs according to GOST 7386-80, GOST 9688-82, GOST 22002.1-82, GOST 22002.2-76 - GOST 22002.4-76, GOST 22002.6-82, GOST 22002.7-76 - GOST 22002.11- 76, GOST 22002.14-76 or directly: by forming into a ring or without it with protection in both cases from extrusion by shaped washers, or by other means;
- lived with a cross section of 16 mm 2 or more - after termination with lugs according to GOST 7386-80, GOST 7387-82, GOST 9581-80, GOST 22002.1-82, GOST 22002.2-76, GOST 22002.6-82, GOST 22002.7-76.
(Changed edition, Rev. No. 1, 2).
2.1.12. It is recommended to connect no more than two conductors to each bolt (screw) of a flat terminal or to a pin terminal, unless otherwise specified in the standards or specifications for specific types of electrical devices.
2.1.13. In collapsible contact connections, fasteners of strength classes according to GOST 1759.4-87 and GOST 1759.5-87, indicated in Table. 6. Screws in contact connections are recommended to be used with a cylindrical or hexagonal head.
Table 6
2.1.14. Requirements for the preparation of working surfaces of contact parts are given in Appendix 3.
2.2. Electrical Requirements
2.2.1. The ratio of the initial electrical resistance of contact connections (except for contact connections with pin leads) to the electrical resistance of the section of connected conductors, the length of which is equal to the length of the contact connection, should not exceed:
- - for class 1 - 1, unless otherwise specified in the standards or specifications for specific types of electrical devices;
- for class 2 - 2;
- for class 3 - 6.
In contact connections of conductors with different electrical resistance, comparison is made with a contact piece with a higher electrical resistance.
2.2.2. The initial electrical resistance of contact connections of class 1 conductors with pin terminals should not exceed the values \u200b\u200bspecified in Table. 7.
Table 7
Requirements for contact connections of classes 2 and 3, if necessary, are specified in the standards or specifications for specific types of electrical devices.
2.2.3. The electrical resistance of contact joints (except for welded and soldered ones) that have passed the test for compliance with the requirements of standards and other technical documentation according to the method specified in GOST 17441-84 should not exceed the initial value by more than 1.5 times. The electrical resistance of welded and soldered contact joints must remain unchanged. The need for the mandatory use of torque indicator keys should be indicated in the standards or specifications for specific types of electrical devices.
2.2.4. When the rated (continuous) current flows, the highest allowable temperature of contact connections of classes 1 and 2 should not exceed the values \u200b\u200bspecified in Table. 8. At the same time, the current loads of conductors are taken according to the "Rules for the Construction of Electrical Installations", approved by the State Energy Supervision Authority on 12.04.69, according to standards or specifications for specific types of electrical devices.
Table 8
| Characteristics of the connected conductors | The highest allowable heating temperature, °С in units | |
|---|---|---|
| up to 1000 V | St. 1000 V | |
| 1. Conductors made of copper, aluminum copper, aluminum and its alloys without protective coatings of working surfaces | 95 | According to GOST 8024-90 |
| 2. Conductors made of copper, aluminum copper, aluminum and its alloys with protective coatings of working surfaces with base metals | 110* | |
| 3. Conductors made of copper and its alloys without insulation or with insulation of classes B, F and H according to GOST 8865-87 with a protective coating of working surfaces with silver | 135 | |
* It is allowed for conductors made of copper without insulation or with insulation of classes B, F and H according to GOST 8865-87 to increase the temperature to 135 ° C, if the possibility of this is confirmed by the test results according to GOST 17441-84 and is indicated in the standards or specifications for specific types electrical devices.
The temperature of contact connections of class 3 is established in the standards or specifications for specific types of electrical devices, depending on the materials used, coatings, insulation class of connected conductors and operating conditions.
(Changed edition, Rev. No. 1, 2, 3).
2.2.5. (Deleted, Rev. No. 1).
2.2.6. After the through current mode, the contact connections should not have mechanical damage that prevents their further operation. The temperature of contact connections in the through current mode should not exceed 200 °C for connections of conductors made of aluminium-copper, aluminum and its alloys, as well as for connections of these conductors with copper, 300 °C - for connections of copper conductors and 400 °C - for connections of steel conductors.
2.2.7. The value of the allowable through current of contact connections must not be less than the allowable through currents of specific types of electrical devices specified in the standards or specifications for these devices.
In the absence of these data, the value of the one-second current density should correspond to 165 A / mm 2 - for copper conductors, 105 A / mm 2 - for aluminum and aluminum-copper, 90 A / mm 2 - for aluminum alloy conductors and 20 A / mm 2 - for steel conductors.
(Changed edition, Rev. No. 1).
2.3. Requirements for resistance to mechanical factors
2.3.1. Contact connections must withstand the impact of mechanical environmental factors according to the group of operating conditions in accordance with GOST 17516-72, which should be indicated in the standards or specifications for specific types of electrical devices.
In the absence of such instructions, contact connections subject to vibration must withstand vibration for 1 h at a constant frequency of 40 to 50 Hz and an amplitude of 1 mm.
2.3.2. Contact joints must withstand the effects of static axial tensile loads, causing stresses not less than:
- - 90% of the tensile strength of the whole conductor - for contact connections of wires of a power line operating in tension;
- 30% of the tensile strength of the whole conductor - for non-separable contact connections that do not work in tension, as well as for connections of conductors with socket terminals, connections of unterminated wires and cables with flat terminals equipped with shaped washers.
For conductors with a cross section of up to 1.5 mm 2, it is not allowed to use a screw clamp, the screw end of which is rotated along the core.
2.3.1.-2.3.3. (Revised edition, Rev. No. 1).
2.3.4. Collapsible contact connections of conductors with leads, single-bolt contact connections that may be exposed to through short-circuit currents, as well as demountable contact connections that are subject to vibration or located in explosive rooms, must be protected from self-unscrewing by lock nuts, spring washers, Belleville springs or other means.
(Revised edition, Rev. No. 2).
2.4. Reliability Requirements
2.4.1. To assess the reliability of contact connections, a gamma-percentage resource is established, unless otherwise specified in the standards or technical specifications for electrical devices of specific types.
The lower value of the gamma percentage resource must ensure the operation of electrical devices in accordance with the reliability requirements established in the standards or specifications for these electrical devices.
(Revised edition, Rev. No. 1).
2.5. Safety requirements
2.5.1. Contact connections in terms of safety requirements must comply with GOST 12.2.007.0-75 and ensure the operating conditions established by the "Rules for the technical operation of consumer installations" and the "Safety Rules for the operation of consumer electrical installations" approved by the State Energy Supervision Authority on April 12, 1969.
2.5.2. Contact connections in terms of fire safety requirements must comply with GOST 12.1.004-91, which is ensured by the fulfillment of the requirements of GOST 10434-82.
(Introduced additionally, Rev. No. 3).
ATTACHMENT 1
Reference
NON-REMOVABLE CONTACT CONNECTIONS
a - welding or soldering; b - with a pin output by welding; c - welding through a transitional copper-aluminum plate; g - connection of cores of wires (cables) through a connecting sleeve by crimping; e - connection of the core of the wire (cable) with the cable lug by crimping (welding, soldering); e - connection of wire cores in oval connectors
1 - flat output (bus); 2 - tire; 3 - pin output; 4 - copper-aluminum plate; 5 - wire (cable); 6 - connecting sleeve; 7 - cable lug; 8 - oval connector
APPENDIX 2
Reference
REMOVABLE CONTACT CONNECTIONS
a - with a locknut; b - with a spring washer; c - single-wire (multi-wire) core of a wire (cable) sec. up to 10 mm 2 with bending into a ring; g - single-wire (multi-wire) core of a wire (cable) sec. up to 10 mm 2 without bending into a ring.
1 - flat output (bus); 2 - bus (cable lug); 3, 4, 5 - steel washer, bolt and nut; 6 - spring washer; 7 - screw; 8 - shaped washer (star washer); 9 - wire (cable); 10 - shaped washer (arched washer)
a - fasteners made of non-ferrous metal with a lock nut; b - fasteners made of non-ferrous metal with a spring washer; c - steel fasteners with a Belleville spring; g - steel fasteners with protective metal coatings of working surfaces with a lock nut (spring washer); e - steel fasteners through an adapter copper-aluminum plate with a lock nut (spring washer); e - steel fasteners through an adapter plate made of hard aluminum alloy with a lock nut (spring washer).
1 - flat output (bus); 2 - bus (cable lug); 3 - 5 - washer, bolt, nut made of non-ferrous metal; 6 - spring washer; 7 - steel nut; 8 - steel bolt; 9 - disc spring; 10 - steel washer (enlarged washer); 11 - steel washer; 12 - flat output (tire) with a protective metal coating of the working surface; 13 - tire (cable lug) with a protective metal coating of the working surface; 14 - copper-aluminum plate; 15 - hard aluminum alloy plate
a - conductor made of copper, hard aluminum alloy or aluminum with a protective metal coating of the working surface; b, c, d - aluminum conductor; d - aluminum conductor through the transitional copper-aluminum plate; e - single-wire (multi-wire) cable wire core sec. 10 mm 2 with bending into a ring.
1 pin copper or brass; 2 - nut made of copper or brass; 3 - tire (cable lug) made of copper, hard aluminum alloy or aluminum with a protective metal coating of working surfaces; 4 - steel nut; 5 - pin copper output; 6 - steel washer; 7 - aluminum bus (cable lug); 8 - pin brass output; 9 - pin steel output; 10 - disc spring; 11 - copper-aluminum plate; 12 - wire (cable); 13 - spring washer; 14 - shaped washer (star washer)
a, b - single-wire (multi-wire, fused into a monolith) core; c - stranded core terminated with a cable lug.
1 - typesetting clip; 2 - wire (cable); 3 - socket output; 4 - pin cable lug
REQUIREMENTS FOR THE PREPARATION OF WORKING SURFACES OF CONTACT DETAILS
1. Contact parts with two or more bolt holes in a transverse row are recommended to be made with longitudinal cuts, as shown in the drawing.
2. The working surfaces of contact parts of collapsible contact joints and non-separable contact joints with linear fittings immediately before assembly must be prepared:
- - uncoated copper and aluminum-copper - cleaned.
When stripping aluminum-copper wires, the copper sheath should not be damaged;
- aluminum and aluminum alloys - cleaned and lubricated with neutral grease (Vaseline KVZ according to GOST 15975-70, TsIATIM-221 according to GOST 9433-80 or other lubricants with similar properties).
The recommended time between cleaning and lubrication is no more than 1 hour;
- working surfaces with protective metal coatings - washed with an organic solvent.
(Revised edition, Rev. No. 3).
3. The working surfaces of copper contact parts connected by crimping must be cleaned, unless otherwise specified in the standards or specifications for specific types of electrical devices.
The working surfaces of aluminum contact parts must be cleaned and lubricated with quartz-vaseline paste or other lubricants, pastes and compounds with similar properties.
4. The surfaces of contact parts connected by welding or soldering must be pre-cleaned, degreased or pickled.
5. The location and size of the bolt holes in the contact details of the collapsible contact connections are recommended to be taken in accordance with GOST 21242-75.
By agreement with the consumer, it is allowed to make oval holes.
(Introduced additionally, Amendment No. 2).
TORQUES
Table 9
| Thread diameter, mm | Torque, N m, for bolted connection | |
|---|---|---|
| with slotted head (screws) | with hexagon head | |
| M3 | 0,5+0,1 | - |
| M3.5 | 0.8±0.2 | |
| M4 | 1.2±0.2 | |
| M5 | 2.0±0.4 | 7.5±1.0 |
| M6 | 2.5±0.5 | 10.5±1.0 |
| M8 | - | 22.0±1.5 |
| M10 | 30.0±1.5 | |
| M12 | 40.0±2.0 | |
| M16 | 60.0±3.0 | |
| M20 | 90.0±4.0 | |
| M24 | 130.0±5.0 | |
| M30 | 200.0±7.0 | |
| M36 | 240.0±10.0 | |
Note. For bolted connections of conductors made of copper and hard aluminum alloy, it is recommended to use torques, the values of which are 1.5 - 1.7 times higher than those specified in the table.
(Revised edition, Rev. No. 3).
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Assembly and Special Construction Works of the USSR
DEVELOPERS
N. N. Dzektser, Ph.D. tech. sciences (topic leader); V. L. Fuchs; O. V. Fesenko, Ph.D. tech. Sciences
2. APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Product Quality Management and Standards of 03.02.82 No. 450
3. REPLACE GOST 10434-76
4. REFERENCE REGULATIONS
| The designation of the NTD to which the link is given | Item number, listing, application |
|---|---|
| GOST 9.005-72 | |
| GOST 9.303-84 | 2.1.6; 2.1.7, listings 3, 8 |
| GOST 12.1.004-91 | 2.5.2 |
| GOST 12.2.007.0-75 | 2.5.1 |
| GOST 1759.4-87 | 2.1.13 |
| GOST 1759.5-87 | 2.1.13. |
| GOST 3057-90 | 2.1.7 item 2 |
| GOST 7386-80 | 2.1.10; 2.l.11 |
| GOST 7387-82 | 2.1.10; 2.1.11 |
| GOST 8024-90 | 2.2.4 |
| GOST 8865-87 | 2.2.4 |
| GOST 9433-80 | Appendix 3 |
| GOST 9581-80 | 2.1.7, listing 4; 2.1.10; 2.1.10; 2.1.11 |
| GOST 9688-82 | 2.1.11 |
| GOST 13276-79 | 2.1.4; 2.1.7 |
| GOST 14312-79 | Introduction |
| GOST 15150-69 | 1.2; 2.1.8 |
| GOST 15543-70 | 2.1.8 |
| GOST 15963-79 | 2.1.8 |
| GOST 15975-70 | Appendix 3 |
| GOST 16350-80 | 2.1.8 |
| GOST 17412-72 | 2.1.8 |
| GOST 17441-84 | 2.1.7 item 8; 2.2.3; 2.2.4 |
| GOST 17516-72 | 2.3.1 |
| GOST 18311-80 | Introduction |
| GOST 19132-86 | 2.1.3 |
| GOST 19357-81 | 2.1.7 item 4 |
| GOST 21242-75 | Appendix 3 |
| GOST 21931-76 | 2.1.8 |
| GOST 22002.1-82 | 2.1.11 |
| GOST 22002.2-76 - GOST 22002.4-76 | 2.1.11 |
| GOST 22002.5-76 | 2.1.8 |
| GOST 22002.6-82 | 2.1.11 |
| GOST 22002.7-76 - GOST 22002.11-76 | 2.1.11 |
| GOST 22002.12-76 | 2.1.8 |
| GOST 22002.13-76 | 2.1.8 |
| GOST 22002.14-76 | 2.1.11 |
| GOST 23598-79 | 2.1.7, listing 6, 7; 2.1.8 |
| GOST 24753-81 | 2.1.2 |
| GOST 25034-85 | 2.1.3 |
| GOST 34-13-11438-89 | 2.1.7 item 4 |
5. The validity period was extended until 01/01/96 by the Decree of the USSR State Committee for Product Quality Management and Standards dated 05/25/90 No. 1309
6. REPUBLICATION (October 1993) with Amendments No. 1, 2, 3, approved in April 1985, June 1987, May 1990 (IUS 7-85, 10-87, 8-90)
Rules and diagrams for connecting PE protective conductors and potential equalization
In all buildings, group network lines laid from group, floor and apartment shields to general lighting fixtures, socket outlets and stationary electrical receivers must be three-wire (phase - L, zero working - N and zero protective - PE conductors).
It is not allowed to combine zero working and zero protective conductors of various group lines.
Zero working and zero protective conductors are not allowed to be connected under a common terminal clamp. The choice of the cross section of conductors should be carried out in accordance with the requirements of the relevant chapters of the PUE.
Single-phase two- and three-wire lines, as well as three-phase four- and five-wire lines when supplying single-phase loads, must have a cross section of zero working N conductors equal to the cross section of the phase conductors.
Three-phase four- and five-wire lines when supplying three-phase symmetrical loads must have a cross section of zero working N conductors equal to the cross section of the phase conductors, if the phase conductors have a cross section of up to 16 mm2 for copper and 25 mm2 for aluminum, and for large cross sections - at least 50 % section of phase conductors, but not less than 16 mm2 for copper and 25 mm2 for aluminum.
The cross section of PEN conductors must be at least the cross section of N conductors and not less than 10 mm2 for copper and 16 mm2 for aluminum, regardless of the cross section of the phase conductors.
The cross section of PE conductors should be equal to the cross section of the phase conductors with a cross section of the latter up to 16 mm2, 16 mm2 with a cross section of phase conductors from 16 to 35 mm2 and 50% of the cross section of phase conductors for large cross sections. The cross section of PE conductors that are not part of the cable must be at least 2.5 mm2 - in the presence of mechanical protection and 4 mm2 - in its absence.
Connection diagrams for protective conductors PE
The combined neutral and working conductor PEN is divided into zero protective PE and zero working N conductors in the input device.
Execution of the TN-C-S earthing system
The letter designations used in the figures have the following meaning. The first letter is the nature of the grounding of the power source: T - direct connection of one point of the current-carrying parts of the power source to the ground; N - direct connection of exposed conductive parts to the ground point of the power supply (usually the neutral is grounded in AC systems).
The following letters define the device of the zero working and zero protective conductors: S - the functions of zero protective (PE) and zero working (N) are provided by separate conductors; C - the functions of the zero protective and zero working conductors are combined in one conductor (PEN-conductor).
Zero working and zero protective conductors are not allowed to be connected under a common terminal clamp. The meaning of this requirement lies in the need, in order to ensure electrical safety conditions, to maintain the connection of the protective conductor to ground in the event of destruction (burnout) of the terminal clamp.
Examples of connecting PE and N conductors to PEN in floor or apartment shields
Examples of connecting PE and N conductors to PEN
Rules for the implementation of the potential equalization system.
To ensure electrical safety conditions in a particular electrical installation, the potential equalization system is important. The rules for the implementation of the potential equalization system are defined by IEC 364-4-41 and PUE (7th edition). These rules provide for the connection of all conductors to be grounded to a common bus.
An example of a potential equalization system.
This solution avoids the flow of various unpredictable circulating currents in the grounding system, causing the occurrence of a potential difference on individual elements of the electrical installation.
An example of a potential equalization system in an electrical installation of a residential building
Recently, with the increase in the equipment of modern residential buildings and industrial buildings with various electrical appliances and the constant development of their electrical installations, the phenomena of accelerated corrosion of pipelines of water supply and heating systems have increasingly become observed. In a short time - from six months to two years - on the pipes of both underground and air laying, point fistulas are formed, rapidly increasing in size. The cause of accelerated pitting (pitting) corrosion of pipes in 98% of cases is the flow of stray currents through them.
The use of RCDs in combination with a properly implemented potential equalization system allows you to limit and even eliminate the flow of leakage currents, stray currents through the conductive elements of the building structure, including pipelines.
The most scandalous issue is grounding (zeroing)
Generally speaking, it can be noted that the great and terrible power of electricity has long been described, calculated, listed in thick tables. The regulatory framework that defines the paths of sinusoidal electrical signals with a frequency of 50 Hz can plunge any neophyte into horror with its volume. And despite this, any frequenter of technical forums has long known that there is no more scandalous issue than grounding.
The mass of contradictory opinions in fact does little to establish the truth. Moreover, this issue is actually serious, and requires closer consideration.
Basic concepts
If we omit the introduction of the "electrician's bible" (PUE), then in order to understand the grounding technology, you need to refer (for a start) to Chapter 1.7, which is called "Grounding and Electrical Safety Protective Measures".
In clause 1.7.2. PUE says:
Electrical installations in relation to electrical safety measures are divided into:
- electrical installations above 1 kV in networks with an effectively grounded neutral (with high earth fault currents), ;
- electrical installations above 1 kV in networks with isolated neutral (with low earth fault currents);
- electrical installations up to 1 kV with dead-earthed neutral;
- electrical installations up to 1 kV with isolated neutral.
In the vast majority of residential and office buildings in Russia, a dead-earthed neutral is used. Clause 1.7.4. reads:
A dead-earthed neutral is a transformer or generator neutral connected to a grounding device directly or through low resistance (for example, through current transformers).
The term is not entirely clear at first glance - a neutral and a grounding device are not found at every step in the popular science press. Therefore, below all incomprehensible places will be gradually explained.
Let's introduce a few terms - so it will be possible to speak at least one language. Perhaps the points will seem "taken out of context". But the PUE is not fiction, and such separate use should be quite justified - like the use of individual articles of the Criminal Code. However, the original PUE is quite available both in bookstores and online - you can always turn to the original source.
Rice. 1. The difference between protective grounding and protective "zero"
So, a simple conclusion follows directly from the terms of the PUE. The differences between "ground" and "zero" are very small... At first glance (how many copies are broken at this point). At the very least, they must be combined (or even can be performed "in one bottle"). The only question is where and how it was done.
In passing, we note paragraph 1.7.33.
Grounding or grounding of electrical installations should be carried out:
- at a voltage of 380 V and above alternating current and 440 V and above direct current - in all electrical installations (see also 1.7.44 and 1.7.48);
- at rated voltages above 42 V, but below 380 V AC and above 110 V, but below 440 V DC - only in rooms with increased danger, especially dangerous and in outdoor installations.
In other words, it is not necessary to ground or neutralize a device connected to 220 volts AC. And there is nothing particularly surprising in this - there is really no third wire in ordinary Soviet sockets. We can say that the Eurostandard (or a new edition of the PUE close to it) that comes into practice in practice is better, more reliable, and safer. But according to the old PUE, we lived in our country for decades ... And what is especially important, houses were built by entire cities.
However, when it comes to grounding, it's not just about supply voltage. A good illustration of this is VSN 59-88 (Goskomarchitectura) "Electrical equipment of residential and public buildings. Design standards" Excerpt from chapter 15. Grounding (zeroing) and protective safety measures:
15.4. For grounding (grounding) of metal cases of domestic air conditioners, stationary and portable class I household appliances (not having double or reinforced insulation), household electrical appliances with a power of over. 1.3 kW, housings of three-phase and single-phase electric stoves, cooking boilers and other thermal equipment, as well as metal non-current-carrying parts of the technological equipment of rooms with wet processes, a separate conductor with a cross section equal to the phase should be used, laid from the shield or shield to which this electrical receiver is connected, and in the lines supplying medical equipment - from the ASU or main switchboard of the building. This conductor is connected to the neutral conductor of the mains. The use of a working neutral conductor for this purpose is prohibited.
This creates a normative paradox. One of the results visible at the household level was the completion of Vyatka-automatic washing machines with a skein of single-core aluminum wire with the requirement to perform grounding (by the hands of a certified specialist).
And one more interesting point: 1.7.39. In electrical installations up to 1 kV with a solidly grounded neutral or a solidly grounded output of a single-phase current source, as well as with a solidly grounded midpoint in three-wire DC networks, zeroing must be performed. The use in such electrical installations of grounding the housings of electrical receivers without their grounding is not allowed.
In practice, this means - if you want to "ground" - first "zanuli". By the way, this is directly related to the famous issue of "batteries" - which, for a completely incomprehensible reason, is mistakenly considered better than zeroing (grounding).
Grounding parameters
The next aspect to consider is the numerical parameters of grounding. Since physically it is nothing more than a conductor (or a set of conductors), its main characteristic will be resistance.
1.7.62. The resistance of the grounding device, to which the neutrals of generators or transformers or the outputs of a single-phase current source are connected, at any time of the year should be no more than 2, 4 and 8 ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source. This resistance must be provided taking into account the use of natural grounding conductors, as well as grounding conductors for repeated grounding of the neutral wire of overhead lines up to 1 kV with a number of outgoing lines of at least two. In this case, the resistance of the ground electrode located in close proximity to the neutral of the generator or transformer or the output of a single-phase current source should be no more than: 15, 30 and 60 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source.
For lower voltage, more resistance is acceptable. This is quite understandable - the first purpose of grounding is to ensure human safety in the classic case of a "phase" hitting the electrical installation case. The lower the resistance, the smaller part of the potential may be "on the case" in the event of an accident. Therefore, the risk for higher voltages must be reduced first.
In addition, it must be taken into account that grounding also serves for the normal operation of the fuses. For this, it is necessary that the line during the breakdown "to the body" significantly change its properties (primarily resistance), otherwise the operation will not occur. The greater the power of the electrical installation (and the voltage consumed), the lower its operating resistance, and, accordingly, the ground resistance should be lower (otherwise, in case of an accident, the fuses will not work due to a slight change in the total resistance of the circuit).
The next normalized parameter is the cross section of the conductors.
1.7.76. Grounding and zero protective conductors in electrical installations up to 1 kV must have dimensions not less than those given in Table. 1.7.1 (see also 1.7.96 and 1.7.104) .
It is not advisable to give the entire table, an excerpt is enough:
For bare copper, the minimum cross section is 4 square meters. mm, for aluminum - 6 sq. mm. For isolated, respectively, 1.5 square meters. mm and 2.5 sq. mm. If grounding conductors go in the same cable with power wiring, their cross section can be 1 sq. mm for copper, and 2.5 sq. mm for aluminium.
Grounding in a residential building
In a normal "household" situation, power grid users (i.e. residents) deal only with the Group network (7.1.12 PUE. Group network - a network from shields and distribution points to lamps, sockets and other electrical receivers). Although in old houses where shields are installed directly in apartments, they have to deal with part of the Distribution Network (7.1.11 PUE. Distribution Network - a network from VU, ASU, Main Switchboard to distribution points and shields). It is desirable to understand this well, because often "zero" and "ground" differ only in the place of connection with the main communications.
From this, the first grounding rule is formulated in the PUE:
7.1.36. In all buildings, group network lines laid from group, floor and apartment shields to general lighting fixtures, socket outlets and stationary electrical receivers must be three-wire (phase - L, zero working - N and zero protective - PE conductors). It is not allowed to combine zero working and zero protective conductors of various group lines. Zero working and zero protective conductors are not allowed to be connected on shields under a common terminal.
Those. 3 (three) wires must be laid from the floor, apartment or group shield, one of which is a protective zero (not earth at all). Which, however, does not prevent at all from using it for grounding a computer, a cable screen, or a "tail" of lightning protection. Everything seems to be simple, and it is not entirely clear why go into such complexity.
You can look at your home outlet ... And with a probability of about 80% you will not see a third contact there. What is the difference between zero working and zero protective conductors? In the shield, they are connected on the same bus (albeit not at one point). What will happen if we use a working zero as a protective one in this situation?
It is difficult to assume that a negligent electrician will confuse the phase and zero in the shield. Although this constantly scares users, it is impossible to make a mistake in any state (although there are unique cases). However, the "working zero" goes through numerous strobes, probably passes through several junction boxes (usually small, round, mounted in the wall near the ceiling).
It is already much easier to confuse the phase with zero there (I did it myself more than once). And as a result, 220 volts will appear on the case of an incorrectly "grounded" device. Or even simpler - a contact will burn out somewhere in the circuit - and almost the same 220 will pass to the case through the load of the electrical consumer (if this is an electric stove for 2-3 kW, then it will not seem enough).
For the function of protecting a person, frankly, this is an unsuitable situation. But for grounding connection, lightning protection of the APC type is not fatal, since a high-voltage decoupling is installed there. However, it would be unequivocally wrong to recommend such a method from a security point of view. Although it must be admitted that this rule is violated very often (and usually without any adverse consequences).
It should be noted that the lightning protection capabilities of the working and protective zero are approximately equal. The resistance (up to the connecting bus) differs slightly, and this is perhaps the main factor affecting the flow of atmospheric pickups.
From the further text of the PUE, you can see that literally everything that is in the house must be connected to the zero protective conductor:
7.1.68. In all rooms, it is necessary to connect the open conductive parts of general lighting fixtures and stationary electrical receivers (electric stoves, boilers, household air conditioners, electric towels, etc.) to the neutral protective conductor.
In general, it is easier to represent the following illustration:
Rice. 2. Grounding scheme.
The picture is quite unusual (for everyday perception). Literally everything that is in the house must be grounded on a special bus. Therefore, the question may arise - after all, they lived without it for decades, and everyone is alive and well (and thank God)? Why change everything so seriously? The answer is simple - there are more consumers of electricity, and they are more and more powerful. Accordingly, the risk of injury increases.
But the dependence of safety and cost is a statistical value, and no one has canceled the savings. Therefore, it is not worth blindly laying a copper strip of a decent section around the perimeter of the apartment (instead of a plinth), leading everything to it, right down to the metal legs of the chair. How not to walk in a fur coat in the summer, and constantly wear a motorcycle helmet. This is a question of adequacy.
Also, independent digging of trenches under a protective contour should be attributed to the area of \u200b\u200ba non-scientific approach (in a city house, apart from problems, this will certainly bring nothing). And for those who still want to experience all the delights of life - in the first chapter of the EMP there are standards for the manufacture of this fundamental structure (in the truest sense of the word).
Summarizing the above, we can draw the following practical conclusions:
- If the Group network is made with three wires, a protective zero can be used for grounding / grounding. It is, in fact, designed for that.
- If the Group network is made with two wires, it is advisable to start a protective neutral wire from the nearest shield. The cross section of the wire must be more than the phase one (more precisely, you can consult the PUE).
3.3. Protective earth requirements
3.3.1. An element for grounding must be equipped with products whose purpose does not require the implementation of a method of protecting a person from electric shock corresponding to classes II and III.
At the same time, it is allowed to perform without a grounding element and not to ground the following products:
intended for installation in inaccessible, without the use of special means, places (including inside other products);
intended for installation only on grounded metal structures, if stable electrical contact of the contacting surfaces is ensured and the requirements of clause 3.3.7 are met;
parts of which cannot be under alternating voltage higher than 42 V and under direct voltage higher than 110 V;
grounding of which is not allowed by the principle of operation or the purpose of the product.
(Changed edition, Rev. No. 1, 3).
3.3.2. To connect the ground conductor, welded or threaded connections must be used.
By agreement with the consumer, the ground conductor can be connected to the product by soldering or crimping, performed by a special tool, fixture or machine.
3.3.3. Grounding clamps must comply with the requirements of GOST 21130-75.
It is not allowed to use for grounding bolts, screws, studs that act as fasteners.
3.2.2-3.3.3. (Revised edition, Rev. No. 1).
3.3.4. The bolt (screw, stud) for connecting the grounding conductor must be made of corrosion-resistant metal or coated with a metal that protects it from corrosion, and the contact part must not have a surface color.
(Revised edition, Rev. No. 4).
3.3.5. The bolt (screw, stud) for grounding must be placed on the product in a safe and convenient place for connecting the grounding conductor. Near the place where the grounding conductor is to be connected, provided for in clause 3.3.2, a grounding sign that is indelible during operation should be placed. The dimensions of the sign and the method of its implementation are in accordance with GOST 21130-75, and for lamps - in accordance with GOST 17677-82.
There must be a contact area around the bolt (screw, stud) for connecting the ground conductor. The platform must be protected from corrosion or made of anti-corrosion metal, and not have a surface color.
Measures must be taken against possible loosening of contacts between the grounding conductor and the bolt (screw, stud) for grounding (locknuts, spring washers).
The diameters of the bolt (screw, stud) and the contact area must be selected according to the current (see Table 1).
Table 1
Rated current of the electrotechnical Nominal thread diameter for the place Diameter of the contact area of the connection point, mm
products, A connection, not less than on the plane of the surface elevated relative to the surface
St. 4 to 6 M 3 10 7
"6" 16 M 3.5 11 8
"16" 40 M 4 12 9
"40" 63 M 5 14 11
"63" 100 M 6 16 12
"100" 250 M 8 20 17
"250" 630 M 10 25 21
"630 M 12 28 24
Notes:
1. For currents over 250 A, it is allowed to put two bolts instead of one, but with a total cross section not less than required.
When choosing the smallest bolt diameter for consumers and electromagnetic energy converters, the current value should be taken as the current. consumed by the product from the source (network), for sources of electromagnetic energy - the value of the rated load current.
2. For sources of electromagnetic energy having several rated currents, the choice of bolt diameter should be made according to the largest of these currents.
(Changed edition, Rev. No. 1, 3, 4).
3.3.6. If the dimensions of the product are small, and also if the grounding bolt (screw) is installed by welding its head, it is allowed to provide the necessary contact surface in connection with the grounding conductor using washers. The material of the washers must meet the same requirements as the material of the grounding bolt (screw, stud).
3.3.7. The product must be provided with an electrical connection of all metal non-current-carrying parts of the product that can be touched, which may be energized, with elements for grounding.
The resistance value between the grounding bolt (screw, stud) and each non-current-carrying metal part of the product accessible to touch, which may be energized, should not exceed 0.1 Ohm.
3.3.8. Elements for grounding must be equipped with the following metal non-current-carrying parts of products to be grounded:
shells, cases, cabinets;
frames, frames, clips, racks, chassis, bases, panels, plates and other parts of products that may become energized if the insulation is damaged.
It is allowed not to carry out elements for grounding in the following parts of the product (from among those listed above):
housings of products intended for installation on grounded shields, metal walls of switchgear chambers, in cabinets;
non-current-carrying metal parts of the product that have electrical contact with grounded parts, subject to the requirements of clause 3.3.7;
parts fixed in or passing through insulating material and insulated from both earthed and live parts (provided that during operation of the product they cannot become live or come into contact with earthed parts).
3.3.9. Each part of the product equipped with an earthing element must be designed so that:
it was possible to independently connect it to the grounding conductor or grounding line by means of a separate branch, so that when any grounded part of the product is removed (for example, for current repairs), the ground circuits of other parts are not interrupted;
there was no need to connect several grounded parts of the product in series.
3.3.10. Grounding of parts of products installed on moving parts must be carried out by flexible conductors or sliding contacts.
3.3.11. If there is a metal shell, the element for its grounding must be located inside the shell.
It is allowed to execute it outside the shell, or to execute several elements both inside and outside the shell.
(Revised edition, Rev. No. 1).
3.3.12. Obtaining electrical contact between the removable and grounded (non-removable) parts of the shell should be carried out by directly pressing the removable part to the non-removable one; at the same time, at the points of contact, the surfaces of the removable and non-removable parts of the shell must be protected from corrosion and not covered with electrically insulating layers of varnish, paint or enamel.
It is allowed to electrically connect the removable part of the shell with the non-removable grounded part through the screws or bolts securing it, provided that 1-2 screws or bolts have an anti-corrosion metal coating, and there is no electrically insulating layer of varnish, paint between the heads of these screws or bolts and the removable metal part of the shell, enamel or toothed washers are installed between them, destroying the electrical insulating layer for electrical connection or without toothed washers, provided that the removable part is fastened to the non-removable grounded one with six or more bolts (or screws) and there is no electrical connection on the removable parts of the electrical devices.
It is also allowed to use toothed washers for electrical connection of the grounded shell and equipment mounted in the product, and install them for grounding the elements of the product through bolted connections.
(Revised edition, Rev. No. 3).
3.3.13. The requirements listed in clause 3.3 do not apply to products intended for operation only in areas with a tropical climate and made in accordance with GOST 15151-69, GOST 9.048-89.
