SF6 gas column switches 110 kV inurl forum. SF6 circuit breakers: guidelines for selection and connection rules. Brief characteristics of SF6 column switches

An article about the advantages and disadvantages of high-voltage SF6 circuit breakers.

High-voltage switches are used to change the on-off state of a high-voltage line for the purpose of operational control of the existing power supply system and to disconnect equipment or a section of the network in emergency situations.

High-voltage switches are used for these purposes:

• oil;

• air;

• vacuum;

• SF6

The names of the switches reflect the composition of the arc extinguishing media between the switch contacts, which occurs when switching high voltages. Some reservations regarding the oil switch are appropriate here - it would be more correct to say that the extinguishing of the arc occurs in a certain gas bubble formed when an arc occurs in the thickness of the oil volume. Oil switches simple and cheap to operate, but fire and explosion hazards.

In an air circuit breaker, the arc is extinguished by a powerful air flow from the tanks high pressure. Like oil circuit breakers, high voltage air circuit breakers can be manufactured to cover the entire range of applicable voltages and currents. But their designs are more complex and more expensive than oil ones, and operation requires compressor station to obtain clean dry air.

The arc of the vacuum circuit breaker goes out in the rarefied space of the arc extinguishing chamber. The electrical strength of a vacuum is extremely high and recovers very quickly after an electrical breakdown. In addition, such switches are distinguished by high reliability, reduced maintenance costs, and simplicity of design.

The disadvantages of vacuum circuit breakers include:

• high cost;

• the possibility of overvoltage occurring in the network under certain network conditions;

• To create switches for higher voltages, certain technical tricks are required.

SF6 high voltage circuit breakers whose arc extinguishing devices operate in an environment that combines the advantages various types switches:

• it is possible to use SF6 switches for any of the voltages used in the domestic energy sector;

• small weight and overall dimensions designs of SF6 switches in combination with silent operation of the drive;

• the arc is extinguished in a closed gas volume without access to the atmosphere;

• harmless to humans, environmentally friendly, inert gas environment of the SF6 circuit breaker;

• increased switching capacity of the SF6 circuit breaker;

• operation in switching mode of high and low currents without the occurrence of overvoltage, which automatically eliminates the presence of surge arresters (overvoltage limiting devices);

• high reliability of the SF6 circuit breaker, the overhaul period is increased to 15 years;

• fire safety of equipment.

The disadvantages of SF6 switches include:

• high cost of equipment and current operating costs, since the quality requirements for SF6 gas are very high;

• ambient temperature affects the physical state of SF6 gas, which requires the use of circuit breaker heating systems when low temperatures(at -40°C SF6 gas becomes liquid);

• the switching life of a SF6 circuit breaker is lower than that of a similar vacuum circuit breaker;

• High-quality seals for tanks and lines are necessary, since SF6 gas is very fluid.
  

At the end of the last century, there was a breakthrough in technology in the global energy sector. Oil and air circuit breakers gradually began to give way to vacuum and SF6 circuit breakers. This is due to the excellent arc extinguishing properties of vacuum, as well as gas with chemical formula SF6, called SF6 gas, and increased operational safety switching equipment with their use. And although vacuum and SF6 equipment are not cheap, a worthy competitor to arc extinguishing media - vacuum and SF6 - has not yet been found.

General information

SF6 gas switches of the VGT series are designed for switching electrical circuits under normal and emergency modes, as well as work in automatic reclosure cycles in three-phase alternating current networks with a frequency of 50 Hz and a rated voltage of 110 and 220 kV.

Symbol structure

switch VGT-XII * -40/2500U1:
VG - SF6 gas switch;
T - symbol design;
X - rated voltage, kV (110 or 220);
II * - category according to the length of the creepage distance along the external insulation
in accordance with GOST 9920-89;
40 - rated shutdown current, kA;
2500 - rated current, A;
U1 - climatic version and accommodation category according to GOST
15150-69 and GOST 15543.1-89. drive PPrK-1800S:
P - drive;
Pr - spring;
K - cam;
1800 - static switching work, J;
S - special.

terms of Use

The installation altitude above sea level is no more than 1000 m. The ambient temperature is from minus 45 to 40°C. Relative humidity air no more than 80% at a temperature of 20°C. Upper value 100% at 25°C. Wind speed is 15 m/s in case of ice with an ice crust thickness of up to 20 mm, and in the absence of ice up to 40 m/s. Environment non-explosive, not containing aggressive gases and vapors in concentrations that destroy metals and insulation. Content of corrosive agents according to GOST 15150-69 (for type II atmosphere). The tension of the wires applied in the horizontal direction is no more than 1000 N. The leakage distance of the external insulation complies with GOST 9920-89 standards for substation insulation (pollution degree II *, performance category B) - at 110 kV - no less than 280 cm, at 220 kV - not less than 570 cm. Switches comply with the requirements of GOST 687-78 “AC switches for voltages over 1000 V. General technical specifications" and TU 2BP.029.001 TU, agreed with RAO "UES of Russia". TU 2BP.029.001 TU

Specifications

The main technical data of the switches are given in the table.

The switches perform the following operations and cycles: 1) shutdown (O);
2) switching on (B);
3) switching on - switching off (BO), including without a deliberate time delay between operations (B) and (O);
4) switching off - switching on (OB) during any non-contact pause, starting from t to corresponding to t;
5) shutdown - enable - shutdown (OBO) with time intervals between operations according to paragraphs. 3 and 4;
6) switching cycles: O-0.3 s - VO-180 s - VO;
O-0.3 s - VO-20 s - VO;
O-180 s - VO-180 s - VO. The number of shutdown operations allowed for each pole of the circuit breaker without inspection and repair of arc extinguishing devices (switching resistance resource) is: for currents in the range of over 60 to 100% of the rated shutdown current - 20 operations;
for currents in the range of over 30 to 60% of the rated shutdown current - 34 operations;
at operating currents equal to rated current - 3000 operations B-t By. The permissible number of operations B for short-circuit currents should be no more than 50% of the permissible number of operations O; the permissible number of operations B at load currents is equal to the permissible number of operations O. The switches have the following reliability and durability indicators: mechanical durability life up to overhaul - 5000 cycles B-t By;
service life before the first repair is 20 years, if before this period the resources for mechanical or switching resistance have not been exhausted;
service life - 40 years. The warranty period of operation is 5 years with operating hours not exceeding the values ​​of resources for mechanical or switching resistance, calculated from the date the circuit breaker is put into operation, but no later than 6 months for existing enterprises and 9 months for enterprises under construction from the date of receipt of products at the enterprise.

Switches of the VGT series belong to electrical switching devices high voltage, in which the quenching and insulating medium is SF6 gas. The VGT-110II switch * (Fig. 1) consists of three poles (columns) mounted on a common frame and mechanically connected to each other. All three poles of the switch are controlled by one spring drive type PPrK-1800S.

General view, overall, installation and connection dimensions of the VGT-110II * -40/2500U1 circuit breaker: 1 - spring drive;
2 - pole (column);
3 - output;
4 - disconnecting device;
5 - tube;
6 - signaling device;
7 - frame;
8 - position indicator;
9 - cable coupling;
10 - M16 bolt;
11 - grounding sign;
12 - frame support The VGT-220II switch * (Fig. 2) consists of three poles, each of which has its own frame and is controlled by its own drive.

General view, dimensions, installation and connecting dimensions switch VGT-220II * -40/2500U1: 1 - spring drive;
2 - column (arc extinguishing device);
3 - tire;
4 - output;
5 - frame;
6 - disconnecting device;
7 - position indicator;
8 - capacitor;
9 - M16 bolt;
10 - grounding sign;
11 - frame support The principle of operation of the switches is based on the extinguishing of an electric arc by a flow of SF6 gas, which is created due to the pressure drop provided by self-generation, i.e. due to the thermal energy of the arc itself. Switching on of the switches is carried out due to the energy of the closing springs of the drive, and switching off is carried out due to the energy of the spring of the switch's tripping device. The frame of the VGT-110 circuit breaker is a welded structure on which a drive, a disconnecting device, columns and electrical contact pressure switches are installed. In the cavity of one of the support channels of the frame, closed with covers, there are series-connected rods connecting the drive lever with the levers of the poles (columns). The cover has a viewing window for the switch position indicator. The frame has four holes with a diameter of 36 mm for fastening to foundation posts and is equipped with a special bolt for connecting a grounding bus. The pole frame of the VGT-220II * circuit breaker has a similar design. The disconnecting device is installed on the end of the frame opposite to the drive and consists of a disconnecting spring, compressed when the switch is turned on by a rod connected to the outer lever of the outer column. The spring is located in a cylindrical body, on the outer flange of which there is a buffer device designed to dampen the kinetic energy of the moving parts and serve as a stop (travel limiter) when the switch is dynamically turned on. The pole of the VGT-110 circuit breaker is a column filled with SF6 gas and consisting of a support insulator, an arc extinguishing device with current leads, and a control mechanism with an insulating rod. The pole of the VGT-220II * circuit breaker consists of two columns, the arc extinguishing devices of which are installed on support insulators and connected in series by two busbars. To distribute voltage evenly across the arc extinguishing devices, shunt capacitors are connected to them in parallel. The arc extinguishing device contains openable main arc extinguishing contacts equipped with arc-resistant tips, a piston device for creating pressure in its internal cavity, and fluoroplastic nozzles in which SF6 gas flows acquire the direction necessary for effective extinguishing of the arc. The high-pressure above-piston cavity and the sub-piston cavity are equipped with a valve system that allows for effective blowing in the arc combustion zone in all switching modes. In the upper part of the arc extinguishing device there is a container filled with an activated adsorbent that absorbs moisture and decomposition products of SF6 gas from the gas area. In the on position, the main and arcing contacts are closed. When disconnecting, the main contacts first open with virtually no arcing effect when the arc extinguishing contacts are closed, and then the arc extinguishing contacts open. Sliding contact between the stationary sleeve of the piston device and the body of the movable contact is carried out by contact elements placed in its recesses, in the form of closed wire spirals. The column control mechanism is housed in a housing and a support insulator and consists of a splined shaft with an outer and inner lever. The splined shaft is mounted in bearings and sealed with cuffs. The internal lever is connected to the movable contact rod through a non-adjustable insulating rod. An autonomous sealing valve is built into the mechanism body, through which, using copper tube a pressure alarm mounted on the switch frame is connected. The autonomous sealing valve consists of a housing and a spring-loaded valve, a connection unit for the alarm tube and a plug installed during transportation and after filling with SF6 gas during commissioning to ensure reliable sealing of the internal cavity of the column. The indicating-type electric contact pressure switch is equipped with a temperature compensation device that brings pressure readings to a temperature of 20°C, and two pairs of contacts closed at the operating pressure of the switch. The first pair of contacts opens when the pressure drops to 0.34 MPa, giving a signal about the need to replenish the pole, the second pair opens at a pressure of 0.32 MPa, blocking the command from the control electromagnets. To eliminate false signals in the event of possible contact activation from vibration when turning the switch on and off, and also due to their low power, an intermediate time relay (for example, RP-2556 or RP-18) with a time delay of 0.8 to 1.2 s must be included in the contact circuit. The signaling device is closed with a special casing that protects it from direct contact with precipitation and sun rays. The switch drive is spring-type with motor and manual winding of working (cylindrical, screw) springs, type PPrK-1800S. The drive is a separate one, placed in a sealed three door wardrobe, unit. The drive has two tripping electromagnets; equipped with devices that block: the passage of a command to the closing electromagnet when the switch is on and when the springs are not charged;
passing a command to the tripping electromagnet when the circuit breaker is open;
“idle” (with the switch on), dynamic discharge of the working springs;
turning on the electric motor for winding springs when winding them manually. The drive allows you to: have an alarm about the following deviations from its normal (operating) state: the SF machine is not turned on;
malfunction in the spring winding system;
automatic motor control is not turned on;
springs are not charged;
slowly operate the switch contacts when setting it up without any additional (for example, jacking) devices. The drive has anti-condensation (non-switchable) and main (controlled by a thermostat) electric heating of the cabinet. The fundamental difference between the PPrK-1800S drive and other drives of the PPrK family is the presence of a buffer that slows down the moving parts of the circuit breaker when disconnected. The drive is easy to adjust, troubleshoot and maintain. At correct operation reliable at work. The drive control circuit is shown in Fig. 3.

Electrical control diagram of the PPrK-1800S drive: a - version with motor power supply from a 380 V network;
b - version with motor power supply from a 220 V network

Table 1 to fig. 3

Table 2 to fig. 3

Note. The position of the contacts of the circuit elements corresponds to the open position of the switch, the discharged state of the operating springs of the drive and the position of the fist that cocks them, in which the finger of the latter does not act on the lever that controls the contacts SQ2.

The delivery set of the VGT-110II circuit breaker * includes: a frame with a drive, three poles (columns) filled with SF6 gas to transport pressure, a single set of accessories and spare parts. The delivery set of the VGT-220II circuit breaker * includes: three frames with drives, six columns filled with SF6 gas to transport pressure, six connecting bars, six capacitors of the DMK-190-0.5 type, a set of capacitor mounting parts, a single set of accessories and spare parts . The delivery package for each switch also includes a passport, a switch operating manual, a drive operating manual, a complete list, a spare parts list, and a set of documents for purchased products. In addition, for a group of switches (1-3 switches delivered to one address), at the customer’s request, a group set of spare parts and accessories is supplied, which includes: cylinders with SF6 gas, a filter for drying SF6 gas, gas hoses with fittings, special tool and devices.

To extinguish an electric arc, various gas mixtures. SF6 circuit breakers 110 kV and 220 kV work exactly on this principle and can be used to work in emergency situations.

Design and types

Gas-insulated high-voltage circuit breakers are operational control devices for monitoring high-voltage power supply lines. These devices have a very similar design to oil ones, but at the same time, they use not an oil mixture, but a gas compound to extinguish the arc. Often this is sulfur. Oil switches require special care: according to regulations, periodic oil changes and cleaning of working contacts are required. SF6 do not need this. The main advantage of SF6 gas is its durability: it does not age and minimally pollutes the mechanical parts of the device.

They are:

1. Core (HPL 245B1, MF 24 Schneider Electric);
2. Tank (ABB 242PMR, DT2-550 F3 - Areva manufacturer).

The SF6 column circuit breaker is a standard disconnecting device that operates on one phase only (for example, LF 10 from Schneider Electric). It is used for 220 kV network. Structurally they consist of two systems: contact and arc extinguishing. Both of them are located in a container filled with SF6 gas. They can be either manual (control is performed exclusively mechanically) or remote. Due to this separation, they have quite large overall dimensions.

The tanks have smaller dimensions and are complemented by the PPRM 2 drive for the SF6 circuit breaker. The drive is distributed over several phases, which allows for soft voltage regulation (switching on and off). Their advantage is also that they can carry heavy loads thanks to the current transformer built into the system.

In addition to design features, gas-insulated switches are classified according to the principle of arc extinguishing:

1. Auto-compression or air;
2. Rotating;
3. Longitudinal blast;
4. Longitudinal blast with additional heating of SF6 gas.

Operating principle and purpose

High voltage SF6 circuit breakers operate by isolating the phases from each other using SF6 gas. When a signal is triggered that the electrical equipment needs to be turned off, the contacts of individual cameras (if the device is a speaker device) open. Thus, the built-in contacts form an arc, which is placed in a gaseous environment. It decomposes the gas into individual components, but at the same time it itself decreases due to the high pressure in the container. If the system is installed at low pressure, then additional compressors are used to increase pressure and create a gas blast. To equalize the current, shunting is additionally used. Visually, the work flow looks like this:

Separately, it is necessary to say about tank-type models. Their control is carried out by drives and transformers. The drive mechanism for this installation is a regulator: it is necessary to turn on, off electrical energy and holding the arc (if necessary) at a certain level. Drives are:

1. Spring;
2. Spring-hydraulic.

The spring type has a very simple principle of operation and high level reliability. In it, all work is performed only by mechanical parts. The spring is clamped and fixed at a certain level, and when the position of the control lever changes, it is released. Based on its operating principle, a scientific presentation of the action of sulfur hexafluoride in an electrical environment is often prepared.

Modern spring-hydraulic drives, in addition to the spring, are additionally equipped with a hydraulic control system. They are considered more effective, because spring mechanisms can themselves change the position of the latch.

Advantages of SF6 circuit breakers:

1. Versatility. These switches are used to control networks with any voltage;
2. Speed ​​of action. The reactions of SF6 gas to the presence of an electric arc occur in a fraction of a second, this allows for quick emergency shutdown of the controlled system;
3. Suitable for use in conditions of fire hazard and vibration;
4. Durability. Contacts in contact with SF6 gas practically do not wear out, gas mixtures do not need to be replaced, and outer shell high performance protection;
5. Suitable for disconnecting high voltage alternating and direct current, while their analogues, vacuum models, cannot be used on high-voltage networks.

But such devices have certain flaws:

1. High price due to the complexity of production and the high cost of the SF6 gas mixture;
2. Installation is carried out only on a foundation or a special electrical panel, and this requires special instructions and experience;
3. Switches do not work in low temperatures;
4. When necessary maintenance, special equipment must be used.

Video: features of SF6 switches

Specifications

Let's consider technical specifications switches different manufacturers and types of work.

MEK SF6 gas spring circuit breaker HD4 (factory ABB factory):

VGBEP-35 (VGB-35, VGBE):

VGT-35 (VMT-35):

Core VGT-110:

VGU-110 (gas power):

Column switch GL314 Alstom:

Generator power switching devices with spring drive – FKG 2:

SF6 gas compression circuit breaker from Siemens (Siemens) 3AP1FG-245 (foundations required for installation):

You can buy suitable SF6 switches at any electrical store. Their cost depends on the type of device and its manufacturer. The price list in Samara, Moscow, Yekaterinburg and other cities varies from 100 dollars to several thousand.

Operation of high voltage electrical networks In terms of current characteristics, it is not comparable with the operation of household analogues. Accordingly, in the event of an emergency, more powerful devices than standard automatic devices are needed to turn off the equipment and extinguish the electric arc.

SF6 circuit breakers (EGS) are used as protective structures, which can be controlled both manually and automatically. We have described in detail design features and the principle of operation of the devices. Provided recommendations for installation, connection and maintenance.

SF6 gas is sulfur hexafluoride, which is classified as an electrical gas. Due to its insulating properties, it is actively used in the production of electrical devices.

In its neutral state, SF6 gas is a non-flammable, colorless and odorless gas. If we compare it with air, we can note high density(6.7) and molecular weight 5 times higher than air.

One of the advantages of SF6 gas is its resistance to external manifestations. It does not change characteristics under any conditions. If disintegration occurs during an electric discharge, then a full restoration necessary for operation soon occurs.

The secret is that SF6 molecules bind electrons and form negative ions. The quality of “electronegation” endowed 6-sulfur fluoride with such a characteristic as electrical strength.

In practice, the electrical strength of air is 2-3 times weaker than the same property of SF6 gas. Among other things, it is fireproof, as it is a non-flammable substance, and has cooling properties.

When the need arose to find a gas to extinguish the electric arc, they began to study the properties of SF6 (sulfur hexafluoride), carbon 4-chloride and freon. SF6 won the tests

The listed characteristics made SF6 gas most suitable for use in the electrical field, in particular in the following devices:

• power transformers operating on the principle of magnetic induction;
• complete type switchgears;
• high voltage lines connecting remote installations;
• high voltage switches.

But some properties of SF6 gas led to the need to improve the design of the switch. The main disadvantage concerns the transition of the gaseous phase into the liquid phase, and this is possible under certain ratios of pressure and temperature parameters.

In order for the equipment to operate without interruption, it is necessary to ensure comfortable conditions. Let's assume that for the operation of SF6 devices at -40º, a pressure of no more than 0.4 MPa and a density of less than 0.03 g/cm³ are required. In practice, if necessary, the gas is heated, which prevents the transition to the liquid phase.

SF6 circuit breaker design

If we compare SF6 devices with analogues of other types, then in design they are closest to oil devices. The difference lies in the filling of the chambers to extinguish the arc.

In order to extinguish an electric arc, many different gas mixtures are often used. Equipment filled with SF6 gas works on this principle and is used for work in emergency situations. In this article we will look at the design, principle of operation and purpose of SF6 switches.

What does the equipment consist of and what types of designs are there?

An SF6 high-voltage circuit breaker is a device whose purpose is to control and control high voltage line energy supply. The design of such equipment resembles the mechanism of an oil device, only a gas compound is used for extinguishing instead of an oil mixture. Typically, sulfur is used. Unlike an oil-based appliance, a SF6 appliance does not require special care. Its main advantage is durability.

SF6 circuit breakers are divided into:

1. Kolonkovy. The use of such a structure is optimal only for a 220 kV network. This disconnecting device operates on one phase. The design includes two systems, which are placed in a container with SF6 gas. This is a contact and arc extinguishing system. They can also be either manual or remote. This is considered the main reason for their large size.
2. Tank. The dimensions are smaller than core ones. The design has an additional drive, which has several phases. Thanks to this, you can smoothly and gently regulate the switching on and off of the voltage. And due to the fact that a current transformer is built into the system, the mechanism is capable of carrying heavy loads.

According to the method of extinguishing the electric arc, SF6 power circuit breakers are divided into:

• air, also called auto-compression;
• rotating;
• longitudinal blast.

Operating principle and scope

How does a high voltage SF6 circuit breaker work? Due to the isolation of the phases from each other through SF6 gas. The principle of operation of the mechanism is as follows: when a signal to turn off electrical equipment, the contacts of each camera open. Built-in contacts create an electric arc, which is placed in a gaseous environment.

This medium separates the gas into individual particles and components, and due to the high pressure in the tank, the medium itself is reduced. Possible use of additional compressors if the system operates at low pressure. Then the compressors increase the pressure and create a gas blast. Shunting is also used, the use of which is necessary to equalize the current.

The designation in the diagram below indicates the location of each element in the switch mechanism:

As for tank-type models, control is carried out using drives and transformers. What is the drive for? Its mechanism is a regulator and its purpose is to turn the electricity on or off and, if necessary, to hold the arc at a set level.

Drives are divided into spring and spring-hydraulic. Spring ones have a high degree of reliability and have a simple operating principle: all the work is done thanks to mechanical parts. The spring is capable of compressing and decompressing under the action of a special lever, as well as being fixed at a set level.

Spring-hydraulic drives of switches additionally have in their design hydraulic system management. Such a drive is considered more efficient and reliable, because the spring device can itself change the level of the latch.

Advantages and disadvantages of equipment

As with any designs and mechanisms, SF6 circuit breakers have their own advantages and disadvantages. The advantages of the device include:

1. Multifunctionality. The purpose and use of such a mechanism is possible for any voltage in the network.
2. Speed ​​of action. SF6 reacts to the presence of an electric arc in a matter of seconds. Thanks to this, in the event of an emergency, it is possible to quickly turn off the controlled system.
3. Possible use in vibration and fire conditions.
4. Longevity. There is no need to replace gas mixtures. The contacts that come into contact with the mixtures are almost not subject to wear, and the outer casing has high protection rates.
5. Can be used on high voltage networks. Their analogues, such as vacuum devices, are not capable of doing this.

But these switches also have their drawbacks. For example:

1. Since the production of devices is very complex and SF6 gas mixtures are expensive, the price of the design itself is high.
2. The device does not operate at low temperatures.
3. When maintenance is required, specific equipment must be used.
4. The device must be installed on a special platform or foundation, and for this you must have experience and special instructions.

So we looked at the design, purpose and principle of operation of SF6 switches. We hope the information provided was useful and interesting for you!

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