High-voltage circuit breakers that use SF6 gas as an insulating and arc-extinguishing medium are becoming increasingly widespread, as they have high switching and mechanical resources, breaking capacity, compactness and reliability compared to air, oil and low-oil high-voltage circuit breakers.
Advances in the development of gas-insulated switchgear have directly had a significant impact on the implementation of compact outdoor switchgear, indoor switchgear and gas-insulated switchgear. In SF6 circuit breakers they are used various ways arc extinguishing depending on the rated voltage, rated breaking current and characteristics of the power system (or individual electrical installation).
In SF6 arc extinguishing devices, in contrast to air arc extinguishing devices, when extinguishing the arc, the outflow of gas through the nozzle does not occur into the atmosphere, but into a closed chamber volume filled with SF6 gas at a relatively low excess pressure.
According to the method of extinguishing the electric arc during shutdown, the following SF6 gas circuit breakers are distinguished:
1. Auto-compression SF6 gas circuit breaker, where the required mass flow of SF6 gas through the nozzles of the compression arc extinguishing device is created along the movable system of the circuit breaker (auto-compression circuit breaker with one pressure stage).
2. SF6 gas circuit breaker with electromagnetic blast, in which the extinguishing of the arc in the arc extinguishing device is ensured by its rotation along the ring contacts under the influence of the magnetic field created by the switched current.
3. SF6 circuit breaker with high and low low pressure, in which the principle of providing gas blast through the nozzles in the arc extinguishing device is similar to air arc extinguishing devices (SF6 gas circuit breaker with two pressure stages).
4. Self-generating SF6 gas circuit breaker, where the required mass flow of SF6 gas through the nozzles of the arc extinguishing device is created by heating and increasing the pressure of the SF6 gas by a shutdown arc in a special chamber (self-generating SF6 gas circuit breaker with one pressure stage).
Let's look at some typical designs of SF6 circuit breakers for 110 kV and above.
SF6 circuit breakers 110 kV and higher per break from various companies have the following nominal parameters: Unom = 110-330 kV, Inom = 1-8 kA, Io.nom = 25-63 kA, SF6 gas pressure pH = 0.45-0.7 MPa(abs), shutdown time is 2-3 periods of short-circuit current. Intensive research and testing of domestic and foreign companies made it possible to develop and put into operation a gas-insulated circuit breaker with one break at Unom = 330-550 kV at Io.nom = 40 - 50 kA and the current interruption time is one short-circuit current period.
A typical design of an auto-compression SF6 circuit breaker is shown in Fig. 1.
The device is in the off position and contacts 5 and 3 are open.
Rice. 1.
Current supply to fixed contact 3 is carried out through flange 2, and to movable contact 5 through flange 9. A chamber with an adsorbent is mounted in the top cover 1. The supporting insulating structure of the SF6 switch is mounted on the footrest 11. When the switch is turned on, a pneumatic actuator 13 is activated, the rod 12 of which is connected through an insulating rod 10 and a steel rod 8 with a movable contact 5. The latter is rigidly connected to a fluoroplastic nozzle 4 and a movable cylinder 6. The entire movable EV system (elements 12-10-8-6-5) moves upward relative to the stationary piston 7, and the cavity K of the arc extinguishing system of the circuit breaker increases.
When the switch is turned off, the rod 12 of the driving power mechanism pulls the moving system down and increased pressure is created in cavity K compared to the pressure in the switch chamber. This self-compression of SF6 gas ensures the outflow of the gas medium through the nozzle, intensive cooling of the electric arc that occurs between contacts 3 and 5 during shutdown. Position indicator 14 gives the initial position of the contact system of the switch. In a number of designs of auto-compression SF6 gas circuit breakers, spring, hydraulic power drive mechanisms are used, and the flow of SF6 gas through the nozzles in the arc-extinguishing chamber is carried out according to the principle of double-sided blasting.
In Fig. Figure 2 shows a tank-type SF6 switch of the VGBU type 220 kV (Inom=2500 A, Io.nom=40 kA NIIVA OJSC with an autonomous hydraulic drive 5 and built-in current transformers 2. The EV has three-phase control (one drive for three phases) and is equipped with porcelain (polymer) tires of 1 air-SF6 inputs.
In the gas-filled tank 3 there is an arc extinguishing device, which is connected to the hydraulic drive 5 through a transmission mechanism located in the gas-filled chamber 4. The design of the tank SF6 circuit breaker is mounted on a metal frame 6. To fill the circuit breaker with SF6 gas, connector 7 is used. When installing the circuit breaker in an outdoor switchgear, the gas pressure in the chambers is usually is equal to one atm (abs.) and then it is necessary to ensure p = pH.
Rice. 2.
The advantages of tank-type SF6 circuit breakers with built-in current transformers over sets of “column SF6 circuit breaker plus a free-standing current transformer” are: increased seismic resistance, smaller area of the alienated territory of the substation, less volume of required foundation work during the construction of substations, increased safety of substation personnel (arc extinguishing devices are located in grounded metal tanks), the possibility of using SF6 gas heating when used in areas with cold climates.
In the designs of tank circuit breakers 220 kV and above, for outdoor switchgear it is necessary to increase the nominal pressure of SF6 gas (pnom > 4.5 atm (abs.)), therefore, heating of the gas medium is introduced in order to prevent liquefaction of SF6 gas at low ambient temperatures or mixtures of SF6 gas with nitrogen are used or tetrafluoromethane.
As practice shows, for a rated voltage of 330–500 kV, tank switches with one break for rated currents of 40–63 kA are the most promising type of switching equipment for outdoor switchgear and switchgear.
Circuit breaker VGB-750-50/4000 U1 developed by OJSC NIIVA (Fig. 3) with a double-break auto-compression arc extinguishing device, built-in current transformers, polymer air-SF6 bushings, is equipped with two hydraulic drives per pole, which allows for a total shutdown time of no more duration of two periods of industrial frequency current.
In the on position of the SF6 circuit breaker, the resistors are bridged by the main contacts. When disconnecting, the resistor contacts open first, then the main ones, then the arcing contacts. When turned on, the resistor contacts close first, followed by the arc extinguishing and main contacts. To equalize the voltage distribution, each gap is shunted with capacitors.
Column SF6 circuit breakers with one break for a rated voltage of 110-220 kV with a rated breaking current of 40-50 kA have become widespread.
Rice. 5
A typical design of a column-type SF6 circuit breaker of the VGP type 110 kV (Inom = 2500 A, Io.nom = 40 kA) with a spring drive by Elektroapparat OJSC is shown in Fig. 5.
To extinguish an electric arc, various gas mixtures. 110 kV and 220 kV SF6 circuit breakers operate precisely on this principle and can be used for operation in emergency situations.
Design and types
SF6 high-voltage circuit breakers are devices operational management for control high voltage line energy supply. 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 standards, periodic oil changes and cleaning of working contacts are required. SF6 ones 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.
Photo – high voltage equipmentThey are:
- Core (HPL 245B1, MF 24 Schneider Electric);
- 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.
Photo – design drawing 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.
Besides design features, SF6 type switches are classified according to the principle of arc extinguishing:
- Auto-compression or air;
- Rotating;
- Longitudinal blast;
- Longitudinal blast with additional heating of SF6 gas.
Operating principle and purpose
SF6 circuit breakers high voltage work 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 gas environment. It decomposes the gas into separate components, but at the same time it itself decreases due to high pressure in a 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:
Photo - work diagram 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:
- Spring;
- 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.
Photo – VGU-35 Modern spring-hydraulic drives, in addition to the spring, are additionally equipped hydraulic system management. They are considered more effective, because spring mechanisms can themselves change the position of the latch.
Advantages of SF6 circuit breakers:
- Versatility. These switches are used to control networks with any voltage;
- 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;
- Suitable for use in conditions of fire hazard and vibration;
- Durability. Contacts in contact with SF6 gas practically do not wear out, gas mixtures do not need to be replaced, and outer shell high protection rates;
- Suitable for disconnecting AC and direct current high voltage, while their analogues - vacuum models cannot be used on high-voltage networks.
But such devices have certain flaws:
- High price due to the complexity of production and the high cost of the SF6 gas mixture;
- Installation is carried out only on the foundation or a special electrical panel, and for this you need special instructions and experience;
- Switches do not work in low temperatures;
- When necessary maintenance, special equipment must be used.
Photo – industrial gas-insulated load switch Video: features of SF6 switches
Specifications
Let's consider 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.
A. Nazarychev, chief engineer of Contact T&D LLC, head. Department of Ivanovo Energy University, Vice-Rector for scientific work PEIPK, Doctor of Technical Sciences, Professor; A. Surovov, director of Contact T&D LLC; V. Chaika, chief designer JSC NPP Kontakt; A. Tadzhibaev, rector of the St. Petersburg Energy Institute for Advanced Studies (PEIPK), Doctor of Technical Sciences, Professor
Technical re-equipment of the electrical distribution grid complex is the basis for modernizing the economy of Russian regions. The Renovation Program for the Electric Grid Complex developed by IDGC Holding for the period from 2011 to 2020 sets the priority objectives to reduce equipment wear and tear to 46-48%, electricity losses to 6.1%, as well as a twofold reduction in the number of technological violations.
Air and oil circuit breakers
The most important equipment of distribution networks are switching devices, the operation of which determines the reliability of all substations, power lines and switchgears in all operating modes.
High-voltage switches are the main switching devices in electrical installations and are used to turn off and turn on circuits in any mode: nominal continuous, overload, short circuit (short circuit), idle, asynchronous operation. The most difficult and responsible operation is to disconnect short-circuit currents and turn on an existing short circuit. The total number of high-voltage circuit breakers with a voltage of 110-750 kV in operation is about 30 thousand. They are distributed according to voltage classes as shown in table. 1.
Table 1. Distribution of the total number of high-voltage circuit breakers by voltage class 110-750 kV
| Nominal voltage, kV |
Total number of switches, pcs.. |
Number of switches from the total, % |
From the table 1 it is clear that greatest number circuit breakers - 95.7% are operated in the voltage class 110-220 kV.
For quite a long time, oil tank, low-oil column and air circuit breakers were used in power systems in these voltage classes. various types. Today, the number of circuit breakers that have completed their standard service life is 40% of the total number of circuit breakers in operation, including 90% of tank oil circuit breakers of the MKP-110 type and 40% of the U-110 type circuit breakers, 30% of air circuit breakers have served their standard service life. VVN-110, 40% of air circuit breakers VVN-220. Behind last years The number of damages to domestic circuit breakers has increased noticeably. The main reasons are:
wear of the main assemblies of switches;
imperfect design of devices in operation;
non-compliance with climatic operating conditions;
defects caused by poor quality of repairs and materials used in repairs;
manufacturing defects;
violations of regulatory and directive documents on repair periods and operating modes;
installation of shunt reactors and capacitor banks in circuits for which switches are not intended;
installation in circuits where short-circuit currents and restoring voltage exceed the normalized parameters of the switch.
The provisions of the Technical Policy in the distribution network complex apply to modern switches high voltage the following are quite high requirements:
reliable shutdown of any currents (including short-circuit currents);
speed of operations, i.e. shortest turn-off and turn-on time;
Suitable for fast automatic reclosing, i.e. quick switching on of the switch immediately after shutdown;
possibility of phase-by-phase (pole) control for circuit breakers 110 kV and above;
availability of switching and mechanical resources, ensuring a service life between repairs of at least 15-20 years;
minimum number of operations Maintenance during operation;
maximum reduction in weight and size indicators;
reduction of operating costs;
explosion and fire safety.
These requirements are difficult to meet with traditional methods of arc extinguishing in oil or air. Opportunities for further significant improvement of switches with traditional ways arc extinction is almost exhausted.
Vacuum and SF6 circuit breakers
Fulfillment of increased requirements for circuit breakers is possible by using modern SF6 and vacuum circuit breakers (VC) in switchgear of substations. Currently, circuit breakers with vacuum and gas-insulated arc extinguishing devices (EA) are replacing oil, electromagnetic and air circuit breakers. The fact is that the remote controls of vacuum and SF6 circuit breakers do not require repair for at least 20 years, while in oil circuit breakers the oil becomes contaminated with free carbon particles during shutdowns and, in addition, the insulating properties of the oil are reduced due to the ingress of moisture and air. This leads to the need to change the oil at least once every 4 years. Arc suppression devices of air circuit breakers require cleaning at approximately the same time. In addition, worn air switches have compressed air leaks from the remote control, which precludes normal operation. The arcing devices of vacuum and SF6 circuit breakers are enclosed in sealed enclosures and their internal insulation is not affected by external environment. An electric arc during shutdowns in a vacuum or in SF6 gas also practically does not reduce the properties of the arc-extinguishing and insulating medium.
Regulatory documents of FGC UES and IDGC Holding enshrine the decision on the primary use of SF6 circuit breakers in the construction, reconstruction, technical re-equipment and replacement of equipment at substations with a voltage of 330-750 kV, and vacuum circuit breakers at substations with a voltage of 6, 10, 20, 35 kV. In the voltage class 110-220 kV today at newly commissioned substations, as a rule, in the absence of any alternative options It is proposed to use SF6 switches, which, for all their advantages, also have a number of the following problematic issues.
The physical features of the use of SF6 gas (sulfur hexafluoride - SF6) in high-voltage switches as an insulating and arc-extinguishing medium imply the need to maintain high pressure in the remote control (1.5-2.5 atm.) to ensure the required level of switching capacity and electrical strength of the intercontact gap. During long-term operation of the circuit breaker, SF6 gas leaks are possible. At the same time, the pressure in the arc-extinguishing chamber decreases. In vacuum circuit breakers modern technologies The manufacture of vacuum arc chambers (VACs) has been brought to a level that guarantees the required vacuum throughout the entire service life of the VACs - 25-40 years.
The pressure in the remote control of SF6 switches can also decrease with significant fluctuations in ambient temperature. If the pressure drops below the specified critical value limits, which are determined individually for different types of remote control, there is a danger of breakdown of the SF6 gap or failure of the switch at the time of switching. To prevent this type of failure, it is necessary to monitor the operating pressure in the arc-extinguishing chamber in the SF6 circuit breaker using a pressure gauge and timely pumping of SF6 gas to the specified limits. In addition, when integrating SF6 switches into a digital substation system, the cost of organizing the transmission of information about SF6 gas pressure is comparable to the cost of the switch itself. The vacuum switch can be operated in the temperature range from +50° to -60°C, and there is no need to install a vacuum state monitoring sensor in the VDK.
For example, there is a known case of blocking the control circuits of 59 110-500 kV SF6 tank switches produced by a number of European companies at an ambient temperature of -41°C in the Tyumen region in 2006 due to design imperfections, insufficient power, low reliability of tank heating devices and system deficiencies control of pressure (density) of SF6 gas. Therefore, when choosing switches for regions with cold climates, preference should be given either to switches filled with a gas mixture that does not require heating, or the following are necessary: installation of additional thermal insulation of tanks, additional heating of pulsed gas tubes, increasing the power of heaters. All this complicates and increases the cost of the design of SF6 switches and increases the consumption of electricity for their own needs, and therefore makes SF6 switches energy inefficient. It should also be noted regarding high cost production, purification and disposal of SF6 gas.
Despite the proven safety of SF6 circuit breakers under normal operating conditions, ecological problems arise acutely during the repair and disposal of circuit breakers that have exhausted their standard service life. The fact is that some SF6 gas decomposition products are very toxic and can harm humans and the environment. In table Table 2 shows the degree of danger of SF6 gas decomposition products.
Table 2. Hazard level of SF6 gas decomposition products
Products |
Degree |
Lifespan after release into the atmosphere |
Hazard to human health |
||
unknown |
|||||
unknown |
|||||
unknown |
|||||
minutes after release) |
|||||
about |
from minutes to hours |
relatively |
|||
by inhalation |
|||||
Very |
not from |
very low |
Analyzing the table. 2, we can conclude that the most dangerous in environmentally is the release into the environment of both the SF6 gas itself and its decomposition products, which contain toxic substances. Since environmental requirements are coming to the fore today, the legislation of Russia and the countries participating in the Montreal Protocol prohibits the release into the atmosphere of fluorine-containing substances, which includes SF6 gas. Therefore, in order to ensure safety and meet modern environmental requirements, improve the quality and culture of operation when introducing SF6 equipment, it is necessary to equip enterprises of the electrical distribution grid complex with modern gas technology devices, as well as equipment for purifying SF6 gas and recycling its decomposition products, which will require serious financial costs.
The agreement (Climate Change Pact), signed by most countries of the world in the Japanese city of Kyoto in 1997, makes explicit reference to SF6 as a potentially dangerous gas with a greenhouse effect, and parties to the agreement are ordered to refrain from using it. Therefore, in many countries, attempts have been made aimed at developing high-voltage VDCs that would replace the SF6 circuit breakers that are in use today.
Vacuum circuit breakers are ideal from an environmental point of view, are highly reliable, have a longer switching life and can operate at temperatures down to -60°C.
In the voltage class of 6-35 kV, vacuum circuit breakers have long replaced the position of SF6 circuit breakers and have been successfully operated for more than 15 years. When modernizing and new construction of 6-10 kV closed switchgear at substations of FGC UES and IDGC Holding, other types of circuit breakers besides vacuum ones are not considered at all. The only exception is the 6 kV indoor switchgear of some nuclear power plants and thermal power plants, where, due to existing stereotypes about possible overvoltages during the operation of vacuum circuit breakers, the installation of SF6 circuit breakers is still being considered, and, as a rule, imported ones - Schneider Electric, ABB, Areva.
The development of 110-220 kV vacuum circuit breakers has been repeatedly discussed in reports and materials International Symposium on discharge and electrical insulation in vacuum (ISDEIV - International Symposium on Discharges and Electrical Insulation in Vacuum), which undoubtedly indicates the interest of developers and manufacturers of vacuum switching equipment in high voltage classes. Based on the materials of the symposium, we can talk about the following trends in the research and development of vacuum switching technology for high voltage classes:
Reducing the dimensions of vacuum circuit breakers is possible by optimizing the electrical strength of the VDC contact system and increasing the density of switched currents per unit contact area;
based latest results research into electrical strength in a vacuum; creation of designs for switches and VDCs for large voltage classes (design of single-break chambers for high voltages) and constructive solutions on multi-break chambers and multi-chamber switches;
solution to the problem of ensuring the restoration of electrical strength in the VDC after the arc is extinguished. Erosion processes and thermal heating of contacts significantly limit the speed and level of restoration of the electrical strength of the VDC. The current level of knowledge has made it possible to develop VDC for voltages up to 145 kV, which makes it possible to create single- and double-break vacuum circuit breakers 110 kV and double-break vacuum circuit breakers 220 kV;
Work continues to optimize contact materials and VDC design.
Vacuum arc chutes
The history of the development of VDCs for high voltage classes goes back many years in the world. Countries such as Russia, Germany, France, Great Britain, the USA, and China are actively conducting research on the creation of vacuum circuit breakers for high voltages and large switched currents. Siemens has developed vacuum generator circuit breakers with rated breaking currents of up to 80 kA. The problem of passing large rated currents in these devices is solved by parallel connection several vacuum arc chutes at each pole.
The most significant results were obtained in Japan, due to the growing energy consumption in this country, as well as aspects national security. As a result, the latest achievements: in the domestic market of Japan, VDCs for voltages of 126 kV, 145 kV appeared (Fig. 1, length 700 mm, diameter 200 mm, Cu-Cr contacts, with axial magnetic field) and even a porcelain double VDC for a voltage of 168 kV.
In Japan's power systems, for several years, double- and single-break vacuum circuit breakers based on VDC have been successfully used for voltages of 126-168 kV, rated currents up to 2000 A and rated breaking current up to 40 kA. In Fig. 2, 3 show examples of such vacuum switches.
Currently, in Japan, one of the main directions has become the use of VDC not only in the medium voltage range, but also in high-voltage switchgear of substations, which is due to such unique properties VDK, as high breaking capacity, durability, safety and efficiency.
There is also a trend in Japan to combine high-speed VDCs with superconductivity technology. Active research is being conducted on the problem of using superconducting materials in VDC structures. It turned out that such an innovation would be suitable for current limiting devices in high-power energy systems. Whole line laboratory research is carried out to establish the principles of operation of such devices in which the current limiter would be connected to an element with high-temperature superconductivity in parallel with the circuit of a powerful energy source. When the superconducting element begins to extinguish the current as a result of an overload, the VDC easily opens the circuit and directs all the current to the current limiter, which leads to the safety of the superconducting material and a reduction in its size.
Russia, in terms of the development and implementation of vacuum circuit breakers for voltages of 110-220 kV, keeps pace with its Japanese colleagues and is significantly ahead of European scientists and engineers. In 2008, FSUE VEI (Moscow) successfully tested prototypes of Russian VDK types KDV-60-31.5/2000 and KDV-126-40/3150, designed for voltages of 60 and 126 kV, respectively. alternating current frequency 50 Hz, intended for completing double-break and single-break vacuum circuit breakers 110-220 kV.
The KDVA-60-31.5/2000 camera is shown in Fig. 4., designed for a rated voltage of 60 kV, 50 Hz and is intended for a double-break vacuum circuit breaker for a voltage of 110 kV (highest operating voltage 126 kV), rated breaking current 31.5 kA, rated current 2000 A.
Rice. 4. Vacuum arc suppression chamber type KDVA-60-31.5/2000
The next generation camera - KDV-126-40/3150, shown in Fig. 5, is intended to be used to complete a single-break vacuum circuit breaker for a voltage of 110 kV, 50 Hz, a rated current of 3150 A, and a rated breaking current of 40 kA. In addition, in the future, a double-break system can be created on its basis vacuum circuit breaker for voltage 220 kV.
Rice. 5. Vacuum arc suppression chamber type KDV-126-40/3150
The first Russian vacuum circuit breaker for a voltage of 110 kV began to be developed in 2007 in Saratov at JSC NPP Kontakt. Technical requirements for the switching device were approved by FGC UES. In 2009, the company manufactured a prototype of a double-break vacuum switch based on KDVA-60-31.5/2000 chambers with a spring-magnetic drive (Fig. 6).
Fig. 6. Double-break vacuum switch type VBP-110III-31.5/2000 UHL 1
In the same year, full-scale testing of the switch began in the laboratories of the plant itself, FSUE VEI and Research Center VVA. At the same time, there was a dialogue with operating specialists, recommendations appeared, and changes were made to the design of the circuit breaker.
In 2010, based on positive test results, a certificate was received for the first Russian 110 kV vacuum circuit breaker and serial production of VBP-110 kV began.
The short period of time spent by NPP Kontakt OJSC on the development and production of VBP-110 kV is explained by the use of a circuit breaker in the design technical solutions and units mass-produced for vacuum circuit breakers of the VBPS-35kV series. These include a spring-magnetic drive (for the VBP-110 kV the drive was strengthened, the settings were changed), switch poles, mechanical units of rods and shafts. The parameters of the VBP-110 switch are given in table. 3.
Table 3 Main parameters of the switch VBP-110III-31.5/2000 UHL 1
| Rated voltage, kV | |
Rated current, A |
|
Rated breaking current, kA |
|
Electrodynamic resistance current, kA |
|
Thermal resistance current, kA |
|
Own time inclusions, ms |
|
Own shutdown time, ms |
|
Wire type |
spring |
Resource for mechanical resistance |
|
Resource for switching resistance |
|
Resource for switching resistance at rated shutdown current |
25 VO cycles |
By the end of 2010, in agreement with IDGC Holding, the first serial VBP-110 kV will be installed at substations of IDGC Holding branches - IDGC of Center and Volga Region, North-West, Siberia, Volga, North Caucasus.
In 2009-2010 Based on the KDV-126-40/3150 chamber, a single-break vacuum circuit breaker for voltage 110 kV, 50 Hz, rated current 3150 A and rated shutdown current 40 kA was developed. The switch has a classic layout for column switches. Appearance switch type VBP-110III-40/3150 UHL1 is shown in Fig. 7. Serial production of such a switch is planned to begin in 2011. As in the double-break switch, the VBP-110III-40/3150 UHL1 is intended to use previously developed and tested under operating conditions (on 35 kV class switches and on the first VBP-110 kV ) units and design solutions.
The advantages of switches VBP-110III-31, 5/2000 and 40/3150 UHL1 are:
environmental Safety;
possibility of manual switching on and off;
large switching and mechanical resource;
stable work in complex climatic conditions;
a free release mechanism for the drive, which allows you to turn off the switch at any time, regardless of the position of the mechanism;
fire and explosion safety;
small dimensions and weight.
For the distribution power grid complex of Russia, when choosing SF6 or vacuum circuit breakers, repair and operating costs for the entire standard period of operation may be of decisive importance. Calculations have shown that the repair and maintenance costs of SF6 circuit breakers are significantly higher (up to 100-300 times) than those of vacuum circuit breakers.
The unique developments of Russian scientists and engineers of double-break and single-break vacuum circuit breakers will not only create a real alternative to SF6 circuit breakers, but also be the basis of a program for replacing oil circuit breakers and separator-short-circuit pairs (OD-short-circuit) 110 kV, and in the future 220 kV. In addition, the use innovative types high voltage vacuum circuit breakers will allow the development and improvement of 110-220 kV switchgear to create new block-modular circuit solutions that provide:
environmental safety of equipment;
high degree reliability and safety of operation;
increasing the level of factory readiness and enlarging delivery blocks;
maximum reduction in weight and dimensions;
reducing operating costs and ensuring ease of maintenance and repair;
development of unattended remotely controlled digital substations;
creation of closed switchgears switchgear and indoor switchgear-110 kV with air and combined insulation, without the use of SF6 gas.
The use of 110-220 kV vacuum circuit breakers is especially important when using maintenance-free, oil- and SF6-free current and voltage transformers in a complete substation. Such transformers - with optical sensors - are widely used in North America and Canada, where the issue of environmental safety of equipment comes first. Optical current and voltage transformers are easily integrated into digital substation systems, because have digital signals at the output.
In the following articles we will look at the ideology of building modern block substations of 110 and 220 kV using the most modern electrical devices and design solutions, including the 110-220 kV vacuum circuit breakers and optical current and voltage transformers described in this article.
General information
Vacuum switches of types VBU-35 and VBU-110 with an electromagnetic drive are designed to perform switching operations in normal and emergency operating modes of transformers of arc steel-smelting furnaces for rated voltages of 35 and 110 kV with a current frequency of 50 Hz.
Symbol structure
VBU-X-5/X U3:
VB - vacuum switch;
U - Ural;
X - rated voltage, kV (35, 110);
5 - rated shutdown current, kA;
X - rated current, A (1000, 1250, 1600);
U3 - climatic version and placement category according to GOST
15150-69 and GOST 15543.1-89.
terms of Use
Altitude above sea level no more than 1000 m.
The lower temperature value for VBU-35 is minus 10, for VBU-110 minus 5°C.
The upper operating and effective value of the ambient air temperature is 30°C.
Environment non-explosive containing corrosive agents in a type II atmosphere according to GOST 15150-69.
Safety requirements according to GOST 12.2.007.3-75.
Switches for domestic and export deliveries of the VBU-35 type comply with the requirements of TU 16-89 IBKZh.674153.013 TU, and VBU-110 comply with the requirements of TU 16-89 IBKZh.674153.011 TU. TU 16-89 IBKZh.674153.013 TU; TU 16-89 IBKZh.674153.011 TU
Specifications
The main technical data of the switches are given in the table.
| Parameter name | Parameter value for switch types | |
| VBU-35 | VBU-110 | |
| Rated voltage, kV | 35 | 110 |
| Highest operating voltage, kV | 40,5 | 126 |
| Rated current, A | 1250; 1600 | 1000 |
| Rated breaking current, kA | 5 | |
| Through short-circuit current, kA: | 80 31,5 |
|
| Thermal resistance current, kA: | 20 31,5 |
|
| Own time of switching off, s | 0,06 | 0,1 |
| Full time switch off, s | 0,085 | 0,12 |
| Own switching time of the switch, s | 0,4 | |
| Rated DC voltage of electromagnets | 220 | |
| Operating voltage range of control electromagnets, % of nominal value: | ||
| disconnecting electromagnet | 65–120 | 70–120 |
| Switch weight, kg, no more | 400 | 350 |
| Resource for switching resistance, VO cycles: | 20 000 150 |
|
| Resource for mechanical resistance, VO cycles | 100 000 | 40 000 |
| Service life before write-off, years | 25 | |
The warranty period is 2 years from the date of commissioning of the switches.
The operating principle of the switch is based on the phenomenon of extinguishing an electric arc in a vacuum, which occurs when the contacts of vacuum arc-extinguishing chambers are opened. Arc combustion in a vacuum is supported by metal vapors entering the intercontact gap as they evaporate from the surface of the contacts.
At the moment the current passes through zero, the electrical strength of the intercontact gap quickly increases, ensuring reliable disconnection of the circuit.
The VBU-35 switch (Fig. 1) is a switching device, the three poles of which are installed on one frame and controlled by an electromagnetic drive. Each pole contains an arc extinguishing module, a support insulator, insulating rods that transmit movement from the drive to the moving contacts of the chambers, and a cover. To lift the switch, there are eye bolts on the frame and covers. There is also an indicator of the on and off position on the frame.
General view, overall and installation dimensions of the VBU-35 circuit breaker:
1 - frame;
2 - support insulator;
3 - traction;
4 - arc extinguishing module;
5 - pole;
6 - cover;
7 - eye bolts;
8 - position indicator;
9 - drive
The VBU-110 switch (Fig. 2) is a switching device consisting of three separate poles, each of which is controlled by an electromagnetic drive. Each pole contains four series-connected arc extinguishing modules mounted on a support insulator, insulating fiberglass rods, through which the movement from the drive is transmitted to the moving contacts of the vacuum arc extinguishing chambers, shunt capacitors, and a top cover with a device for lifting the pole.
General view, overall and installation dimensions of the VBU-110 switch:
1 - drive;
2 - support insulator;
3 - traction;
4 - arc extinguishing module;
5 - pole;
6 - cover;
7 - capacitors
The arc extinguishing module (Fig. 3) contains a vacuum arc extinguishing chamber of the KDV-35-20/1250 UHL2 type, enclosed in an insulating housing, a control unit for the moving contact of the chamber, and flanges for mounting the module.
General view of the arc extinguishing module:
1, 6 - flanges;
2 - body;
3 - vacuum arc extinguishing chamber;
4 - moving contact;
5 - control unit ^ The delivery set includes: switch, spare parts kit, operational documentation.
Various gas mixtures are often used to extinguish an electric arc. 110 kV and 220 kV SF6 circuit breakers operate precisely on this principle and can be used for operation 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 ones 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.
Photo – high voltage equipmentThey are:
- Core (HPL 245B1, MF 24 Schneider Electric);
- 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.
Photo – design drawing 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:
- Auto-compression or air;
- Rotating;
- Longitudinal blast;
- 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:
Photo - work diagram 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 and off electrical energy and hold the arc (if necessary) at a certain level. Drives are:
- Spring;
- Spring-hydraulic.
The spring type has a very simple principle of operation and a high level of 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.
Photo – VGU-35 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:
- Versatility. These switches are used to control networks with any voltage;
- 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;
- Suitable for use in conditions of fire hazard and vibration;
- Durability. Contacts in contact with SF6 gas practically do not wear out, gas mixtures do not need to be replaced, and the outer shell has high protection rates;
- 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:
- High price due to the complexity of production and the high cost of the SF6 gas mixture;
- Installation is carried out only on a foundation or a special electrical panel, and this requires special instructions and experience;
- Switches do not work in low temperatures;
- When necessary maintenance, special equipment must be used.
Photo – industrial gas-insulated load switch Video: features of SF6 switches
Specifications
Let's consider the technical characteristics of switches from different manufacturers and types of operation.
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.