What are the working principles and abnormal handling methods of SF6 circuit breaker?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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What are the working principles and abnormal handling methods of SF6 circuit breaker?

发布时间：2019-02-28 来源：ydlcb 浏览次数：33次

SF6 circuit breaker is one of the main electrical equipment in substation. It can not only cut off and connect high-voltage lines and various no-load and load currents during the normal operation of the system, but also automatically, quickly and reliably cut off various overload currents and short-circuit currents through the role of relay protection devices to prevent the occurrence and expansion of the accident range.

With the rapid development of the national economy, the demand for electricity in all walks of life has also increased sharply, the load of the power system is growing day by day, and the reliability of power supply is gradually improved. The switch of the substation is gradually replaced by the oil switch into the new SF6 circuit breaker. Since SF6 circuit breakers are widely used in power systems, the following talks about the working principle and abnormal handling of SF6 circuit breakers.

SF6 circuit breaker is a new type switch which uses SF6 gas as insulation medium and arc extinguishing medium. SF6 gas is colorless, tasteless, non-toxic, non-flammable inert gas, with high electrical strength and good arc extinguishing performance, dielectric strength far exceeds the traditional insulating gas. Therefore, it is used in electrical equipment, which can reduce the size of equipment, eliminate fires, and improve the reliability and safety of the power system.

SF6 circuit breaker is composed of three parts: body structure (three-box structure), operating mechanism and arc extinguishing device. It has the advantages of simple structure, small size, light weight, large breaking capacity, rapid arc extinguishing, many allowable breaking times, long maintenance cycle, etc., and it is the direction of popularization and application of power system in the future.

The SF6 circuit breaker is often filled with 3 to 5 atmosphere-pressure SF6 gas as the internal insulation of the circuit breaker, in the process of breaking the circuit breaker, the piston is driven by the moving contact to form the air flow used to blow off the arc.

The basic structure of the SF6 circuit breaker interrupter is connected by the moving contact, the insulating nozzle and the pressure piston, which is driven by the operating mechanism through the insulating connecting rod. The fixed contact is made of tube shape, the moving contact is a socket type, and the end of the moving and fixed contact are inlaid with copper tungsten alloy. The insulated nozzle is made of high temperature and corrosion resistant polytetrafluoroethylene.

When the switch is opened, the moving contact and the piston move to the right together. The arc is generated after the moving and fixed contacts are separated. When the piston moves rapidly to the right, the gas on the right side is compressed, and the air flow is generated through the nozzle to blow the arc and extinguish the arc. Thereafter, the gas in the extinguishing chamber is discharged into the switch body through the inner hole of the fixed contact and the cooler.

When the switch is closed, the operating mechanism drives the moving contact, nozzle and piston to move to the left, so that the fixed contact is inserted into the moving contact seat, so that the moving contact and the fixed contact have good electrical contact to achieve the purpose of closing.

SF6 circuit breaker secondary wiring in wiring debugging should pay attention to the following points:

① The switching electrical chain is realized by converting FK, and there is a reliable switching mechanical interlock inside the mechanism. When manually opening the brake, if you cannot pull the opening ring (opening lock), do not pull hard; If you want to close and can not pull the closing ring, do not pull hard. At this time, you should observe the position of the pointer, and then perform the parting and closing operation.

② Electric contact vacuum pressure gauge lead is in the lower part of the cover, from the normal open contact of the pressure gauge. When leaving the factory, the lower limit pointer has been adjusted to 200KPa (according to 200KPa, -10℃), when the SF6 pressure is reduced to at least 200KPa, the contact is closed and the relay protection circuit is connected. The user can adjust the lower limit according to the operation requirements, but not lower than 0.2Mpa.

③ The outside of the box is the closing pull ring, and the inside of the box is the opening pull ring. Do not pull wrong when manually operating.

④ Stored energy motor must use AC power supply.

SF6 circuit breakers use SF6 density relays to monitor changes in gas pressure. When the SF6 gas pressure drops to the first alarm value, the density relay operates and gives a signal of the recharge gas pressure. When the SF6 gas pressure drops to the second alarm value, the density relay operates, reports the signal of the locking pressure, and disconnects the jump circuit of the switch to realize the opening and closing of the lock.

Pure SF6 gas is colorless, odorless, non-toxic, and chemically stable. The SF6 gas in the switch, after arc decomposition, will produce many toxic, corrosive gases and solid decomposition, which not only affects the performance of the equipment, but also endangers the safety of the operation and maintenance personnel. Therefore, we must pay attention to protective measures when dealing with air leakage failures. SF6 circuit breaker in the operation of SF6 gas leakage, such as a strong irritating smell, in this case, the operation or maintenance personnel must wear protective equipment. Pay special attention to the work site no smoking. If tears, runny nose, hot sensation in throat, hoarseness and dizziness, chest tightness, nausea, neck discomfort and other poisoning symptoms occur during work, you should leave the scene quickly and take a rest in fresh air. If necessary, go to the hospital for examination and treatment.

When the density relay operates and reports the signal of gas pressure, check the indication of the pressure gauge in time to check whether the signal is correct and whether the switch is leaking; In operation, when the pressure value of the two adjacent records at the same temperature is different (0.1 ~ 0.3 atmospheres), the switch may leak, and the leak detector can be checked if conditions are available. During the inspection, if you feel a pungent smell or self-discomfort, you should leave the site immediately 10 meters away. At the same time, you must wear protective gear to approach the equipment. If there is no air leakage in the inspection, it is a normal drop in air pressure during long-term operation, and it should be reported to the leaders of the work area in time, and the professional maintenance personnel should carry out air replenishment on the line. After replenishing the air, continue to monitor the air pressure. If there is gas leakage phenomenon, it should be reported to the dispatch in time to transfer the load or change the operation mode, and the faulty switch will be cut off.

When the density relay operates and reports the signal of the locking pressure, it indicates that the gas pressure drops more, indicating that there is a serious gas leakage phenomenon. In this case, the switch trip circuit has been locked. Under normal circumstances, before the blocking pressure signal is reported, the gas supply pressure signal should be reported first, and if there is leakage phenomenon after inspection, measures should be taken quickly: (1) First unplug the operating safety of the switch to prevent the switch from extinguishing the arc when the switch trip is caused by the unreliable locking, and then report the scheduling; ② Use the special locking tool as soon as possible to lock the transmission mechanism of the switch. After that, the operation insurance can be installed again to prevent the failure of the switch protection starting circuit can still work when there is a fault on the road; ③ Transfer the load immediately, use the method of backward running mode, the fault switch power off processing, and supplement. If the reverse operation mode is not possible, the load should be transferred immediately. The switch can only be disconnected when it is not energized (110kv and above switches), and then the power is cut off for maintenance.

In addition, if there is a large amount of SF6 gas leakage, the operator should clean the used protective appliances after checking, operating and arranging safety measures near the equipment, and the personnel should also wash their hands or operate in time. A guardian must be present during the above work to ensure safety.