The LW13-550 tank SF 6 circuit breaker produced by a factory is a three-pole split-type and double-fault structure with a pneumatic operating mechanism for single-pole operation or three-pole linkage by electrical connection. The utility model has the advantages of simple structure, small volume, strong earthquake resistance, good arc extinguishing performance, and can be shut off for 20 times without full capacity, and is a circuit breaker with superior performance. However, since the circuit breaker used by a power supply company has been in operation since 1996, there have been many cases where the air compressor does not start after the reclosing lock, which causes the emergency shutdown of the circuit breaker to repair and repair, which poses a serious safety hazard to the grid operation. After analysis, it was found that this was caused by the unreasonable structure of the original air pressure pipeline, which made it difficult to accurately verify the air pressure switch density relay. After the modification of the high pressure pipeline of the air compressor, the accuracy and reliability of the air pressure switch are improved, and no problems have occurred since the operation.
2 Problems The LW13-550 tank SF 6 circuit breaker has an air operating mechanism and a gas storage tank in each phase. The three-phase gas storage tanks are connected by a gas pipe, and the three phases share a compressed air monitoring system. The air compressor and the compressed air monitoring system including the air pressure gauge and the air pressure switch are installed in the B-phase mechanism box. The air pressure switch 63AG is used to control the start of the air compressor. When the compressed air pressure is lower than 1.45 MPa, the contact is closed, and when the pressure is higher than 1.55 MPa, the contact is opened.
63AL is used for the operation and blocking control of the circuit breaker. When the pressure is lower than 1.20MPa, the contact is closed. When the pressure is higher than 1.30MPa, the contact is opened. The 63AR is used for the circuit breaker reclosing lockout control, and the reclosing lock signal is issued when the compressed air pressure is lower than 1.43 MPa. After analysis, it was found that the failure of the air compressor to start in time was mainly caused by the inaccuracy of the air pressure switch density relay verification.
According to the manufacturer's requirements, the circuit breaker needs to be routinely repaired every 6 years, and the setting value of the air switch pressure should be checked during maintenance. Check the starting and stopping pressure of the air compressor according to the equipment manual. The method of opening the venting valve to open the venting valve after starting the compressor; checking the opening and closing of the circuit breaker, reclosing the lock and releasing the air pressure should be cut off. Power on the machine, open the vent valve exhaust, and then press again after the signal appears.
However, in fact, due to the large volume of the gas storage tank, when the pressure switch is verified by this method, the process of one-time exhaust pressure takes nearly three hours. If the setting value of the pressure switch is adjusted, it is necessary to arrange multiple times. It takes a long time to get angry and suppress. In addition, the long-time pressure has a great impact on the life of the air compressor, and it is not uncommon for the air compressor to fail due to repeated pressure cracking during the overhaul process. Therefore, it is worth more than 10,000 yuan to replace damaged equipment parts every year. The most important thing is that because the air pressure gauge is directly connected to the gas storage tank, the portable inspection instrument cannot check the air pressure gauge because the pressing speed is too slow. If the air pressure gauge is inaccurate for some reason, then the setting value according to the air pressure gauge verification is also wrong, which poses a great threat to the safe operation of the circuit breaker.
3Technology Improvement The power supply company's test center analyzed and studied this phenomenon and thought that this problem could be solved by adding a normally open valve to the high-pressure pipeline of the B-phase mechanism of the circuit breaker, and the improved compressed air monitoring system.
After installing the normally open valve, if the air pressure gauge needs to be calibrated, first close the normally open valve to disconnect the pressure switch from the gas storage tank, and then open the normally open valve after the calibration is completed. In this way, it is not necessary to discharge the air in the gas storage tank during the calibration, and the air compressor is not required to replenish the pressure, which greatly shortens the inspection time and prolongs the service life of the air compressor.
When using the portable Fluke calibrator, the calibration value of the air pressure switch can be accurately verified. The calibration takes only about 15 minutes, which saves the inspection time, and the calibration accuracy is higher than the air pressure gauge. The value is more accurate. Comparing the value of the calibrator with the indicated value of the air pressure gauge, the accuracy of the air pressure gauge can also be checked, and the unqualified air pressure gauge can be found in time. In addition, if it is necessary to replace the air pressure gauge, it is no longer necessary to drain the air in the air tank, as long as the normally open valve is closed.
Using this scheme, the air compressor high-pressure pipeline was modified for the two circuit breakers of Feixichang 5012 and 5013, and a normally open valve was installed on the high-pressure pipeline between the switch B-phase split closing control valve and the air pressure switch. . Practice has proved that the transformation plan is simple, economical and feasible. As long as the qualified accessories are used, it will not cause other adverse effects on the safe operation of the circuit breaker.
4 After the transformation according to the above method, the accuracy of the pressure switch calibration is improved, the calibration time is reduced from at least 3h to 15min, which saves a lot of maintenance time, improves the accuracy and reliability of the pressure switch, and removes the power grid. A big hidden danger of running. After the transformation, the circuit breaker was tracked for four months, the equipment was in good condition, the air pressure switch setting value was accurate, and the accuracy rate was 100%. There was no accident during the period due to a pressure contact failure that caused an emergency power outage.
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