PreventHigh-voltage shunt capacitor deviceTechnical measures of the accident.
1.Circuit breaker for shunt capacitor installation.
Strengthen the selection and management of circuit breakers for capacitor devices. The type test items of the selected circuit breaker are complete, and the type test items must include the switch capacitor bank test.
The new device prohibits the use of vacuum circuit breaker switching capacitor banks with a circuit breaker serial number less than 12. If the circuit breaker used in the operating capacitor bank is a vacuum circuit breaker with a serial number of less than 12, it should be actively replaced to avoid the failure of the capacitor bank due to the high heavy breakdown rate of the circuit breaker.
The vacuum circuit breaker used for capacitor banks should be aged to reduce the heavy breakdown rate of the vacuum circuit breaker and improve the operational reliability of the capacitor bank. The circuit breaker manufacturer can be required to carry out the vacuum circuit breaker aging test, or the power department can use a single-phase test circuit to carry out the aging test. The specific method is to switch the vacuum circuit breaker with capacitive load for 30 times, and no heavy breakdown is qualified. If there is a heavy breakdown in the middle, the next 30 times without heavy breakdown from that time are qualified, otherwise it shall not be used for capacitor switching. If possible, 35 capacitor bank switching experiments can also be carried out in the field.
Regularly test the closing and opening bounce of the vacuum circuit breaker. 40.The closing and bounce time of vacuum circuit breaker below 5kv should not be greater than 2ms, 40The closing bounce time of vacuum circuit breakers of 5kv and above should not be greater than 3ms;The opening bounce should be less than 20% of the break spacing. Once the circuit breaker is found to be too large, it should be adjusted in time.
Regularly test the vacuum level of the vacuum circuit breaker or conduct a withstand voltage test. When the vacuum level is damaged, it should be replaced in time.
It is forbidden to use the wiring method of the circuit breaker installed on the neutral point side to avoid the occurrence of expansion accidents caused by the failure of the circuit breaker although the circuit breaker has been disconnected under fault conditions.
When a circuit breaker registered with a higher voltage is used for a capacitor device with a lower voltage level, a switching test of the capacitor device must be performed at the operating voltage.
2.High-voltage shunt capacitor banks.
The explosion-resistant energy of a single capacitor is not less than 15kws。
The internal fuse structure is preferentially used in the selection of capacitor units, and the protection of a single capacitor should avoid the use of external fuse and internal fuse protection at the same time.
The high-voltage shunt capacitor bank prohibits the use of triangle wiring, compared with the star wiring, in the case of fault, the capacitor bank of the delta wiring directly bears the line voltage, and when any phase capacitor is broken down, it will form a short circuit between phases, resulting in a large fault current, which is easy to cause the capacitor fuel tank to burst. In the case of star wiring, when one phase of the capacitor bank is broken down, the fault current generated will not be too large due to the impedance limitation of the two non-fault phases, so the high-voltage shunt capacitor bank adopts the star wiring method.
The connection between the capacitor terminals or between the terminals and the busbar shall be a soft copper wire with an insulating sheath. Avoid the leakage and oil failure of the capacitor due to the force of the casing due to the thermal expansion and cold contraction of the connecting wire.
The capacitor joints should be tightened one by one with a torque wrench to ensure that the connector and the connecting wire have sufficient contact area and that the contact is intact.
During the routine power failure test of the capacitor, the capacitance of a single capacitor should be measured one by one, and the measurement method of not disassembling the connecting wire should be used to avoid the failure of oil leakage due to the force of the casing due to the disassembly and installation of the connecting wire.
For internal fuse capacitors, when the capacitance is reduced by more than 3% of the standard capacitance of the nameplate, the operation should be withdrawn to avoid the development of an extended fault due to the faulty operation of the capacitor. For capacitors without internal fuses, once the capacitance increases by more than one serial breakdown, the operation should be withdrawn immediately to avoid the development of extended faults due to faulty operation of the capacitors.
3.Outer fuse.
The poor breaking performance of the external fuse is one of the important reasons for the damage of the capacitor unit and even the bursting of the shell. The fuse used in the protection of the capacitor unit belongs to the jet fuse, and its working principle mainly relies on the energy of the fuse current itself to generate gas to extinguish the arc and break the fault current, which is used as a main protection for internal faults in some capacitor devices. If the external fuse can successfully open the faulty capacitor, the capacitor will not be damaged. In the long-term operation of the external fuse, the dampness and expansion of the arc extinguisher will block the pipeline, which will cause failure due to poor breaking performance. In addition, improper installation or spring installation angle is not in place, and the tail wire cannot be quickly popped out in time after the fuse is blown will also affect the arc breaking.
Therefore, it is necessary to strengthen the management of external fuses, and replace external fuses that have been installed for more than 5 years in time.
4.Reactor.
When the series reactor for shunt capacitor is used to suppress harmonics, the reactance rate should be configured according to the test value of the background harmonic content at the connection of the shunt capacitor device to the power grid, so as to avoid excessive amplification of resonance and harmonics.
35kV and think about indoor series reactors should choose dry core or oil-immersed reactors. Dry air-core reactors should be preferred for outdoor series reactors, and oil-immersed reactors should be selected when the outdoor on-site installation environment is limited and dry air-core reactors cannot be used.
35kV and above dry hollow series reactor should not be used in stacked structure, 10kV dry hollow series reactor should take effective measures to prevent the reactor single-phase accident from developing into phase.
accidents. The dry-type air-core series reactor should be installed at the front end of the capacitor bank, and its dynamic and thermal stability should be checked to meet the requirements of the short-circuit current of the system.
For dry hollow reactors used outdoors, the outer surface of the encapsulation should be protected from fouling and ultraviolet rays. The exposed metal parts of the reactor should have a good corrosion-resistant coating.
The grounding wire below the dry-type aircore reactor should not constitute a closed loop, and when the fence is made of metal materials, the metal fence is forbidden to be connected into a closed loop, and there should be an obvious isolation and disconnection section, and a closed loop should not be formed through the grounding wire.
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Zhejiang Yishuo Electric Co., Ltd. is a high-tech company specializing in R&D, design, production, sales and service of low-voltage power capacitors, smart capacitors, reactors, reactive power compensation controllers, and reactive power compensation devices.
The company adheres to the tenet of "taking science and technology as the driving force and seeking development by quality", and is committed to building a leading brand of smart grid professional services. The company adheres to the tenet of "taking science and technology as the driving force and seeking development by quality", and is committed to building a leading brand of smart grid professional services.
The company has a high-level R&D management team, integrating R&D, production, sales and service, focusing on intelligent reactive power compensation, harmonic control, energy saving and power quality management and other high-tech industries of power automation.
Over the years, we have adhered to the mission of "making products intelligent and services intimate". In line with a high sense of responsibility to the society and users, Yishuo Electric adheres to the road of specialization, continues to innovate and transcend, and strives to make greater contributions to China's smart grid power automation