In the high-voltage switchgear, the contact heating case has appeared in the past two years, and the contact heating has occurred. For example, the Dahua 10KV station incoming line cabinet hand truck plum blossom contact burned, the ammonium phosphate two feedback line cabinet contact burned, The 35KV station also found four duck-billed contact heating phenomena. These problems have been dealt with despite the discovery of opportunities in time. However, this kind of fever is a serious potential hidden danger to the safe operation of the power supply system. Therefore, these problems have been analyzed and the corresponding preventive measures have been formulated. Two. Reasons for the heating of the contacts and preventive measures After the faulty contacts and the corresponding circuit breakers are observed afterwards, it is found that there are some common problems with these faulty contacts, which are intertwined to cause problems in the contacts. There are problems in design selection, acceptance, environmental corrosion, equipment expansion, and infrastructure construction. 1. There are omissions in the bidding of technical documents or acceptance at the design stage. In the KYN and JYN switchgears configured by Chuxing Company, the rated current of the circuit breaker is 1250A, which is the main type, and the contacts with problems in this specification are also the most. Observation of the faulty contacts revealed that the configuration of the contacts was inconsistent with the rated current of the circuit breaker, and no clear requirements were found for the previous bidding technical documents. For example, the rated current of the ammonium phosphate two-circuit breaker of 110KV station is 1250A, but the configuration of the plum blossom contact is 630A. The actual running current of this section fluctuates around 700A with the expansion of production scale. For the plum blossom contacts, the 630A specification contacts were found by reference, and the number of contact blades was 24, the switch cabinet contacts were 24, and the 1250A was 30. Obviously, the rated current configuration of the circuit isolation contact is inconsistent with the circuit breaker. At 6KV, 10KV, 35KV stations, 630A or 1000A duckbill contacts or plum blossom contacts were found to be used on the 1250A circuit breaker. From the inspection status of each switch station, inconsistent conditions are common. After replacing the contact arm and the contact of the ammonium phosphate twice (for the contact of the ammonium phosphate secondary circuit breaker) with the 30-piece 1250A contact, the contact arm temperature (the contact cannot be measured) drops from 87 ° C to 48 ° C. After replacing the 35KV Chuda line duckbill contact with 1000A to 32 pieces of 1600A, the temperature dropped from 84 °C to 34 °C.

2. The impact of operating environment factors. The corrosion of various gases is also the cause of the gradual oxidation contact resistance of the contacts. The expansion of the production equipment leads to the increase of the line load and the impact of the short-circuit current during the fault. These are changes in the operating environment, and the contacts themselves are small. In the case, the defect is gradually evolved into a failure. 3. Poor contact of the contacts caused by improper installation after maintenance. When entering the working position after the hand truck is maintained, the position of the contact is not entered into the handcart room for detailed inspection, so that the duckbill contact is inserted too deep or too shallow, so that the moving contact is in contact with the pressure spring or the contact surface is too small. 4. The contact of the handrails caused by the infrastructure construction of the switch station is not good. For the hand-operated switchgear, the flatness of the foundation is required to be high, and the unevenness of the foundation causes the contact surface of the static and dynamic contacts to be skewed. It is necessary to push the handcart into the working position vigorously, and the impact of the contact surface is damaged or the contact pressure is uneven. In view of some of the contact heating phenomena that Chuxing Company has, there are the following experiences and lessons. 1. In the technical requirements for the new design of the switchgear in the future, the switchgear that requires the isolated contact and the contactor’s rated current to be consistent with the rated current of the circuit breaker should be clearly specified. It should be used for the incoming cabinet, the communication cabinet, and its contacts. Consistent with or greater than the rated current of the circuit breaker, it is especially important for the structure of the duckbill contact. This is controlled during the manufacturing and acceptance phases to prevent suppliers from lowering product standards and causing difficulties in later operation and maintenance. 2. For the incoming line cabinets and feeders that have been formed with heavy loads, check the rated current of the contacts actually used, and gradually replace the mismatched ones. For the 35KV system, the duckbill contacts are fully enlarged by 1-2 levels. Such as: 1250A zoomed to 1600A or 2000A. The static and dynamic contacts are purchased and replaced synchronously. The manufacturer is carefully selected when purchasing the contacts, and the surface of the contacts is to be silver-plated. 3. In order to reduce the damage of the air to the contact, in addition to the hole sealing, the industrial Vaseline which has been deteriorated should be wiped off during the overhaul, and the thin layer of Vaseline should be reapplied. The boring tool should not be used for the contact inspection, and the oxide layer can only be used. 0# Abrasive cloth, sandpaper or rag should be wiped gently to minimize damage to the surface coating. 4. Check the position of the moving and contact contact as much as possible before replacing the contact. Make sure to mark and measure the installation position or size of the new contact. In this way, the contacts are installed in place at the same time, and there is basically no need to adjust. In order to ensure the proper installation size, the newly purchased static and dynamic contact copper bars are not drilled, and the dimensions are processed after verification on the spot to avoid the new contact aperture and distance deviation. Unable to install. 5. Conditional installation of on-line temperature measuring device. If the temperature of one phase contact on the outlet side of Chu nitrogen line is changed by online temperature measurement, there is a defect here, and it should be treated during maintenance. If there is no online temperature measurement, regular temperature measurement work will be carried out. When the load is suddenly changed, the inspection work should be carried out immediately, and some defects can be found. 6. Master the judgment standard of the upper limit value of the contact temperature and temperature rise of the high-voltage switchgear, and provide the basis for the hidden danger judgment: in the case of the air temperature of 40 °C, the bare copper contact in the air: 75 ° C, temperature rise 35K, plating After silver: 105 ° C,