1.1 The pre-test cycle for newly installed electrical equipment (such as transformers, instrument transformers, circuit breakers, coupling capacitors, high-voltage bushings, and 6-10kV busbars, disconnecting switches, etc.) is once a year within two years after commissioning. After two years, the pre-test cycle can be carried out according to the following regulations (the circuit breakers on each side of the main transformer, current transformers, etc. follow the main transformer cycle).
1.2 For 500kV electrical equipment, it shall be carried out according to the requirements of relevant documents of State Grid Corporation of China.
1.3 For 220kV electrical equipment, each equipment maintenance unit can conduct a pre-test once every three years according to the equipment health condition.
1.4 For 110kV electrical equipment, each equipment maintenance unit can conduct a pre-test once every three years according to the equipment health condition.
1.5 For 6-35kV electrical equipment, once every three years.
1.6 Surge arresters are generally tested once a year (the surge arrester at the neutral point of the main transformer can follow the main transformer cycle). For surge arresters produced by Zhengzhou Shunda, due to frequent damage found, it is necessary to insist on testing once a year.
1.7 When the pre-test cycle of the protected equipment is longer than that of the surge arrester, the surge arrester can be tested online instead of the pre-test during this period. For surge arresters equipped with leakage current detection discharge counters, under reliable leakage current detection records, comprehensive judgment can be made through detection data (historical data comparison, comparison among three phases) to replace the pre-test. The online test cycle for surge arresters is once every six months (can be extended by up to three months).
1.8 For 6-10kV outgoing line zinc oxide surge arresters in substations (including capacitor banks and surge arresters of 6-10kV station service transformers), once every three years.
1.9 The pre-test cycle for suspension insulators is once every 1-5 years. One of the following can be selected: measuring voltage distribution (or zero value), measuring insulation resistance, or AC withstand voltage test.
1.10 For equipment where the influence of environment and test equipment on test results has been excluded but the results vary greatly (even within the qualified range), the test cycle should be shortened and monitoring strengthened.
1.11 Any equipment that has been out of service for more than 6 months must be retested. Generally, it is carried out according to the pre-test items and standards.
1.12 The "before commissioning" in Table 7 of the "New Regulations" includes inspection and test items that should be carried out before re-commissioning for equipment that has not been put into operation after testing or has been out of service for a long time, with a time interval exceeding half a year.
1.13 For cascade-type voltage transformers of 110kV and above, after major repair, the dielectric loss factor of the iron core support should be measured, and its value should not be greater than 6%, with a test voltage not less than 10kV.
1.14 For insulating pull rods of low-oil circuit breakers of 110kV and above, an AC withstand voltage test must be carried out during new installation. For those that fail due to moisture, after major repair and drying treatment, an AC withstand voltage test should also be carried out. The test can be carried out in sections, but for 252kV, it can be divided into at most 6 sections, and for 126kV, at most 3 sections. The withstand voltage value of each section = 1.2 × test voltage / number of sections. The test voltage is implemented at 80% of the specified value in DL/T 593, with a continuous pressurization time of 300 seconds. No breakdown, no flashover, and no overheating are considered qualified. For insulating pull rods of circuit breakers of 110kV and above that have been replaced or dried, a DC leakage test should also be carried out, and the leakage current should not be greater than 5 μA.
1.15 For centralized online monitoring devices in operation, generally, a patrol test should be carried out once a month (for distributed online monitoring devices, once every six months). If abnormalities are found, the cause should be identified in a timely manner. After one year of normal operation of newly installed devices, if there are no abnormalities in the monitoring data, except for electromagnetic voltage transformers which should follow the original pre-test cycle, the outage pre-test cycle of other monitored equipment can be appropriately extended.
1.16 The preventive test items, standards, and cycles for imported equipment should be based on the product standards of the equipment, with reference to the "Regulations for Preventive Tests of Power Equipment".
1.17 Test cycles for 20kV and static compensation equipment at Zhengzhou Station:
1.17.1 For the 1# 20kV station service transformer, once every three years.
1.17.2 For discharge capacitors on the 20kV side of the main transformer and static compensation capacitor banks (including shunt compensation capacitor banks at other stations), once every four years. However, an oil leakage inspection should be carried out at least once every six months. If oil leakage is found, they should be taken out of service.
1.17.3 Dry-type reactors, according to regulations, only need an AC withstand voltage test during major repair of the connected system equipment. The test voltage is 65kV.
1.17.4 For polymer insulator bottles on the silicon valve frame, generally, insulation tests are not carried out. Only during major repair of the silicon valve, their insulation resistance is measured. Generally, each unit should not be less than 500 MΩ. However, they should be cleaned once a year.
1.17.5 Except for the equipment listed in items (1) to (4), other 20kV equipment is tested once every two years.
1.18 For Zheng 1# main transformer, the additional measurement of insulation resistance of the yoke to ground should not be less than 70% of the initial value, but the minimum should not be less than 300 MΩ.
1.19 Test items and cycles for insulating oil in operation:
1.19.1 Power transformers 220kV and above: simplified, interfacial tension once a year
Moisture, dielectric loss once every six months
Chromatography once every three months
Breakdown voltage with pre-test
110kV: simplified, moisture, dielectric loss, interfacial tension once a year
Chromatography once every six months
Breakdown voltage with pre-test
35kV moisture, dielectric loss, chromatography once a year
Breakdown voltage with pre-test
