Article 14.6.1.1 Lightning arresters with voltage levels of 110 (66) kV and above should be installed with AC leakage current monitoring devices consistent with the voltage level.
This clause is 14.6.3 of the 2012 version of the "Eighteen Countermeasures". Based on the original clause, the 66kV voltage level is added, and the "AC leakage current online monitoring meter" is modified to "AC leakage current monitoring device consistent with the voltage level."
The original article does not have specific requirements for the range of the leakage ammeter. Many high-voltage arresters on site have leakage ammeters with a large range, resulting in inconspicuous changes in indications when there is an abnormality. It is difficult for inspection personnel to detect abnormal situations. It is recommended that the reference range of the leakage current range corresponding to the arrester of each voltage level is: 0~3mA for 220kV and below, 0~6mA for 330~750kV, and 0~20mA for 1000kV.
Online monitoring of leakage current of metal oxide arresters should be carried out strictly in accordance with the cycle, and the monitoring data should be analyzed. It is recommended that when the full current increases by more than 20% or abnormally decreases significantly, a live test should be conducted to measure the full current and resistive current, analyze and judge, and conduct a power outage test if necessary.
Article 14.6.1.2 For substation arresters in strong wind areas, differentiated designs should be adopted, and reinforcement measures such as increasing fixed points, number and width of support ribs should be adopted for the voltage equalizing ring of the arrester.
Based on the actual operating experience of operation and maintenance units in strong wind areas such as Xinjiang and Eastern Mongolia, the differentiated design standards for voltage equalizing rings of pressure arresters are improved to prevent breakage and damage to the voltage equalizing rings caused by strong winds.
Article 14.6.2 Infrastructure Phase
Article 14.6.2.1 Before installing porcelain jacketed arresters with voltage levels of 220kV and above, check whether the upper and lower flanges of the arrester are glued correctly, and drainage holes should be provided in the lower flange.
According to the requirements of the "State Grid Corporation of China Nanyang Golden Crown 500kV Lightning Arrester Accident Case in 2013" (Yunqin No. 1 [2013] No. 233), in order to prevent the upper and lower flanges of the arrester from being glued incorrectly, causing moisture inside the arrester and causing discharge accidents, this clause is proposed based on actual operating experience.
[Case] On March 19, 2013, the 500kV II female A-phase arrester in a substation failed. On March 21, live inspection found that the upper section of the 500kV I female C-phase arrester was seriously overheated. The arrester model is Y20W−420/995W, a product of Nanyang Jinguan Electric Co., Ltd. in 2007. The cause of the failure was: the upper and lower flanges of this batch of lightning arrester porcelain sleeves (provided by Hunan Liling Huaxin Factory) were incorrectly glued, resulting in no drainage hole in the lower flange, and the accumulated water could not be discharged. The sealing device and explosion-proof membrane were immersed in water for a long time, and the explosion-proof membrane was damaged. The seal failure caused internal moisture, which caused internal discharge of the arrester.
Article 14.6.3 Operation phase
Article 14.6.3.1 For metal oxide arresters, live tests must be carried out in accordance with the requirements of the regulations during operation. Metal oxide surge arresters with voltage levels of 35 to 500 kV can be tested with live power in place of regular power outage tests.
The live test includes leakage current (full current, resistive current) test and infrared temperature measurement. The live test can detect the dampness of the arrester during operation and the deterioration of the valve plate. Therefore, the live test should be carried out during operation. Live tests should be carried out strictly on a periodic basis, and the analysis of test data should be strengthened. If the resistive current increases by more than 50%, the test period should be shortened and monitoring should be strengthened. If the resistive current exceeds 100%, the power supply should be stopped for inspection and testing. For arresters with voltage levels above 500kV, considering their importance, in addition to routine live testing, power outage tests should also be conducted regularly. The test cycles and projects should be strictly implemented in accordance with the test procedures.
[Case] From 2016 to 2018, during the live test process, it was found that the 110kV composite jacket structure arrester produced by a certain company had abnormal parameters in many provinces. The reasons for the abnormal parameters of the arrester were:
During the mass manufacturing process, there were deviations in the process control of individual products (shifts). Because the thread sealant was unevenly applied and the curing time was not in place, the uncured thread sealant was removed during the subsequent vacuum filling process, resulting in uneven distribution of sealant at the threads and the formation of channels for moisture to enter. Professionals carry out live detection and leakage current monitoring of arresters to promptly discover equipment abnormalities and family defects, and take corresponding measures to effectively prevent arrester accidents.
Article 14.6.3.2 For arresters that have been in operation for 15 years or more, the changes in leakage current should be tracked, and the pressure relief plate should be inspected for corrosion or damage after outage.
According to the requirements of Article 16 of the "Operation Specifications for 110 (66) kV ~ 750kV Lightning Arrester of the State Grid Corporation of China", this provision is proposed to prevent the arrester from getting damp and strengthen the operation and maintenance measures of the old arrester. Based on operation and maintenance experience, it is recommended that the main sealing structure of porcelain jacketed arresters of 110kV and above adopts a double-pass sealing ring design, and the outer end face of the sealing ring should be evenly coated with waterproof glue.
[Case] On September 15, 2018, on September 15, 2018, the pressure of the upper and lower sections of the A-phase arrester on the 220kV side of ×× Power Supply Company’s 220kV ×× substation No. 1 main transformer was released, causing the arrester to breakdown, causing the No. 1 main transformer to trip. The arrester was put into operation in 2004. Through disassembly analysis of the arrester, it was found that the seal of the upper section was aged and damaged, causing internal moisture. When the temperature dropped suddenly at night, water vapor in the valve plate condensed, causing internal discharge, which in turn caused the pressure release action of the upper section. After the upper section broke down, the lower section could not withstand the operating voltage, causing the overall breakdown of the arrester.
