Key Properties Test and Analysis of Gas Density Monitor Used for Gas-Insulated Switchgear after Long-term Operation

The gas density monitor used for GIS (Gas-Insulated Switchgear) reports SF
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gas leakage of GIS in time, by monitoring internal pressure in gas chamber of GIS and sending out alarm or lockout signals. At present, most operating units do not perform regular maintenance or online verification for gas density monitors. Usually, they are replaced in batches after ten years or more of use, which makes the accuracy and reliability of gas density monitors lack of verification during operation. To research key properties of gas density monitor during operation, this paper conducts experiment on gas density monitors replaced after 17 years of operation from a power supply bureau, including indication test, temperature compensation test and electric contact performance test. The experiment results show that, the pass rate of tested sample are all lower than 50% in the basic error test and the set point deviation test of indication test, and the -30°C low temperature compensation test. It reflects the severe aging of the Baden tube and the magnetically assisted electrical contacts in gas density monitors that have been running for a long time, and on the other hand, it reflects that the low-temperature compensation performance of this batch of gas density monitors are abnormal at the factory. According to test and analysis of this paper, it is recommended to modify the interface of the existing gas density monitors and upgrade in order to carry out periodic online inspection without disassembly, to avoid the failure of the monitoring function of gas density monitors during operation.