How to Conduct On-site Induced Withstand Voltage Test and Partial Discharge (PD) Test for the Chinese First Set of 750kV Power Transformer

HIMALAYAL-SHANGHAI-CHINA
Li Zhen
Abstract: The paper presents the standard, procedure and process of on-site PD commissioning test for power transformer among Chinese 750kV power transmission and distribution project. The PD test voltage of 750kV power transformer is compared with power frequency withstand voltage value. The problems, which often arise in the PD test, are analyzed. Some suggestions are proposed as follows: ① Improve the insulation level of 750kV power transformer; ② loosen the restrictions on PD commissioning test of power transformer to 1000pC; ③ redefine initial voltage and extinction voltage of partial discharge; ④ conduct more researches on practical technologies; ⑤ testers work with certification; ⑥ calibrate test instrument on a regular basis; ⑦ adopt on-line monitoring if necessary. The above suggestions also provide references for conducting on-site PD commissioning test for 1000kV power transformer.
1.Introduction
On September 26th 2005, Guanting - Eastern Lanzhou 750kV power transmission and distribution demonstration project was put into operation, including two substations (Eastern Lanzhou substation and Guanting substation) and one power transmission line. Until December 2011, each substation had four sets of 750kV transformers, three for three-phase transformer in operation and one as standby. The 750kV power transformer in the demonstration project is independently developed by China. During the on-site hand-over test, PD of A-phase main transformer at the Eastern Lanzhou 750kV substation exceeds a limit. 12 PD tests are conducted before and after the test in total. The reference standard, test procedure, measuring data and existing problems of PD test are presented in the paper. Suggestions are put forward from the point view of engineering practicality, which provides reference for 750kV and above power transformer on-site test.