Successful replacement: Diverter Switch Insert VM replaces conventional Diverter Switch
MRT engineers on site
In mid-to-late April, MRT successfully replaced the old diverter switch insert (DSI) of a competitive product with VM-type DSI in Wulidui 220kV substation of SGCC Sichuan PSB in the southwest of China, to ensure the smooth power transmission.
The transformer in Wulidui substation has been in operation for more than 20 years and and was previously equipped with a CZ OLTC. While recently, abnormalities were found in routine inspection. Acetylene was exceeded the standard in the analysis of the tap changer oil sample. Moreover, the phenomenon of exceeding appears repeatedly, but the root cause cannot be found out. Out of concern for the reliability of tap-changer operation, the substation immediately asked MRT for supporting.
Through accurate measurement by specialized tools, calculation and analysis by professional technical teams, MRT recommended to replace the tap changer in service with the VACUTAP® VM® vacuum tap changer.
The complete replacement of the tap-changer would require a large amount of on-site construction and the substation’s power off for a long time. Considering the high cost of power outage of substation, and the huge impact on the local area, a compromise was negotiated with the customer ˗ only replacing the diverter switch insert. Although this solution does not increase reliability to the maximum, it was a good compromise that the customer accepted. This solution made it possible to achieve increased reliability while at the same time reducing the scope of on-site measures. Meanwhile, through the retrofitting of DSI, the conversion to vacuum technology can also be easily completed.
With the cooperation of MRT technicians and substation construction personnel, the replacement of diverter switch insert was successfully completed. The replacement and commissioning work of motor drive unit and bevel gear unit were also completed.
After replacement, the tap-changer and transformer test data are qualified. Now, the transformer releases the abnormal state and delivers power smoothly.