First Russian-Made 500 kV Oil–SF6 HV Bushing Made and Tested

On 22 March 2017, Izolyator plant successfully ran acceptance tests of a 500 kV oil–SF6 HV bushing.

The KTkb-90-550/1000 O (drawing IVUE.686355.404) was designed under the order of Togliatti Transformer Ltd for replacement of bushings of a foreign manufacturer.

It was designed and detailed in the graduate thesis of the National Research University “MPEI” student Sergey Khlopotin. What is peculiar about its design, the external insulation is absent not only on the bottom side of the bushing, but also on the top of it. Therefore, a technology container was made to imitate a GIS tank, filled with SF6 gas under minimal working pressure. Another 500 kV bushings was used for power applying, it was mounted on the cover of the technology container.

To qualify the requirements of the technical standards, the plant ran a complete acceptance tests set, including special tests typically done on SF6 devices:

• test on the external pressure of SF6 gas at 11.5 ATMG
• test on SF6 gas leak through the bushing at 7.5 ATMG
• test on mechanical strength of the fastening fitting of the bushing to the GIS with fastening torque 40 kNm.

The bushing went through all tests successfully, and that allows for making the first batch of the bushings in the shortest available time and ship it to the customer in line with the signed contract.

Presently, one more 500 kV bushings of oil–SF6 type is being tested at Izolyator plant. It is designed for replacement of foreign-made bushings in the Main Power Transmission Lines of Center that were damaged in operation.

500 kV oil–SF6 bushing’s tests at Izolyator plant. At the test, the bottom part of the bushing is immersed into a tank with oil, while its upper part is inside a service tank with SF6 gas. Above, there is a temporary 500 kV bushing installed to feed the voltage for testing