Testing a 27.5kV Voltage Transformer

This photo shows a 27.5kV/55kV Voltage Transformer designed for Siemens AU/NZ and Auckland railway KiwiRail for the North Island Main Trunk (NIMT) Traction Substation Refurbishment Project in New Zealand.
The VT is an oil impregnated VT, which is designed for outdoor conditions.
The test specifications are as follows:
a) Impulse level test at 170kVp
b) High Voltage power frequency test level at 70 kV rms for 1 minute
c) Partial discharge is ≤ 5 pc @ 36kV rms

The most important part of the design of this VT is the external high voltage fuse connected in series with the VT on the HV Terminal. This fuse is enclosed in a UV stabilized epoxy bushing with a replaceable high rupture capacity fuse. This fuse can be mounted at 0° / 90° / 180° / 270° around the top of the housing of the VT.
Designed by Mike Larkin to overcome the placement of the fuse inside the top vessel of the VT; making it very difficult to replace/change.
This was a unique solution to the customer’s problem of HV fuse in the HV circuit, connected to the HV terminal of the VT.

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