Transformer Testing

A transformer is the single most expensive item in most HV installations and the least forgiving of an unproven fault. Field testing exists to confirm three things: that the unit arrived and was installed without damage, that its electrical characteristics match the nameplate and design, and that every protection and cooling device wired to it will actually operate.

We test winding resistance across all taps, turns ratio and vector group, insulation resistance with polarisation index, magnetising current and — where specified or where condition is in question — tan delta and capacitance. Oil is sampled for dissolved gas analysis, moisture content and dielectric strength so a baseline exists from day one of service life.

Alarm and trip devices are proven by operation, not by continuity alone: Buchholz surge and gas stages, winding and oil temperature indicators at their set points, pressure relief, oil level, tap changer operation and its limit and out-of-step logic, plus fan and pump control and the associated SCADA signalling. Each device is confirmed to its correct alarm or trip destination.

Numbers only help if they are compared to something. We benchmark against nameplate values, factory test certificates where available, phase-to-phase symmetry and the previous test history. Deviation is reported with an engineering view on cause and risk — not simply flagged as out of tolerance — so the client can make an informed energisation decision.