A Test Method for Instrument Transformer Wiring that supports Polarity Detection and Phase Identification

Wiring errors are one of the reasons for malfunctions of protection systems in a substation, which can result in unnecessary outages, destroyed assets and serious personal injury. Therefore, it is important to check for the correct wiring as part of the pre-commissioning process and after circuit disturbance during maintenance.This presentation will provide an overview of common wiring check methods, the challenges with instrument transformer circuits and how the correct polarity and phase-assignment can be detected.We will present a method to encode the phase number to a sawtooth-based polarity check signal by modifying the amplitude and phase alignment of its harmonics. This allows us to check the wiring of all three phases in parallel, while avoiding many problems with other wiring check methods. We will analyze the performance of the presented method using simulations and summarize the overview of performed lab and field tests.