CANADA - Manitoba Hydro investigated the application of controlled switching, also known as Point-on-Wave (POW) switching, a technology that can safely energize large power transformers using standard circuit breakers.

The utility used this relatively new technology to resolve the issue of residual magnetic fields that can make energizing power transformers difficult, and also, to enhance the standard approach of using capacitor voltage transformers for measuring remnant flux inside the transformer.

The technology was thoroughly tested in the case of two parallel HVDC converter transformers, which were safely energized using controlled switching.

According to the utility, this is also a cost-saving solution, as it doesn't require using special circuit breakers with pre-insertion resistors, which are quite expensive and require frequent maintenance.

Source: Canadian Electricity Association