Electricity production is increasingly carried out using non-synchronous generators such as solar panels or wind generators. These units are connected to the power grid through electronic power converters, which saturate the network with high-frequency harmonics. Most modern consumers of electricity (energy-saving lamps, LED lamps, power supplies for computers and household appliances, inverter drives, mobile phone chargers, etc.), in turn, distort the electrical network. Traditional measuring transformers are not intended for use in networks with a high content of high-frequency harmonics, which is a limitation for accurate metering of electricity and analysis of its quality. New current transformers of the XCTB series manufactured by MBS AG retain the accuracy of signal transmission at frequencies up to 20 kHz, which allows them to be used both for commercial metering and for determining power quality indicators in the presence of non-sinusoidal current distortions.