Polarity of current transformers used in relay protection
The ANSI/IEEE standard for transformers states that the high voltage should lead the low voltage by 30° with wye–delta or delta–wye banks. Polarity is very important for the operation of transformers and protection equipment. How are current transformers used in protection systems for power grids and substations? Current transformers (CTs) are the primary sensing interfaces between high-current power circuits and the low-voltage protection and metering equipment used in substations and transmission networks. One of the most critical aspects of using CTs in these systems is ensuring correct CT polarity for differential protection.
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