Grounding Transformer Sizing Program for Ungrounded Medium Voltage Power Systems Using Distribution Transformers in Wye - Broken Delta Configuration with 600 Volt Secondary Resistor

A computer program has been developed to calculate a grounding transformer design using 3 single phase distribution transformers in wye/broken delta configuration with an external 600 V resistor. The program selects the optimum size transformer kVA rating and resistor size based on the given design parameters. Transient overvoltage criteria are checked, and grounding transformer design is modified when necessary to satisfy the criteria.