Conducted immunity requirements for equipment operational during high voltage network switching operations

Primary plant in modern substations is controlled and protected by electronic equipment. When breakers and disconnecters operate, very large electric and magnetic transients may be radiated from the plant as interference. This radiated interference can be picked up by cables and wiring in the substation and converted to conducted interference. The results of measured data on conducted interference are reported and the characteristics of these results and their correlation to existing standards discussed. The test results show that different discrete ranges of frequencies exist and have to be accommodated by substation equipment. Of these, two frequencies (10 kHz and 10 MHz) are not included in IEC 61000-4-12, and it is recommended that these frequencies should be included. Furthermore, for an air-insulated substation with air-blast circuit breakers, it is recommended that the test level be increased to as high as 10 kV where auxiliary equipment is within 10 m of the switchgear