Radiated immunity requirements for equipment operational during high-voltage network switching operations

It is well known that EMI arises from any operation that interrupts or changes an electrical current. During switching operations in substations, very fast, high field transients occur which can adversely affect, whether by radiated or conducted interference, the electronic equipment in equipment rooms unless it is adequately protected. The environment in which this equipment is installed therefore needs to be fully characterised in terms of electromagnetic interference levels. With this knowledge it is possible to provide adequate immunity for electronic equipment, and design efficient, effective and reliable protection, control and monitoring systems. The paper identifies two areas where the IEC 61000-4-10 Standard appears to be deficient. These are the required test frequencies of 10 kHz and 10 MHz, and testing at these frequencies are recommended at repetition rate as determined by the formula given in the Standard