The measurement of fast transient electromagnetic interference within power system substations

Substations are expected to transform and direct electrical power to customers with high reliability, even when exposed to transient electromagnetic interference (EMI) from high voltage (HV) events such as switching, faults and lightning strikes. 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, amongst other things, secondary equipment in control if it is adequately protected. With increase microprocessor based systems for the monitoring and protection of power equipment, the detection of equipment faults, before they lead to major outages, is possible. The placement of electronic equipment which is, by nature, highly susceptible to electromagnetic interference, within the switchyard EMI environment is becoming more common. This raises the level of concern for the electromagnetic compatibility of such equipment with the EMI environment in which it must operate. Therefore, the environment in which this equipment is placed needs to be fully characterised in terms of electromagnetic interference levels. With this knowledge it is possible to provide adequate protection for electronic equipment and design efficient, effective and reliable control systems. This paper looks at a variety of methods, and their suitability, to characterise the electromagnetic environments in substations.