Low-frequency electromagnetic field measurements near FACTS devices

Flexible AC Transmission system (FACTS) devices are installed in substations in order to enhance the operation of the electric power transmission and distribution system. As the thyristors within the FACTS device switch on and off, they inject high frequency voltages and currents into the power system. There has been limited information to date regarding the magnetic flux density (B) and electric field strength (E) in the 60 Hz to 3 kHz range resulting from this switching. The objective of the project described here was to investigate the spatial and temporal variations in B and E in this frequency range for contemporary FACTS devices. Measurements were made at three stations. Three-axis B sensors and a single axis (vertical) E sensor were moved around the station to various strategic locations. Measurement traverses were taken at a height of 1 meter in the control room, the pump room, the inverter hall and the switchyard. In general it appears that the stations considered were designed and are operating in such a manner that reference levels for magnetic flux density and electric field strength for either occupational or general public exposure identified by various standard setting agencies (IEEE, ACGIH, ICNIRP) are not exceeded.