Application of finite difference time domain method to high voltage substations: switching transient fields

Operation of switchgear equipment in high voltage substations results in the propagation of transient currents in bus bars. The bus bars temporarily act as antennae, producing transient electromagnetic fields within the substations. With the introduction of new technology (microelectronics) into the substations for measurement and control purposes, there is renewed interest in the assessment of the electromagnetic environment of substations to ensure electromagnetic compatibility. This assessment is gaining increased importance as new equipment could be located very close to the switch being operated, potentially making the electronic equipment more vulnerable to disturbance. This paper discusses the prediction of transient electromagnetic field emissions due to switching operations in a typical 400kV air insulated substation using the Finite Difference Time Domain (FDTD) method. Electromagnetic fields radiated by bus bars due to transient currents during switching were evaluated at various positions within the substation. The effects of adjacent substation equipment and of ground conditions on the radiated fields were also investigated. Finally the dominant frequency components of the radiated fields were identified and were found to be in general agreement with measured values.