E-fields inside 765 kV substation: Influence of conductor & bay arrangements

Increasing voltage level in generation and transmission system have become inevitable. The threats of non-ionizing radiation and their biological effects at substations have increased. As per International Commission for Non-Ionizing Radiation and Protection (ICNIRP) guidelines suggest maximum limits for electric and magnetic field exposure is 10 kV/m and 1 mT for occupational and 5 kV/m and 250 μT for public exposure. Keeping this in view results of a case study of electric field distribution in an upcoming 765 kV substation in India are computed and discussed in this paper. Using the existing layout of this substation, the E-fields at 2 m height above the ground plane are computed using FEMM (a free ware). Results show that Bays which are at a height of 14 m from ground are dominant and contributing more to the E-fields. The paper further computes and compares E-field strength due to (i) a single conductor (a phase of bay alone), (ii) single bay (iii) and with all the bays of substation with buses, overhead headlines and ground wires. The effect of bay height (around 14 m) on the E-field is also reported. The average E-field in substation arena is well within the ICNIPR suggested limit of 10 kV/m, whereas E-field at some places exceeds this value.