Phase voltage measurement on very fast transients in non-symmetrical three-phase enclosed gas insulated substation

The method to measure the phase voltage on very fast transients in a non-symmetrical three-phase enclosed gas insulated substation is described. In order to measure three phases voltage, three capacitive sensors are needed and each capacitive sensor is coupled with the electric field of (A, B, and C) three phases voltage. The linear relation between the output of three capacitive sensors and the three phases voltage is established by a factorial matrix, which is equal to the product of a constant matrix and the electric coupling coefficient matrix. As a result of the analysis of the electric coupling coefficient matrix, the dominant electric coupling coefficients are proposed, which have an approximate analytic expression. Furthermore, according to characteristic of the electric coupling coefficient functions, three capacitive sensors are fixed at the shortest points of phase A, B, and C. Finally, the curves of three phases voltage on very fast transients in a non-symmetrical three-phase enclosed gas insulated substation bus model are given and discussed.