Research On The Electromagnetic Disturbance And Suppression Measures Due To Gas Insulated Substation Switching Operations

With the gradual improvement of the grid voltage level, the very fast transient overvoltage and transient enclosure voltage generated by the gas insulated switchgear present more strict requirements to insulation level of primary equipments and anti-jamming capability of field installed intelligent equipments. In this paper, the frequency, amplitude and distribution of the very fast transient overvoltage at the primary system and secondary system are studied quantitatively through field measurements and simulation modeling. The corresponding measures are also proposed to suppress the very fast transient overvoltage at the primary system. The main contents of this paper include:(1) According to the propagation characteristics of electromagnetic wave in the power transmission line, the characteristics of the very fast transient overvoltage generated by switching operation are derived theoretically. The conductive coupling path through current/voltage transformer and grounding grid, the radiative coupling path through space transient electromagnetic field and the signal processing circuit of the secondary equipments for suppressing high frequency interference signal are also introduced in detail.(2) During the operation of isolation switch and current breaker, the disturbance voltage on the ports of field installed intelligent equipments and transient enclosure voltage are measured in a 500kV gas insulated substation through electromagnetic transient measurement system. The frequency, amplitude and distribution of the electromagnetic disturbance due to the switching operation are obtained, and the electromagnetic immunity requirements on the signal port of field installed intelligent equipments in 500kV substation are put forward.(3) The transmission line model with distributed parameter and the isolation switch model with repeatable breakdown are built by the electromagnetic transient simulation software. Numerical calculations of power network model under the operation mode of single-phase transformer and single circuit line are conducted.When the isolation switch closed, the transient process is simulated and analyzed, and characteristics of overvoltage and overcurrent at every part of the primary system are evaluated synthetically.(4) According to the characteristic parameters of the very fast transient overvoltage at the primary system due to the switching operation, the isolation switch with opening and closing resistors and phase-controlled circuit breaker are applied to suppress the operation voltage at the primary system. By constructing the isolation switch with closing resistor and phase-controlled circuit breaker models, the numerical calculation of overvoltage is carried out generated by switching unloaded line.Thesimulation results show that the isolation switch with closing resistor and phase-controlled circuit breaker make the amplitude and duration of operation overvoltage decrease significantly.