Modelling the Propagation of Partial Discharge Signals Inside Gas Insulated Transmission Line Sections

Real-time monitoring and detection of partial discharges (PDs) inside gas insulation transmission lines (GITLs) are necessary to avoid complete breakdown of insulation. Understanding PD signal propagation through GITLs provides insight on the PD signals. GITLs are of length several kilometres, and so, studying PD characteristics on real GITL is expensive and time consuming. A simulation environment is a better alternative in which the entire GITL can be modelled for design and analysis. But high computational resources are required for simulation. So, a hybrid modelling technique is proposed to simulate PD propagation in GITL with reduced computational burden. Numerical modelling is studied for Corona PD signal propagation through straight and L sections of a GITL. The time and frequency domain characteristics of the PD signal after propagation through straight and L sections of GITL were used to compare model results with measurements. The pulse width of Corona PD signal through a 1 m long straight GITL was estimated to be 3.4 ns as compared with measured pulse width 4.4 ns with spectrum content of 0.5 to 4 GHz. The pulse width of measured and modelled Corona PD signal after propagation through a 3 m long L-GITL was 2.7 and 2.8 ns, respectively, and bandwidth spanned over 0.5 to 3 GHz.