Characteristics of partial discharge pulses propagation in shielded power cable

Partial discharges originates from defects in the insulation material of shielded power cable, joints and machine coil. In cable the discharges induce small high frequency pulses which propagate to both cable ends and the time domain reflectometry detection method of the PD pulse is suitable in this case. In this paper, a new experimental method has been introduced, it consist to inject at one end of the power cable one high frequency pulse generated by negative corona discharge in point-plane system. Understanding high-frequency attenuation in transmission cable is relevant for PDs detection and wideband signals distributions over such cable. We have realized in laboratory a high frequency pulse generator and 50 m length of 30 kV XLPE power cable is used for the tests. The experimental results show that the pulse amplitude decreases and the pulse width increases with the propagated distance and this result is in good agreement with the actual theoretical analysis based on the frequency attenuation. Important characteristics of PD pulse are successively determined at high frequency with maximum accuracy possible such as the wave speed, the relative permittivity, the characteristic impedance and the XLPE attenuation factor.

► In power cable PD discharges induce small high frequency pulses which propagate to both cable ends.
► The time domain reflectometry detection method of the PD pulse is suitable in Power cable.
► One high frequency pulse generated by negative corona is injected at one of end of 50 m length of 30 kV XLPE power cable.