Calculation of Discharge Inception Voltage Due to the Presence of Voids in Power Cables

Field distortion by a single cavity in HVDC XLPE cable under steady state

“…when x = R c . Temperature at the middle of insulation can be calculated according to (17). Under the constant DC applied voltage, value of k is determined by the thermal condition (T c ) and the material properties (j).…”

“…Local field distortion by a single spherical or ellipsoidal cavity has been investigated and published in several papers [15][16][17][18]. Under AC condition, the presence of cavity enhances the local field strength due to the difference in permittivity between air inside the cavity and the surrounding dielectric, and the relative permittivity of dielectric determines the enhancement percentage.…”

“…In the early research, simplified 2D model was often used to investigate the influence of the cavities [15][16][17][18]. In reality, the single spherical cavity described in 2D model simulates a cylindrical cavity with its axis parallel to the cable axis and having the same length as the cable, which does not exist in the real cables.…”

Influence of irregularities within electric fields in high voltage cables

“…The maximum applicable voltage in a cable without partial discharges is called inception voltage. The value of V inception has been analysed for AC cables by Nosseir [11] and Malik [12]. The breakdown strength value in gaseous cavities has been empirically calculated by Hall [13] and adjusted by Malik [12] with the Paschen's curve, according to the expression:…”

Some Aspects of Stress Distribution and Effect of Voids Having Different Gases in MV Power Cables

“…Expressions are derived for determining the PD inception voltage in typical voids in cables. Since the ionization and occurrence of partial discharges within the voids would cause erosion and local deterioration of the insulation, which leads to a complete failure of the cable, hence the importance is given to knowledge of the conductor voltage at which partial discharges takes place inside the void [5].The main degradation products were found to be hydrogen, carbon monoxide, methane and carbon dioxide which are produced in a power cable when exposed to PD activity. Droplets were formed on the surface of XLPE only when an atmosphere containing water and carbon monoxide is present.…”