Electric field computation for HVDC GIS/GIL spacer under superimposed impulse conditions

Transient surface charge of SF 6 ‐filled direct current gas‐insulated transmission lines insulator under thermal‐electric coupled fields: effects of ambient temperature, load current and gas pressure

“…By substituting (5) into (7), the ion transport equation was obtained in (8) for positive and negative, respectively.…”

“…This thermal field will affect the electric field distribution of the DC-GIL via the temperature-dependent electric conductivity of the insulator [6], which will further show influence on the charge accumulation. Besides, this temperature-dependent conductivity would directly affect the charge accumulation process via the conduction through the insulator volume [7,8]. Moreover, the ion transport in the gas is directly affected by this thermal gradient, since the ion mobility varies with temperature [9].…”

A Review on Real-Size Epoxy Cast Resin Insulators for Compact High Voltage Direct Current Gas Insulated Switchgears (GIS) and Gas Insulated Transmission Lines (GIL)—Current Achievements and Envisaged Research and Development

“…Regardless the employed calculation method (Section 3.1.1 or Section 3.1.2), the most relevant results of the electric field distribution along full-size spacers performed under different operating conditions of the HVDC GIS/GIL: transient, DC steady state, DC polarity reversal and superimposed lightning/switching impulse voltages on DC pre-stress with and without load (temperature gradient) [11,12,[35][36][37][38][39][40][41][42][43][44][45][46], are summarized as follows:…”

“…-An increase of gas ion-pair (IP) generation rate by a factor of 10 of the natural ionization causes an increase of the electric field as shown in Figure 3 [12,34]. Such enhancement of the electric field is also observed when additional source of ions generation in the gas is increased by electrons field emission [37,45]. -The temperature gradient across the insulation has a large effect on the electric field distribution due to the temperature dependency of the electric conductivity of the epoxy spacer's material.…”

“…Without temperature gradient (ΔT = 0), the maximum electric field stress is in contrast within the spacer near the HV conductor. -The electric field distribution under impulse voltage superimposed on pre-stress DC voltage is different from that under impulse voltage alone [35,36,45] due to surface charges accumulation. Furthermore, it has been found that the resulting calculated electric field intensity when the impulse voltage is superimposed on pre-applied DC voltage of opposite polarity, is higher than the electric field intensity under the condition of DC voltage polarity reversal [35,36].…”