Very fast transients in 1000 kV gas insulated switchgear

Abstract

For lOOOkV transmission system, disconnecting switches (DSs) fitted with resistors and high-speed grounding switches (HSGSs) were developed. At the UHV Equipment Test site, DS surge and HSGS closing surge tests were conducted. Then, the very fast transient overvoltage (VFTO) controlling performance of the DS and the surge voltage level due to HSGS closing were confirmed. In the same tests, the surge level transferred into the protecting and controlling components were confirmed low enough for them to operate properly. The transferring mechanism was clarified by an electromagnetic wave propagation analysis.

Grounding System Transient Characteristics of Underground GIS Substations

“…Following an elaborate observation of the frequency characteristics of the grounding impedance ( Fig. 7) at the point (9) in CASE 3, the impedance represented virtually linear characteristics up to a frequency of about 15 MHz. And the data showed some dispersion and tended to saturate at frequencies exceeding 15 MHz.…”

“…In CASE 2, the current was injected at point (8), and the injected current waveform and voltage at the current injection point were measured at the same time. Also, in CASE 3, the current was injected at point (9), and the injected current waveform and voltage at the current injection point were measured at the same time. For the measurement system, which could be approximated by using pure resistance or a distributed constant for the load, the rise time of the injected current was about 2 ns.…”

“…In Fig. 5 of CASE 1, the value of the inductance was 0.22 H. For the measuring point (9) in CASE 3, the measured waveforms of the injected current and grid voltage are shown in Fig. 6 and the frequency characteristics of the impedance are presented in Fig.…”

3-MV compact very fast transient overvoltage generator for testing ultra-high-voltage gas-insulated switchgear

“…[3]. For systems above 330 kV, the insulation strength of the GIS under VFTO is of concern as insulation failures caused by VFTO have exceeded those caused by lightning impulse (LI) [4]. This characteristic has attracted the attention of researchers worldwide and currently is a hot topic in the field of ultra-highvoltage (UHV) GIS insulation.…”

A review of some critical aspects of insulation design of GIS/GIL systems

“…In Japan a 275 kV, 3.3 km line has been installed [4]. Field tests on a 1000 kV GIS have been conducted recently in Japan [5]. Currently, GIL in use number over 200.…”