| With the continuous improvement of the voltage level of the power system, powersystem overvoltage is also rising, the UHV system insulation design put forward higherrequirements in order to maintain the stability and reliability of the power systemoperation. The object of this paper is the Very Vast Transient Overvoltage (VFTO) whichcaused by the operation of disconnecting switch in GIS, its amplitude has a proportionalrelationship with the voltage level of the power system, at a lower voltage level, VFTO inGIS is not a factor need to be considered in insulated design, but when the voltage level isincreased, the corresponding insulation design doesn’t increase proportionally, accidentscaused by VFTO have occurred in systems with a higher voltage level. This paperfocused on the very fast transient overvoltage caused by1100kV voltage level GIS inWuhan Phoenix Mountain UHV AC test base with Field measurements and simulationstudies.In field tests, using a convenient, practical and high reliability tapered capacitivepartial voltage sensor, with a total set of5different points in the load side and the powersupply side of the GIS, and the DC power supply in load-side charging the GIS is equalwith the residual pressure in actual power system. In order to get the maximum VFTOhundreds of tests have been taken due to the uncertainly phase of switch operation. Thetest results show the overvoltage amplitude of closing the gate slightly larger than that ofopening; there will be a higher amplitude VFTO at the end of the GIS; the overvoltageamplitude has a downward trend in the points much more away from the operating knife.In simulation numerical calculation, first of all, we get the transient model of variouscomponents of the test system, using EMTP/ATP transient simulation software to modeltest system, enter the correct parameters, by changing the length of the GIS short tube busand the parallel resistor to see the characteristics of VFTO. The simulation results showthat the GIS generated VFTO trial the same segment characteristics, and that there will bea higher amplitude in the short end of the tube in GIS due to the total reflection oftraveling wave; the GIS side tube bus terminus generated VFTO amplitude value whichincreases while decreasing its own length, and also has a tendency to increase thecorresponding frequency component; taking brake resistors will have good inhibition of VFTO, but inhibition decreases with the increase of the parallel resistance, recommendedclosingresistors of500Ω resistance. |
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