Overvoltage protector parameters and selection

Overvoltage protector parameters and selection

The mechanism of the overvoltage protector was analyzed by the mechanism of the high voltage motor insulation damage caused by the overvoltage of the vacuum switch. Determined the more commonly used series with four-star gap over-voltage protection device selection, installation, regular test methods and precautions. The selection of the overvoltage protector's rated voltage should not be less than 9.94kV; the selection of the overvoltage protector's continuous operating voltage should be greater than the maximum operating line voltage that is 7.21. And less than the frequency of discharge voltage value; overvoltage protection residual voltage value should be selected less than 15.9kV; the frequency of discharge voltage selection value according to different negative. Should be 9.3kV~12.48kV.

Selection of Combined Overvoltage Protector Parameters Rated Voltage UR

The main basis for determining the rated voltage of the combined overvoltage protector is the maximum transient overvoltage of the sound phase in single-phase grounding according to the Ministry of Electric Power, January 30, 1993 “to increase the rated voltage of 3kV to 66 kV gapless metal oxide arrester” "Continuous operating voltage information", for motors from 6kV to 10kV ≥ 1.38, according to domestic standards, the maximum operating line voltage is equal to = 1.15, then = 1.15 ~ 6.3 = 7.2 for 6kV motors ( kV), rated voltage of 6 kV motor over-voltage protection ≥1.38~7.2=9.94(kV).

Selection of Combined Overvoltage Protector Continuous Operating Voltage

Because 6kV ~ 35 kV systems are mostly neutral ungrounded systems. After a single phase has appeared. The relative voltage rises to the line voltage and can continue to operate for 2h. According to the standard, for the 6kV neutral point • 40 • Non-directly grounded system and the fault removal time is greater than l0 s. Should be greater than or equal to 1.1, less than the frequency of discharge voltage. Therefore, the continuous operating voltage should be chosen 7.9kV. Through the protective effect of the gap, the charge rate of the zinc oxide resistive sheet is O. In normal operation or single-phase grounding. Overvoltage protector can operate safely for a long time

Overvoltage protector residual pressure U thi

The residual voltage of the overvoltage protection device determines the protection level of the motor insulation according to the national standard GB755-2000 (Rate and Performance of Rotary Motors), and the voltage value of the lmin power frequency withstand voltage test for the insulation level of the high voltage motor is 2+1. The motor in operation takes 75% of the pressure resistance value above. The impact withstand voltage value of the motor, Is, is = ,/2(2Uo+1)~1.15~75% (1) where 1.15 is the motor insulation. Impact factor: rated voltage of motor for 6 kV motor. Its phase to phase and relative impact withstand voltage is U:, / (2x6+1)x1.15x75% = 15.9(kV) (2)

and so. The residual voltage of the 6 kV motor overvoltage protector should be less than 15.9 kV. Can effectively insulate the protected equipment, see Gaogewang overvoltage protector channel.

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