The insulation level of the electrical equipment in the neutral grounding system shall be consideredA. phase voltage;The square root of 2 phase voltage B.;The square root of 3 phase voltage C..Great God in the end this election? I am very tangled!
According to the line voltage, the neutral grounding is star type connection, line voltage is 3 times the square root of the phase voltage, so the choice of C
This is a bit of a problem, because there are different levels of insulation in the neutral grounding system. Some places are determined in accordance with the graded insulation, that is, the first and the end of the neutral point of the different requirements
For example, 220kV transformer (YNYnd11) insulation level high voltage side is LI950AC395-LI400AC200, the front half part (head) of the lightning impulse voltage and power frequency withstand voltage were significantly higher than that of the second part (neutral side). According to the power frequency withstand voltage needs to achieve 1.6 times the rated voltage requirements, the first end of the line voltage is considered in accordance with 220kV, the neutral point according to the phase voltage (127kV) considerations. But there are some places are fully insulated, that is, according to the line voltage calculation.The triangle connection must be considered by the line voltage. Overall, C is definitely right.
