Overvoltages due to system grounding
Overvoltages due to system grounding
(OP)
I got a bit confused with some manufacturers application notes stating that no overvoltages occur in systems with neutral grounding resistors...I understand that from phasor diagrams the neutral point will shift during line-to-ground faults, for both low resistance and high resistance grounding....correct me if I am wrong!
It seems that they meant by overvoltages the dangerous transient oscillations due to arcing ground faults, where system inductance and capacitance inter-exchange energy (this happens in IT systems). However, the NGR systems will have a line-to-line voltages appearing on healthy phases to ground.
Any clue?
It seems that they meant by overvoltages the dangerous transient oscillations due to arcing ground faults, where system inductance and capacitance inter-exchange energy (this happens in IT systems). However, the NGR systems will have a line-to-line voltages appearing on healthy phases to ground.
Any clue?






RE: Overvoltages due to system grounding
RE: Overvoltages due to system grounding
As for the transient oscillations due to arcing ground faults; any value of neutral grounding resistance that allows more fault current than the charging current will stop that escalating voltage buildup.
RE: Overvoltages due to system grounding
Is there any clue about the selection of resistor value? I have read somewhere that the resistance value should checked against the power loss during faults? I couldn't get that as the power loss during faults will be Vph^2/R, or I^2.R, i.e. for a 33 kV transformer and about 500 A fault current, the power loss during faults will be 9.5 MW, this can be multiples of transformer rating but the fault acts for very short time....
any clue?
RE: Overvoltages due to system grounding
This is explained through an example in IEEE C62.92.3.