Over Voltage on The Other Two Phases...
Over Voltage on The Other Two Phases...
(OP)
In case of phase to ground short circuit, will we experience a case of over voltage on the other two phase in a specific earthing system? Please elaborate.
Elecme





RE: Over Voltage on The Other Two Phases...
If you get a ground on one phase which is not immeidately removed by protective relaying, the other phases will rise to VLL above ground.
Draw an equilateral triangle representing the three phases. In the unfaulted case, ground lies in the center of the triangle.
In the case of ground fault, ground moves toward one corner of the triangle... distance from ground to the other corners is longer.
RE: Over Voltage on The Other Two Phases...
Add that in an oscillatory or resonant condition, the "neutral" may be Displaced Outside the ø-ø voltage triangle.
RE: Over Voltage on The Other Two Phases...
See W.D. Stevenson Jr "Elements of Power System Analysis," 3rd Ed., McGraw-Hill Book Company, 1975, Chapter 11 Symmetrical Three-Phase Faults on Synchronous Machines.
Equation 11.1
Vmax sin(wt + alfa)=Ri + Ldi/dt
The di/dt will cause the higher voltage.
RE: Over Voltage on The Other Two Phases...
Thread238-3370 High Resistance Grounding
Thread238-6870 Alarm system for 480V ungrounded systems