Negative Sequence Relay Working

Try reading this. And try google sometime - first.

Strange how this thread follows on from:

http://cr4.globalspec.com/thread/109447/What-are-the-Problems-and-Failures-That-Would-Be-Hidden-in-Traditional-Relays

This is figure 3.51(d) from "Protective Relays Their Theory and Practice" by A.R. Van C. Warrington Vol.2 published by Chapman & Hall.

What it does is phase lag the B-C voltage until it is 180 degrees out of phase with the A-B voltage. Transformer T (or with electronic amplifier, in place of T, a resistive divider) provides an equal voltage to the capacitor voltage, giving a resultant voltage V2 of zero for positive sequence voltages. However, for negative sequence voltage, this balance is not got and only the negative sequence voltage is present in V2.

There are other forms of negative [and positive] sequence filters.

The symmetrical components can exist in reality - you can set up a system of 2 x balanced, 120 degree spaced, 3 phase and 1 x single phase generators to give any 3 (voltage and phase un-balanced) vectors of a 3 phase supply required.

67model