diff protection, primary injection test
diff protection, primary injection test
(OP)
Dear engineers,
I need your opinion.... Is it possible to test ''stability'' of line differential Protection on 36kV cable on way that we inject, for example, 100A on one phase (to ground) and connect this phase to ground on other side? So that we close loop through ground. Cable lenght is around 2km. Will be ground resistance to big problem to make this test.
We have fibre optic cable beetwen relays on both sides and we would like to check that CT's are connected correctly and of course that fiber optic cable is ok.
Thanks all,
I need your opinion.... Is it possible to test ''stability'' of line differential Protection on 36kV cable on way that we inject, for example, 100A on one phase (to ground) and connect this phase to ground on other side? So that we close loop through ground. Cable lenght is around 2km. Will be ground resistance to big problem to make this test.
We have fibre optic cable beetwen relays on both sides and we would like to check that CT's are connected correctly and of course that fiber optic cable is ok.
Thanks all,






RE: diff protection, primary injection test
Load Bank
RE: diff protection, primary injection test
RE: diff protection, primary injection test
I am thinking between two possibilities.
One is with 3ph source like Diesel generator and connect around 400V on one side with 3ph short circuit on another side.
Another is with Omicron CPC100 set, to inject for example 200 A AC in one phase and connect it to ground on other side to get closed loop. Rated power, according manual, for 200A is 1300VA. My concern is will the ground resistance be too high (or have some other influence) to perform this test. I have done similar test before but in small distance (around 30meters) but now I have a 2km long path.
Is it possible to get some ground resistance data and how?
RE: diff protection, primary injection test
How good are the earth electrodes at the ends of the cable?
RE: diff protection, primary injection test
We simply parallel the new line into service. If it trips, no outage occurs and the event report is available for diagnosing the problem. If it doesn't trip, the load current can be examined for polarity, phase, or magnitude issues. It does help to use a smart relay.
RE: diff protection, primary injection test
As alluded to, connecting 400V through an unknown impedance (cables + earth) may cause a few surprises you may not want during a commissioning test. Perhaps a lower source voltage 220?
Primary Injection is generally something where the expected results are know, prior to testing.