Transformer Protection

MY GOD MAN! TAKE A CLASS! DO SOME RESEARCH! QUIT ASKING OTHER PEOPLE TO THINK FOR YOU! DO YOUR OWN HOMEWORK!

Busbar Protection

How do you ever keep a job?

appreciate that

Ask you’re supervisor / mentor to explain it to you.

I’m not wasting my time with you on basic and dangerous engineering principals.

Relay K1 is therefore a neutral current trip unit, and cannot protect for phase over-currents downstream, as that's not what it is designed for.

<...what are the disadvantages of not providing tripping functions of the ACB?...> The the above single line diagram does not necessarily show all the protection in the circuits, for that is the job of the "as built" schematic wiring diagrams, which have been withheld from the forum. The documentation cannot be seen from here, therefore no-one in the forum can answer the question.

• Where is the design documentation and commissioning records that cover the equipment that has been queried over the last few occasions? Where is the name of the Design Engineer on that documentation? Where is the design and the commissioning organisation's telephone number on that documentation? Please explain why this avenue has not yet been explored?

Coolyaar, K1 protects the transformer and HV from faults on the LV side. The LV side receives power from the HV side. It is a passive receipient. Now if power was to flow from the LV side to the HV side then the proposal you have (tripping the ACB to protect the transformer and the LV cct) will be needed. This time the fault will be on the HV side, say, like a ground fault.

Hope there is phase O/C in 6kV switchgear panel. This can take care of phase to phase / three phase faults in 400V system as well as high current earth faults.

The 400V earth fault protection connected to the transformer 400V neutral CT should help in isolating the transformer for those low current faults which may not be good enough to operate the 6kV overcurrent protection.

Generally speaking, the earth faults yield low magnitude of currents due to fault impedance / earth loop impedance.

Here's a disadvantage:

If You Are Wrong

Do your own work and witness the commissioning up close, alone!

ON that 115 kV line, about 5' off to the side on the ground should about take care of it!

No, the only fault that will be detected is one that causes a sufficiently high level of zero sequence current to flow in the grounded neutral. Your cost saving scheme cannot discriminate between high vs. low impedance faults; and if set too low, will result in nuisance trips due to any phase current imbalances caused by motor starting, varying supply voltages, single phase loads, etc., etc. It also provides NO protection against balanced conditions such as a three phase fault, overcurrent, locked rotor, overload, winding overtemperature, etc., etc.

If the ACB tripping functions were enabled you might get some protection against some of the faults mentioned in the last line of the above paragraph, but that would depend upon your skill in choosing the correct ACB tripping element and settings.