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hi, the use of class x, p, t CT's for unit protection is what is normally recommended, were we can specify what knee point is wanted etc... what are the implications when we use class 5P or 10P ct's for unit protection. will the ct's satuarate more easily? are these types normally used for unit...

hey thanks guys... this is for 400kv ac transmission so reliabilty is very imp. just for clarity:-- i have 2 different dc supplies,which powers up two different relays and the relays each have tripping contacts (one from each relay) tripping the CB. the CB has 2 trip coils and each coil gets...

hi i want to find out if there is a specific standard when it comes to duplicate protection. when wiring two differnet protection relays for a transmission bay, should the tripping circuit for the trip coils be seperated. i know that in my experience when we have 2 distance relays they are...

hi people can a single distance relay be used to provide permissive under-reach or over-reach protection? from what i understand there must be 2 same relays across either end of the line to use POTT or PUTT. we have a 7sa512 and a REL521 on one end and then ONLY a REL 521 on the remote end, but...

hi again, can the earth grid from a windfarm be connected to the substation earthgrid (10 km away ) via the cable earth sheaths? the fault current at the substation is 10kA, will the cable heat when a earthfault occurs? will the earth sheath handle 10 kA? the cable from the customer's windfarm...

hi people.. i have two 110kv line bays at a loop station and this is in turn connected to a transformer that also feeds into our grid. the protection for the line bays is required to trip the transformer. i asked why the transformer needs to be tripped for a lin fault and the answer i got was...

hi ppl 2 questions 1.why is the white phase of a voltage transformer normally earthed? 2.I have a delta system. W-phase grounded, when I measure between phases I get 110V. What u are actually measuring is the voltage across a voltage coil. If I measure between the A-B = 110V, B-C = 110Vand...

hi need to know if any utilities out there are using ni-cad batteries for substations that are 110kv and above. just to get a number ...i need to order batteries for all our subs but i am worried as to wheter this is tried and tested before, as i dont want to get caught out with problems later...

a distance relay is also called an impedance relay.yeh you are right about the word distance. in 1968 ( when engineers first started to introduce these relays they were purely used to detect faults on lines and somehow the relay manages to measure the disance to the fault. by doing this it...

hi ppl. can step and touch be measured or tested. Also after the earth grid in contructed can we measure its resistance?

hi ... what is zero seq impeadance? were does it come from?

What is Power Factor Correction? Most loads on an electrical distribution system fall into one of three categories; resistive, inductive or capacitive. In your own plant, the most common is likely to be inductive. Typical examples of this include transformers, fluorescent lighting and AC...

hi have the same problem.we put in larger capacity cables but the busbars and cts are under-rated. so now the only solution is to re-design and increase the capacity of the b/b including all the ct's. so unfortunately theres nothing else that can be done .if you really want the circuit to carry...