Sir we have 12.5 MVA(110/11KV) transformer (Y-Y)
connected,which tripped showing earth fault,when we charged
transformer it stood OK ,but on connecting 11 KV feeders it
tripped showing earth fault.our service engineers found that
the B phase and R phase phase connecting to neutral broken
from HV OLTC(on load tap changer),and R phase and Neutral is
ok.Dissolved gas analysis shows that accetline content is
high,tan delta value is 12.My dout is it is an internal
fault of transformer,why REF or diffrential relay is not
acted?
- 1 Answers
- 4209 Views
- I also Faced
- E-Mail Answers
Answer Posted / k.prakashchandra
REF relay does not act as the unbalanced current is equal to
NCT current in all respects. And for diff relay, it also
does not act as the corresponding ct currents in HT and
sides for each phase are equal.If there is current in only
one phase ,EFR will trip as current's return path is through
the EFR.But why there is current in the single good phase as
all dist Trs are delta/ star connected ? May be due to star
connected line capacitors or dist trs/loads are also star
connected with neutrals earthed.
| Is This Answer Correct ? | 0 Yes | 0 No |
Post New Answer View All Answers
Hi Everyone ! My Name is Hakim ullah khan please i need formula of Cable Rating because i want to calculate by self without check any Table Chart... Thank you.....
I have done my m.tech in electrical engg discipline. Can any one please suggest me how should I prepare for getting into phd in iit or nit.How should I prepare for getting into lecturership
IF TVM OF TRANSFORMER SHOWS POWER FACTOR ON 33 KV SIDE AS 0.97 LAGGING AND ON 132 KV SIDE IS 0.75 LEADING.IS THIS CORRECT.WHERE IS PROBLEM.
What is the physical significance of phase.. i.e. what is exactly the meaning in layman's language.. 1 phase, 3 phase etc ???
when we design electrical schemes of 11/.415kv distribution..wen and were should we show the relays??what is the function of it?for example..we place EFR Relay CT between transformer neutral link and transformer earth.Like this what are the other type of relays we should use?why?where?Explain please..Thank you
how many types are their in switchyard or substation(like D,I TYPE), what is differant between them
Is it possible to download the Siemens Selection Chart(TYPE 2 coordination) for 1) fuseless selection 2)Fuse selection
what are your career plans upon completion of the programme and the relevance of recity generation to your professional development?
What is transmittance?
I don't understand why when we connect high voltage source in DC to electronic motor , we must add capacitor and resistor in parallel ? (I know that we use capacitor because we want to absorb the current that in the first second electronic motor in opposed with current course produce. ) what are the feature of Resistor and in such situation ?
What is a differential amplifier? Also, explain cmrr.
what is laser diodes?
What are the advantages and disadvantages of closed-loop control system?
what is differant beetween overload current and phase current?
previous year paper of ntpc bhel for degree in electrical enng
