What is the difference between sensitive earth fault and
restricted earth fault in power transformers?
- 4 Answers
- 50472 Views
- I also Faced
- E-Mail Answers
Answer Posted / raghavendran
Sensitive Earth fault protection: Normally used on systems
where the earth fault current is limited to a very low
value. Scheme consists out of a ring CT (Core Balance CT)
around the three phase conductors, and the relay connected
to the secondary side of the CT. A very low setting is
possible, even sometimes lower then 1% FLA. Need to
coordinate with similar relays downstream. This method is
based on primary current vector addition or flux summation.
The conductor
cables pass through the center hole of the core balance CT.
Secondary current is the system zero-sequence current
3I_0.This scheme provides increased sensitivity with no
false residual currents. However,
care must be taken to prevent false tripping from unbalanced
inrush currents that may
saturate the current transformer core.
residual Earth Fault Relay:Restricted Earth Fault Protection
Is a type of zone of protection, or a differential scheme.
You get two types, low impedance and high impedance. Low
impedance is normally current operated and high impedance
voltage operated. High impedance REF is the most commonly
used. Relay connected in parallel with three phase CTs and
one neutral CT. It will look just for faults inside the
transformer, and need not to coordinate with relays
downstream (can operate very fast). With this kind of
protection you can protect over 90% transformer windings.
Need to use special class CTs, previously called class X
CTs.low impedance REF, are incorporated into some the new
microprocessor relays.
| Is This Answer Correct ? | 42 Yes | 5 No |
Post New Answer View All Answers
what is tri state logic gate
WHICH SIZE A.B.CABLE IS USED FOR 11KV.
What is process of anneling transformer core
Define ampere
how the CT and PT is connected in the circuit during testing of transformer explain with diagram
sugest any typical project ?
What are the basic elements used for modeling mechanical rotational system?
explain different types of d.c motors?
what rectifiers is and what are the types of rectifiers?
How Diesel Generator start ?
The slip during plugging operation is given by= A 1-s B 2+s C 1+s D 2-s
In what cases (circumstances)we should apply P controller, PD controller, PI controller & PID controller ?
How to Decide(calculate) Bush bar size for copper and aluminiam ?
why we setting 95 deg and 105 deg in wti and oti of distibution transformer ? give the reson for that ?
How to calculate main incomer rating of APFC Panel ? Let's say i want to find main incomer for 11kV, 1000kVAR Panel.
