Why Neutral Busbar CT & transformer neutral CT connected
with phase CT in Restricted Earth Fault?
Answers were Sorted based on User's Feedback
Answer / vinod g
In Restricted earth fault protection Three phase CT is
parralleling (shorting all S1 andshorting all S2 together)
and paralleel conection with Neutral Relay and CT. IN
Healthy conditon current in all the three phase will be
balanced and summation will be zero. During earth fault out
side CT area summation of phase CT currents and Neutral CT
zero, so relay will not pick up. When earth fault inside
the transformer the current in the CT will differ and Relay
will pick and trip the tranformer breaker,so it is clear
that REF is for Transformer Winding protection and Bushing
CT is normally using for phase CT
Is This Answer Correct ? | 3 Yes | 0 No |
Answer / pintu
THIS IS CALLED 5 CT CONFIGURATION (3 PH. CT + 1 X'MER NCT +
1 BB N CT)OF REF PROTECTION. ALL THESE FIVE CTS ARE TO BE
CONNECTED IN PARALLEL. TRANSFORMER NCT SHOULD BE LOCATED
AFTER NEUTRAL BIFERCATION (I.E. PATH TOWARDS EARTH) AS THIS
IS DEDICTAED FOR DETECTING THE RESIDUAL CURRENT IN CASE OF
GROUND FAULT. BUT NEUTRAL BUSBAR CT IS NOT FOR DETECTING
THE FAULT CUURENT BUT FOR THE UNBALANCE CURRENT IN THE
SYSTEM. IT SHOULD NOT BE TRIPPED DURING THE EARTH FAULT.
IN 4 CTS CONFIGURATION OF REF PROTECTION, NEUTRAL BUSBAR CT
CONNECTION WILL NOT BE THERE. YOU SHOULD DECIDE THE 5 OR 4
CT CONFIGURATION AS PER YOUR SYSTEM DESIGN.
Is This Answer Correct ? | 3 Yes | 2 No |
Answer / anup mahajan
The purpoae of Restricted earth fault (REF) is to provide
the protection of transformer neutral in case of residual
current. As the fault which lies near phases are known as
external faults and is to be detected by differential
protection but the residual current which is not going to
ground and circulates between neutral and phases are
detedted by REF protection. Please keep in mind that CT
characteristics of this REF must be matched with phase side
CT characteristics.
Is This Answer Correct ? | 2 Yes | 8 No |
Why the rotor winding is short circuited of induction motor
What kind of socket shall be provided for window type air conditioner with cooling capacity upto 18000 BTU/hr
What is the funstion of buscoplure in LT panel? which propouse using the buscoplre
can a generator with 15AH specified battery for starting can be connected to a battery of greater capacity?
in 33/11kv stepdown transfomer, transformer will stepdown to 11kv & remaining 22kv where it will go..
I want formula to calculate cable size as per load given in kw & amp.I searched many sites but didn't right answer.Plz reply me asap.
41 Answers Armco, BEL, BGS, Biocon, BRB Cable, Crystalline Chemical Industries, DLF, Doshion, Electrical, Gold Roof, L&T, Lanco, MEIL, Oman Cables Industry SAOG, PK Services, Polycab, Sabic, SLV, System Electrical, Tata Motors, UEM, UMIC, Vega, Vertex, Voltas,
Can you any explain about active,reactive and apparent power in power system with example.
when the diameter of the core and cable is doubled, the value of capacitance ?
Form fator is the ratio of?
when we r using single phase load and we have power cable of 3.5core with .5 of neutral and neutral is suppose to the returen path of the phase how much current will flow in the neutral.reply.
what is tha online tapping and offline tappchange? which side connected primary or secondary and explain ?
what is difference between inductive and reactiveload?