Answer / shailesh aggarwal

Basically Earth faults are caused if high fault current
flows through the neutral of the transformers. This type of
fault arises mainly in Star connected transformers.Earth
faults are specified in many categories:
1. Restricted Earth faults(Inside the zone HT/LT side of
trafo) Connection are done b/t Phase CT & Neutral CT of
tranformer)Indicated as REF(64)
2. Standby Earth Faults(Directly linked with neutral of
trafo)connection only done b/t neutral CT.Indicated as SBEF
(51N).
Both the protection give signals to the numerical relays
and cause the tripping as earth faults and directly trip
the transformer.
Thus in order to save transformers a proper earthing is
required whether solid or usong NGRs.

Answer / nilkanth tailor

EARTH FAULT REQUIRE C.T.(CURRENT TRANSFORMER)..TO SENSES
IMBALANCE IN 3 PHASE..GENERALLY 3PHASE SYSTEM IS IN BALANCE
CKT...IF SINGLE OR MULTI PHASE WAS EARTHED..AND AT THAT
TIME IMBALANCE PRODUCED..CT WILL BE DETECT FAULT CURRENT
AND CIRCUIT BREAKER WILL BE OPEN...THATS CALLED EARTH FAULT
PROTECTION OF X'MER...

What will the effect on a motor designed at 60 HZ, and operated on 50 HZ ??

8 Answers  

---

what is diffrent between plc and clc??

1 Answers  

---

Two 11 kv lines are feeding to common bus in a substation,I have one set of CT & PT(3ct,2pt), How can I measure both lines power using single set.

6 Answers   L&T,

---

In an ACB shunt trip coil and undervoltage coil operated normally( breaker open and charged). But closing coil not operating untill manually discharge and recharging. Any help.

0 Answers   PPIL,

---

can transformer of different kvas be paralled

2 Answers  

---

Electricty is generated at around 16kV, then step up to 220kV for transmission then steped down to power transformers then DTs and then through the LT n/w it reaches the consumer end. At the consumer end 230V supply is required. So, why is electricity not generated directly at 230V and transmitted?

4 Answers  

---

whats is the role of power factor in designing a tariff structure?

1 Answers   IIT,

---

What is the make of breakers, transformers, generators? What are their capacities and ratings?

4 Answers   Bharat Bijlee, GHPPL, Tata Motors,

---

what is meant by phase transformation ratio in induction motors?

2 Answers  

---

what is meant by switch fuse unit ?

3 Answers   Thermal Powertech Corporation India Ltd TPCIL,

---

Refernce currents are to be generated using refernce cueernts how can this be done

0 Answers   ABC, Wipro,

---

How to calulate the NGR resistance ?

1 Answers   L&T,

---