Answer / amit khamesra

As neutral of the generator is approched, the driving
voltage available between the fault point and the neutral
is very low & hence not detectable. So last 5% of the
generator winding remains nprotected with the conventional
schemes of E/F protection. that is why it is called 95%
stator earthfault protection. For covering the rest of 5%
winding other techniques like 3rd harmonic principle ets
are available.

Answer / a.p.nanjappa

This is an application with power plant genrator protection.
In early 1950-75,only 90% stator earth fault protection
used for Generator Stator winding.
GE,westinghouse,hitahachi,GEC,BBC,KWU.ON 1975 ONWARDS,
THEN 100% STATOR EARTH FAULT DEVELOPED USING OPEN DELTA
VOLTAGE OFGENERATOR AND USING FIRST AND THIRD HARMONIC
BRIDGE.
WEST AND EUROPE,INDIA USED GENERATOR NETRAL GROUNDING
TRANSFORMER AND ON SECONDARY OF THIS TRANSFORMER90%STATOR
EARTH FAULT PROTECTION IS USED.
FOR 100% STATOR EARTF FAULT USE OPEN DELTA VOLTAGE.
Russian practice is use voltage transformer for generator
neutral gounding.
when I was DISCUSSING this with european manufacturer, they
want to delete 100% protection.In a generator it is meaning
less.fault is fault.It is time consuming for repair.
As a new challenge-generator manufacture claim 100%
availabilty of Generator with VIP.
/MICADOUR ELASTIC INSULATION. In gas turbine a single
generator rating is selected for single shaft gas turbine
and steam turbine. upto 275MW. AND 400MW

Answer / saka

90% Stator earth fault protection achieved through NGR and
100% Stator earth fault achieved through REF ( NGTR )

Answer / k.prakashchandra

90% means providing protection for 90% of stator winding and
100% means for entire winding

how to calculate the minimum permissible limts of insulation resistance of switchyard equipments

1 Answers   HVPNL,

---

Battery is a voltage source? give one example of current source and why?

1 Answers   Suzlon,

---

Is only insulation the difference between High voltage and Medium voltage cable?

1 Answers  

---

why in some trains in India Electric equipment such as Fans , tube light not work until locomotive or engine is attached to the train ??

1 Answers  

---

what is skin effect and corona discharge ?

4 Answers   Asian Paints,

---

where this neutral connection goes after returning from the load(home ,factory,industries).Is it grounded at the transformer side or atthe generator side .If it is grounded then we also ground the earth connection.is there any problem with this.

1 Answers   IOCL,

---

what need of NGR(neutral grounding registor)? What it works?

2 Answers  

---

how many earthing is required for sever room?

4 Answers  

---

what are the parameters plays a major role in Potential transformer Burden calculation??

1 Answers   ABB,

---

Why the tank of transformer is made rectangular not circular??

9 Answers  

---

why our power production in multiple of 11, in strictlly asking why our o/p voltage of alternators is 11kv only and whynot graterthan 15 and016KV?

4 Answers  

---

how power factor improves by connecting syncronous motor

2 Answers   ACC,

---