why restricted earth fault protection can not operate for
phase faults??as there will be a current in secondary of
ct,when a phase fault occurs!
- 1 Answers
- 2304 Views
- GMR, I also Faced
- E-Mail Answers
Answer Posted / tapas
* In REF scheme 4 nos of CTs are used. 3 for phase and 1 for Neutral.
* It operates in the principle of balance current between phase and neutral and only inside In-zones. i.e. it protects Transformer, Busduct, LV switchgear.
* In this protection phase CTs are connected in such a way that it forms a close path between phase CT secondaries and this close path is connected with neutral CT secondary.
* In between the close path connected to common terminals of phase CT secondary and Neutral CT secondary REF relay is connected.
* When a phase fault occurs there is also residual current in Neutral. So current between both paths oppose each other and hence there will be no current in REF relay. So it won't operate.
| Is This Answer Correct ? | 1 Yes | 0 No |
Post New Answer View All Answers
What is “pu” in electrical engineering?
Why syn. Generators are used for the production of electricity?
how single phase preventer works ?
why do we use spark detector inside the slip ring brush compartment 0ona slip ring induction motor?
how to get bearing & winding temperature of an induction motor?
What was your role in the silicon evaluation/product ramp? What tools did you use?
how we explain parallel paths armature winding?
How to calculate energy stored in a capacitance
why wire sizes are 3/29 or 7/29 and why not wire sizes are 2/29 or 6/29?
How many size of cable required for a 300m long and 30kw inductive lode
What is core CT & it's function?
What is the resistance of the field winding of a d.c. Shunt generator kept low?
What will be the voltage regulation of a full load and 0.80 power factor lagging load transformer when a two winding single phase transformer has a voltage regulation of 4.5% at full load and unity power factor?
how hazordious area is classified at an oil & gas plant and categorise suitable class of electric equipment in that area like induction motors, LCS, Lighting Fixtures Fluerescent/Flood lights Mercury& sodium lights, J.Bs, Power Cables etc
how i calculate the syncrones generator NGR resistance .if we have a 6mw generator line voltage of generator 11kv also line current 393.3 ampere.
