Earth Leakage Relay

hi..frnd. yes u can use earth fault relay in delta connection.its depends on equipmnt to be protected. In generator u can use EFRelay via earthing transformer.Earthing transformer star point sense earth faul current which tripped EFR . Earthing x'mer also known as NGT. in deta x'mer earth fault protection core ballence type earth fault protk. Use.also current ballencing prote. Can use.more details u can get from switchgear & protection book.

All these devices operate the same way. They work out the vector sum of all of the current frlowing through them at any instant. If the magnitude of that sum exceeds the trip setting, trip they do.

yes. it is applicable.TheVector Sum of 3 phase current is zero that is IR
+IY+IB=0.If anyone get deviation the Earth Leakage relay act and trip the circuit breaker. Whether it is delta or star connection.

Earth leakage relay operates on the core balance principle. Core balance current transformers (CBCT) to sense the leakage current. CBCT is mounted externally and load carrying cable are passed through it.

Ideallly, the vector sum of three phase currents is zero and can be expressed as:

IR+IY+IB = 0, For 3-phase 3 wire system (i.e. Delta circuit with no neutral)

IR+IY+IB+IN = 0, For 3-phase 4 wire system (i.e. start circuit with neutral)

In case of a leakage current either due to insulation failure or direct line to ground fault, the balance of vector sum of currents is disturbed causing the electronic circuit to operate a relay within the unit. In this event the relay that is generally connected to circuit breaker operates thus tripping the main circuit.

For more understanding: Follow links

http://www.prokdvs.com/products/1%20EARTH%20LEAKAGE%20RELAY.pdf

[CR4 Admin: deactivated broken link]

http://www.navago.in/relay2.html

Vinu_answers Sure_Answers

Thank you.Really ur link was very useful....keep it doing

Good links by Vinu_Answers.

If you want to understand earth leakage phenomenon in more depth, here is a good paper from Schneider Electric : ect114.pdf

It will work for sure as long as the Delta connected apparatus is connected to an earthed source.

If the source is not earthed then there will be no earth leak current with which to create a vector sum imbalance.

Yes, you are right.

But the OP wants to know how a DELTA source gets to be earthed so as to have an earth leakage return.

Please. can you explain, and thanks

See #3⇑.