Relay Coordination

Parameters are current & time. The question is not clear. IDMT over current relay co-odinated as well as Earth fault. This is a vast and interesting subject.I will suggest you to refer GEC Measurement Book or IEEE 242 (Buff Book).

Basicly.., You have to know how many impedance (R & X) of the instalation such the cable power between the node you want to setting and the nearest node. Then you must find out about the short-circuit level on the node of the circuit. Further you can implement the short circuit current on the other node you want to setting ..

I think CR4 forum is not a place for marketing of ones product or services. If the question is a basic one it can be briefly described or suggestion can be given for some technical docs standards etc.

Anyway, for any electrical installation our target is to maximise the availability of the system into operation and isolate the particular zone where the electrical fault occured. The back-up protection also considered for that zone. In case that too fails next upstream system is required to operate to isolate the fault. The co-ordination study required to minimise the outage of circuits while isolating a faulty zone.

This is an important subject to properly deal with which require experience and expertise, for the healthy operation of electrical systems/circuits.

I am sorry,if i have used CR4 for marketing my services.

I have given the extract from my write up for the guest to understand.

I have contributed in this forum and many private queries have been sent to me based on my contribution in this forum. Only on this context I have requested guest to contact me privately if they seek any queries and not to promote me.

Thanks for your comment.

Hi Ram,

Your reply to thread is good and you gave a brief reply. I do not think you have done any marketing by telling others that you can be contacted, if they want to know more about the subject. I feel you must write a full article on this subject considering your experience on the subject and publish in CR4. It may benefit many young engineers.

In fact relay coordination is a subject many electrical engineers do not understand.In Indian conditions I have experienced that many of our power tripping could be avoided if proper relay coordination is done.Many of the down stream faults are carried over in many distribution net works causing avoidable main feeder trips affecting larger number of out going feeders. The power outing due to tail end fault could be localised with proper relay coordination.In many of the meetings with Electricity Board authority during our discussions,they have privately accepted the fact that the engineers are at least not conscious about the importance of relay coordination if not ignorant. So let us give better publicity to the subject.

what you are saying is very correct.But will you explain me how power gets trip? How can i study relay co ordination in deep?

regards,

Yojana

Eelctrical Engineer.

Dear Sir,

1) iI like to know what is the detail calculations to work out relay co ordination.

2) I am working on Mumbai Monorail project. I like to know that our client is asking earth gride for EARTHING. But our substation of 22 /0.433 kV 315 kVA is INDOOR and they are asking for TOUCH & STEP Potential.

So I like to know that in INDOOR substation earth gride and step / touch potential is applicable or not?

Sudhanva Madhuka Mahamuni

9769317386

Hi, I am interested to know more about ground grid design for indoor substations. I believe that if the substations is 22 kV and only 315 kVA you will NOT need a step/touch potential calculation if you have a concrete floor and all cables entering the premises are insulated and carried by conduits and raceways. My name is Ruben Corvalan my email is corvalan@ampsafe.com and telephone number is 210.241.4276 in USA. Please get it contact to further discuss this issue. Thanks.

Kindly gve me your email add. My official email add is sudhanvamahamuni@unikengg.com

dear mr.ramvinod

can you contact me in my e mai id

anandan_cud@yahoo.co.in

regards

Dear Sir,

I am verymuch intrested to know more about Power syatem Protection design ,

Kindly send me a test mail for discussing further,My Mail id:avenkatasubramaniyan@yahoo.com

With ^ Regards

A.Venkatasubramaniyan

Dear Sir, i am a newbie in designing field and my hod given the task to do the relay settin for the 33/11kv substation and also it grading from downstream to upstream. i am confused how to get the time multiplier setting. suppose if my plug settin is 100% thn i have to get the TSM value because actual time of operation= T.M * T1 T1= TIME OBTAINED FRM STANDARD GRAPH FOR A GIVEN FAULT CONDIT PLEASE HELP ABOUT IT AND ENLIGHTMENT WITH YOUR KNOWLEGDE.

the main parameters for the relay co-ordination are current flow from the CT, plug settings of the relays, time of operation of each relay and have to calculate the primary operated relay and the back up of that relay.... thenwe have to decide the definite time characteristics and inverse characteristics oe those relays....

As an maintenance engineer/safety consultant, these are some of the facts in Indian industries 1. regular testing of relays are done with a motive to improve system reliability is done in few companies 2. digital relays are tested very rarely 3. relay testing companies don't do full testing and doesn't possess full knowledge in the relays it is time that we should have a certifying body for testing professionals like NETA in US.

All protective relays must follow the rules

1. They should not interfere with normal operating conditions, temporary over load conditions, temporary but acceptable abnormal conditions.

2. Subject to the condition 1 above, all primary relays must operate as quickly as possible to isolate the fault within its primary protective zone.

3. When primary relays as in step 2 fails to operate to clear faults within its primary zone, backup relays must next function with a time discrimination to isolate the faults. This usually results in isolation of larger part of the network.

4. The instantaneous settings or definite time settings of backup relays if any should not interfere with the operation of primary relays

Backup protection of electrical transformer is simple Over Current and Earth Fault protection applied against external short circuit and excessive over loads. if you doesn't satisfy, Plz Visit Relay-coordiation study