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hien.nguyenquoc
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Protection Relays Coordination

05/08/2011 7:38 AM

If we don't have any software of relay coordination, how can we plot the coordination curves for relays?

Sometimes, several relay characteristic curves and transformer inrush current curves, or motor starting characteristic curves are not plotted in the same scale in term of time and current. Do we have any standard sample of paper which show us time and current scale?

In the case that software is available, but for some manufacturers we cannot update the equipment series number, how can we know the characteristic curve?

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kvsridhar
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#1

Re: Protection Relays Coordination

05/08/2011 10:30 AM

Please don't get me wrong, but relays and co-ordination existed before the advent of computers. i have seen old salts poring over transparent log-log paper working out equipment choice. Of course, relays were not as sophisticated as the ones today (since the microprocessor didn't exist) so we were only using time-based discrimination. So LV CBs had 1 sec and 3 sec SC withstand ability. i must say here that the induction disc relays of English Electric were a joy to test ... marvelous precision.

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hien.nguyenquoc
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#2
In reply to #1

Re: Protection Relays Coordination

05/08/2011 10:38 AM

Totally agreed, but why don't we find any log-log papers for this purpose today?

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kvsridhar
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#5
In reply to #2

Re: Protection Relays Coordination

05/08/2011 10:53 AM

You can get them at the stationers i am sure. Or you can create your own in Excel for example. Or you can take advantage of someone else having done this for free from http://incompetech.com/graphpaper/logarithmic/

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electricalexpert65
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#3
In reply to #1

Re: Protection Relays Coordination

05/08/2011 10:40 AM

I fully agree with you, KVS! It was real joy & good pastime to test those CDGs, CDAGs, CDDs, CTUMs, CDDs & DTHs. One got to understand a lot about relays during such testings.
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hien.nguyenquoc
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#4
In reply to #3

Re: Protection Relays Coordination

05/08/2011 10:46 AM

Ok, then what is that? Please be more specified.

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electricalexpert65
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#6
In reply to #4

Re: Protection Relays Coordination

05/08/2011 12:33 PM

CDG - Current opearted Disc type General Purpose (Electro-mechanical inverse time overcurrent relay)

CDAG - Current opearted Disc type & Attracted armature type General Purpose (Electro-mechanical inverse time overcurrent relay for phase overcurrents and Instantaneous relay for the earthfault element)

CDD - Current opearted Disc type Directional Purpose (Electro-mechanical inverse time directional overcurrent relay)

DTH - Differential current operated Transistorised with Harmonic restraint (Transformer Differential Relay with 2nd Harmonic Restraint Feature)

But, forget it! With the advent of micro processor & numerical relays, the above terminologies have no meaning anymore.
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nesubra
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#7
In reply to #1

Re: Protection Relays Coordination

05/10/2011 1:03 AM

You are right.The induction relays of EE were so good and reliable.I enjoyed working with them .There are some who still prefer only this type and TNEB is one of them.

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hkian
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#8

Re: Protection Relays Coordination

05/13/2011 12:23 PM

you can always use ms excel.. for free version you can also use.. open office calc..
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Users who posted comments:

electricalexpert65 (2); hien.nguyenquoc (2); hkian (1); kvsridhar (2); nesubra (1)

Previous in Forum: Earth Fault Relay 64   Next in Forum: Commissioning of Repaired 132kv/6.6kv Transformer

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