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mohsinhamid
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Join Date: May 2011
Posts: 91

Definite Time Relay

08/06/2011 10:20 AM

what is definite time relay...?? i have seen the relay in tat sme time setting is there... for what these time setting is mentioned...??? psl explain in detail....
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RAMConsult
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Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
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#1

Re: definite time relay

08/06/2011 10:40 AM

Please Google for lots of detail...

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 “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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hbadhan
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Join Date: Aug 2011
Location: India
Posts: 29
Good Answers: 2
#2

Re: definite time relay

08/06/2011 11:04 AM

To understand DTR (definite time relay), you need to also understand the other category i.e. ITR (inverse time relay) for a better clarity. Over current relays can be broadly categorized in two class:

1. Definite Time O/C Relay

2. Inverse Time O/C Relay

As the name suggest, DTR needs DEFINITE time to operate whenever the current reaches or EXCEED the current (I) set value. In case of even higher fault currents then the set value, the time of operation will not change and will remain same thus DEFINITE time.

On the other hand, for ITR, operating time changes with current magnitude and in inverse fashion i.e. more the fault current lesser will be the operating time and hence the name INVERSE time O/C relay.
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mohsinhamid
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Join Date: May 2011
Posts: 91
#3
In reply to #2

Re: definite time relay

08/07/2011 5:18 AM

tnks frnd... but in our feeder in that relay it has 2 timings...

1. delay on drop OFF

2. delay on pick UP...

what these means explain clearly...???
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hbadhan
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Location: India
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#4
In reply to #3

Re: definite time relay

08/07/2011 11:58 AM

This query is different then your original query wherein DTR was clarified in the context of overcurrent relay. Further, in your orginal posting you metioned 'relay has same time setting' while now it is mentioned 'relay has two timings'.

Notwithstading the confusion, pl. note below reply to the new query:

1. Delay-On Drop-Off: Upon closing of an external initiating contact, the relay contacts c/o immediately and hold. Upon opening of this initiating contact, delay is ON (i.e. countdown starts). The contacts positions are still same until after the set time (say 10 sec.) after which relay contacts return to their normal position (drop off).

2. Delay-On Pick-Up: When relay is powered through closing of an external initiating contact, Delay is ON (i.e. countdown starts). However, contacts c/o takes place only after the set time (say 5 sec.). Relay contacts continue to stay in that position (pick-up) till relay coil is de-energised (i.e. external initiating contact reopens).

Hope this helps in understanding the concepts. However, I suggest you refer a schematic diagram wherein drop-off/pick-up timer is implemented for a better understanding.
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mohsinhamid
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Join Date: May 2011
Posts: 91
#5
In reply to #4

Re: definite time relay

08/08/2011 1:25 AM

frnd tnsk for ur reply....

i never said it is mentioned DTR O/C RELAY... it is mentioned definite time relay only... there are 2 difinite time relay... one is delay-on drop-off and another DTR is delay-on pick-up...

pls brother elecborate the explanation u had give on two timings... i can understnd... what is external initiating contact... what ur refering too... psl eleborate...
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hbadhan
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Join Date: Aug 2011
Location: India
Posts: 29
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#6
In reply to #5

Re: definite time relay

08/08/2011 12:45 PM

Pl. refer below link (Typical wiring diagrams by Allen-Bradley):

http://samplecode.rockwellautomation.com/idc/groups/literature/documents/wd/gi-wd005_-en-p.pdf
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mohsinhamid
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Join Date: May 2011
Posts: 91
#7
In reply to #6

Re: definite time relay

08/09/2011 4:11 AM

tnks frnd i downloaded the pdf... but i cant find the deifnite time relay in tat... where is tat...????
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