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parimalam
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Join Date: Feb 2009
Posts: 34

Droop CT to be Shorted When Running Single, Why?

09/28/2012 7:02 AM

Hi All,

Good day. Why all the AVR drawings shows that to short the Droop CT when running single. I understand that all the Un used CT secondary needs to be shorted when not connected to the system with the appropriate burden. In case of AVR the droop CT is connected to the AVR and the burden resistor is installed on the AVR, but one switch is shown to short the CT when the Alternator running as single and to open the switch when alternator is running as parallel.

My Question

1. Why we need to shrot when running single

2. What happens if we dont short when running single.

thanks and best regards

K.Parimalam
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harry potter
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Join Date: Nov 2008
Location: India
Posts: 333
Good Answers: 6
#1

Re: Droop CT to be shorted when running single, why?

09/28/2012 7:20 AM

CT will burst on full load.To prevent this, it is shorted. In fact, whenever CT secondary is open in any of the applications, it is shorted, because on load, open circuit voltage induced is much much more than the rated voltage, leading to flash over / bursting of CT.

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parimalam
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Join Date: Feb 2009
Posts: 34
#2
In reply to #1

Re: Droop CT to be shorted when running single, why?

09/28/2012 7:51 AM

Hi Harry, Thanks.

Undetstood, un used CT secondary need to be shroted, my question is to know why CT to be shorted when not running on Parallel while it is connected to AVR and it has Burden resistor is installed.

thanks and best regards

K.Parimalam
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Joshi
Guru

Join Date: Oct 2007
Location: India
Posts: 1246
Good Answers: 34
#3

Re: Droop CT to be Shorted When Running Single, Why?

09/28/2012 8:42 AM

Is your answer HERE ?
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parimalam
Associate

Join Date: Feb 2009
Posts: 34
#4
In reply to #3

Re: Droop CT to be Shorted When Running Single, Why?

09/28/2012 10:13 AM

Hi Joshi,

Good day. I could not find the answer from the link that you have given.

thanks and best regards

K.Parimalam
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RAMConsult
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#5

Re: Droop CT to be Shorted When Running Single, Why?

09/28/2012 10:19 AM

The answer is that when you are running Isolated there is no need for droop compensation, it is only used when you are running in parallel with other machines when drrop is necessary to make sure the vars are shared with other machines.

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parimalam
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Join Date: Feb 2009
Posts: 34
#6
In reply to #5

Re: Droop CT to be Shorted When Running Single, Why?

09/28/2012 7:58 PM

Hi RAMConsult,

Good day. thanks, please advice what if we kept the droop CT connected to the AVR while single running? Is there going to be any issues?

thanks and best regards

K.Parimalam
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MarkTheSecond
Active Contributor

Join Date: Sep 2012
Posts: 12
Good Answers: 3
#7
In reply to #6

Re: Droop CT to be Shorted When Running Single, Why?

09/29/2012 10:46 AM

Hi

What will happen is that as the current from your generator increases/decreases during running, the voltage with alter from your rated voltage. This does not happen when you are connected to the grid as the grid holds the voltage. It is set to droop when connected to the grid in order that your generator shares VARs with the grid.

However, when you disconnect and run single you do not need to share VARs with the system. And to prevent the voltage swaying with the current the droop needs to be neutralised. This is done by shorting the CT
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parimalam
Associate

Join Date: Feb 2009
Posts: 34
#8
In reply to #7

Re: Droop CT to be Shorted When Running Single, Why?

09/29/2012 8:21 PM

Hi Mark,

Good day. Thanks a lot, you have given very good explanation and my doubts are cleared.

thanks and best regards

K.Parimalam
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MAfzal
Active Contributor

Join Date: Sep 2012
Location: Pakistan
Posts: 17
#9

Re: Droop CT to be Shorted When Running Single, Why?

10/04/2013 1:51 AM

Another question has arised in my head is that Normally CTs are wired such that one terminal is of each CT is shoted with Earth. Does that also apply to the droop CT? its k terminal should be earthed or not for proper operation?
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Users who posted comments:

harry potter (1); Joshi (1); MAfzal (1); MarkTheSecond (1); parimalam (4); RAMConsult (1)

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