Previous in Forum: Induction Lighting in Warehouse/DC setting   Next in Forum: CT Magnetization Curve in MATLAB
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
4 comments
Rate Comments: Nested
Leo342
Active Contributor

Join Date: Mar 2010
Posts: 10

Separate CT Core for Generator Differential Protection?

11/09/2011 1:10 PM

Is it necessary for the differential protection system, especially of a generator, to have a pair of dedicated CT cores? Is it possible to share CT output from a CT core for the differential protection? I'm guessing otherwise. Anyways, please help remove my doubt with some solid reasons!

__________________
 leokhk@yahoo.com
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
2
msamad
Guru

Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#1

Re: Separate CT Core for Generator Differential Protection?

11/09/2011 10:24 PM

The question is not clear to me. However, it appears you do not want to use dedicated CT pair for differential protection, rather want to use same CT for other protections such as short circuit protection etc. You cannot do this because

(1) For differential protection, the burden for both side CTs should be same. If you add other protection relay to the one side CT, there will be load imbalance and it will initiate false trip signal.

(2) Differential protection requires special type of CT, not the regular protection CT.

Hope it was helpful.

- MS

__________________
 "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
Register to Reply Good Answer (Score 2)
No more Good Answers.
Leo342
Active Contributor

Join Date: Mar 2010
Posts: 10
#2
In reply to #1

Re: Separate CT Core for Generator Differential Protection?

11/10/2011 1:20 AM

Thanks! One more question, though. Does the CT secondary current for both the CTs in the pair also need to be equal. For instance, for transformer differential protection, is it possible to use a CT at the LV side with secondary current 5A while using CT at HV side of secondary current 1A?

__________________
 leokhk@yahoo.com
Register to Reply
electricalexpert65
Guru

Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#3
In reply to #2

Re: Separate CT Core for Generator Differential Protection?

11/10/2011 3:47 AM

Nope! IOf so, even during healthy conditions, assume taht the transforemr is fully loaded, the LV CT will feed in 5A and the HV CT will feed in 1A; then there would be differential current and the relay would trip for sure. If unavoidable, you can use an interposing CT to match the current at the relay point.
Register to Reply
biswanath.das
Power-User

Join Date: Oct 2006
Location: Kolkata, India
Posts: 447
#4
In reply to #3

Re: Separate CT Core for Generator Differential Protection?

11/10/2011 5:17 AM

I hope we should think the ans w.r.t todays advanced digital relay. It will see the magnitude. The CT secondary current is converted to voltage of very low magnitude to operate relay. In a broad sense old concept of Diff CT philosophy is now a days is very much modified. Please see manual of relay manufacturer.

__________________
 BNDas
Register to Reply
Register to Reply
Have a Different Question?
4 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

biswanath.das (1); electricalexpert65 (1); Leo342 (1); msamad (1)

Previous in Forum: Induction Lighting in Warehouse/DC setting   Next in Forum: CT Magnetization Curve in MATLAB

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (71 right now)
Show Members
Advertisement