IET
Decrease font size
Increase font size
Topic Title: Transformer Auxiliary Control Cabinet
Topic Summary: short circuiting links at Current Transformer
Created On: 26 November 2012 10:33 AM
Status: Read Only
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 26 November 2012 10:33 AM
User is offline View Users Profile Print this message



shenshenshen

Posts: 1
Joined: 26 November 2012

Hi, would like to know for the Current Transformer, the auxiliary control cabinet, what is the purpose of having short-circuiting links with easy access? one side of the secondary winding of each current transformer is grounded.

Thanks.
 26 November 2012 11:49 AM
User is offline View Users Profile Print this message


Avatar for JonathanHill.
JonathanHill

Posts: 225
Joined: 09 September 2002

A CT with current in the primary will develop a potentially dangerous high voltage if the secondary circuit is opened. These voltages can be life threatening and damage insulation. Therefore, it's essential that a short circuit is applied to the secondary circuits before any disconnections/ insertion of test plugs etc are done and this activity should be planned into the safe system of work for the task in hand. This process requires training/ competency and untrained persons should not attempt this.

Whilst it can be argued that if the primary circuit is disconnected, then there's no possibility of developing any voltage on the CT secondary, it is good practice to apply the short circults in any case to avoid the nasty consequence of any memory lapse.

-------------------------
Jonno
 26 November 2012 09:07 PM
User is offline View Users Profile Print this message



cookers

Posts: 205
Joined: 10 February 2012

There are one or two people I know who wished either themselves or others had the knowledge to apply the short circuit.
 01 December 2012 10:00 AM
User is offline View Users Profile Print this message



fredman

Posts: 221
Joined: 26 July 2007

Always short down the CT's when doing any work on the the meter side, As Jonathon has stated the voltages are high and damaging to cable insulation and also to anyone who comes in contact with the open ends.

Safe system of work required and correct training needs to be in place, have seen the shorting terminals installed round the wrong way!
 02 December 2012 04:46 AM
User is offline View Users Profile Print this message



maharaja

Posts: 2
Joined: 25 July 2008

Originally posted by: shenshenshen

Hi, would like to know for the Current Transformer, the auxiliary control cabinet, what is the purpose of having short-circuiting links with easy access? one side of the secondary winding of each current transformer is grounded.



Thanks.
 02 December 2012 04:54 AM
User is offline View Users Profile Print this message



maharaja

Posts: 2
Joined: 25 July 2008

The CT seconadry shorting llinks are extremely useful for number of online tets carried out whic are mandatorily to be carried out ON LINE ie without isolating CT from primary circuit . The typical tests are 1) phase angle measurement in the metering and protection circuit 2) Busfault stability and 3 ) Transformer differentiial protection stability test. They are also used to isolated particular circuit from Busfault looping .
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.