1177   Winding ratio for TCTR and TVTR

Created: 16 Oct 2013

Status: In Force (green)

Part: Part 7-4 (2010; Edition 2)


Page: 97, 104, 143

Clause: 5.15.4, 5.15.20, 6


Category: Issue for edition 2 of this part


TVTR and TCTR have a setting Rat (Winding ratio of an (external) instrument transformer/transducer). Not in all cases this is really a winding ratio which is clear e.g. for a capacitive divider. The value which is of common interest is the ratio between the primary values and secondary values.


Update the description of Rat to about -> "Ratio between the primary and secondary value of an instrument transformer/transducer"

Discussion Created Status
Rod, I would like to refer to IEC 61869-9. We have introduced a couple of changes acc. to their requirements in the current draft for FDIS. E.g. Class P and PX are assigned as values to the enum TransientPerformanceClass. 03 May 18 In Force (green)
I know this is a few years late ... but the proposed change in text is not true in all cases
a class P CT specifies the CURRENT ratio between the primary and secondary measured currents and that has a certain defined measurement accuracy, i.e. you specify for 1000 A primary it produces 1 A and that the accuracy is within 10% upto 20 kA primary i..e it is 20 A secondary +/-10% which is achieved by removing a few turns to compensate for losses

a PX class CT specifies the physical TURNS ratio (a true WINDING ratio) and there is no specific accuracy definition of the measured current e.g. 1000/1 says that for every single primary turn there is EXACTLY 1000 secondary turns
02 May 18 In Force (green)
08 Jan 14 In Force (green)
08 Jan 14 In Force (green)
Improve the text: Ratio of the primary value to the secondary value of an instrument transformer/transducer. 10 Dec 13 Ballot Period
11 Nov 13 Ballot Period
Agree 18 Oct 13 Discussion (red)


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