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3
Operation
Theory
PCS-978 Transformer Relay
3-10
Date: 2013-01-16
I’’_H, I’’_L are secondary corrected currents of HV and LV sides respectively.
M1, M2 are matrixes of phase shifting and zero sequence current elimination of HV and LV sides
respectively.
2
2
1
2
,
bBr
bBr
I
I
are rated secondary currents at HV and MV sides respectively.
To clarify the situation, three important operation conditions with ideal and matched measurement
quantities are considered.
1. Through-flowing current under undisturbed conditions or external fault:
I
’_H flows into the protected zone, I’_L leaves the protected zone, i.e. is negative according to
the definition of signs in above figure, therefore I
’_H=–I’_L.
Moreover |I
’_H|=|I’_L|
Id=|I
’_H+I’_L|=|I’_H–I’_H|=0;
Ir=(|I
’_H|+|I’_L|)/2=(|I’_H|+|I’_H|)/2=|I’_H|
No differential current (Id=0), restraint current (Ir) corresponds to double the through-flowing
current, and current differential protection does not operate.
2. Internal short-circuit. e.g. fed with equal currents each side:
The following applies I
’_L=I’_H, moreover |I’_L|=|I’_H|
Id=|I
’_H+I’_L|=|I’_H+I’_H|=2|I’_H|;
Ir=(|I
’_H|+|I’_L|)/2=(|I’_H|+|I’_H|)/2=|I’_H|
Differential current (Id) are two times of restraint current (Ir) and corresponding to the total
fault, and current differential protection operates.
3. Internal short-circuit, fed from one side only:
The following applies I
’_L=0
Id=|I
’_H+I’_L|=|I’_H+0|=|I’_H|;
Ir=(|I
’_H|+|I’_L|)/2=(|I’_H|+|0|)/2=|I’_H|/2
Differential current (Id) are two times of restraint current (Ir) and corresponding to single-sided
fault, and current differential protection operates.
3.2.3.6 Sensitive Biased Differential Protection
The currents used in this section analysis and the following analysis have been corrected, that
means the currents for following calculation are the products of the actual secondary current of
each side multiplying its own correction coefficient
The sensitive biased differential protection with low pickup setting and restraint slope is much
more sensitive for a slight internal fault. Four blocking elements, CT saturation, inrush current, CT
Содержание PCS-978
Страница 1: ...PCS 978 Transformer Relay Instruction Manual NR Electric Co Ltd ...
Страница 2: ......
Страница 6: ...Preface PCS 978 Transformer Relay IV Date 2013 01 16 ...
Страница 10: ...Preface PCS 978 Transformer Relay VIII Date 2013 01 16 ...
Страница 62: ...3 Operation Theory PCS 978 Transformer Relay 3 p Date 2013 01 16 ...
Страница 250: ...4 Supervision PCS 978 Transformer Relay 4 b Date 2013 01 16 ...
Страница 264: ...4 Supervision PCS 978 Transformer Relay 4 14 Date 2013 01 16 ...
Страница 266: ...5 Management PCS 978 Transformer Relay 5 b Date 2013 01 16 ...
Страница 272: ...5 Management PCS 978 Transformer Relay 5 6 Date 2013 01 16 ...
Страница 334: ...6 Hardware Description PCS 978 Transformer Relay 6 60 Date 2013 01 16 ...
Страница 370: ...8 Human Machine Interface PCS 978 Transformer Relay 8 d Date 2013 01 16 ...
Страница 404: ...8 Human Machine Interface PCS 978 Transformer Relay 8 34 Date 2013 01 16 ...
Страница 406: ...9 Configurable Function PCS 978 Transformer Relay 9 b Date 2013 01 16 ...
Страница 446: ...10 Communication PCS 978 Transformer Relay 10 26 Date 2013 01 16 ...
Страница 448: ...11 Installation PCS 978 Transformer Relay 11 b Date 2012 10 09 ...
Страница 456: ...11 Installation PCS 978 Transformer Relay 11 8 Date 2012 10 09 ...
Страница 458: ...12 Commissioning PCS 978 Transformer Relay 12 b Date 2012 12 07 ...
Страница 468: ...12 Commissioning PCS 978 Transformer Relay 12 10 Date 2012 12 07 ...
Страница 470: ...13 Maintenance PCS 978 Transformer Relay 13 b Date 2012 10 09 ...
Страница 474: ...13 Maintenance PCS 978 Transformer Relay 13 4 Date 2012 10 09 ...
Страница 476: ...14 Decommissioning and Disposal PCS 978 Transformer Relay 14 b Date 2012 10 09 ...
Страница 478: ...14 Decommissioning and Disposal PCS 978 Transformer Relay 14 2 Date 2012 10 09 ...
Страница 480: ...15 Manual Version History PCS 978 Transformer Relay 15 2 Date 2013 01 16 ...