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3 Operation Theory
PCS-978 Transformer Relay
3-25
Date: 2013-01-16
3.2.3.14 CT Supervision for Differential Protection
3.2.3.14.1 CT Circuit Abnormality of Differential Protection
If the differential current in any phase is greater than the alarm setting [87T.I_Alm] without fault
detector of differential protection pickup for over 10s, differential current abnormality alarm
[87T.Alm_Diff] will be issued without blocking the protection.
3.2.3.14.2 CT Circuit Failure of Differential Protection
Criteria
The following two cases are considered as CT circuit failure, and the protection relay can
discriminate which side the CT circuit failure by the unbalanced currents.
Differential CT secondary circuit failure can be judged more accurately and reliably by adopting
combined method of voltage and current.
1) First case, if none of following four conditions is satisfied after the fault detector of biased
differential current, or biased residual differential current, or biased winding differential current
picks up, it will be judged as CT circuit failure and CT circuit failure alarm will be issued.
Negative-sequence voltage at any side is greater than 2%Upp (Upp is the secondary
phase-to-phase rated voltage).
Any phase current of any side increases after fault detector picks up.
The maximum phase current is greater than 1.1pu after the fault detector picks up.
DPFC element of any phase-to-phase voltage of any side picks up.
2) Second case, if CT circuit abnormality of differential protection alarm (i.e. [87T.Alm_Diff]) is
issued and negative-sequence current of one side is greater than 0.04 times maximum phase
current of the corresponding side or greater than 0.01In, and then CT circuit failure will be
judged.
Influence of CT circuit failure on differential protections
User can configure the output of CT circuit failure alarm to block transformer sensitive biased
differential protection, reactor sensitive biased differential protection, biased REF protection and
biased winding differential protection via logic settings [87T.En_CTS_Blk], [87R.En_CTS_Blk],
[64REF.En_CTS_Blk], and [87W.En_CTS_Blk] respectively. The CT circuit failure alarm is latched
once issued, it can be reset only after the failure is cleared and equipment is reset (i.e. the binary
input [BI_RstTarg] is energized).
1) Transformer conventional biased differential protection and instantaneous differential
protection are always not blocked during CT circuit failure.
2) Transformer DPFC biased differential relay is always blocked during CT circuit failure.
3) Transformer sensitive biased differential protection can be blocked when CT circuit failure is
detected by configuring the logic setting [87T.En_CTS_Blk].
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 ...