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3
Operation
Theory
PCS-978 Transformer Relay
3-2
Date: 2013-01-16
There are two optional modes for harmonic criterion: self-adaptive blocking mode and
phase-to-phase cross blocking mode. Self-adaptive blocking mode can enhance ability of
differential protection to avoid maloperation during transformer energization effectively and
ensure high speed of differential protection for faults under normal operation.
Fifth harmonic or third harmonic criterion applied continuously to detect overexcitation
condition.
Three slopes biased differential protection are settable by users.
Unrestrained instantaneous differential protection is equipped.
Distinct method of phase compensation
△
→Y and Y→
△
transfer methods can be selected by user through settings, and
△
→Y
transfer method is recommended. During transformer energization,
△
→Y transfer method is
used to adjust phase angle of secondary current on each side of the transformer, and thus the
faulty and healthy phase can possess its characteristic. Therefore, restraint current and
differential current can be phase-segregated, which can distinguish the faulty phase from
phase only with inrush current characteristic when transformer is energized. Zero-sequence
current is always eliminated both at Y and Δ windings by adopting Δ→Y method.
High sensitive and securable DPFC biased differential protection
DPFC biased current differential protection is regardless of the load current and is sensitive to
small internal fault current within the transformer. Its performance against current transformer
saturation is also good.
Reliable biased current differential protection
Biased current differential protection with initial restraint slope consists of sensitive and
conventional differential elements as well as independent CT saturation criterion.
Differential CT Circuit Failure Detection
With the adoption of voltage and current combination method, CT secondary circuit failure can
be distinguished.
3.2.3 Protection Principle
3.2.3.1 Overview
Current differential protection includes biased differential protection, unrestrained differential
protection, DPFC biased differential protection. Biased differential protection is three-slope
differential protection with biased characteristic. Unrestrained differential protection is to
accelerate the operating speed for transformer’s severe internal faults without biased
characteristic and blocking elements. DPFC biased differential protection calculated by current
variation has high sensitivity to inter-turn faults and high impedance fault) under heavy load.
Above three differential protection elements work coordinately to form the high-speed current
differential protection with high sensitivity.
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 ...