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3 Operation Theory
PCS-978 Transformer Relay
3-105
Date: 2013-01-16
No.
Setting Item
Range
Step
Unit
Description
t
transducer input.
0: 0~20mA DC signal
1: 0~5V DC signal
3.11 Impedance Protection
3.11.1 Application
When phase overcurrent protection and ground overcurrent protection can not meets the
sensitivity requirement of transformer backup protection, impedance may be configured. The
operation mode of power system has little effect on impedance protection, so impedance
protection cooperates with protections of adjacent equipment more easily.
3.11.2 Function
Two stage phase-to-phase impedance protection elements.
Two stage phase-to-earth impedance protection elements
Power swing blocking releasing function.
3.11.3 Protection Principle
3.11.3.1 Overview
Impedance protection consists of phase-to-phase impedance protection and phase-to-earth
protection. CT polarity of each side is at busbar side, and directions of settings are based on this
polarity.
3.11.3.2 Fault Detector
The fault detector of impedance protection includes the fault detector of DPFC phase-to-phase
current and the fault detector of negative-sequence current. Impendence protection will be
enabled for 500 ms if any fault detector picks up, and will keep being enabled if phase-to-phase or
phase-to-earth impedance relay operates.
Fault detector of DPFC phase-to-phase current
Criteria of this fault detector:
th
t
I
I
I
25
.
1
Equation 3.11-1
Where:
t
I
is the floating threshold value which will arise automatically and gradually according to
increasing of the output of deviation component. In order to ensure the threshold voltage is
slightly greater than the unbalance voltage, multiple 1.25 of the deviation component is
reasonable.
Summary of Contents for PCS-978
Page 1: ...PCS 978 Transformer Relay Instruction Manual NR Electric Co Ltd ...
Page 2: ......
Page 6: ...Preface PCS 978 Transformer Relay IV Date 2013 01 16 ...
Page 10: ...Preface PCS 978 Transformer Relay VIII Date 2013 01 16 ...
Page 62: ...3 Operation Theory PCS 978 Transformer Relay 3 p Date 2013 01 16 ...
Page 250: ...4 Supervision PCS 978 Transformer Relay 4 b Date 2013 01 16 ...
Page 264: ...4 Supervision PCS 978 Transformer Relay 4 14 Date 2013 01 16 ...
Page 266: ...5 Management PCS 978 Transformer Relay 5 b Date 2013 01 16 ...
Page 272: ...5 Management PCS 978 Transformer Relay 5 6 Date 2013 01 16 ...
Page 334: ...6 Hardware Description PCS 978 Transformer Relay 6 60 Date 2013 01 16 ...
Page 370: ...8 Human Machine Interface PCS 978 Transformer Relay 8 d Date 2013 01 16 ...
Page 404: ...8 Human Machine Interface PCS 978 Transformer Relay 8 34 Date 2013 01 16 ...
Page 406: ...9 Configurable Function PCS 978 Transformer Relay 9 b Date 2013 01 16 ...
Page 446: ...10 Communication PCS 978 Transformer Relay 10 26 Date 2013 01 16 ...
Page 448: ...11 Installation PCS 978 Transformer Relay 11 b Date 2012 10 09 ...
Page 456: ...11 Installation PCS 978 Transformer Relay 11 8 Date 2012 10 09 ...
Page 458: ...12 Commissioning PCS 978 Transformer Relay 12 b Date 2012 12 07 ...
Page 468: ...12 Commissioning PCS 978 Transformer Relay 12 10 Date 2012 12 07 ...
Page 470: ...13 Maintenance PCS 978 Transformer Relay 13 b Date 2012 10 09 ...
Page 474: ...13 Maintenance PCS 978 Transformer Relay 13 4 Date 2012 10 09 ...
Page 476: ...14 Decommissioning and Disposal PCS 978 Transformer Relay 14 b Date 2012 10 09 ...
Page 478: ...14 Decommissioning and Disposal PCS 978 Transformer Relay 14 2 Date 2012 10 09 ...
Page 480: ...15 Manual Version History PCS 978 Transformer Relay 15 2 Date 2013 01 16 ...