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3
Operation
Theory
PCS-978 Transformer Relay
3-22
Date: 2013-01-16
current blocking.
2) Protection equipment can be self-adaptive to enable the phase-to-phase crossing block mode
according to the comprehensive characteristics of three-phase differential current. If inrush
current is distinguished, equipment enables phase-to-phase crossing block mode for short
time, and then switches to phase-segregated blocking mode after a period.
3) If the second harmonic percent of differential current used as auxiliary criteria continues to
rise, then biased differential protection is kept being blocked
Phase-to-phase Crossing Blocking Mode
Only if two phases current are distinguished not inrush current, then differential protection of
corresponding two phases will be released to operate.
Comparison Between Different Blocking modes
Convention blocking mode is phase blocking mode (mode 3), and a list is given below to compare
operation of differential protection in following situations.
It is supposed that three differential currents are Ida, Idb, and Idc
Table 3.2-2 Comparison of different blocking modes
Situation
Harmonic
of
each
phase current
Mode 1:
self-adaptive
blocking
mode
Mode 2:
phase-to-phase
crossing
block
mode
Mode 3:
Phase
blocking
Mode
1
Ida
(
great harmonic
)
Diff prot not operate
Diff prot not operate
Diff prot not operate
Idb
(
great harmonic
)
Idc
(
great harmonic
)
2
Ida
(
little harmonic
)
Diff prot operate
Diff prot operate
Diff prot operate
Idb
(
little harmonic
)
Idc
(
little harmonic
)
3
Ida
(
great harmonic
)
Diff prot may operate or
not
according
to
differential
current
waveform
Diff prot not operate
Diff prot not operate
Idb
(
great harmonic
)
Idc
(
little harmonic
)
4
Ida
(
great harmonic
)
Diff prot operate
Diff prot operate
Diff prot not operate
Idb
(
little harmonic
)
Idc
(
little harmonic
)
From above list, it can be concluded that:
1) The blocking level of three blocking modes is increased one by one.
2) The difference between blocking mode 2 and 3 is the operation of differential protection in
situation 4. Differential protection will operate in the situation that greater harmonic in one phase
differential current but little harmonic in other two phases if blocking mode 2 selected, but
differential protection will not operate in the situation if blocking mode 3 selected. Situation 4 is
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 ...