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3 Operation Theory
PCS-978 Transformer Relay
3-15
Date: 2013-01-16
When an external fault occurs, the short-circuit current rise strongly, causing a correspondingly
high restraint current (2 times through-flowing current) with little differential current. After CT
reaches saturation (point B), a differential quantity is produced and the restraint quantity is
reduced. In consequence, the operating point may moves into the tripping area of sensitive
biased differential protection. Because CT saturation criterion is equipped, sensitive biased
differential protection will no maloperate even the fault point moves into the tripping area.
2) Conventional biased differential protection element will send tripping signal monitored by
inrush current only. It eliminates the influence of transient and steady saturations of CT during
an external fault and ensures reliable operation even if CT is in saturation condition during an
internal fault by means of its biased characteristic. Its operation area is the deeper shadow
area in the figure above.
When an internal fault occurs, differential current rises greatly and the operating point moves
to F in the tripping area of conventional biased differential protection.
NOTE!
Only the second harmonic criterion is adapted to distinguishing inrush current for
blocking conventional biased differential protection.
3) Unrestrained instantaneous differential protection element will send tripping signal without any
blocking if differential current of any phase reaches its setting. Its operation area is over the
above two areas with the deepest dark shadow.
When a severe internal fault occurs, differential current rises sharply and the operating point
moves to E in the tripping area of instantaneous differential protection.
3.2.3.10 DPFC Biased Differential Protection Element
3.2.3.10.1 DPFC Concept
)
24
(
)
(
k
I
k
I
I
DPFC (Deviation of Power Frequency Component) is the power frequency component of fault
component, which is the differential value between the sampling value at this time point and that at
a cycle before.
)
(
k
I
is the sampling value at the time point.
)
24
(
k
I
is the sampling value at a cycle before, 24 is the sampling points in one cycle.
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 ...