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3 Operation Theory
PCS-978 Transformer Relay
3-117
Date: 2013-01-16
constants
K
,
and
C
.
Define-time or inverse-time ground overcurrent protection drops off instantaneously.
3.12.3.4 Voltage Control Element
Phase overcurrent protection is equipped as the backup protection of transformer and adjacent
power equipment, and voltage is usually used to control phase overcurrent protection to improve
sensitivity of the protection. Unsymmetrical faults result in unsymmetrical sequence voltages and
symmetrical faults lead to low three phase voltages at relay location, so phase overcurrent
protection can operate if the sequence voltage greater than a setting or phase voltage lower than a
setting. Therefore, current settings of phase overcurrent protection can be set lower with high
sensitivity.
Operation criterion of VCE
The voltage control element picks up if phase-to-phase voltage is lower than its setting or
negative-sequence voltage is greater than its setting.
Criteria:
U
< [
x.
50/51P.Upp_VCE] or
2
U
[
x.
50/51P.U2_VCE]
Equation 3.2-3
Where:
U
is the phase-to-phase voltage of x side.
2
U
is the negative-sequence voltage of x side.
[
x.
50/51P.Upp_VCE] is the phase-to-phase undervoltage setting of x side.
[
x.
50/51P.U2_VCE] is the negative-sequence overvoltage setting of x side.
Voltage of any side can be used as the input of voltage control element, and there are logic
settings used to select which side voltage control element to control OC protection of some side.
Table 3.12-2 Voltage used for VCE
Overcurrent Element
Voltage for Controlling
Ia>
Uab< or Uca< or U2>
Ib>
Ubc< or Uab< or U2>
Ic>
Uca< or Ubc< or U2>
In above table, Uab, Ubc and Uca are phase-to-phase voltage, and U2 is negative-sequence
voltage.
Effect of VT Circuit
When VT circuit fails (i.e. message [x.Alm_VTS] being issued) or VT is not put into service (i.e.
[x.
In_VT] is “0”), then voltage control element resets instantaneously and voltage controlled phase
overcurrent protection is blocked, and if the setting is set to”0” then voltage control element picks
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 ...