
3 Operation Theory
PCS-978 Transformer Relay
3-153
Date: 2013-01-16
the setting [x.27.
t_Recov] can be set to “4.5s~5s”. If the voltage does not recover to the value
greater than the setting [x.27.U_Recov] after the time delay [x.27.t_Recov], alarm signal
[x.27.Alm_Unrecov] will be issued.
When system voltage is lower than stage 1 voltage setting, stage 1 operates after corresponding
time delay to shed part of loads. If system voltage continues to decrease lower than stage 2
voltage setting, stage 2 operates after corresponding time delay, and so on.
In order to prevent the maloperation of undervoltage caused by abnormality contestations such as
load back feed, higher harmonics, circuit connection etc., following blocking criteria are equipped.
(1) Undervoltage blocking
If positive-sequence voltage is lower than 0.15Un, undervoltage protection is blocked.
(2) Negative-sequence blocking
If negative-sequence voltage is greater than 0.15Un, undervoltage is blocked.
(3) Rate of change of voltage blocking
If the rate of change of voltage (du/dt) is greater than the setting [27.du/dt_Blk], undervoltage is
blocked and the blocking is not released until the system voltage greater than the recovery voltage
and above (setting [27.U_Recov])
When any one criterion is met, undervoltage protection is blocked.
3.17.4 Logic
Logic diagram of undervoltage protection is shown in the following figure.
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 ...