3
Operation
Theory
PCS-978 Transformer Relay
3-60
Date: 2013-01-16
[x.64REF.Slope_Biased] is the percent restraint coefficient of biased REF protection of x side and
0.5 is recommended.
3.4.3.6 Operation Characteristic Curve
Operation characteristic of restricted earth fault protection is showed in the following figure.
[64REF.I_Knee]
d
iif
e
re
n
ti
a
l
c
u
rr
e
n
t
[x.64REF.I_Biased]
restraint current
K
=
m
I0d
I0r
[64REF.Slope]
Figure 3.4-5 Operating characteristic of REF protection
Where:
The value of m is defined by the branch number for REF protection calculation. For example, there
are two branches at HV side (wye winding with neutral point earthed), so there are three branches
constitute the REF protection of HV side and m is equal to 3.
3.4.3.7 Detection of CT Transient Characteristic Difference
Non-identical CT characteristics can cause unbalance current. During phase-to-phase faults and
three-phase faults, the unbalance of three-phase CTs results in residual current which may lead to
maloperation of RFE protection. Therefore, positive sequence current restraint blocking criterion is
adopted to prevent maloperation of REF protection in above mentioned conditions.
When the residual current of each side REF protection is greater than
0 times positive sequence
current, it is decided that zero-sequence current is caused by a fault and release REF protection.
Positive sequence current restraint blocking criterion is showed below.
1
0
0
I
I
Equation 3.4-7
Where:
0
I
is the zero-sequence current at a side.
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 ...