3
Operation
Theory
PCS-978 Transformer Relay
3-12
Date: 2013-01-16
restraint current
[87T.I_Knee1]
[87T.I_Knee2]
0.8
Ir(pu)
0
[87T.I_Biased]
Id(pu)
1.2
Differential
current
[87
T.S
lop
e2
]
[87T.I_Instant]
O
pe
ra
tin
g
ar
ea
o
f
se
ns
iti
ve
B
ia
se
d
D
iff
.
[8
7.
S
lo
pe
3]
K=
0.
6
[87T
.Slop
e1]
K
=
2
Figure 3.2-2 Operation characteristic curve of transformer sensitive biased differential protection
In above figure:
[87T.I_Instant] is the current setting of unrestrained instantaneously differential protection.
3.2.3.7 Conventional Biased Differential Protection
Conventional biased differential protection with higher setting and restraint coefficient comparing
with sensitive biased differential protection is blocked only by an inrush current detection.
Conventional biased differential protection provides faster operation for severe internal faults.
Operation criterion of this biased differential protection is:
pu
I
pu
I
I
pu
I
pu
I
r
r
d
r
d
8
.
0
)
8
.
0
(
6
.
0
8
.
0
2
.
1
Equation 3.2-12
Where:
d
I
,
r
I
and pu have same definitions as mentioned above.
NOTE!
The slope and the knee point are fixed in program, values of which eliminate the
influence of CT saturation during an external fault and ensures reliable operation even if
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 ...