3 Operation Theory
PCS-978 Transformer Relay
3-5
Date: 2013-01-16
Limitation of secondary current
For all differential protections, the secondary currents of each branch must follow below criterion.
)
/
,...,
/
,
/
{
)
/
,...,
/
,
/
{
2
2
2
2
2
2
1
2
1
2
2
2
2
2
2
2
1
2
1
2
nBrm
bBrm
nBr
bBr
nBr
bBr
nBrm
bBrm
nBr
bBr
nBr
bBr
I
I
I
I
I
I
in
M
I
I
I
I
I
I
Max
<16
Equation 3.2-6
For DPFC biased differential protection, the secondary currents of each branch must follow below
criteria in addition to the previous one.
)
/
,...,
/
,
/
{
2
2
2
2
2
2
1
2
1
2
nBrm
bBrm
nBr
bBr
nBr
bBr
I
I
I
I
I
I
Max
>0.4
)
/
,...,
/
,
/
{
2
2
2
2
2
2
1
2
1
2
nBrm
bBrm
nBr
bBr
nBr
bBr
I
I
I
I
I
I
Min
>0.1
Equation 3.2-7
Where:
Br
m=Branch (side) “m”.
bBrm
bBr
bBr
I
I
I
2
2
2
1
2
,
,
are rated secondary current of branch 1, branch 2 and branch m of
transformer.
nBrm
nBr
nBr
I
I
I
2
2
2
1
2
,
,
are rated secondary current of CT at branch 1, branch 2 and branch m of
differential protection.
NOTE!
If
Equation 3.2-6 is not met, alar
m signals [ProtBrd.Fail_Settings] and
[FDBrd.Fail_Settings] are issued and displayed on LCD and the protective equipment
being blocked at the same time.
NOTE:
Equation 3.2-7 is no
t met, DPFC biased differential protection must not be
enabled. Otherwise, alarm signals [ProtBrd.Fail_Settings] and [FDBrd.Fail_Settings] are
issued on LDC and the protective equipment being blocked at the same time.
When viewing settings and values of conventional current differential protection in the relay, user
will find th
e unit “pu” (per unit). The current in differential protection calculation is not actual
secondary value but per unit value which is got by actual secondary value of each branch of
transformer divided by transformer secondary rated current of each branch (i.e.
bBrm
I
2
).
3.2.3.4 Phase Compensation
Phase Compensation Principle
False differential current is caused by phase shift between the power transformer primary and
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 ...