F-2
MIFII Digital Feeder Relay
GEK-106237P
F.2 TIME OVERCURRENT ELEMENTS
APPENDIX F
F
F.2TIME OVERCURRENT ELEMENTS
Follow on an example will be defined to explain the timing accuracy for 51 element.
According to the manual, the general formula for the
IEC Very Inverse Curve
is as follows:
Since
IEC Standard
does not fix time error limits for current ratios below 2 (see F.4 of this appendix for more information),
GE MII Family Relays fixes a maximum error of 5% maximum permitted in all range for
I / Ipu > 2
. Care must be taken to
use (in the formula) the current measured by the relay.
Figure F–1: MAXIMUM ERROR
The lower limit means 1.5 times the pickup multiplied by a coefficient for the error:
For the upper limit:
Using a real case, where the time dial is 0.45 for an injected current of 4 A and a pickup of 3.5 A, the limits are as follows:
1
*
5
.
13
1
−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
pu
I
I
D
T
Applied Current
MIFII
Measured current
Resultant
Operation Time
5%max. Error for I/Ipu<2
3%max. Error for I/Ipu>2
(
)
s
T
4
.
23
1
05
.
1
*
5
.
1
1
*
5
.
13
1
=
−
=
(
)
s
T
8
.
31
1
95
.
0
*
5
.
1
1
*
5
.
13
1
=
−
=
s
T
375
.
30
1
05
.
1
*
5
.
3
4
45
.
0
*
5
.
13
1
=
−
⎟
⎠
⎞
⎜
⎝
⎛
=
s
T
875
.
70
1
95
.
0
*
5
.
3
4
45
.
0
*
5
.
13
1
=
−
⎟
⎠
⎞
⎜
⎝
⎛
=
Summary of Contents for MIFII GEK-106237P
Page 91: ...4 28 MIFII Digital Feeder Relay GEK 106237P 4 7 VIEW 4 COMMUNICATIONS 4 ...
Page 124: ...GEK 106237P MIFII Digital Feeder Relay 8 7 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 8 5MENU TREE ...
Page 125: ...8 8 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 126: ...GEK 106237P MIFII Digital Feeder Relay 8 9 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 127: ...8 10 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 128: ...GEK 106237P MIFII Digital Feeder Relay 8 11 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 129: ...8 12 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 130: ...GEK 106237P MIFII Digital Feeder Relay 8 13 8 KEYPAD AND DISPLAY 8 5 MENU TREE 8 ...
Page 131: ...8 14 MIFII Digital Feeder Relay GEK 106237P 8 5 MENU TREE 8 KEYPAD AND DISPLAY 8 ...
Page 185: ...A 10 MIFII Digital Feeder Relay GEK 106237P A 6 MIFII THERMAL CURVES APPENDIXA A ...
Page 203: ...B 18 MIFII Digital Feeder Relay GEK 106237P B 3 IAC CURVES APPENDIXB B ...
Page 245: ...F 8 MIFII Digital Feeder Relay GEK 106237P F 5 CONCLUSIONS APPENDIXF F ...