GE Power Management
745 Transformer Management Relay
5-93
5 SETPOINTS
5.9 TIME OVERCURRENT CURVES
5
5.9.3 DEFINITE TIME CURVE
The Definite Time curve shape causes a trip as soon as the pickup level is exceeded for a specified period of
time. The base Definite Time curve has a delay of 0.1 seconds. The curve multiplier makes this delay adjust-
able from 0.000 to 10.000 seconds in steps of 0.001 seconds.
5.9.4 IEC CURVES
For European applications, the relay offers the four standard curves defined in IEC 255-4 and British standard
BS142. These are defined as IEC Curve A, IEC Curve B, IEC Curve C, and Short Inverse. The formula for
these curves is:
where:
T
= Operate Time (seconds)
M
= Multiplier Setpoint
I
= Input Current
I
pkp
= Pickup Current Setpoint
K
,
E
= Constants
Table 5–12: IEC CURVE CONSTANTS
IEC (BS) CURVE SHAPE
CONSTANTS
K
E
IEC CURVE A (BS142)
0.140
0.020
IEC CURVE B (BS142)
13.500
1.000
IEC CURVE C (BS142)
80.000
2.000
IEC SHORT INVERSE
0.050
0.040
T
M
K
1.03
(
)
E
1
–
-----------------------------
, 1
I
I
pkp
---------
1.03
<
≤
×
M
K
I I
pkp
⁄
(
)
E
1
–
--------------------------------
, 1.03
I
I
pkp
---------
20.0
<
≤
×
M
K
20.0
(
)
E
1
–
-----------------------------
,
I
I
pkp
---------
20.0
≥
×
=
Summary of Contents for 745 TRANSFORMER MANAGEMENT RELAY
Page 30: ...2 8 745 Transformer Management Relay GE Power Management 2 3 SECURITY 2 GETTING STARTED 2 ...
Page 210: ...7 36 745 Transformer Management Relay GE Power Management 7 2 BLOCK DIAGRAMS 7 SCHEME LOGIC 7 ...
Page 322: ...9 12 745 Transformer Management Relay GE Power Management 9 3 USING 745PC 9 745 PC SOFTWARE 9 ...
Page 396: ...A 4 745 Transformer Management Relay GE Power Management A 1 FIGURES AND TABLES APPENDIXA A ...
Page 400: ...C 2 745 Transformer Management Relay GE Power Management C 1 WARRANTY INFORMATION APPENDIXC C ...
Page 406: ...vi 745 Transformer Management Relay GE Power Management ...
Page 407: ...GE Power Management 745 Transformer Management Relay NOTES ...