GE 489 Instruction Manual page 72

4.6 S5 CURRENT ELEMENTS
c) 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 = Trip Time in seconds
M = Multiplier setpoint
I = Input Current
I = Pickup Current setpoint
pickup
K, E = Constants
Table 4–3: IEC (BS) INVERSE TIME CURVE CONSTANTS
IEC (BS) CURVE SHAPE
IEC CURVE A (BS142)
IEC CURVE B (BS142)
4
IEC CURVE C (BS142)
SHORT INVERSE
d) IAC CURVES
The curves for the General Electric type IAC relay family are derived from the formula:
where: T = Trip Time in seconds
M = Multiplier setpoint
I = Input Current
I = Pickup Current setpoint
pickup
A, B, C, D, E = Constants
Table 4–4: IAC INVERSE TIME CURVE CONSTANTS
IAC CURVE SHAPE
IAC EXTREME INVERSE
IAC VERY INVERSE
IAC INVERSE
IAC SHORT INVERSE
4-22
×
T M
=
CONSTANTS
K
0.140
13.500
80.000
0.050
⎛
B
×
T M ⎜ A ------------------------------------ -
= + +
( ⁄ ) C
⎝ I I
–
pickup
A
0.0040
0.0900
0.2078
0.0428
489 Generator Management Relay
⎛ ⎞
K
⎜ -------------------------------------- - ⎟
E
( ⁄ )
⎝ I I 1 ⎠
–
pickup
E
0.020
1.000
2.000
0.040
D E
-------------------------------------------- - -------------------------------------------- -
+
2
( ( ⁄ ) C ) ( ( ⁄
I I I I
–
pickup pickup
CONSTANTS
B C
0.6379 0.6200 1.7872
0.7955 0.1000 –1.2885
0.8630 0.8000 –0.4180
0.0609 0.6200 –0.0010
4 SETPOINTS
⎞
⎟
3
) C ) ⎠
–
D E
0.2461
7.9586
0.1947
0.0221
GE Multilin
(EQ 4.5)
(EQ 4.6)