A-4 BE1-951 Time Overcurrent Characteristic Curves 9328900990 Rev L
In applications where the time coordination between curves is extremely close, we recommend that you
choose the optimal time dial setting by inspection of the coordination study. In applications where
coordination is tight, it is recommended that you retrofit your circuits with Basler Electric electronic relays
to ensure high timing accuracy.
Table A-3. Time Dial Setting Cross-Reference
Electromechanical Relay Time Dial Setting
0.5 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
Curve
Equivalent
To
Basler Electric Equivalent Time Dial Setting
S, S1
ABB CO-2 0.3 0.8 1.7 2.4 3.4 4.2 5.0 5.8 6.7 7.7 8.6 9.7
L, L1
ABB CO-5 0.4 0.8 1.5 2.3 3.3 4.2 5.0 6.0 7.0 7.8 8.8 9.9
D
ABB CO-6 0.5 1.1 2.0 2.9 3.7 4.5 5.0 5.9 7.2 8.0 8.9 10.1
M
ABB CO-7 0.4 0.8 1.7 2.5 3.3 4.3 5.3 6.1 7.0 8.0 9.0 9.8
I, I1
ABB CO-8 0.3 0.7 1.5 2.3 3.2 4.0 5.0 5.8 6.8 7.6 8.7 10.0
V, V1
ABB CO-9 0.3 0.7 1.4 2.1 3.0 3.9 4.8 5.7 6.7 7.8 8.7 9.6
E, E1
ABB CO-11 0.3 0.7 1.5 2.4 3.2 4.2 5.0 5.7 6.6 7.8 8.5 10.3
I2
GE IAC-51 0.6 1.0 1.9 2.7 3.7 4.8 5.7 6.8 8.0 9.3 10.6
N/A
V2
GE IAC-53 0.4 0.8 1.6 2.4 3.4 4.3 5.1 6.3 7.2 8.4 9.6
N/A
S2
GE IAC-55 0.2 1.0 2.0 3.1 4.0 4.9 6.1 7.2 8.1 8.9 9.8
N/A
L2
GE IAC-66 0.4 0.9 1.8 2.7 3.9 4.9 6.3 7.2 8.5 9.7 10.9
N/A
E2
GE IAC-77 0.5 1.0 1.9 2.7 3.5 4.3 5.2 6.2 7.4 8.2 9.9
N/A
THE 46 CURVE
The 46 curve (Figure A-17) is a special curve designed to emulate the (I
2
)
2
t withstand ratings of
generators using what is frequently referred to as the generator K factor.
The 46 Curve Characteristics
46 Pickup Current
Generators have a maximum continuous rating for negative sequence current. This is typically expressed
as a percent of stator rating. When using the 46 curve, the user should convert the continuous I
2
rating
data to actual secondary current at the relay. This value (plus some margin, if appropriate) should be
entered as the pickup setting. For example, if a generator’s rated full-load current is 5 amperes, a pu
setting of 0.5 A would allow 10% continuous I
2
.
46 Time Dial (= Generator K factor)
The amount of time that a generator can withstand a given level of unbalance is defined by Equation A-3.
()
2
2
I
K
t =
Equation A-3
The K factor gives the time that a generator can withstand 1 per unit negative sequence current. For
example, with a K factor of 20, since (I
2
)
2
becomes 1 at 1 per unit of current, the generator can withstand
the condition for 20 seconds. Typical values for generator K factors are in the 2 to 40 range. The relay
uses the “nominal current” setting of the relay (front panel Screen 6.3.7 or via the SG-NOM command) to
determine what corresponds to 1 per unit current in the generator.
To Next Page
Loading...