Sel SEL-787 - Figure 4.38 Dual-Level Volts;Hertz Time-Delay Characteristic, 24 CCS = DD; Figure 4.39 Composite Inverse;Definite-Time Overexcitation Characteristic, 24 CCS = ID

4.52
SEL-787 Relay Instruction Manual Date Code 20150130
Protection and Logic Functions
Voltage-Based Protection
Figure 4.38 Dual-Level Volts/Hertz Time-Delay Characteristic, 24CCS = DD
Figure 4.39 Composite Inverse/Definite-Time Overexcitation Characteristic, 24CCS = ID
.01 0.1 1.0 10 100 1000
100
110
120
130
140
24D2P2 = 118%
24D2D2 = 6 s
24D2P1 =
110%
Time (Minutes)
Transformer Limit Curve
on Gen. Voltage Base
Mfg-Generator
Limit Curve
Volts/Hertz (%)
Relay Characteristic
Time (Minutes)
Generator Manufacturer's
Recommended Protection Curve
Transformer Limit Curve on
Generator Voltage Base
.001 .01 0.1 1.0 10 100
100
110
120
130
140
Volts/Hertz (%)
1000
24D2P2 = 118%
24D2D2 = 1.2 s
24IP=108%