Relay Element Settings 2-27
SEL-300G Instruction Manual Date Code 20020206
Relay Word Bits
Relay Word Bit Function Description Typical Applications
32P1
Level 1 Reverse/Low-Forward Power Pickup Indication, Event Triggering,
SER Triggering, Testing
32P1T
Level 1 Reverse/Low-Forward Power Pickup
With Definite-Time Delay
Tripping, SER Triggering,
Pickup Definite-Time Delay
32P2
Level 2 Reverse/Low-Forward Power Pickup Indication, Event Triggering,
SER Triggering, Testing
32P2T
Level 2 Reverse/Low-Forward Power Pickup
With Definite-Time Delay
Tripping, SER Triggering,
Pickup Definite-Time Delay
Setting Calculation
Information Needed
• Prime Mover Manufacturer’s Rated Motoring Power and Motoring Withstand Time Limit
• Generator Rated Power
Recommendations
Calculate the prime mover rated motoring power in per unit of generator rated power by dividing
motoring power by the generator rating.
PowerRatedGenerator
PowerMotoringRated
PowerMotoringUnitPer
−
=
Motoring power is negative by definition, since it is flowing into rather than out of the generator.
To ensure that the element securely detects this level of power, the element setting should be
adjusted to account for measuring errors in the relay, voltage transformers, and current
transformers. A 0.7 to 0.5 multiplier will provide secure detection of motoring conditions as low
as 0.02 per unit, suggesting a 32P1P setting of 0.014 to 0.01 per unit. Relay measuring error for
the power element is specified as ±0.0015 per unit, ±2% of setting.
32P1P = (0.7 to 0.5) • (Per Unit Motor Power) per unit
Use a 32P1D time delay of 20.0 to 30.0 seconds or as recommended by the prime mover
manufacturer. This delay prevents reverse-power tripping during machine paralleling operations.
Use the Level 2 reverse/low-forward power element as a sequential tripping interlock or an
overload element.
When the Level 2 element is applied as a sequential tripping interlock, the 32P2P setting should
be set using a low-forward power value, 5 to 10% of machine rating. The element only should be
permitted to cause a generator breaker trip after the prime mover trip has occurred. The
SEL
OGIC Control Equations used to implement sequential generator tripping are described in
Section 4: SEL
OGIC
®
Control Equations of this instruction manual.
To Next Page
