4-50 SEL
OGIC
Control Equations
Date Code
20060731
SEL-300G Instruction Manual
times rated stator current from the system. These high stator currents induce high currents in the
rotor, quickly damaging the rotor.
The SEL-300G INAD SEL
OGIC
control equation is intended for use as dedicated inadvertent
energization protection. Two accepted approaches are voltage supervised overcurrent relays and
auxiliary contact supervised overcurrent relays. The INAD SEL
OGIC
control equation supports
both.
The objective of inadvertent energization protection is to detect that the generator has been
removed from service, but has suddenly been reenergized. We can begin to build the INAD
equation:
INAD = [Generator was de-energized] * [Generator is now energized]
If we use an overcurrent element, 50L, to detect that the generator has been reenergized, then the
INAD equation can be described:
INAD = [Generator was de-energized] * 50L
It now remains to define the [Generator was de-energized] conditions.
Some indicators that the generator is removed from service include:
•
Low terminal voltage
•
Field circuit breaker is open
•
No phase current
We can require that all these conditions be true to arm Inadvertent Energization tripping by using
the SEL
OGIC
control equation AND operator:
Generator is de-energized = !50L * 27V1 * !IN102
where
!50L = 50L sensitive phase overcurrent element is not picked up
27V1 = positive-sequence phase undervoltage element is picked up
!IN102 = field circuit breaker auxiliary contact is open
We need to add time-delay pickup and dropout timers to this logic equation. The time-delay
pickup timer adds an arming delay so that the inadvertent energization scheme is not armed until
a few seconds after the generator is removed from service. The dropout timer ensures that the
scheme will trip when current is applied during an inadvertent energization. A SEL
OGIC
control
equation is used to provide the arming delays:
SV2 = !50L * 27V1 * !IN102
SV2PU = 2.0 seconds
SV2DO = 1.0 second
With these settings, the INAD settings become:
INAD = SV2T * 50L
Generator was de-energized and current is now detected
INADPU = 0.25 second
1/4-second time delay on inadvertent energization trip
INADDO = 0.13 second
One-eighth second time delay on INAD trip dropout
The INADT Relay Word bit is added to the SV3 SEL
OGIC
control equation to trip the generator
main circuit breaker, the field breaker, the prime mover, and the generator lockout relay when an
inadvertent energization occurs. The logic diagram in Figure 4.26 summarizes the logic.
Summary of Contents for SEL-300G
Page 1: ...SEL 300G Multifunction Generator Relay Instruction Manual 20060731 PM300G 01 NB ...
Page 4: ......
Page 6: ......
Page 138: ......
Page 166: ......
Page 170: ......
Page 288: ......
Page 290: ......
Page 328: ......
Page 442: ......
Page 456: ......
Page 458: ......
Page 468: ......
Page 470: ......
Page 512: ......
Page 516: ......
Page 518: ......
Page 552: ......
Page 554: ......
Page 560: ......
Page 578: ......
Page 626: ......
Page 724: ......
Page 728: ......