4-52 SELOGIC
®
Control Equations
Date Code 20000616 SEL-300G Instruction Manual
Continually Display a Message
To continually display a message in the rotation, set the SEL
OGIC Control Equation display point
setting directly to 0 (logical 0) or 1 (logical 1) and the corresponding text setting. For example,
if an SEL-300G Relay is protecting a generator labeled “Unit 1A,” the generator name can be
continually displayed with the following settings
DP5 = 1 (set directly to logical 1)
DP5_1 = UNIT 1A (displays when DP5 = logical 1)
DP5_0 = (“blank”)
This results in the continual display of text setting DP5_1 on the front-panel display:
UNIT 1A
This also can be realized with the following settings:
DP5 = 0 (set directly to logical 0)
DP5_1 = (“blank”)
DP5_0 = UNIT 1A (displays when DP5 = logical 0)
This results in the continual display of text setting DP5_0 on the front-panel display:
UNIT 1A
INADVERTENT ENERGIZATION
Inadvertent energization occurs when the generator main circuit breaker or auxiliary transformer
circuit breaker is incorrectly closed to energize the generator while the generator is out of
service. When this occurs, the generator can act as an induction motor, drawing as much as four
to six times rated stator current from the system. These high stator currents induce high currents
in the rotor, quickly damaging the rotor.
The SEL-300G Relay 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 deenergized] * [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:
To Next Page
