4.62
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
The negative-sequence time-overcurrent element operates with an I
2
2
t time
characteristic. Set the pickup value equal to the minimum percent of nominal
current to which the element must respond. Set the 46Q2K setting equal to the
generator-rated I
2
2
t short time-current capability rating defined by the
generator manufacturer.
The 46Q2 Relay Word bit asserts without time delay when the measured
negative-sequence current is greater than 46Q2P percent of INOM. The
46Q2T Relay Word bit asserts in a time defined by the time-overcurrent
element operating characteristic.
The negative-sequence time-overcurrent element resets after a fixed linear
time of 240 seconds. The 46Q2R Relay Word bit asserts when the element is
fully reset.
The negative-sequence overcurrent elements are disabled (except the linear
reset described previously) when the 46QTC SEL
OGIC
control equation
equals logical 0. The elements are allowed to operate when the 46QTC
SEL
OGIC
control equation equals logical 1. With the example setting, the
elements are always allowed to operate.
Setting Calculation
Gather the following information to calculate the negative-sequence
overcurrent setting.
➤
Generator continuous current unbalance withstand capability,
percent of rated current
➤
Generator negative-sequence current short-time withstand
capability, seconds
Recommendations
Set the 46Q1P equal to or less than the generator continuous unbalance
current capability.
46Q1P := 8.0–12.0%
Set the 46Q1D time delay greater than the maximum time of normal
unbalance current periods, including system phase-fault clearing time. This
delay setting prevents unwanted unbalance current alarms.
46Q1D := 30 seconds
Set the 46Q2P setting equal to or less than the generator continuous unbalance
current capability.
46Q2P := 8.0–12.0%
Set the 46Q2K setting equal to or less than the generator short-time negative-
sequence current capability.
46Q2K = 10
You can define conditions that prevent negative-sequence overcurrent element
operation in the 46QTC torque-control setting. Normally, the negative-
sequence overcurrent elements should be enabled all the time.
46QTC = 1
Generally, negative-sequence overcurrent tripping is applied to the generator
main breaker only. This permits rapid resynchronization after the system
unbalance condition clears. The Relay Word bit 46Q2T is configured to trip
the generator breaker in the factory-default logic (see Trip/Close Logic
NOTE:
The reset of 46Q2 element is
independent of the 46QTC setting.
Summary of Contents for SEL-700G Series
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