7-4
Setting the Relay
Date Code 20010731
SEL-352-1, -2 Instruction Manual
element before the timer expires, the ST Relay Word bit asserts declaring a slow trip condition.
B- and C-phase logic are similar.
The SlowTr setting should be set slightly longer than the Topen setting. Sometimes breaker
manufacturers provide a range for the operating time of the breaker. Set the SlowTr setting at
the longest value provided by the manufacturer or slightly longer. If these times are unknown,
use 125 percent–150 percent of the worst case of actual timing tests.
Slow Close Alarm (SlowCl)
SlowCl is the slowest time the breaker will take to close before declaring a failure mode. The
SlowCl setting is used by the SC breaker alarm logic. After the CCA Relay Word bit asserts, the
SlowCl timer starts timing. If the breaker has not closed based on 52AA before the timer
expires, the SC Relay Word bit asserts declaring a slow close condition. B- and C-phase logic
are similar.
The SlowCl setting should be set slightly longer than the Tclose setting. Sometimes breaker
manufacturers provide a range for the operating time of the breaker. Set the SlowCl setting at
the longest value provided by the manufacturer or slightly longer. If these times are unknown,
use 125 percent–150 percent of the worst case of actual timing tests.
Current Transformer Ratio (CTR)
The current transformer ratio (CTR) setting is based on the actual CT ratio of the current inputs.
The setting is entered as a ratio to 1. For example, if the current transformers that are connected
to the SEL-352 Relay are connected on a tap of 600:5, set CTR to 120. Note that if the CTs are
connected in a delta configuration, assuming the same tap, set the CTR to 120
•
, which
equals 204.
The CTR setting is used for all reports that display current or power in primary values, such as
the event report. All actual relay calculations are done using secondary values, so this setting
does not affect relay performance, only reporting.
X-Side Potential Transformer Ratio (XPTR)
The potential transformer ratio (XPTR) setting is based on the actual PT ratio of the X-side
voltage inputs. The setting is entered as a ratio to 1. For example, if the potential transformers
that are connected to the X side of the SEL-352 Relay are connected on a tap of 1200:1, set the
XPTR to 1200.
The XPTR setting is used for all reports that display voltage or power in primary values, such as
the event report and metering. All actual relay calculations are done using secondary values, so
this setting does not affect relay performance, only reporting.
Y-Side Potential Transformer Ratio (YPTR)
The potential transformer ratio (YPTR) setting is based on the actual PT ratio of the Y-side
voltage inputs. The setting is entered as a ratio to 1. For example, if the potential transformers
that are connected to the Y side of the SEL-352 Relay are connected on a tap of 4300:1, set the
YPTR to 4300.
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