
Date Code 20001006
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
3-51
SEL-351 Instruction Manual
Synchronism Check Applications for Automatic Reclosing and Manual Closing
Refer to
Close Logic
and
Reclose Supervision Logic
in
Section 6: Close and Reclose Logic
.
For example, set 25ANG1 = 15
°
and use the resultant synchronism check element in the reclosing
relay logic to supervise automatic reclosing:
e.g., 79CLS = 25A1 + ...
(see Figure 6.2)
Set 25ANG2 = 25
°
and use the resultant synchronism check element in manual close logic to
supervise manual closing (for example, assert IN6 to initiate manual close):
e.g., CL = IN6 * (25A2 + ... )
(see Figure 6.1)
In this example, the angular difference across the circuit breaker can be greater for a manual close
(25
§
) than for an automatic reclose (15
§
).
A single output contact (e.g., OUT2 = CLOSE) can provide the close function for both automatic
reclosing and manual closing (see Figure 6.1 logic output).
F
REQUENCY
E
LEMENTS
Six frequency elements are available. The desired number of frequency elements are enabled with
the E81 enable setting:
E81 = N (none), 1 through 6
as shown in Figure 3.30. Frequency is determined from the voltage connected to voltage terminals
VA-N (or VA-VB for delta).
Frequency Element Settings
Figure 3.29: Undervoltage Block for Frequency Elements
Summary of Contents for SEL-351
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