< 27VLO (live polarizing/dead sync) for VCT time. When PSVC = E, the relay asserts
Relay Word bit VSC when either voltage condition is true for VCT time.
Select 59VHI and 27VLO settings based upon your utility standards. Select standard voltage
levels where the line is considered live and dead for reclosing purposes.
You can set the Relay Word bit VSC in a programmable logic mask and connect the program-
mable output contact for that mask in the close path. With this connection, a close is only
allowed if the VSC condition is valid.
In the example, we intend to supervise reclose operations with live-bus/dead-line conditions.
The relay uses line-side polarizing potential transformers, thus the sync voltage must be taken
from the bus side. Based upon the voltage sources and desired performance, we set the relay
to perform live-sync/dead-polarizing supervision; PSVC = S.
We only want to close if the voltage conditions have been valid for at least 30 cycles; VCT =
30 cycles. The voltage VS is taken from a bus-side PT attached to A-phase; SYNCP = A.
Synchronism Checking Function
The relay may perform synchronism checking to supervise breaker closures when the line and
bus are energized. The sync-check feature in the SEL-221F relay checks the vector difference
between a selected polarizing voltage, VP, and the synchronizing voltage, VS. This
difference voltage is then compared against the 25DV setting. When the phasor difference
between VP and VS is less than the 25DV setting for 25T time, the relay asserts the SSC bit
in the Relay Word.
The relay calculates V1 from the positive-sequence voltage presented to the relay polarizing
inputs:
The relay checks the magnitudes of V1 and VS to ensure that both voltages are above the
59VHI setting. The relay only performs the sync check if both the bus and line are live.
Using the positive-sequence voltage for magnitude comparison adds security to the scheme by
ensuring that all three potentials are good on the polarizing side of the breaker.
If both voltages are live, the relay calculates the vector difference between VS and the phase
voltage selected by the SYNCP setting. If the vector difference is less than the 25DV setting,
the 25T timer starts. If the voltages remain in sync, as determined by the magnitude of the
vector difference voltage, for 25T time, the relay asserts the SSC bit in the Relay Word.
If the 25T time is relatively short, the breaker close time may become a factor. For example,
if 25T is set for 60 cycles and the breaker close time is 10 cycles, it actually takes 70 cycles
to parallel the line. If this time is critical, the breaker close time should be taken into account
when the 25T time is set so that, in this case, a 25T setting of 50 cycles might be more
appropriate.
Date Code 920508
Applications
SEL-221F, -1 Instruction Manual
5-9
Summary of Contents for SEL-221F
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Page 110: ...Example Event Report 2 4 12 Event Reporting SEL 221F 1 Instruction Manual Date Code 930830 ...
Page 158: ...SETTINGS SHEET FOR SEL 221F RELAY PAGE 2 OF 6 DATE Date Code 921110 ...
Page 160: ...SETTINGS SHEET PAGE 4 OF 6 FOR SEL 221F RELAY DATE Date Code 930601 ...
Page 161: ...SETTINGS SHEET PAGE 5 OF 6 FOR SEL 221F RELAY DATE Date Code 961208 ...
Page 229: ...SEL 200 Series Relay Main Board Troubleshooting Test Points and Jumper Locations ...