Basler Electric BE1-25A - Manual (Page 12)

APPLICATION
General
From large, single or multiple generators to small, multiple-unit applications, slip frequency synchronizers
such as the BE1-25A provide fast, accurate, synchronization of generator-to-bus or bus-to-bus breaker
closures if a slip rate exists between the two sides of the open breaker. For the BE1-25A to be capable of
closing the breaker, the phase angle between the two voltage inputs must first pass through 180 electrical
degrees and maintain a slip rate until the synchronizer issues a breaker close signal.
Excluded from this discussion are phase lock type synchronizers (such as the BE3-25A) that do not
require nor allow a slip to occur between the oncoming generator and the bus.
Generator-to-Bus Application
For a slip frequency synchronizer to operate properly in a generator-to-bus application, the following listed
operational parameters are entered into the memory of the synchronizer using the front panel
LOAD/FUNCTION select switch.
• Generator breaker closing time (calculates advance angle)
• Generator speed correction pulse width(maximum correction pulse width)
• Generator speed correction pulse interval (maximum correction pulse interval)
• Maximum slip frequency (maximum slip frequency and still allow breaker closing)
• Generator undervoltage (inhibits synchronization below this limit)
• Lockout ON/OFF (arms or disarms lockout feature)
Synchronization is enabled when the slip frequency is less than the maximum slip setting and the
generator voltage is greater than the generator undervoltage setting. Synchronization is NOT enabled
(inhibited) when the slip frequency is greater than the maximum slip setting, the generator voltage is less
than the generator undervoltage setting, or a lockout condition exists. If a voltage acceptance option is
included, synchronization is NOT enabled if the bus voltages are out of limits, the voltage difference
between generator and bus is greater than the setting, or the phase angle difference is greater than the
calculated advance angle. If a dead bus option is included, immediate synchronization is enabled if the
bus voltage is less than the setting and the dead bus enable input is closed.
When generator speed correction pulses are required, proportional pulses are generated based on the
slip frequency and the maximum slip frequency setting. If the slip frequency is greater than four times the
maximum slip frequency setting, proportional pulse are generated that are equal to 100 percent of the
correction pulse width. Correction pulses proportionally reduce in duty cycle (ration of ON time to OFF
time) down to zero for slip frequencies less than four times the maximum slip frequency setting. At one-
half the setting, correction pulses are disabled. If the slip frequency falls below one-sixteenth of the
maximum slip frequency setting for ten seconds, target pulses are generated to prevent a hung-scope or
non-slip condition.
Bus-to-Bus Application
Some transmission circuits, when split apart, assume a phase angle difference that stabilizes as a steady
offset. When this occurs, it is possible to reclose by supervisory means (usually supervised by a sync-
check relay) if the angle is small enough or the shock to the system can be tolerated. In cases where a
slip exists, re-connection can be attained using a BE1-25A. In this case, one of the following conditions
must be met for the BE1-25A to initiate closure.
• A slip frequency exists the prescribed limit (i.e., within the setting adjustment of the synchronizer).
• The phase angle difference is less than three degrees, with no system slip. In this case, the
phase angle between the two systems must have passed through 180 degrees to enable the
synchronizer.
If either of the two conditions is met, the BE1-25A will operate in a bus-to-bus environment as it would in
the case of an oncoming generator. It provides a closure command so that breaker closure occurs when
the phase difference is near zero. To achieve this advance timing, the closing time of the controlled
breaker must be set into the synchronizer memory.
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