Basler Electric BE1-25A - Manual (Page 13)

Application Checklist
When developing the appropriate operating parameters and safeguards for synchronizing a generator
with a bus, the following items should be considered.
1. Secondary potential transformer voltage waveforms should be carefully compared with the
primary voltages. Consider the following:
a. Are the secondary and primary voltages identical for both bus and generator?
b. Is there a power transformer involved? (Suppose, for example, that the generator is
operating at 2,400 volts, delta, and the bus at 34,500 volts, wye. Are the power
transformer secondary voltages the same when the bus and generator voltages are
proper?)
c. Is there a phase shift?
d. Is the phase rotation correct?
e. Do the potential transformers reflect the actual primary voltage changes without
significant delay?
2. When switching the auto-synchronizer from one generator to another, ALL of the auto-
synchronizer/generator control inputs must be simultaneously transferred to the correct oncoming
breaker and the associated generator. During this transfer, the 52b contact of the breaker must
be closed. Otherwise, an interlock (in the software) prevents the auto-synchronizer from
operating. The signals that must be switched include (but are not limited to):
a. Breaker status signal (i.e., 52b)
b. Generator voltage
c. Breaker close (contact input) circuit
d. Breaker closing time
3. Whenever frequency or voltage control options are used, their outputs must also be switched to
the correct machine governor and voltage regulator.
4. The frequency correction pulse width (the amount of time a raise or lower signal remains ON)
should be coordinated with the speed of response of the governor, the fuel system, and the prime
mover to minimize the time required bringing the generator frequency into the required
relationship with the bus frequency without excessive overshoot or hunting.
5. The voltage correction pulse width and frequency should be coordinated with the response time
of the voltage regulator/exciter/generator combination to minimize the time required to correct the
voltage without overshooting or hunting.
6. If a dead bus closing is desired
− i.e., if the machine can be started without the bus (to which it is
to be synchronized) being energized two conditions must be met:
a. Operating power for the synchronizer must come from a separate source (like a battery)
or from the generator bus.
b. A dead bus option must be included in the unit and be programmed to allow closure to a
dead bus.
7. Some systems, where speed of synchronizing is a primary consideration, allow an oncoming
generator to be closed onto the bus from either the fast or slow side, and with the voltage either
high or low.
a. Fast means that the machine is running with a positive slip (faster than the bus).
b. Slow indicates a negative slip (i.e., slower than the bus).
c. High is generator voltage greater that bus voltage.
d. Low is generator voltage less than bus voltage.
Most systems include a provision to permit closing only with the speed fast and voltage high. This allows
the generator to pick up some watt and var load at once, thus stabilizing the system quickly.
By contrast, when the speed is slow and the voltage low, the system must feed watts and reactive VA to
the machine (to add power to the prime mover and excitation to the exciter field), thereby raising both
speed and voltage. Since this action is controlled only by the sub-synchronous reactance of the machine,
it can cause uncontrolled swings of both vars and watts. The resulting tendency toward destabilization
9146600990 Rev S BE1-25A General Information 1-3