Page 88 - Uninterruptible Power Supplies

Interconnecting the Standby and Normal Supplies
86 Chapter Two

For manual synchronizing, the switchboard should include a synchro-
scope, capable of being connected to any generator and indicating any dif-
ference frequency and the phase relationship between the busbars and
the generator before paralleling. It is usual to include synchronizing
lamps or a zero voltmeter and a check synchronizer as back-up features.
For automatic synchronizing, the switchboard should include an
automatic synchronizer feeding signals to motor operated adjustments
of the voltage and speed regulators of individual sets.
Other indications which should be considered include:
The frequency of any set or of the busbars to be available for display
when required
Operating hours, that is, a cumulative hours-run counter for each set
Indication of kVAr, power factor, and cumulative kWh for each set
Indication of total kW, total kVAr, and the standby supply power factor

Sets Intended to Run in Parallel with the Normal Supply The information
relating to multiple sets applies, with the addition of the following:

Voltage, provision for indication of the busbar voltage which, when
the standby supply is shut down is the normal supply voltage.
The synchronizing features should operate between the busbars and
the normal supply, and between the busbars and the standby supply,
thus enabling synchronizing in either direction. For multiple-set
installations the synchronizing features should also operate between
any individual set and the busbars.

Other indications which should be considered include:

The frequency of any set or of the busbars to be available for display
when required
Operating hours, that is, a cumulative hours-run counter for each set
Indication of kVAr, power factor, and cumulative kWh for each set
Indication of total kW, total kVAr, and standby supply power factor if
more than one generating set is installed

The Synchronizing Facility
A switchboard which provides a paralleling facility will include one set
of synchronizing equipment which the user is able to connect between
any incoming supply and the busbars. Selection is by a switch, plug and
sockets, or any other means, it must not be possible to select more than
one incoming supply.

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