Page 4 - Uninterruptible Power Supplies

Standby Power Generating Sets
2 Chapter One

Standby generation is often installed to provide a long-term back-up
to an uninterruptible power supply which will have been installed for
one of the reasons mentioned above.

The Generating Set and Its Supporting
Systems
The major components of a generating set are the power unit and the
generator; these are considered in the sections titled “The Power Unit”
and “Alternating Current Generators” which follow. The remaining sec-
tions of this chapter are devoted to the many supporting components and
systems such as speed governors, voltage regulators, cooling and fuel
systems, ventilating and exhaust systems. Many of these components
will include a control system which may operate independently or may
be linked to other control systems, thus the cooling system will initiate
an over-temperature shut down procedure, the mains monitoring system
will initiate a starting procedure, and the loss of one set in a multiset
installation may initiate load shedding.
The International Standard for diesel driven generating sets is ISO
8528—Reciprocating internal combustion engine driven alternating
current generating sets. This is a comprehensive document containing
a wealth of information and well worth studying for anyone wishing to
acquire detailed information about generating sets.
There is no equivalent standard for gas turbine–driven generating
sets.

The Power Rating Classification of Diesel
Engine–Driven Generating Sets
Rating classes applicable to diesel engine–driven generator sets are
described in ISO 8528 and are discussed in the following paragraphs.
None of the ratings include any overload capacity.

Continuous Power (COP)
Continuous power (Fig. 1.1) is the power which the set can deliver con-
tinuously for an unlimited number of hours per year between the stated
maintenance intervals.

Prime Power (PRP)
This rating is applicable to sets supplying a variable power sequence.
The sequence may be run for an unlimited number of hours per year
between the stated maintenance intervals. Prime power is the maxi-
mum power generated during the sequence and the average power over

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