Handbook of Electrical Installation Practice - BeKnowledge

20 Handbook of Electrical Installation Practice
Fig. 1.6 High voltage consumer with switchable reactors.
near that of the switchgear rating. Switchable reactors may be required to
overcome this problem; one such arrangement is shown in Fig. 1.6. There is
also a problem of earthing the generators should they become separated
from the power system and its source earth point.
This method of supply seems a good one for the application of microprocessors.
On the metering side they could calculate the value of the
units on an incremental worth basis to suit a time/load/power factor agreement.
On the control side they could monitor the number of generators
and reactors to contain the short-circuit level within limits. They could
be used to control voltage and reactive power generated, and also for
protection.
(3) Standby generation. Load shedding due to shortage of fuel or other industrial
action caused an upsurge in the installation of small generators by those consumers
whose business could not stand the risk of loss of supply, ranging from
just a few kilowatts at low voltage to several thousand kilowatts switched at
high voltage.These cause some anxiety on safety grounds as cases have occurred
where the generator has been started up and connected to the installation
without the latter being disconnected from the incoming supply.
It is easy to imagine a small l.v. generator being plugged in to supply a milking
machine on a farm at the end of a line and a linesman repairing the fault receiving
a shock and being thrown to the ground. Problems have also occurred on
large sets due to incorrect changeover arrangements, for example, in one case
a loss of supply on one phase only brought in the standby set without the normal
feed being disconnected.
The local DNO is generally pleased to give advice on appropriate changeover
arrangements.