Page 57 - Offshore Electrical Engineering Manual

44 CHAPTER 3 Emergency Generators

2. Interlocking facilities must be provided to ensure that the generator circuit
breaker cannot close on to an existing fault when the generator is automatically
started.
3. In the event of a fault, means should be provided to maintain the generator
output current for long enough to operate protection devices, where this is pos-
sible with the limited magnitude of fault current available from such a machine.
Leaving the machine running with collapsed excitation is dangerous, as the fault
may disappear followed by a sudden and possibly unexpected reappearance of
full voltage on the system. Fig. 2.3.1 shows a photograph of the typical current
design of an emergency diesel generator set.
4. The generator container should satisfy the following:
a. Be pressurised, with automatic shutdown on loss of pressure, or alternatively

all equipment within the container (including the prime mover) would need
to be approved for use in a Zone 2 area (as per BS-EN 1834).

b. Be fitted with overspeed protection on the diesel engine.

c. Be fitted with appropriate noise suppression for its location.
d. Be fitted with vibration reducing measures and sound isolating deck/struc-

tural connections/supports.
e. The exhaust pipe on the engine to be fitted with an approved spark arrester.

f. The electrical start battery to be fitted with a circuit breaker for ‘Level Zero’
installation ESD.

g. A drip tray for collecting any oil or diesel leaks to be placed under the
engine.

FIGURE 2.3.1
A typical packaged generator set.
Courtesy Gen Ex Design Ltd.