Page 241 - Offshore Electrical Engineering Manual

228 CHAPTER 5 Conductor Sizing, Load Flow and Fault Calculation

FIGURE 4.5.1
Miniature circuit breaker and fuse characteristic comparison. LV, low voltage; MCCB,
moulded case circuit breaker.
Courtesy GEC Alstom Measurements, now GE Alstom Grid Solutions.

proportion of the platform load is on the switchboard being fed. This is because
the steady-state fault current available from the platform generators will be of
the order of three to four times the full-load current; therefore, if fault clearance
times are to be kept short, generator and feeder relay current settings will need to
be close. Voltage-controlled relays may be used on generator circuit breakers to
overcome this problem, as discussed earlier for generator protection (see PART 4
Chapter 1).