tor Generator Bulk Fuel Storage Tank Figure 24.1 Basic engine-generator standby plant achieved by the insertion of the mountings between the main and not lead to the complete isolation of the communications complex sub-frames. (Nightingale, 1971). The main set auxiliaries, day fuel service tank, fuel transfer pump, Figure 24.2 shows in schematic form a typical a.c. plant installa- lubricating oil and water make-up tanks, (if required to achieve tion. With loads in the megawatt range, high voltage supplies have extended unattended engine running), together with, perhaps, an been assumed, and the essential loads have been divided into two exhaust silencer, can then be mounted on the main frame work. modules, each fed by a discrete transformer. Each essential load is Associated with the set will be the control system, normally backed up by an engine-generator at the medium voltage stage. A cubiclised, which can contain the control logic and monitors, super- separate transformer has been used to feed non-essential services. It visory lamp displays, and the isolating and emergency by-pass will be noted that a spare transformer has been provided capable of switch-gear. Additionally, the main power switching circuits and backing up either the essential or non-essential, loads in the event interlocked mains and standby supply contractors may be housed in of a failure; or when a working unit is withdrawn from service for the same cubicle, as can be the starter battery charging system. maintenance purposes. Switching and isolating facilities are pro- To ensure adequate cooling air is available, automatically oper- vided to ensure the safety of personnel and plant during mainten- ated louvres are often fitted in wall openings to allow fresh air to be ance operations. Additionally, a switching facility is shown inducted to the engine room. allowing the ready interconnection of a mobile plant if, and when, Similar principles apply to installations only requiring a few required. kilowatts of power, but whilst water cooled engi