Standby Engine-Generator System

Automatic starting and synchronizing controls are used for multiple-engine-generator installations. The output of two or three smaller units can be combined to feed the load. This capability offers additional protection for the facility in the event of a failure in any one machine. As the load at the facility increases, additional engine-generator systems can be installed on the standby power bus. 

The engine-generator shown in Fig. 10.175 is the classic standby power system. An automatic transfer switch monitors the AC voltage coming from the utility company line for power failure conditions. 

FIGURE 10.175 The classic standby power system using an engine-generator set. This system protects a facility from prolonged utility company power failures. 

FIGURE 10.181 Simplified installation diagram ofa high reliability power system incorporating dual utility feeds, a standby gas-engine generator, and five battery-backed DC m-g sets. 

Operational Behavior Demonstrated in a Standby Power Plant. The plant consists of a diesel engine, the attached generator, and a number of auxiliary systems. Figure 5.25 shows the general plan of the installation. Important auxiliary systems of the plant are the fuel supply system, the lubrication system, the coolant circuits, the generator excitation system, the starter system, the air supply, and the circuitry. 

Optional standby power systems are for systems whose failure could cause effects such as damage to process equipment, interruption of manufacturing processes, loss of airflow to maintain cleanliness conditions, etc. Although not required by code, process engineers may want selected production equipment on optional standby power. Loads which are not related to life safety, yet are desired to be connected to the emergency power system, must be separated and controlled by their own transfer switches. The nonlife-safety loads must be able to be shed, if necessary, due to a generator malfunction. 

A backup lead-acid battery system, unlike a standby battery system, normally does not have the function of automatic outage detection. With a backup power system, when utility power fails, the user usually must start the battery system manually by connecting extension cords directly from the backup battery to the appliance to be powered. Note that all of the battery systems discussed in the standby power applications section can be used as backup systems. In addition, there are several other small-scale applications such as engine starting for portable generators, cable TV applications, cordless power tools, portable printers, battery-powered camping equipment, handheld home devices such as vacuums and razors, and medical equipment. 

Engineers designing the next generation of space shuttles plan to include two fuel pumps—one active, the other standby. If the primary pump malfunctions, the second is immediately brought into service. Suppose a typical mission is expected to require that fuel be pumped for at most 50 hours. According to the manufacturer s specifications, pumps are expected to fail once every 100 hours. What are the chances that such a fuel pump system would completely fail for the next 50 hours ... 

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