Genset Control and Protection
This paper examines the fundamental principles of controlling an engine-driven generator set (genset). It focuses on control, protection, load sharing, and integration of the genset into load management and power systems. NFPA 110 requirements for standby generators and how these requirements can be met with modern electronic genset controllers are presented. In addition, various considerations of paralleled generator sets and implications of paralleling on the engine governor and genset controller are examined.
Generator sets come in a variety of sizes, ratings, and prime mover types and can accept a variety of fuels. Our discussions focus on the diesel driven genset; however, the concepts can be used for many other types of configurations. We look at a genset in an emergency standby application that must comply with requirements of the NFPA 110 standard as well as applications where the genset is paralleled to other generators in an island system or paralleled to the utility as distributed generation.
In basic terms, the genset controller is responsible for starting and stopping the genset. A user input (pushbutton, contact input, key switch, or via communications) is given to the genset controller. When the input is recognized by the genset controller, it will energize the fuel solenoid as well as begin the crank cycle. While cranking the genset controller will monitor a signal from the engine, such as the engine speed or oil pressure, to determine that the engine has started at which time it will disengage the starter.
When the engine run input signal has been removed, a stop command is given, or a critical parameter is detected outside of its preset operating range, resulting in an engine shutdown, the genset controller deenergizes the fuel solenoid to cut fuel flow and stop the engine. In order to fully define requirements for cranking, control, and protection for the genset, we must understand (1) how the genset will be operated, (2) the application requirements, and (3) the power delivery expectations.
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