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7 Surge Protection Is a Balancing Act Type 1 Surge protection is permanently connected between the secondary of the service transformer and the line side of the service equipment overcurrent device as well as the load side. For photovoltaic (PV) systems, it is connected between the PV array and the main service disconnect. Surge protection is permanently connected on the load side of the service equipment overcurrent device. Surge protection is installed in the protected device, which is connected to power by a plug receptacle or a power strip that has internal surge protection. An assembly of type 5 components with internal or external disconnect. Consists of a type 4 component assembly with internal or external short-circuit protection. Discrete surge suppression components made from technologies such as metal oxide varistors (MOVs) and gas discharge tubes (GDTs). These components are mounted on printed circuit boards (PCBs). These components are used to create types 1, 2, and 3 surge-suppression and component assemblies. 2 3 4 5 1, 2, 3 Component Assemblies Component Assemblies Description Table 1: UL 1449 Standard, Edition 5, Surge Protection Types. This is illustrated in Figures 1 and 2. In many cases, surge protection specifications are regulation driven, based on the environment in which a device will operate. There is a big difference between the level of surge suppression required in a piece of low-voltage equipment mounted on top of an antenna tower where it could be struck by lightning, in a control system in a factory packed with high-voltage machinery, and in a home appliance. Applications may require compliance with a particular type of surge protection specified in the Underwriters Laboratory (UL) 1449 Standard, Edition 5, "Surge Protective Devices." (UL standards are widely used in the United States; equivalent International Electrotechnical Commission standards are commonly used in Europe.) Table 1 lists these UL 1449 surge protection types.