Surge protection devices (SPDs) - SPDs shield equipment from damaging voltage spikes and transients.
A Surge Protection Device (SPD), also known as a surge suppressor or transient voltage surge suppressor (TVSS), is an electrical component or appliance designed to protect electronic devices from power surges or voltage spikes. These devices limit transient voltages by diverting or limiting surge current to a safe level, thus preventing damage to downstream equipment.
How SPDs Work
The core of an SPD is a non-linear component that, under normal operating conditions, acts as an open circuit (high impedance) and does not affect the system. When a voltage surge occurs and exceeds a safe threshold, the device's internal components instantly become conductive (low impedance), providing a path for the excess energy to be diverted to the ground or back to its source. After the surge has passed, the SPD automatically reverts to its high-impedance state, allowing the circuit to return to normal operation.
The most common components used in SPDs are:
Metal Oxide Varistors (MOVs): These are the most common component in consumer surge protectors. An MOV is a voltage-dependent resistor that has a very high resistance at normal voltages but a very low resistance when the voltage exceeds a certain level, allowing it to shunt the surge current.
Gas Discharge Tubes (GDTs): These are a type of voltage-switching device. When a surge occurs, the gas inside the tube ionizes, creating a conductive path that diverts the current.
Silicon Avalanche Diodes (SADs): These diodes are known for their extremely fast response time, making them ideal for protecting sensitive electronics from fast-rising voltage spikes.
Types of SPDs
SPDs are classified by their location and the level of protection they provide, as defined by standards like UL 1449 and IEC 61643.
Type 1 SPDs: These are heavy-duty devices designed to protect against large external surges, most notably direct lightning strikes. They are installed at the main service entrance or at the utility meter.
Type 2 SPDs: These are the most common type of SPD for residential and commercial applications. They are installed on the load side of the main service disconnect, such as in a subpanel. Their purpose is to protect against residual lightning energy and surges generated internally from the switching of large loads like motors or HVAC systems.
Type 3 SPDs: These are point-of-use devices, such as plug-in surge protectors and power strips. They provide a final, localized layer of protection for individual pieces of equipment and must be installed at least 30 feet from the main panel to be effective.
Key Benefits and Market Trends
Surge protection is crucial for protecting modern electrical and electronic equipment from damage. Even small, frequent surges generated internally can degrade sensitive electronics over time.
The market for SPDs is experiencing strong growth, driven by:
The proliferation of sensitive electronics: As homes, businesses, and industrial facilities become more reliant on technology, the need for robust protection against voltage spikes increases.
Growing adoption of smart grids and renewable energy: The integration of intermittent renewable energy sources and the use of power electronics in grid infrastructure introduce new power quality challenges, boosting the demand for SPDs to ensure system reliability.
Stricter regulations: Many building codes and national electrical codes now mandate or recommend the installation of SPDs in both new and existing construction to enhance safety and protect assets.
