Created by: Glen Zhu | Updated Date: November 19th, 2024
Since 2010, LSP has been dedicated to designing and manufacturing surge protective devices protecting installations from transient overvoltages that result from switching events and lightning strikes.
We’ll explain how do surge protection work from the perspective of Monobloc, pluggable, data/signal line surge protective device (SPD) basic on IEC/EN standards.
What is a surge protective device (SPD)?
According to standard IEC 61643-11:2011 – 3.1 Terms and definitions – 3.1.1 surge protective device (SPD) is a device that contains at least one nonlinear component that is intended to limit surge voltages and divert surge currents. (Note: An SPD is a complete assembly, having appropriate connecting means.)
Generally speaking, surge protective device (in short: SPD) is a device used to suppress abnormal overvoltage and transient overcurrent in circuits, thereby avoiding damage to electronic devices.
A surge protection device (SPD) or simply a surge protector is a device used to protect electronic devices from power surges or transient voltage.
This device is connected in parallel to the power supply circuit of the loads that it has to protect. It can also be used at all levels of the power supply network.
In other words, surge protective device is a device used to protect electrical equipment from damage caused by surges (voltage transients).
Surges are transient voltage fluctuations caused by lightning strikes, grid faults, motor starts, etc., which may damage or malfunction equipment. Surge protectors absorb, disperse, or suppress surges and divert over-voltages to the ground wire to protect equipment from the effects of surges.
A surge protective device is a protective device for limiting transient voltages by diverting or limiting surge current.
The surge protective device are used to protect sensitive electronic equipment connected to the installation, such as computers, televisions, washing machines and safety circuits, such as fire detection systems and emergency lighting. Equipment with sensitive electronic circuitry can be vulnerable to damage by transient overvoltages.
Generally speaking, the working principle of surge protective device (SPD) is based on limiting voltage and diverting current. When the voltage exceeds a safe threshold, nonlinear components (such as metal oxide varistors MOV, gas discharge tubes GDT, diodes, etc.) quickly reduce resistance to guide excess energy to the ground, thus protecting equipment.
Surge protection devices contain at least one non-linear component (a varistor or spark gap), its electrical resistance varying in the function of the voltage which is applied to it. Their function is to divert the discharge or impulse current and to limit the overvoltage at the downstream equipment.
The operating principle of a surge protection device is as follows:
During normal operation (e.g., in the absence of surges), the surge protection device has no influence on the system where it’s installed. It acts as an open circuit and maintains the isolation between the active conductors and earth.
When a voltage surge occurs, the surge protection device reduces its impedance within a few nanoseconds and diverts the impulse current. The surge protection device behaves like a closed circuit, the overvoltage is short-circuited and limited to an acceptable value for the electrical equipment connected downstream.
Once the impulse surge has stopped, the surge protection device will return to its original impedance and return to the open circuit condition.
In other words, the working principle of surge protective device (SPD) is mainly based on their internal nonlinear components, such as varistors (MOV), gas discharge tubes (GDT), or semiconductor devices (such as TVS diodes), which quickly conduct when the voltage exceeds their specified value, converting overvoltage into current and releasing it to the ground, thereby limiting the voltage peak at the equipment end.
The ability of an SPD to limit overvoltages on the electrical distribution network by diverting surge currents is a function of the surge-protective components, the mechanical structure of the SPD, and the connection to the electrical distribution network. An SPD is intended to limit transient overvoltages and divert surge current, or both. It contains at least one nonlinear component. In the simplest terms, SPDs are intended to limit transient overvoltages with a goal of preventing equipment damage and downtime due to transient voltage surges reaching the devices they protect.
A surge protective device (SPD) is designed to protect electrical systems and equipment from surge events by limiting transient voltages and diverting surge currents.
Surges can originate externally, most intensely by lightning, or internally by the switching of electrical loads. The sources of these internal surges, which account for 65% of all transients, can include loads turning on and off, relays and/or breakers operating, heating systems, motors, and office equipment.
Without the appropriate SPD, transient events can harm electronic equipment and cause costly downtime. The importance of these devices in electrical protection is undeniable, but how do these devices actually work? And what components and factors are central to their performance?
In the most basic sense, when a transient voltage occurs on the protected circuit, an SPD limits the transient voltage and diverts the current back to its source or ground.
To work, there must be at least one non-linear component of the SPD, which under different conditions transitions between a high and low impedance state.
At normal operating voltages, the SPDs are in a high-impedance state and do not affect the system. When a transient voltage occurs on the circuit, the SPD moves into a state of conduction (or low impedance) and diverts the surge current back to its source or ground. This limits or clamps the voltage to a safer level. After the transient is diverted, the SPD automatically resets back to its high-impedance state.
When it comes to the working principle of the surge protective device (SPD), it is necessary to mention the internal nonlinear components, it include:
Metal Oxide Varistors (MOV)
Working principle: MOV is mainly composed of metal oxide such as zinc oxide. Under normal operating voltage, MOV is in a high impedance state. Once the voltage exceeds its breakdown voltage, the resistance of MOV rapidly decreases, entering a conductive state and dissipating excess energy in the form of heat.
Characteristics:
Gas Discharge Tubes (GDT)
Working principle: GDT is filled with inert gas. When the voltage exceeds its breakdown voltage, the gas is ionized, forming a conductive channel to quickly dissipate excess energy.
Characteristics:
Transient Voltage Suppressors (TVS)
Working principle: The core working principle of TVS diodes is avalanche breakdown. When the voltage applied across the two terminals of the TVS exceeds its breakdown voltage, the number of charge carriers in the PN junction increases sharply, causing avalanche breakdown and putting the TVS into a conducting state. At this point, excess voltage will be clamped at a relatively stable level to prevent damage to sensitive components.
Characteristics:
LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!
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