Classification of Surge Protection Device?

Now there are all kinds of surge protection devices on the market. Among those protection products, what kind of products do we need? What should we rely on to distinguish types? Let’s see it follow Okmarts.

Figure 1: Different surge protection device.

1. Classification By Purpose

Surge protection devices are divided into two categories: power surge protection devices and signal surge protection devices.

There are many kinds of power surge protection devices (SPDs), such as T1 level SPD, primary SPD, secondary SPD and tertiary SPD, DC SPD, etc

Figure 2: A video signal surge protection device.

Signal surge protection devices are divided into telephone signal SPD, modem signal SPD, digital SPD, analog SPD, network SPD, video SPD, etc.

2. Classification By Working Principle

2.1 Voltage Switching Type SPD

When there is no instantaneous overvoltage, it presents a high impedance. Once it responds to the lightning instantaneous overvoltage, its impedance will suddenly change to a low value to allow the lightning current to pass through. Such devices include: discharge gap, gas discharge tube, thyristor, etc.

2.2. Voltage Limiting Type SPD

Figure 3: A voltage limiting type SPD.

It has high resistance when there is no instantaneous overvoltage, but its impedance will decrease with the increase of surge current and voltage. Its current and voltage characteristics are strongly nonlinear. Such devices include: zinc oxide, varistor, suppression diode, avalanche diode, etc

3. Classification By Composition

3.1 Air Gap SPD

Open gap type: Based on arc discharge technology, when the voltage between electrodes reaches a certain degree, the air arc will be broken down and creepage on the electrode.

Closed gap type: it is a multi-layer graphite gap SPD. This SPD mainly uses multi-layer gap continuous discharge and each layer of discharge gap is insulated from each other. This laminated technology not only solves the problem of continuous current, but also discharges layer by layer which virtually increases the flow capacity of the product itself.

3.2 Discharge Tube SPD

Open discharge tube: in essence, it is the same product as open gap SPD which belongs to air arrester. However, compared with the gap SPD, its current carrying capacity is reduced by a level.

Closed discharge tube: closed gas discharge tube, also known as inert gas discharge tube, is mainly filled with inert gas. The discharge mode is gas discharge which can discharge current at one time by breaking down the gas. Generally, there are two kinds of structures: 2-pole and 3-pole.

3.3 Varistor SPD

Figure 4: A varistor SPD.

Monolithic varistor: it makes use of the nonlinear characteristics of varistor. When the voltage does not fluctuate, zinc oxide is in a high resistance state. When the voltage fluctuates and reaches the starting voltage of the varistor, the varistor quickly presents a low resistance state, limiting the voltage to a certain range.

Multi varistor: multi varistor combined SPD mainly solves the problem that the flux of single varistor is small and can not meet the use of class B occasions. The production of multiple varistors fundamentally solves the problem of flow through varistors.

3.4 Suppression Diode SPD

Suppression diode SPD is mainly used in a large number of signal lightning protection products such as network. It mainly adopts P * KE (avalanche tube) and other products.

3.5 Combined SPD

Figure 5: A combined SPD.

Simple combined type: the typical structure of combined SPD is N-PE structure. Compared with single structure SPD, this SPD combines the advantages of two different products. Therefore, it can reduce the disadvantages of a single device.

Complex combination type: This SPD gives full play to the advantages of various components. In structure, it generally uses a large number of varistors and gas discharge tubes. The SPD with this structure generally has high current carrying capacity and low residual voltage.

3.6 Silicon Carbide SPD

Silicon carbide SPD is mainly used in high-voltage power lightning protection. At present, it is still a power lightning protection product with high utilization rate in power system.

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