1) Arc chopping
There are two electrodes shaped like horns, with a short distance between them. When the potential difference between the two electrodes reaches a certain level, the gap is pierced and sparked and discharged, thereby releasing the overcurrent into the ground.
Advantages: strong discharge capacity, large current capacity (over 100kA can be achieved), low leakage current;
Disadvantages: high residual voltage (2～4kV), slow response time (≤100ns), follow current (freewheeling).
At a certain temperature, the electrical conductivity of the device increases sharply with the increase of voltage. It is a metal oxide semiconductor non-linear resistor with zinc oxide as the main component. When there is no overvoltage, it is in a high resistance state. Once overvoltage, the voltage is immediately limited to a certain value, and its impedance suddenly changes to a low value.
Advantages: large flow capacity, low residual voltage, faster response time (≤50ns), no following current (freewheeling);
Disadvantages: The leakage current is large, and the aging speed is relatively fast.
Also known as Zener diode, it is a device specially used to suppress overvoltage. The core part is a PN junction with a larger cross-sectional area. The PN junction has a strong pulse absorption capability when working in an avalanche state.
Advantages: low residual pressure, high accuracy of action, fast response time (<1ns), no following current (freewheeling);
Disadvantages: poor flow resistance, small flow capacity, generally only a few hundred amperes.
Ceramic gas discharge tubes can be used for surge protection in data lines, cable television, AC power supplies, telephone systems, etc. The general device voltage ranges from 75 to 10000V, withstands impulse peak currents of 20000A, and can withstand up to several thousand joules of discharge.
Advantages: large flow capacity, high insulation resistance, low leakage current;
Disadvantages: high residual voltage, slow response time (≤100ns), low operating voltage accuracy, and following current (freewheeling).
The common feature of various surge suppression devices is that the devices present high impedance below the threshold voltage. Once the threshold voltage is exceeded, the impedance drops sharply, and all have a certain suppression effect on the peak voltage. But each has its shortcomings, so according to specific applications, one or a combination of the above-mentioned devices is generally used to form the corresponding protection circuit.