Surge protector

Surge protector
(Surge Protection Devices, referred to as SPD), also known as surge protectors, overvoltage protectors, commonly known as lightning arresters, lightning arresters.
 
In view of the emergence of various types of lightning arresters on the market, the quality is uneven, and some are even unheard of (such as: lightning arresters without grounding, until now, they can not understand how it works), therefore, By introducing the working principle and composition of the arrester, it is helpful to identify the true and false, good and bad customers.
 
The lightning arrester components are available in both soft and hard from the perspective of response characteristics. The discharge element belonging to the hard response characteristic has a spark gap (angular spark gap and coaxial discharge spark gap based on xenon arc technology) and a gas discharge tube, and the discharge element belonging to the soft response characteristic has a metal oxide varistor and transient suppression. diode. The difference between these components is the discharge capacity, response characteristics and residual voltage. The arresters use their different advantages and disadvantages, and they are combined to form various arresters and protect circuits.
 
The spark gap (Arc chopping)
 
1. Discharge gap:
 
The principle is two electrodes such as horns, the distance is very short, separated by insulating material, when the electric field strength between the two electrodes reaches the breakdown strength, a current path is formed between the electrodes. When the lightning wave arrives, it first breaks down at the gap, so that the air in the gap is ionized to form a short circuit, and the lightning current flows into the earth through the gap, and the voltage at both ends of the gap is low, thereby achieving the purpose of protecting the line. When the electric field strength is lower than the breakdown gap, the discharge gap type arrester returns to the insulated state. Commonly used in lightning protection of high voltage lines. In low voltage systems, Commonly used for pre-protection of power supplies. The advantages and disadvantages of spark gap type arrester products are the material of the electrode, the gap distance and the insulating material.
 
Advantage:
 
It has strong discharge capacity and large flow rate. The 10/350μs pulse waveform can divert 50KA pulse current for 8/20μs pulse current, which can be greater than 100KA, high insulation resistance and small parasitic capacitance, and low leakage current. It does not have any harmful effects on equipment that is working properly.
 
Disadvantages:
 
The residual voltage is high (2.5~3.5KV), the reaction time is long (≦100ns), the operating voltage accuracy is low, and there is power frequency freewheeling. Therefore, a fuse should be connected in series in the protection circuit, so that the power frequency freewheeling is quickly cut off.
 
Note: Since the two discharge tubes are respectively installed on the two wires of one circuit, they sometimes discharge at different times, so that a potential difference occurs between the two wires. In order to make the discharge tube on the two wires close to a uniform time discharge, reduce two A three-stage discharge tube was developed for the potential difference between the lines. It can be seen as consisting of two secondary discharge tubes combined together. The first stage in the middle of the three-stage discharge tube is used as a common ground line, and the other two stages are respectively connected to the two wires of the loop.
 
2, Gas discharge tube (GDT): is a ceramic or glass package, the tube is filled with a certain pressure of inert gas (such as argon), switch-type protection components
There are two structures of two electrodes and three electrodes. When the electric field strength reaches the breakdown inert gas intensity, a gap discharge is caused, thereby limiting the voltage between the poles. 8/20μs pulse current can channel 10KA. The discharge voltage is unstable. When the voltage is greater than 12V and the current voltage is 100mA, a subsequent current is generated. Usually used in measurement, control, regulation technology circuits and electronic data processing transmission circuits.

For more news and events on surge protective device, please pay attention to our official website:www.fatech-surge-protection.com.

FATECH ELECTRONIC LTD.

Feb.12, 2019