What is the difference between lightning arresters for power distribution and motors?
Lightning arrester manufacturer, European cable joints, cold shrink cable terminals
The arrester for motors is mainly used to prevent inductive power frequency operation overvoltage. This kind of overvoltage often occurs during operation. For example, when the arc is interrupted before the arc crosses zero when the switch is opened, there will be overvoltage. When the circuit is opened, due to the different loop wave impedance, the voltage reflection wave superposition of the operating overvoltage is generated. These overvoltages are all power frequency overvoltage, that is, the frequency of the voltage waveform remains unchanged at 50HZ.
In addition to preventing operating overvoltage, lightning arresters for power distribution must also prevent atmospheric lightning overvoltage. This overvoltage waveform has a steep front end and high frequency, but the subsequent current is very small. The arrester can discharge the peak value of the lightning wave to ensure the safety of the electrical appliances behind it.
There are many types of lightning arresters, including metal oxide arresters, line-type metal oxide arresters, gapless line-type metal oxide arresters, fully insulated composite jacket metal oxide arresters, and detachable arresters.
The main types of arresters include tube arresters, valve arresters and zinc oxide arresters. The main working principles of each type of lightning arrester are different, but their working essence is the same, which is to protect communication cables and communication equipment from damage.
Tubular arrester
The tubular arrester is actually a protective gap with high arc-extinguishing capability. It consists of two gaps in series. One gap is in the atmosphere, called the outer gap. Its task is to isolate the working voltage and prevent the gas production pipe from being burned by the power frequency leakage current flowing through the tube; the other is installed in the gas pipe, called the inner gap or arc-extinguishing gap. The arc-extinguishing ability of the tubular arrester is related to the size of the power frequency freewheeling current. This is a protection gap type lightning arrester, which is mostly used for lightning protection on power supply lines.
Valve type arrester
The valve type arrester is composed of a spark gap and a valve resistor. The valve resistor is made of special silicon carbide. Chip resistors made of silicon carbide can effectively prevent lightning and high voltage and protect equipment. When there is high lightning voltage, the spark gap is broken down, the resistance value of the valve resistor decreases, and the lightning current is introduced into the earth, which protects cables or electrical equipment from the harm of lightning current. Under normal circumstances, the spark gap will not be broken down, and the resistance value of the valve resistor is relatively high, which will not affect the normal communication of the communication line.
Zinc oxide arrester
Zinc oxide arrester is a kind of lightning protection equipment with superior protection performance, light weight, pollution resistance and stable performance. It mainly uses the good nonlinear volt-ampere characteristics of zinc oxide to make the current flowing through the arrester at normal operating voltage extremely small (microamperes or milliamperes); when overvoltage occurs, the resistance drops sharply and discharges the energy of the overvoltage to achieve a protective effect. The difference between this kind of arrester and traditional arrester is that it has no discharge gap and uses the nonlinear characteristics of zinc oxide to play the role of discharge and breaking.
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