1) An electrical appliance used to protect electrical equipment from high transient overvoltage hazards and limit the freewheeling time and often limit the freewheeling amplitude. This term includes any external clearances necessary for the normal function of the appliance during operation and installation, regardless of whether it is a part of a whole.
Note 1: The lightning arrester is usually connected between the grid wire and the ground wire, but sometimes it is also connected near the electrical winding or between the wires.
Note 2: Lightning arresters are sometimes also called over-voltage protectors, surge dividers.
Lightning arrester: An electrical appliance used to protect electrical equipment from high transient overvoltages during lightning strikes, and to limit the freewheeling time and the amplitude of freewheeling. Lightning arresters are sometimes called overvoltage protectors and overvoltage limiters. As shown in the figure is a lightning arrester.
AC gapless metal oxide surge arresters are used to protect the insulation of AC power transmission and transformation equipment from lightning overvoltage and operating overvoltage damage. It is suitable for over-voltage protection of transformers, power transmission lines, power distribution panels, switch cabinets, power metering boxes, vacuum switches, parallel compensation capacitors, rotating electrical machines and semiconductor devices.
The AC gapless metal oxide arrester has excellent nonlinear volt-ampere characteristics, good response characteristics, no freewheeling, large current capacity, low residual voltage, strong suppression of overvoltage, pollution resistance, anti-aging, and no altitude constraints. Simple structure, no gap, tight sealing, long life and other characteristics.
The arrester presents a high resistance state under normal system operating voltage, and only microampere current passes. Under the action of over-voltage and large current, it presents low resistance, thereby limiting the residual voltage at both ends of the arrester
The lightning arrester is connected between the cable and the ground, usually in parallel with the protected equipment. The lightning arrester can effectively protect the communication equipment. Once an abnormal voltage occurs, the arrester will act and play a protective role. When the communication cable or equipment is running under the normal working voltage, the arrester will not have any effect, and it is regarded as open circuit to the ground. Once high voltage occurs and the insulation of the protected equipment is endangered, the arrester will act immediately to direct the high-voltage impulse current to the ground, thereby limiting the voltage amplitude and protecting the insulation of communication cables and equipment. When the overvoltage disappears, the arrester quickly returns to its original state, allowing the communication line to work normally.
Therefore, the main function of the arrester is to clip the intruding flowing wave through the parallel discharge gap or nonlinear resistance, reduce the overvoltage value of the protected equipment, and protect the communication line and equipment.
Lightning arresters can be used not only to protect against high voltages generated by lightning, but also to protect against operating high voltages.
The function of the lightning arrester is to protect various electrical equipment in the power system from damage caused by lightning overvoltage, operating overvoltage, and power frequency transient overvoltage. The main types of lightning arresters include protective gaps, valve arresters and zinc oxide arresters. The protective gap is mainly used to limit the atmospheric overvoltage, and is generally used for the protection of the power distribution system, the line and the incoming line of the substation. Valve-type arresters and zinc oxide arresters are used for the protection of substations and power plants. In 500KV and below systems, they are mainly used to limit atmospheric overvoltages. In ultra-high voltage systems, they will also be used to limit internal overvoltages or as internal overvoltages. Backup protection.
In daily operation, check the pollution of the surface of the porcelain sleeve of the arrester, because when the surface of the porcelain sleeve is seriously polluted, the voltage distribution will be very uneven. In an arrester with shunt resistors in parallel, when the voltage distribution of one of the components increases, the current through its parallel resistors will increase significantly, and the parallel resistors may burn out and cause malfunctions. In addition, it may also affect the arc extinguishing performance of the valve arrester. Therefore, when the surface of the arrester porcelain sleeve is seriously dirty, it must be cleaned in time.
Check the lead wire of the arrester and the ground down conductor. There are burn marks and broken strands and whether the discharge recorder is burnt. Through this inspection, the invisible defect of the arrester is most likely to be found; check whether the upper lead of the arrester is well sealed. Ingress of water and damp can easily cause accidents. Therefore, check whether the cement joint between the porcelain sleeve and the flange is tight. A waterproof cover can be installed on the lead wire of the 10 kV valve-type arrester to prevent rainwater infiltration; check the arrester and the protected electrical Whether the electrical distance between the equipment meets the requirements, the lightning arrester should be as close as possible to the protected electrical equipment, the lightning arrester should check the action of the recorder after a thunderstorm; check the leakage current, if the power frequency discharge voltage is greater or less than the standard value, it should be overhauled And test; when the discharge recorder has too many movements, it should be overhauled; the porcelain sleeve and cement joints are cracked; when the flange and rubber gasket are off, it should be overhauled.
The insulation resistance of the arrester should be checked regularly. When measuring, use a 2500 volt insulation shaker. The measured value is compared with the previous result. If there is no obvious change, it can continue to be put into operation. When the insulation resistance drops significantly, it is generally caused by poor sealing and dampness or spark gap short-circuit. When it is lower than the qualified value, a characteristic test should be performed; when the insulation resistance rises significantly, it is generally due to poor contact or fracture of the internal parallel resistance And caused by spring slack and separation of internal components.
In order to discover invisible defects inside the valve arrester in time, a preventive test should be carried out before the thunderstorm season each year.