Damage causes of the hottest metal oxide arrester

2022-08-18
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Reasons for damage of metal oxide arresters

in order to protect power facilities from lightning overvoltage and system overvoltage, metal oxide arresters are widely installed and used. In particular, gapless metal oxide arresters are widely used in 10 kV power distribution. With the passage of operation time, line tripping and grounding accidents caused by the damage of metal oxide arresters often occur in 10 kV power distribution, which seriously affects the safe operation of 10 kV power distribution

1 damage cause analysis

according to the damage of gapless metal oxide arrester, the damage with good quality is less, while the damage with poor quality is more; Less damage in sunny days, more damage in thunderstorms; Less damage when there is no operation, and more damage when there is operation; There is less damage in normal operation and more damage in abnormal operation

1.1 wetted

metal oxide arrester is sealed with silicone rubber as the arrester shell. The silicone rubber sleeve is of poor quality, mainly fake and shoddy products from small factories. The technology adopted by the manufacturer is imperfect, or the anti-aging performance of the sealing material is unstable, resulting in poor sealing when the temperature difference changes greatly or the operation time is close to the late life of the product. The two ends of the arrester are rough processed, so that moisture or moisture can be immersed, causing internal insulation damage, accelerating the deterioration of the resistor and causing damage. From the debris of the lightning arrester after the accident, it can be seen that there is no flow trace on the valve plate, and there is no discharge mark after the large current passes through the aluminum spraying surface at both ends of the valve plate. However, there are obvious flashover traces on the inner wall of the silicone rubber sleeve or the side of the valve plate, and there are rust spots or zinc white on the metal accessories, which is the influence of moisture on the metal oxide arrester

can be used as an excellent high molecular polymer sand fixation material. 1.2 the value of rated voltage and continuous operating voltage is low

4 The rated voltage of metal oxide arrester is not only an important parameter to show its operating characteristics, but also an index of the ability to withstand power frequency voltage. The ability of the valve slice of metal oxide arrester to withstand power frequency voltage is closely related to the duration of voltage when it operates for a long time without experiment. Continuous operating voltage is also an important characteristic parameter of metal oxide arrester. The selection of this parameter has a great impact on the reliability of metal oxide arrester. The effective value of power frequency voltage allowed to be permanently applied to the arrester terminal during operation, which covers the maximum value of power frequency voltage that may be continuously applied to the metal oxide arrester during power system operation

1.3 electric voltage fluctuation

the voltage fluctuation range of power distribution is very wide. For metal oxide arrester, if it is required to absorb a large amount of energy in a stable state, it may cause thermal collapse. When using gapless metal oxide arrester, the fluctuation range of system working voltage must be met. Otherwise, because the steady-state voltage is too high, the damage is not one arrester, but many arresters will be damaged at the same time

1.4 aging problem

the valve slice of gapless metal oxide arrester has poor uniformity, which makes the potential distribution uneven. After running for a period of time, some valve slices first deteriorate, causing the reference voltage of the arrester to drop and the resistive current and power loss to increase. As the electric voltage remains unchanged, the rest of the normal valve blades in the metal oxide arrester increase due to the increase of the charge rate (the charge rate is the ratio of the peak value of the maximum operating phase voltage of the metal oxide arrester to the peak value of its DC reference voltage or power frequency reference voltage), resulting in the accelerated aging rate and the formation of a vicious cycle, which eventually leads to the heating and collapse of the metal oxide arrester. The aging rate of arrester valve is the key factor affecting its service life. The oxide arrester operates in the late stage of its product life. The deterioration of the valve plate causes the leakage current to rise, and even causes internal discharge. When the discharge is serious, the internal gas pressure and temperature of the arrester increase sharply, causing the breakdown of the oxide arrester body. When the internal discharge is not too serious, it can cause the single-phase grounding of the system

1.5 harmonics

the application of large tonnage electric arc furnaces, large rectifiers, frequency conversion equipment and the impact load of steel rolling production in metallurgical enterprises have a great impact on electricity, making the high-order harmonic value of electricity seriously exceed the standard. Due to the nonlinearity of the valve plate, under the action of sinusoidal voltage, what if there was no transformation and new cable development at that time? The high-order harmonics in the column, and under the action of the high-order harmonics, it accelerates the deterioration speed of the valve plate

1.6 poor impact resistance

oxide arresters often have accidents under operating overvoltage or lightning conditions. The reason is that during the manufacturing process of the valve slice, due to the lax control of its process quality control points, the ability of the valve slice to withstand impulse voltage is not strong, and in the process of frequently absorbing overvoltage energy, the deterioration of the valve slice is accelerated and damaged. When the resonance is caused by disconnection, grounding or other reasons in the electricity, its amplitude can reach 3 times the phase voltage, which may cause the damage of metal oxide arrester

1.7 the self overvoltage protection ability of metal oxide arrester is poor

for overvoltage with limited energy, such as lightning overvoltage and switching overvoltage, the discharge of arrester can play a role of voltage limiting protection. For overvoltage with infinite energy (with supplementary energy), such as transient overvoltage (the general term of power frequency overvoltage and resonance overvoltage), its frequency may be an integral or fractional multiple of power frequency to form transient overvoltage. The power frequency power supply can automatically supplement overvoltage energy, so that the amplitude of arrester discharge overvoltage does not decay or weakly decay. If the transient overvoltage enters the arrester protection action area, it is bound to act repeatedly for a long time until thermal collapse, Therefore, transient overvoltage is fatal to gapless metal oxide arrester

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