Metal oxide arrester test selection scheme

**Metal Oxide Surge Arrester Selection Scheme** Testing and maintenance of metal oxide surge arresters are essential to ensure the safety and reliability of power systems. The following procedures outline the key tests and their specifications. --- ### **Insulation Resistance Test** - **Cycle**: 1) Before the annual thunderstorm season at power plants and substations. 2) When necessary. - **Requirement**: 1) For voltages above 35kV, insulation resistance should be no less than 2500MΩ. 2) For 35kV and below, it should be no less than 1000MΩ. - **Description**: Use a megohmmeter rated at 2500V or higher for testing. This test helps identify any degradation in the arrester's insulation. --- ### **DC 1mA Voltage (U1mA) and Leakage Current at 0.75U1mA** - **Cycle**: 1) Before the annual thunderstorm season at power plants and substations. 2) When necessary. - **Requirement**: 1) U1mA must not be lower than the value specified in GB11032. 2) The measured U1mA should not differ by more than ±5% from the initial or manufacturer’s value. 3) The leakage current at 0.75U1mA should not exceed 50μA. - **Description**: Record ambient temperature and humidity during the test. Use shielded cables for current measurement. The initial value refers to the value obtained during handover or production testing. --- ### **AC Leakage Current at Operating Voltage** - **Cycle**: 1) For new 110kV and above arresters: once after 3 months of operation, then every six months. After one year, once before the thunderstorm season each year. 2) When necessary. - **Requirement**: Measure full current and resistive current at operating voltage. Compare with initial values. If there is a significant change, increase monitoring. If the resistive current doubles, perform a power-off inspection. - **Description**: Record ambient temperature, humidity, and operating voltage. Conduct the test when the porcelain housing is dry and be cautious of phase interference. --- ### **Base Insulation Resistance** - **Cycle**: 1) Before the annual thunderstorm season at power plants and substations. 2) When necessary. - **Requirement**: Self-regulated based on standard practices. - **Description**: Use a megohmmeter rated at 2500V or higher to test the base insulation. This ensures that the foundation remains intact and free from moisture or damage. --- ### **Discharge Counter Operation Check** - **Cycle**: 1) Before the annual thunderstorm season at power plants and substations. 2) When necessary. - **Requirement**: Perform 3–5 tests; the counter should operate normally. Reset the counter to “0” after testing. - **Description**: This test verifies that the discharge counter functions correctly, ensuring accurate recording of lightning strikes and system disturbances. --- These tests help maintain the performance and longevity of metal oxide surge arresters, ensuring they can effectively protect electrical equipment from overvoltage events. Regular checks and proper documentation are crucial for maintaining system integrity and safety.

Composite Fuse Cutout

Drop Out Fuse Cutout is a kind of outdoor high voltage protection device, lt is connected with the incoming feeder of thedistribution transformer or distribution lines and primarily used to protect transformers or lines against the impact raised by shortcircuit, overload and switching current. The drop-out fuse cutout is composed of insulator support and a fuse carier, staticcontacts that are fxed on two sides of insulator support and moving contact installed on two ends of fuse carrier, The interior ofthe fuse carrier is the extinguishing tube while the exterior is made of phenolic compound paper tube or epoxy glass.

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