Troubleshooting for poor insulation of vacuum pressure switches

Poor insulation of vacuum pressure switches may cause faults such as leakage and signal interference, affecting the normal operation and safety of the equipment. When conducting inspections, one can start from aspects such as visual inspection, electrical performance testing, component disassembly and analysis, and environmental factor investigation.

Visual inspection

Check the integrity of the casing: Carefully observe the casing of the vacuum pressure switch to see if there is any damage, crack or deformation. Damage to the casing may expose the internal insulating components to the external environment, reducing the insulation performance. For instance, if the casing cracks due to external force impact, moisture, dust and other impurities may enter the interior of the switch, resulting in poor insulation.

Check the sealing condition: Confirm whether the sealing parts of the switch, such as sealing rings and sealing adhesives, are in good condition. Poor sealing can cause external moisture, dust and other substances to invade the interior of the switch, adhering to the insulating components and forming conductive channels, thereby affecting the insulation effect. It is possible to check whether the sealing ring has aged, deformed, missing or other problems, and whether the sealant has cracked or fallen off.

Observe the condition of the leads: Check whether the leads of the switch are damaged or exposed. If the insulation layer of the lead is damaged, the wire will be directly exposed, making it easy to come into contact with other metal parts or grounding parts, resulting in poor insulation. Check whether the leads have any marks such as cuts, wear or compression, and whether the connection between the leads and the switch body is well sealed.

Electrical performance test

Insulation resistance measurement: Use an insulation resistance tester (megohmmeter) to measure the insulation resistance between each live part of the vacuum pressure switch and the housing. Before measurement, make sure that the switch is powered off and the part to be measured is disconnected from other circuits. Operate in accordance with the user manual of the tester, apply the specified test voltage (such as 500V or 1000V), and read the insulation resistance value. Generally speaking, the insulation resistance value should not be lower than the specified minimum value (different models of switches may have different requirements, which can be referred to the product manual). If the measured value is lower than the standard value, it indicates poor insulation.

Withstand voltage test: Conducting a withstand voltage test can further verify the insulation performance of the switch. Connect the high-voltage output terminal of the withstand voltage tester to the live part of the switch, and the low-voltage terminal to the housing. Conduct the test according to the specified test voltage (usually higher than the working voltage) and duration (such as 1 minute). During the testing process, observe whether there are any phenomena such as breakdown or discharge. If breakdown or discharge occurs, it indicates that the insulation strength is insufficient and there is a problem of poor insulation.

Leakage current test: The leakage current test can detect whether there is a tiny current leakage in the insulation part of the switch under normal operating voltage. Connect the leakage current tester to the circuit of the switch, apply the normal working voltage, and measure the magnitude of the leakage current. If the leakage current exceeds the specified limit, it indicates that there is a problem with the insulation.

Component disassembly and analysis

Check the insulating components: If both the visual inspection and the electrical performance test indicate the existence of poor insulation issues, it may be necessary to disassemble the switch for a more in-depth inspection. When disassembling, pay attention to recording the positions and connection methods of each component to ensure correct assembly in the future. Focus on inspecting the internal insulating components, such as insulating gaskets, insulating sleeves, insulating varnish, etc. Check whether these components have any signs of aging, carbonization, damage, etc. For instance, insulating gaskets may age and become brittle due to long-term exposure to heat, and insulating sleeves may be damaged by friction.

Analysis of contacts and terminal blocks: The insulation condition around the contacts and terminal blocks may also affect the overall insulation performance of the switch. Check whether there is oxidation, erosion or other conditions on the contact surface, and whether the terminal blocks are loose. If the contacts are oxidized or eroded, it may lead to a reduction in the gap with the surrounding insulating components, increasing the risk of leakage. Loose terminal blocks may cause arc discharge and damage insulating components.

Investigation of environmental factors

Humidity influence: A high-humidity environment is one of the common causes of poor insulation in vacuum pressure switches. Moisture can reduce the surface resistance of insulating materials, forming a conductive path. Check whether the humidity of the environment where the switch is located is too high. If the humidity is relatively high, you can consider taking dehumidification measures, such as installing dehumidifiers and enhancing ventilation, to reduce the impact of environmental humidity on the insulation performance of the switch.

Dust and contaminants: Dust, oil stains and other contaminants adhering to the surface of insulating components will reduce the insulation resistance. Check if there is a large amount of dust or contaminants around the switch. If so, the switch needs to be cleaned. Clean compressed air can be used to blow away dust. For stubborn contaminants such as oil stains, appropriate cleaning agents can be used for cleaning, but it should be noted that the cleaning agents must not cause damage to the insulating components.

Chemical corrosion: Certain chemical substances may corrode insulating materials, leading to a decline in insulation performance. Check whether there are corrosive gases or liquids around the switch, such as acids, alkalis, etc. If there is chemical corrosion, protective measures need to be taken, such as installing the switch in a sealed protective box or replacing it with corrosion-resistant insulating materials.