Key Technologies For Insulation Performance Testing Of Terminal Blocks
The insulation performance testing of terminal blocks is the core link to ensure the safe operation of electrical systems. Its key technologies cover four dimensions: testing indicators, methods, environmental control, and equipment selection. A systematic evaluation should be conducted based on material characteristics and actual working conditions.
1、 Core testing indicator system
Insulation resistance: Use a megohmmeter to measure the resistance between conductors, reflecting the ability of insulation materials to prevent current leakage. The standard requires a resistance value of megaohms or higher. During testing, it is necessary to ensure that the contact points are not contaminated to avoid misjudgment caused by surface conductive substances.
Breakdown voltage: Apply AC/DC high voltage through a voltage tester to verify the insulation material's ability to withstand extreme voltages. For example, high-voltage equipment needs to withstand 1500V/10s without breakdown, and voltage gradients need to be set and leakage current transients monitored during testing.
Partial discharge: Use ultrasonic detectors or high-frequency current sensors to capture small discharge signals caused by insulation defects. This method can locate the internal air gap or crack of high-voltage terminals, avoiding the destructive risk of traditional withstand voltage testing.
Dielectric loss: Measuring the energy loss of materials in an alternating electric field through a bridge to evaluate the degree of insulation aging. This indicator is particularly important for materials with polarization characteristics, such as ceramics, and needs to be combined with frequency response analysis.
2、 Multi dimensional testing method combination
Rapid screening of megohmmeter: suitable for daily maintenance, but attention should be paid to environmental humidity correction. For example, in high humidity environments, the testing time needs to be extended to more than 1 minute, and the values should be read after the charging current stabilizes.
Voltage withstand test to reproduce faults: By simulating actual voltage surges, investigate temporary poor contacts. During testing, ultrasonic testing should be combined to distinguish between surface discharge and internal breakdown.
Environmental simulation testing: For extreme working conditions such as high temperature and vibration, a combination of a constant temperature test chamber and a vibration table is used for testing. For example, evaluate the insulation stability of outdoor terminals under thermal shock from -40 ℃ to+125 ℃.
3、 Key technical details control
Testing voltage frequency matching: The results of DC testing and AC withstand voltage may differ significantly, and the testing mode should be selected based on the polarization characteristics of the material. For example, insulators containing ferroelectric materials should prioritize AC testing.
Electromagnetic interference shielding: In strong electromagnetic environments, shielded cables and grounding devices should be used to avoid measurement deviations in leakage current. For example, when testing substation terminals, they need to be kept away from high-voltage busbars.
Contact reliability verification: The four wire method is used to measure the contact resistance, ensuring uniform contact pressure between the testing fixture and the terminal. For example, when crimping terminals, it is necessary to check the size of the horn mouth and the angle of the insulation crimping wings to avoid virtual connections.
