Mechanical characteristic testing

Mechanical characteristic testing is the core of circuit breaker testing, focusing on evaluating the time, speed, stroke, and synchronization (synchronicity) of its opening and closing operations and three-phase actions. These parameters directly affect whether the circuit breaker can accurately and quickly cut off the fault current. Special high-voltage switch dynamic characteristic testers are usually used for testing, combined with linear or angle sensors to record data. If the mechanical characteristics do not meet the standards, it may lead to arc reignition or increased contact wear, causing serious malfunctions.

Insulation performance testing

The insulation performance testing aims to verify the insulation strength of the main circuit, fracture, and control circuit of the circuit breaker, in order to prevent breakdown or flashover during operation. The main methods include power frequency withstand voltage test and DC withstand voltage test. The power frequency withstand voltage test is closer to the operating conditions and is commonly used for medium and low voltage circuit breakers; The DC withstand voltage test is more suitable for on-site testing of high-voltage and ultra-high voltage circuit breakers due to its lightweight equipment. In addition, a megohmmeter will be used to measure insulation resistance and monitor the gas density and micro water content of SF6 circuit breakers to ensure the reliability of the insulation medium.

Conductive circuit and breaking ability detection

The detection of conductive circuits mainly relies on measuring the resistance of the circuit to determine whether the contact of the contacts is good. Excessive circuit resistance may cause abnormal heating. During testing, a DC current of not less than 100A should be applied in the closed state, and the voltage drop should be measured and the resistance value calculated. The breaking and closing ability test simulates fault conditions such as short circuits in the laboratory to verify the ability of the circuit breaker to cut off fault currents, which is crucial for evaluating its protective function.

Operating mechanism and online monitoring

The reliability testing of the operating mechanism includes measuring the operating voltage of the opening and closing coils to ensure that they can reliably open within the range of 65% to 120% of the rated voltage, and can reliably remain inactive at 30% of the rated voltage. Modern technology has also introduced online monitoring, such as analyzing the current waveform or mechanical vibration signals of the opening and closing coils, to diagnose potential faults in the mechanical components of the circuit breaker in real time without power outage, providing a basis for achieving condition based maintenance.

Testing cycle and safety regulations

According to regulations, the regular inspection cycle for high-voltage switchgear is usually one year. Comprehensive characteristic testing is also required before the new installation and handover. All testing operations must strictly comply with safety regulations, including power-off isolation, full discharge, setting up safety fences, etc., to prevent personal and equipment accidents.