Many high current electrical equipment in the power system require accurate measurement of circuit resistance values during preventive and handover tests. Circuit breakers are important electrical equipment in power systems. The national standards GB763 and GB50150, as well as the power industry standard DL/T596, stipulate that the measurement of the conductive circuit resistance of circuit breakers should be carried out using the DC voltage drop method, with a current not less than 100A.
The resistance of the conductive circuit of a circuit breaker mainly depends on the contact resistance between the moving and stationary contacts of the circuit breaker. The existence of contact resistance increases the loss of the conductor when it is energized, causing the temperature at the contact to rise. The magnitude of its value directly affects the current carrying capacity during normal operation and to some extent affects the ability to cut off short-circuit current. Therefore, the resistance value of each phase conductive circuit of the circuit breaker is an important data for the installation, maintenance, and quality acceptance of the circuit breaker.
There are many methods for measuring contact resistance. Japanese scholar Isao Minowa proposed using superconducting quantum devices to measure contact resistance, H. Archi proposed using electrolytic cell method to measure contact resistance, and Polish scholar Jerzy Kaczarek proposed using third harmonic method to measure contact resistance. These methods are generally used for electrical contact research under laboratory conditions. In engineering, the four terminal method is commonly used to measure the contact resistance of actual contacts.
Previously, the contact resistance of circuit breakers was usually measured using a DC double arm bridge. However, when using a double arm bridge to measure the resistance of a circuit breaker's conductive circuit, due to the weak current passing through the measuring circuit, it is difficult to eliminate the oxide film with high resistance. The measured resistance reading is biased, but the oxide film is easily broken down under high current, which does not hinder normal current flow. Therefore, when using the DC voltage drop method for testing, the current should not be too small.
TheUHV-H100A circuit resistance testerindependently developed by Wuhan UHV Power adopts the latest power technology, with high accuracy, small size, light weight, and simple wiring, making the previously troublesome on-site circuit breaker circuit resistance testing easier and more convenient.
