The load capacity of the high-current generator is suitable for primary busbar protection and calibration of current transformer ratios, and can also perform setting calibration for current relays and switches. It is mainly used for testing items such as primary busbar protection and the ratio of various current transformers. Due to the use of low-power consumption, large-capacity auto-transformer and a current transformer made of high-permeability core, it has the advantages of large output power, small size, and light weight.
"Doubts" in high-current generator testing:
Why use high current to measure the loop resistance of circuit breakers?
1. Many high-current electrical equipment in the power system require accurate measurement of loop resistance during preventive tests and acceptance tests. Circuit breakers are important electrical equipment in the power system. The national standard GB and the power industry standard DL/T both stipulate the measurement of the conductive loop resistance of circuit breakers: the DC voltage drop method should be used, with a current not less than 100A.
2. The resistance of the conductive loop of a circuit breaker mainly depends on the contact resistance between the moving and static contacts. The existence of contact resistance increases the loss when current passes through, raises the temperature at the contact point, and its value directly affects the current-carrying capacity during normal operation and, to a certain extent, the ability to interrupt short-circuit currents. Therefore, the resistance value of each phase conductive loop of a circuit breaker is an important data for installation, maintenance, and quality acceptance.
3. There are many methods for measuring contact resistance. Foreign scholars have proposed using superconducting quantum devices to measure contact resistance, using the electrolytic cell method, and using the third harmonic method. These methods are generally used in laboratory conditions for electrical contact research. In engineering, the four-terminal method is usually used to measure the contact resistance of actual contacts.
4. Previously, a DC double bridge was usually used to measure the contact resistance of circuit breakers. However, when using a double bridge to measure the conductive loop resistance of a circuit breaker, since the measurement circuit of the double bridge passes a weak current, it is difficult to eliminate the relatively large resistance of the oxide film, and the indicated resistance value is too large. However, the oxide film is easily broken down under a large current and does not hinder the normal current flow. Therefore, when using the DC voltage drop method for testing, the current should not be too small.
