In the power system, many high-current electrical equipment need to accurately measure the resistance value of the circuit during preventive tests and handover tests. Circuit breakers are important electrical equipment in the power system. According to the latest standard JJG1052-2009 Verification Regulation of Loop Resistance, national standard GB763, GB50150, and power industry standard DL/T596, the measurement of the conductive circuit resistance of circuit breakers has been specified: the DC voltage drop method should be used, 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 static contacts. 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 the electrolytic cell method, and Polish scholar Jerzy Kaczarek proposed 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.
Previously, the DC double bridge was commonly used to measure the contact resistance of circuit breakers. However, when using a double bridge to measure the conductive circuit resistance of a circuit breaker, because the measurement circuit of the double bridge passes a weak current, it is difficult to eliminate the oxide film with high resistance, and the measured 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.
The resistance of the conductive circuit of a high-voltage circuit breaker mainly depends on the contact resistance between the moving and static contacts. The existence of contact resistance increases the loss when the conductor is energized, 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 current. Therefore, the resistance value of the conductive circuit of each phase of the circuit breaker is an important data for installation, maintenance, and quality acceptance of circuit breakers.
Loop Resistance Tester Assembly (3 pictures)
Due to the oxide film between switch contacts, if a small current is used for detection, the test result is generally much larger due to the influence of the oxide film. However, the oxide film can be broken down under a large current. Theoretically, as long as the test current does not exceed the rated current, the larger the better. However, when the regulation was formulated, considering the production level of relevant domestic instruments at that time, it was stipulated that the current should not be less than 100A. Power Equipment and Ground Grid Continuity Resistance Tester
The reliable and effective connection between the grounding down conductor of power equipment and the ground grid is the fundamental guarantee for the safe operation of power equipment and the personal safety of operators. Although necessary anti-corrosion treatment has been applied to the connection of the grounding down conductor during the production of the grounding device, the connection point in the soil is still affected by moisture and other factors for a long time, leading to corrosion, disconnection, loosening, and other phenomena, resulting in an increase in the resistance value of the contact point between the grounding down conductor and the ground grid, which cannot meet the requirements of power regulations, causing potential safety hazards in equipment operation, and in severe cases, causing the equipment to detach from the ground
Loop Resistance Tester (3 pictures)
grid operation. It can be used for accurate measurement of the continuity resistance between the grounding down conductor of power equipment and the grounding grid or adjacent equipment.
The ground grid continuity resistance tester is used to measure the continuity resistance value of the grounding down conductor, and determine the fault point by comparing historical test values and adjacent point test values. The working power of the ground grid continuity resistance tester is provided by an internal lithium battery, no external AC power supply is needed. The test process is controlled by a microcontroller, with the characteristics of simple operation, fast test speed, stable test data, and easy portability.
Since the contact resistance of circuit breakers is very small, only a high current can ensure a certain accuracy, and the anti-interference ability is also stronger.
It is used for high-precision measurement of circuit breaker contact resistance and current-carrying conductor resistance, and can output large current stably for a long time, complying with the relevant provisions of DLT845.4-2004 "General Technical Conditions for Resistance Measuring Devices Part 4: Loop Resistance Tester".
Technical Parameters
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1. Measurement range: 0~4mΩ (50A gear) 0~2mΩ (100A gear) 0~1.33mΩ (150A gear) 0~1mΩ (200A gear)
2. Test current: DC50A, 100A, 150A, 200A fixed output
3. Measurement accuracy: ±(0.5% rd+2d)
4. Continuous working time: 5s~599s
5. Display mode: large-screen Chinese LCD display
6. Communication mode: RS232 serial port
7. Working power: AC220V±10% 50Hz
8. Total power: 1200W
