The Function of Circuit Resistance Tester

The circuit resistance tester is a key tool in electrical maintenance, mainly used to accurately measure the resistance value in electrical circuits, ensuring the safe and efficient operation of the system.

Core role

Detecting contact resistance

1. Application scenarios: Key connection points such as high-voltage switches, circuit breakers, busbars, cable joints, etc.

Importance: Excessive contact resistance can lead to local overheating, accelerate equipment aging, and even cause fires or power outages. For example, if the contacts of a circuit breaker have poor contact, they may not be able to cut off the fault current properly, posing a threat to the safety of the power grid.

2. Evaluate the conductivity performance

Standard compliance: By measuring to ensure that the circuit resistance meets international (such as IEC 62271) or national standards, energy efficiency losses caused by excessive resistance can be avoided.

Problem identification: Abnormal resistance may indicate oxidation, corrosion, or mechanical looseness, and should be promptly addressed.

3. Diagnostic connection status

Key detection points: cable terminals, grounding devices, welding points, etc.

Case: In the subway power supply system, the increased resistance of loose grounding wires may cause signal interference or equipment damage. Regular testing can prevent such faults.

Quick fault location

Practical application: Combined with infrared temperature measurement, quickly locate abnormal hotspots. For example, if the resistance of a certain terminal in the distribution cabinet suddenly increases, the tester can accurately identify it and shorten the maintenance time.

4. Working principle and technical characteristics

High current method (four wire measurement)

Inject a constant DC (usually 100A-600A), calculate the resistance (R=U/I) by measuring the voltage drop (μ V level), eliminate the influence of wire resistance, and achieve an accuracy of 0.1 μ Ω.

Advantages: Strong anti-interference ability, suitable for high noise industrial environments.

5. safety design 

Automatic discharge function and overcurrent protection ensure that there is no residual voltage in the equipment after testing, ensuring safe operation.

6. Expansion of application areas

New energy systems: such as DC combiner boxes for photovoltaic power stations and connection resistance testing for battery energy storage systems.

Rail transit: Contact resistance detection between high-speed rail pantograph and overhead contact system to ensure stable current collection.

Industrial manufacturing: Calibration of circuit resistance for large motors and transformers before leaving the factory to ensure quality.

7. Precautions for use

Power off test: Live operation is strictly prohibited to prevent electric shock or damage to the instrument.

Clean contact points: Polish the oxide layer before testing to avoid errors caused by dirt.

Current selection: Adjust according to equipment specifications, such as using 300A for GIS switches and 100A for small circuit breakers.

Calibration and maintenance: Regularly calibrate instruments to ensure accurate data, especially in extreme temperature or humidity environments.

HZ-5200 200A Contact Resistance Measuring Instrument