Table of Contents
CONTACT RESISTANCE TESTING
Contact resistance testing, also known as Ductor testing, is used to measure the resistance across electrical connections such as breakers, busbars, joints, and terminations. This test helps you to evaluate how effectively the current flows through contact surfaces when the equipment is in closed condition.
In high-current systems, even a small increase in resistance can lead to excessive heat generation and there by resulting in energy losses and can even cause long-term damage to the equipment. Regular testing ensures that all electrical connections remain secure, conductive, and are capable of handling their rated load without risk.
Why Contact Resistance Test is Important
Electrical contacts are constantly exposed to operational stress, switching its operations, and also environmental factors. Over time, this can result in deterioration that is not visible externally.
Contact resistance testing helps to:
- Identify any kind of loose connections or any improperly tightened connections
- Detect corrosion, oxidation, or pitting on the contact surfaces
- Prevent the overheating and localized hot spots
- Reduce the power losses and thereby improving system efficiency
- Avoid unexpected failures in the critical electrical systems
Also, the key point is that higher resistance at the contact points can reduce the current carrying capacity and can lead to insulation damage or fire risks if it was not addressed early.
How the Test is Performed
The test is carried out by using a specialized instrument (micro-ohmmeter / (Digital Low Resistance Ohmmeter [DLRO]), which measures very low resistance values with high accuracy.
Typical testing approach is:
- Preliminary Inspection
This is actually the visual examination of contacts for signs of wear, pitting, discoloration, or any mechanical damage.
- Current Injection Method
in this method, a controlled DC current (commonly 100A or higher depending on equipment) is passed through the contact path.
- Voltage Drop Measurement
The voltage drop across the connection is measured and the measured voltage is used to calculate resistance using Ohm’s law.
- Low Resistance Evaluation
Then the measurements are recorded in micro-ohms (µΩ) or milli-ohms (mΩ) and the values are being compared with previous readings or with the manufacturer guidance.
- Connection Assessment
The results help to determine the condition of busbar joints, breaker contacts, and the cable terminations.
This method enables accurate detection of hidden issues such as loose joints, surface contamination, and contact degradation.
Typical Areas of Application
Contact resistance testing is widely used across electrical systems where reliable connections are critical:
- Low and medium voltage switchgear
- Circuit breakers and isolators
- Busbar joints and panel connections
- Cable terminations and link points
- Generator and transformer connections
It is particularly important in systems carrying high current, where even minor resistance variations can significantly impact performance.
Our Field Approach in UAE
Our testing approach is based on the practical site experience and the real operating conditions rather than theoretical checks alone.
- Testing is performed under controlled and safe conditions
- Measurements are taken by using calibrated equipment for high accuracy
- Results are analyzed with a focus on identifying developing faults
- Reports include clear observations and practical recommendations
With experience in UAE environments where electrical systems often operate under continuous load and high temperatures, we focus on ensuring long-term reliability, safe operation, and reduced risk of unexpected failures.
