ZXR-3A TWRT: Technical Performance & Power Industry Applications

Abstract

DC winding resistance testing is a mandatory diagnostic procedure for power transformers in factory inspection, handover acceptance, and preventive maintenance, serving as a core method to detect winding defects such as inter-turn short circuits, poor tap changer contact, and loose connection joints. Traditional DC single/double bridges, the conventional testing tools, have inherent limitations including extremely slow measurement speed, poor on-site adaptability, and low reading accuracy in outdoor environments. This paper introduces the ZXR-3A Transformer Winding Resistance Tester, a high-precision next-generation instrument developed to replace traditional bridges. It elaborates on the instrument’s core design, key technical specifications, performance advantages, and application value in power system operation and maintenance, providing technical reference for power industry practitioners engaged in transformer testing and asset management.

Power transformers are the most critical and high-value assets in power transmission and distribution systems. The integrity of transformer windings directly determines the safety, reliability, and service life of the entire power grid. DC winding resistance measurement is the most straightforward and effective non-destructive testing method to verify winding manufacturing quality, identify installation defects, and monitor insulation degradation during operation.

For decades, DC single and double bridges have been the mainstream devices for winding resistance testing. However, these tools have significant drawbacks in practical engineering applications:

Extremely slow measurement speed for large inductive transformer windings, as they cannot effectively compensate for current inertia and accelerate core saturation, leading to long test cycles and extended power outage durations;

Poor readability of traditional LED displays under direct sunlight, which severely affects measurement accuracy in outdoor field operations;

Weak anti-interference performance in complex electromagnetic environments of substations, resulting in unstable test data and poor repeatability;

Lack of portable power supply solutions, limiting their application in remote field sites without mains power.

To address these technical pain points, the ZXR-3A Transformer Winding Resistance Tester is developed with advanced power electronics and measurement technology. It fully replaces traditional bridge instruments, delivering breakthrough improvements in test efficiency, measurement accuracy, and on-site adaptability for power industry testing scenarios.

2. Core Technical Design and Performance Features

2.1 High-Speed Measurement with Optimized Constant Current Source Technology

The ZXR-3A is integrated with an advanced high-power switching power supply system, which delivers a maximum output charging current of up to 3A. For transformer windings, a typical large inductive load, the instrument’s proprietary control algorithm effectively compensates for the current inertia of the inductor, accelerates the saturation of the transformer core, and drastically reduces the charging time required for stable measurement. Compared with traditional single and double bridges, the test speed of the ZXR-3A is hundreds of times faster, which significantly shortens the duration of transformer maintenance outages and improves the efficiency of on-site testing, especially for large-capacity power transformers.

2.2 High-Precision Measurement with Four-Terminal Sensing Technology

To eliminate the influence of lead resistance and contact resistance on low-resistance measurement, the ZXR-3A adopts a professional four-terminal measurement architecture paired with a high-stability constant current source. This design ensures that the charging current of the inductive load maintains a stable value throughout the measurement process, effectively suppressing the impact of on-site electromagnetic interference on test results.

The instrument uses high-quality imported core components, which guarantees a measurement accuracy of 0.5 grade and an ultra-high resolution of 1μΩ. Meanwhile, it provides excellent measurement repeatability, even in harsh substation environments with strong electromagnetic fields, avoiding repeated measurements and ensuring the reliability of diagnostic data. In addition, the instrument is equipped with a reliable automatic arc suppression function, which effectively eliminates the arc risk caused by inductive load discharge at the end of the test, ensuring the safety of both operators and the tested transformer equipment.

2.3 Field-Adaptable Design for Power Industry Scenarios

The ZXR-3A features a dual-LCD display design: a 4.5-digit LCD for core measurement results, and a 3.5-digit LCD for real-time ambient temperature or test current value monitoring. This design completely overcomes the critical shortcoming of similar products with LED displays, which suffer from unreadable values under direct sunlight in outdoor field operations.

For maximum on-site flexibility, the instrument adopts an AC/DC dual power supply design. It is equipped with a built-in 12V rechargeable battery pack (2.2Ah) with an operating voltage range of 12V to 16.8V, and also supports 220V AC mains supply. With a compact size of 335×275×175mm and an ultra-light weight of only 2.8kg, the portable design makes it extremely suitable for on-site testing in urban substations and field operations in remote areas without stable mains power.

3. Key Technical Specifications

The ZXR-3A is designed in full compliance with the testing standards of the power industry, with core technical indicators as follows:

Operating environment: Ambient temperature range of 0℃～40℃, relative humidity ≤85％RH, adapting to the vast majority of on-site working conditions in power systems;

Measurement range: 6 automatic switching ranges covering 1mΩ～20mΩ, 20mΩ～200mΩ, 0.2Ω～2Ω, 2Ω～20Ω, 20Ω～200Ω, and 200Ω～2kΩ, with a full measurement range of 1μΩ～2kΩ;

Measurement accuracy: 0.5 grade, minimum resolution: 1μΩ;

Graded constant current output: Automatically adjusted according to the measured resistance: 3A (1μΩ～2Ω), 0.3A (2Ω～20Ω), 0.03A (20Ω～200Ω), 0.003A (200Ω～2000Ω);

Ammeter display range: 0.30A～3.00A;

Power supply: DC 12V～16.8V (2.2Ah built-in battery), AC 220V; power consumption ≤15W;

Dimensions and weight: 335×275×175mm / 2.8kg.

4. Application Value in Power System Operation and Maintenance

In the full life cycle management of power transformers, the ZXR-3A plays an irreplaceable role in multiple core scenarios of the power industry:

A.Transformer factory inspection: For transformer manufacturers, the instrument provides fast and batch winding resistance measurement in production and final inspection processes, ensuring the welding quality of winding joints and the consistency of tap changer contact performance, and guaranteeing the quality of outgoing products.

B.Grid handover acceptance: For power grid enterprises, it is an essential tool for transformer handover acceptance tests before commissioning, verifying that the equipment meets design and operational requirements, and avoiding equipment defects entering the grid operation stage.

C.Preventive maintenance and fault diagnosis: In routine substation maintenance, the instrument enables early detection of potential winding defects, including inter-turn short circuits, loose connections, and tap changer contact degradation, providing data support for condition-based maintenance and preventing unplanned outages caused by sudden transformer failures.

D.Emergency field troubleshooting: The AC/DC dual power supply design and portable structure make it ideal for emergency fault handling in remote areas where mains power is unavailable, helping maintenance teams quickly locate winding faults and shorten power recovery time.

Compared with traditional test instruments, the ZXR-3A significantly reduces the test time for large-capacity power transformers, which is particularly critical for shortening power outage windows in urban power grids with high reliability requirements. Its strong anti-interference capability ensures stable and reliable test data in complex on-site environments, reducing the workload of technical personnel and improving the standardization of transformer testing work.

5. Conclusion

The ZXR-3A Transformer Winding Resistance Tester is a professional high-performance diagnostic instrument fully tailored to the needs of the power industry. It comprehensively solves the inherent limitations of traditional DC bridge instruments, with outstanding advantages in test speed, measurement accuracy, on-site adaptability, and operational safety. For power industry technical personnel engaged in transformer testing, operation and maintenance, the ZXR-3A is an indispensable tool that can significantly improve test efficiency, ensure the accuracy of defect diagnosis, and provide strong technical support for the safe, stable, and reliable operation of power transmission and distribution systems.

GDZX is a manufacturer of power detection equipment, offering a diverse range of products with comprehensive models and providing professional technical support. Contact us at +86-27-6552607 or +86-17396104357.Website: http://en.gdzxdl.com/