ZXR-20A DC Resistance Tester: Precision Tool for Transformer Winding Testing

Introduction

Power transformers are the most critical and high-value assets in power transmission and distribution networks. DC winding resistance measurement is a mandatory, fundamental test for transformer factory inspection, on-site handover commissioning, and periodic preventive maintenance. This test enables power technicians to identify incipient and critical defects at an early stage, including poor welding of winding joints, inter-turn short circuits, inadequate tap changer contact, broken conductor strands, and loose connections, thus preventing catastrophic transformer failures and ensuring grid reliability.

Traditional DC resistance testing solutions face notable limitations in field applications: insufficient output current for large and medium-sized transformers leads to excessive stabilization time; poor anti-interference performance undermines data accuracy in harsh substation environments; inadequate back electromotive force (back EMF) protection risks instrument damage; and complex operation procedures increase safety hazards during discharge. To address these technical pain points, the ZXR-20A DC Resistance Tester is developed with advanced power electronics and intelligent control technologies, delivering a high-precision, efficient, and safe testing solution for power industry technical professionals.

Instrument Architecture and Core Control Design

The ZXR-20A is built around a high-speed single-chip microcontroller (MCU), which enables full automation of the entire testing workflow, including constant current output, high-precision data acquisition, automatic discharge protection, and test result output. This intelligent control architecture eliminates redundant manual operations, minimizes human-induced measurement errors, and ensures excellent test repeatability — a critical requirement for longitudinal comparison of winding resistance data across transformer maintenance cycles.

Optimized for field deployment in power systems, the instrument adopts a vertical chassis structure, with a compact dimension of 440×240×390 mm and a net weight of 12 kg. This design balances portability and on-site operability, allowing technicians to easily transport and deploy the device in various scenarios, from indoor switchgear rooms to outdoor transformer yards.

Key Technical Features and Field Advantages

1. High-Power High-Frequency Switching Power Supply System

A core technical highlight of the ZXR-20A is its advanced high-frequency switching power supply technology, which provides four selectable output current levels: 2.5A, 5A, 10A, and a maximum of 20A. This wide current range fully meets the DC resistance measurement requirements of large and medium-sized power transformers. For large-capacity transformers with high winding inductance, the high output current can rapidly magnetize the iron core, drastically shortening the stabilization time of the test current and improving on-site testing efficiency compared to traditional low-current testers.

2. Comprehensive Protection and Safety Mechanism

Transformer windings are highly inductive components, and the high back EMF generated during test termination and discharge poses a major threat to both testing instruments and on-site operators. The ZXR-20A is equipped with a complete protection system that reliably suppresses and isolates back EMF impacts, ensuring long-term stability of the instrument's internal circuits.

In addition, the instrument integrates an automatic discharge function with an audible discharge alarm. This feature provides clear, real-time indication of the discharge state throughout the testing process, effectively reducing misoperations caused by incomplete discharge, and significantly enhancing on-site operational safety.

3. Fast Response for On-Load Tap Changer (OLTC) Testing

The ZXR-20A features ultra-fast response performance, which allows direct switching of the transformer's load tap changer in the measurement state, with the instrument automatically refreshing test data in real time. This function eliminates the need for repeated charge and discharge cycles when testing DC resistance at each tap position of the OLTC — a highly time-consuming process with conventional testers. For transformers with multi-position tap changers, this feature can reduce total test time by over 70%, greatly optimizing the work efficiency of field technicians.

4. Intelligent Power Management and User-Friendly Operation

The instrument adopts intelligent power management technology, which dynamically adjusts the power consumption of internal circuits according to the actual test state, ensuring the device always operates at the minimum required power level. This design effectively reduces internal heat generation, extends the instrument's service life, and achieves energy savings during long-term field operation.

For operational convenience, the ZXR-20A is equipped with a dot-matrix liquid crystal display (LCD) with a full English menu interface, enabling intuitive parameter setting, data viewing, and function operation. It also supports built-in print output, allowing technicians to directly print and archive test results on site, avoiding manual data recording errors and ensuring test data traceability.

Core Technical Specifications

The key performance indicators of the ZXR-20A are tailored to the strict requirements of power system transformer testing, as detailed below:

The 0.2% measurement accuracy and 0.1μΩ high resolution enable the instrument to capture tiny changes in winding resistance, supporting early detection of incipient defects such as slight contact deterioration of tap changers. The wide measurement range, matched with adjustable output current, covers the testing requirements of transformers with different voltage levels and capacity ranges.

Field Application Scenarios

The ZXR-20A DC Resistance Tester is widely applicable to core testing scenarios in the power industry, including:

Factory type tests and routine tests of power transformers in manufacturing facilities;

Handover commissioning tests of newly installed transformers in transmission and distribution projects;

Periodic preventive maintenance tests of transformers in substations;

Fault diagnosis and defect analysis of faulty transformers in power systems;

Routine inspection and maintenance of distribution transformers in power distribution networks.

Conclusion

The ZXR-20A DC Resistance Tester integrates advanced high-frequency power technology, intelligent MCU control, comprehensive safety protection, and user-centric design, addressing the key pain points of traditional DC resistance testing instruments in power field applications. With its high output current, high measurement accuracy, fast response speed, and reliable safety performance, it provides an efficient, precise, and safe solution for transformer winding resistance measurement. For power industry technicians, this instrument is an indispensable tool for transformer testing and maintenance, which can effectively improve work efficiency, ensure test data reliability, and support the safe and stable operation of power 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/