In the realm of electrical power systems, accurate measurement of contact resistance in high-voltage switching equipment is critical for ensuring operational reliability and safety. The ZXHL-200A Loop Resistance Tester emerges as a sophisticated solution designed to address the challenges of micro-ohm-level measurements under high-current conditions. Compliant with the DL/T845.4-2004 standard, this instrument integrates high-frequency switching power technology and advanced digital signal processing to deliver precision, stability, and adaptability for field and industrial applications.
Core Design Philosophy
The ZXHL-200A distinguishes itself through its dual-range DC output capability (100A and 200A), aligning with IEC and national standards for contact resistance testing. Unlike conventional impulse current methods that risk incomplete oxidation layer penetration, its continuous DC output ensures sustained current flow, effectively breaking through oxide films on switch contacts. This design minimizes measurement uncertainty caused by transient effects, offering a true reflection of contact resistance under operational loads.
Key innovations include:
1.High-Frequency Switching Power Supply: Enables stable, ripple-free DC output (50A–200A) with minimal thermal drift.
2.Digital Noise Suppression: A proprietary algorithm filters electromagnetic interference (EMI) from high-voltage environments, achieving a ±1 LSD (Least Significant Digit) stability on the 3½-digit LCD.
3.Temperature-Compensated Precision Resistors: High-precision shunt resistors (0.01% tolerance) combined with thermal management ensure ±0.5% accuracy across -10°C to 40°C.
Measurement Performance and Specifications
1. Metrological Capabilities
Range: 1–1999 μΩ (1 μΩ resolution)
Accuracy: ±(0.5% rdg + 2 μΩ)
Current Output: 50A/100A/150A/200A (fixed modes)
2. Comparative Advantages
Oxide Layer Penetration: Sustained DC current eliminates the "false low-resistance" phenomenon observed in pulse-driven testers, which often fail to disrupt insulating surface layers.
Repeatability: Tests on oxidized Cu-Cu contacts (200A, 60s) show ≤1.5% variation, outperforming pulsed systems by a factor of 3.
3. Environmental Resilience
Operates at 80% RH non-condensing and subzero temperatures, critical for outdoor substation diagnostics.
IP52-rated enclosure protects against particulate ingress.
Operational Features for Field Technicians
1.Ergonomic Design
Compact footprint (380×350×260 mm³) and 5kg weight enable single-operator portability.
Direct-read LCD with analog-style bargraph simplifies data interpretation in low-light conditions.
2.Safety and Durability
Gold-plated Kelvin clamps reduce contact resistance and withstand 10,000 mating cycles.
Reinforced input protection (AC 220V ±10%, 50Hz) with surge suppression.
3.Application Versatility
Beyond HV circuit breakers, the ZXHL-200A serves busbar joints, transformer tap changers, and rail bonding systems. Case studies in 500kV GIS substations demonstrate a 40% reduction in diagnostic time compared to traditional bridge methods.
Case Study: Addressing Transient Resistance in SF6 Breakers
In a 2023 field trial at a coastal substation, the ZXHL-200A identified intermittent resistance spikes (1,200–1,550 μΩ) in 145kV SF6 breaker contacts under 200A load. Conventional 100A testing had reported "passing" values (≤800 μΩ), but prolonged 200A testing exposed arcing-induced carbon deposits—validating the necessity of higher test currents for aged equipment.
The ZXHL-200A redefines micro-ohmmeter standards by merging high-current robustness with metrological precision. Its ability to deliver repeatable, interference-free measurements in harsh environments positions it as an indispensable tool for predictive maintenance programs. As grid infrastructure ages, such technologies will play a pivotal role in minimizing unplanned outages and extending asset lifecycles.
GDZX is a manufacturer of power testing equipment, offering a wide range of product categories with comprehensive models and providing professional technical support. Contact: +86-17396104357. Website: https://www.highvoltage-testequipment.com/
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