Resistance tester UHV-S20A

for transformersfor substationsfor power systems

Overview
Can simultaneously test the DC resistance of the three-phase winding of the transformer. Equipped with comprehensive protection functions and an LCD with full English menu for intuitive operation.

Product parameters
The three-phase DC resistance tester is a latest-generation instrument designed for measuring DC resistance of transformers, optimized for large-capacity three-phase windings. It enables simultaneous measurement of all three phases to reduce test time and simplify field procedures.

Technical parameters

• Measurement modes: Single-phase (two-phase) and Three-phase
• Current gears (single-phase): 1A, 5A, 10A, 20A, 40A
• Current gears (three-phase): 1A, 5A, 10A, 20A
• Measuring range (single-phase by gear): 1A: 10 mΩ–20 Ω; 5A: 1 mΩ–4 Ω; 10A: 1 mΩ–2 Ω; 20A: 1 mΩ–1 Ω; 40A: 1 mΩ–0.5 Ω
• Measuring range (three-phase, each phase by gear): 1A: 10 mΩ–6 Ω; 5A: 1 mΩ–1 Ω; 10A: 1 mΩ–0.6 Ω; 20A: 1 mΩ–0.3 Ω
• Maximum resolution: 0.1 mΩ
• Measurement accuracy: ±0.2% (full range) ±2 digits
• Data storage: 150 groups
• Power supply: AC 220V ±22V, 50Hz ±2Hz
• Operating environment: temperature 0℃–40℃; relative humidity ≤80% RH

Features

• Simultaneous three-phase measurement reduces total test time on transformers
• Fast and accurate DC resistance measurement on windings
• Comprehensive protection functions for safe field use
• Compact design for easy transport and on-site deployment
• LCD with full English menu for straightforward operation
• High accuracy, good repeatability and strong anti-interference capability

Characteristics / technical specifications

• Model: UHV-S20A
• Application: DC resistance measurement of transformer windings (single-phase and three-phase)
• Selectable current ranges: up to 40A (single-phase) and up to 20A per phase (three-phase)
• Measurement ranges: from 1 mΩ up to tens of ohms depending on current gear (see table)
• Resolution: 0.1 mΩ
• Accuracy: ±0.2% (full range) ±2 digits
• Data memory: 150 groups
• Power: AC 220V ±22V, 50Hz ±2Hz
• Working conditions: 0℃–40℃, ≤80% RH
• Key functions: simultaneous three-phase testing, multiple protections, portable design, LCD menu

Note:

• ① During the measurement process, it is not allowed to dismantle the wiring or directly turn off the power.
• ② For no-load tap changers, it is not allowed to switch tap changers during the measurement process.
• ③ If the power suddenly shuts down during the measurement process, this machine will automatically start discharging. Please do not immediately remove the wiring, wait at least 30 seconds before removing the wiring.
• ④ Three phase measurement is applicable to YN connected windings. For yn connected windings, due to the influence of copper bar resistance, the results of three-phase and single-phase measurements may differ. It is recommended to use single-phase measurement.
• ⑤ Note: The results of three-phase measurement do not include the resistance value of the neutral lead wire. Therefore, it is recommended to verify at least one data point for each phase using single-phase testing method after measuring the three-phase resistance value to determine whether the neutral lead wire is normal