1. Core Parameter Interpretation: How to Understand Technical Specifications?
When selecting an insulation resistance tester, pay attention to the following core parameters:
Table
Core Parameter Meaning Selection Advice
Test Voltage The DC high voltage level output by the instrument (e.g., 500V, 1000V, 2500V). Match equipment: choose 500V for low-voltage equipment, 1000V or 2500V for medium-voltage cables, and above 2500V for high-voltage motors.
Range/Accuracy The maximum resistance value measurable (e.g., 20000MΩ) and measurement error (e.g., ±5%). Accuracy: ±5% is sufficient for maintenance, ±3% for R&D. Range: recommend above 1TΩ (1000GΩ) to cover aging equipment.
Short-Circuit Current The maximum current output when measuring low resistance values (e.g., 3.5mA). Importance: the higher the current, the faster the charging of capacitive equipment (such as long cables) and the more stable the reading.
Special Functions Such as absorption ratio (DAR), polarization index (PI), automatic discharge, etc. Essential: PI/DAR are key diagnostic functions to determine if insulation is damp.
2. Purchase Scenarios and Recommendations
Based on different usage scenarios, different types of instruments are recommended:
Scenario 1: General Electrical Maintenance (low-voltage equipment, motors, cables)
Recommended Type: Multifunctional Digital Insulation Resistance Tester
Such instruments typically have multiple voltage levels like 500V/1000V/2500V, a range of 1TΩ, short-circuit current ≥3.5mA, and support automatic calculation of absorption ratio (DAR) and polarization index (PI).
Reason for Recommendation: Comprehensive functions, can test both low-voltage lines and high-voltage motors and cables, cost-effective.
Reference Model: ZEC3150B-A (Zhongke Xinyi) and similar models, with insulation resistance, polarization index, absorption ratio testing functions, and automatic discharge for high safety.
Zhongke Xinyi ZEC3150B-A Insulation Resistance Tester
Scenario 2: High-Voltage Power Systems (transformers, GIS, high-voltage cables)
Recommended Type: High-Voltage High-Current Insulation Resistance Tester
Such instruments typically support 2500V, 5000V or even higher voltages, with a range up to 2TΩ or more, short-circuit current usually above 5mA, and have step voltage (SV) and dielectric discharge (DD) testing functions.
Reason for Recommendation: High-voltage equipment requires extremely high insulation standards, needing higher test voltages and stronger anti-interference capability to ensure potential insulation weaknesses are detected.
Reference Model: Should be selected based on specific voltage levels and equipment capacity, usually professional-grade equipment.
3. Operational Safety and Precautions
Safety First: Before measurement, ensure the equipment is de-energized and fully discharged to prevent residual charge from harming personnel or damaging the instrument.
Correct Wiring: Connect L terminal to the line (conductor under test), E terminal to ground (equipment housing or ground wire), and G terminal to the guard ring (to suppress surface leakage current).
Environmental Impact: Insulation resistance values are greatly affected by temperature; record ambient temperature and humidity during measurement for comparative analysis.
Stable Reading: Keep test leads firmly connected to the equipment during measurement, and record after the reading stabilizes (usually 1 minute or 10 minutes).
4. Market Brands and Price Reference
International Brands: Megger (UK), Hioki (Japan), Fluke (USA). These brands have mature technology and high accuracy, with prices typically in the tens of thousands of RMB.
Domestic Brands: Wuhan Huading, Shanghai Shengxu, Zhongke Xinyi, Shenggao Electric, etc. Domestic brands offer high cost-performance, complete functions, with prices ranging from a few thousand to tens of thousands of RMB, suitable for most domestic industrial and mining enterprises and power systems.
Summary Recommendation: For most industrial and mining enterprises or power maintenance personnel, choosing a digital insulation resistance tester with 500V/1000V/2500V three voltage levels, a range of 1TΩ, short-circuit current ≥3.5mA, and supporting PI/DAR functions is the most reliable choice.
