but are intelligent devices integrating multiple diagnostic functions: Multi-voltage level output: Typically provides multiple test voltages such as 50V, 100V, 250V, 500V, 1000V, 2500V, 5000V, 10000V, adapting to different needs from low-voltage household appliances to ultra-high-voltage cables. Polarization Index (PI) and Dielectric Absorption Ratio (DAR): Automatically calculates and records PI (10-minute/1-minute resistance ratio) and DAR (60-second/15-second resistance ratio), which are key indicators for judging insulation moisture and aging degree, more accurate than a single resistance value. Automatic discharge function: After the test, the instrument automatically releases residual charge on the tested equipment, ensuring operator safety (this is the biggest difference from traditional hand-cranked megohmmeters). Real-time monitoring and plotting: High-end models can display resistance versus time curves in real time, helping analyze the absorption characteristics of insulating materials. Anti-interference capability: For strong interference environments such as variable-frequency motors and long cables, digital filtering technology is adopted to ensure stable readings. Data management: Built-in storage, Bluetooth/WIFI transmission, USB export, supports generating test reports compliant with IEEE 43 / DL/T 596 standards. 2. Mainstream brands and market landscape in 2026 The market is mainly divided into international high-end brands and domestic cost-effective brands. Domestic equipment has fully met the requirements of State Grid and China Southern Power Grid in technical indicators, and offers extremely high cost performance. Leading domestic brands (recommended first choice) Wuhan UHV Electric Power Technology Co., Ltd.: Status: In recent years, it has performed excellently in the high-voltage testing field, and its products have been listed as preferred centralized procurement choices by multiple provincial power companies. Features: Its insulation resistance testers use military-grade high-voltage modules with high output stability, especially excellent in the 5000V/10000V high-voltage range. It has strong anti-electromagnetic interference capability, suitable for complex substation environments. Advantages: Full Chinese large-screen touch operation, built-in expert diagnostic system, can automatically judge insulation status (pass/caution/fail). Wuhan Huadian Keyi / Wuhan Weian Electric Power: Features: Established manufacturers with rich product lines, covering from portable handheld meters to large desktop insulation testers. Advantages: Complete after-sales service network, free software upgrades, high cost performance, suitable for engineering companies and maintenance teams. Yangzhou Tuopu / Shanghai Shengxu: Features: High market share in East China, product design focuses on lightweight and durability, suitable for field operations. International well-known brands USA Fluke: Such as Fluke 1550C, 1587 FC. Features: Extremely simple operation, excellent safety design (CAT IV rating), powerful data recording functions, but expensive (usually 5-10 times the price of domestic products). Germany GMC (METRISO series): Features: Extremely high accuracy, rugged and durable, suitable for extreme harsh environments, often used in high-end laboratories and foreign-related projects. Japan Hioki / Kyoritsu: Features: Compact and portable, fast response, good reputation in the Asian market. 3. Key indicators for selection When purchasing, please pay attention to the following parameters based on actual application scenarios: Test voltage levels: Low-voltage equipment (<500V): choose 500V or 1000V range. High-voltage cables/motors (6kV-35kV): choose 2500V or 5000V range. Ultra-high-voltage equipment (110kV and above): need to choose 5000V or 10000V range. Measurement range: Conventional needs to reach 1TΩ (1000GΩ), high-end applications need to reach 10TΩ or even higher. Short-circuit current: The larger the short-circuit current (e.g., >5mA), the faster the charging speed for capacitive loads (such as long cables), and the higher the test efficiency. It is recommended to choose models with >3mA. Functional requirements: Do you need automatic PI/DAR calculation? Do you need data storage and upload? Do you need explosion-proof certification (chemical environment)? Protection level: For outdoor operations, it is recommended to choose IP65 and above, dustproof, waterproof, and drop-resistant. 4. Price reference range (2026 market conditions) Entry-level/handheld: ¥800 - ¥3,000 (suitable for general electricians, basic functions). Professional/digital: ¥4,000 - ¥15,000 (with PI/DAR calculation, data storage, high short-circuit current, mainstream in the market). High-end/specialized: ¥20,000 - ¥80,000+ (ultra-high voltage 10kV, large capacity, imported brands or special explosion-proof types). 5. Usage precautions and safety specifications Power off and discharge: Before testing, the power of the tested equipment must be cut off, and full discharge must be performed (especially for capacitive equipment such as cables and capacitors). Clean the surface: Wipe off dirt on the insulation surface to eliminate surface leakage current effects; use the guard terminal (G terminal) if necessary. Correct wiring: L (Line): Connect to the conductor under test. E (Earth): Connect to ground or housing. G (Guard): Connect to the guard ring (to eliminate surface leakage). Test process: After pressing the test button, keep the test leads stable, and record after the reading stabilizes or reaches the set time (e.g., 1 minute, 10 minutes).
