Second Tier: Leading Domestic Brands (High Cost-Effectiveness, Fast Service, Full Features) With technological maturity, domestic brands have taken a dominant position in power maintenance and factory inspections. 6. UNI-T * Features: Leading domestic instrument manufacturer with an extremely wide product line. Its UT500 series sells massively in civil and industrial general-purpose fields, offering high cost-effectiveness. 7. VICTOR * Features: A veteran domestic instrument brand, known for durability, with after-sales service outlets nationwide, suitable for grassroots electricians and routine maintenance. 8. Tonghui * Features: Specializes in electronic measurement instruments; its insulation resistance testers excel in laboratory and precision manufacturing fields. 9. Ainuo * Features: Deep accumulation in safety regulation testing and specialized high-voltage testing. 10. Other professional power brands: Such as Wuhan Ultra-High Voltage, Yangzhou Darui (a load off one's mind, referencing the loop resistance tester brands mentioned earlier), in high-power insulation testers for power systems (e.g., transformers, GIS) at 5kV/10kV, these specialized manufacturers often have advantages over general-purpose instrument manufacturers. (Note: Some lists such as "Anli Touch" and "Jinguan Electric" mainly appear in specific niche or emerging voting lists; when purchasing, verify their specific qualifications and market share.) 3. 2025-2026 Industry New Trends Intelligence and IoT: New instruments commonly come with Bluetooth/WIFI as standard, allowing test data to be uploaded in real-time to mobile apps or cloud management systems, automatically generating electronic reports compliant with State Grid/China Southern Power Grid standards, reducing manual entry errors. Large-Capacity Batteries and Fast Charging: Abandoning traditional dry batteries or bulky lead-acid batteries, fully adopting lithium-ion batteries, supporting long-duration continuous testing and fast charging. Multi-Parameter Integration: A single instrument simultaneously possesses insulation resistance, polarization index, dielectric loss (some high-end models), and even leakage current testing functions, achieving "one machine, multiple uses." Safety Upgrades: Enhanced automatic discharge logic for capacitive loads (such as long cables) to prevent residual high voltage from harming people; housing protection levels generally reach IP65 or even IP67, adapting to harsh outdoor weather. 4. Selection and Usage Recommendations Select by Voltage Level: 380V motor/line -> choose 500V/1000V range. 10kV switch/cable -> choose 2500V/5000V range. 35kV and above main transformer/long cable -> must choose 5000V/10000V models with high output power (otherwise charging time is too long, making accurate measurement impossible). Focus on Short-Circuit Current: The short-circuit current of quality instruments should be ≥1mA (or even 5mA) to ensure charging speed for large capacitive test objects. Operating Specifications: Power Off and Verify: Before testing, confirm the equipment is de-energized and fully discharged. Correct Wiring: L connects to the line, E to ground, G to the guard ring (to eliminate surface leakage effects, especially important when testing cables). Reading Timing: Read values at 15 seconds (R15) and 60 seconds (R60) to calculate the absorption ratio, or at 1 minute and 10 minutes to calculate the polarization index. Post-Test Discharge: After testing, ensure the instrument auto-discharges or manually discharge, and confirm no voltage before disconnecting wires.
