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Advanced Insulation Testing for Water-Cooled Generators
Insulation testing is critical for assessing the health of generator insulation systems. Water-cooled generators present unique challenges due to their internal water systems, which can introduce low resistance paths and polarization effects. Traditional high-voltage insulation testers may provide inaccurate readings or even be unable to perform tests under these conditions. The ZXC38 Internal Water Cooling Generator Insulation Tester is specifically engineered to overcome these challenges, offering a robust and precise solution for maintenance engineers and technicians.
Challenges in Water-Cooled Generator Testing
A primary challenge is the inherent low insulation resistance between the generator's stator winding and the water-collecting pipe. This resistance can often fall below the minimum required by standard 5kV megohmmeters, preventing them from applying the full test voltage and yielding a valid measurement. Furthermore, the presence of water can create a polarization potential that interferes with the DC measurement, leading to significant errors.
ZXC38: A Purpose-Built Solution
The ZXC38 directly addresses these issues with advanced features not commonly found in general-purpose testers:
1.Auto Polarization Potential Compensation: This is a key differentiator. The ZXC38 automatically nullifies the voltage generated by the water system, ensuring measurement accuracy even when the resistance to the water-collecting pipe is as low as 10 kΩ. A standard insulation tester would be unable to provide a stable reading under such conditions.
2.High Output Power and Current: With a short-circuit current ≥25mA and the ability to maintain this under load, the ZXC38 ensures stable test voltages. It can drive a load resistance as low as 100kΩ at 2500V. This high power allows it to charge the large capacitance of generator windings quickly and is highly resistant to surface leakage currents, which can plague testers with lower output current (<5mA).
3.Comprehensive Diagnostic Testing: The instrument automates standardized insulation diagnostic tests:
Dielectric Absorption Ratio (DAR): Calculates the R60s/R15s ratio.
Polarization Index (PI): Calculates the R10min/R1min ratio.
It automatically records values at the required time intervals, eliminating manual timing errors.
Technical Comparison and Advantages
Feature | Standard 5kV Megohmmeter | ZXC38 Insulation Tester | Advantage for the User |
Min. Measurable R@5kV | Typically 1-5 MΩ | Can measure down to 2 MΩ at 5kV | Confidently tests generators with lower initial insulation resistance. |
Low Load Resistance | May fail or reduce voltage | Stable operation down to 150kΩ at 5kV | Reliable testing even with significant moisture or contamination. |
Polarization Compensation | No | Yes, automatic | Eliminates a major source of measurement error, providing true insulation resistance. |
Output Short-Circuit Current | Typically 5-10mA | ≥25mA | Superior anti-interference ability, ideal for noisy HV substation environments. |
Generator-Specific Features | Basic insulation resistance | Automated DAR/PI, discharge monitoring, water system connection | Streamlined, error-free procedure specifically for water-cooled generators. |
Key Technical Indicators at a Glance:
1.Test Voltage: 2500V / 5000V
2.Measurement Range: 0.1 MΩ to 200 GΩ (up to 2 TΩ)
3.Output Short-Circuit Current: ≥ 25 mA
4.Accuracy: ±(10% + 5 digits)
5.Special Feature: Accurate measurement with water-pipe resistance < 10 kΩ
Conclusion：
For technicians responsible for the maintenance of large water-cooled generators, the ZXC38 is more than just an insulation tester; it is a dedicated diagnostic system. Its high output power, robust anti-interference design, and unique automatic polarization compensation make it vastly superior to standard megohmmeters in this application. By providing accurate and reliable data for DAR and PI indices, it empowers technicians to make informed decisions about generator condition, supporting predictive maintenance strategies and preventing costly forced outages.
GDZX is a manufacturer of power detection equipment, offering a diverse range of products with comprehensive models and providing professional technical support. Contact us at +86-27-6552607 or +86-17396104357.Website: http://en.gdzxdl.com/
