What tests is the SF6 dew point analyzer primarily used for?
SF₆ Gas Dew Point Analyzer is primarily used for precise measurement and analysis of humidity (trace moisture content) in sulfur hexafluoride (SF₆) gas. As a critical insulating and arc-quenching medium in high-voltage electrical equipment (such as GIS, circuit breakers, transformers, etc.), the moisture content of SF₆ is a key performance and safety indicator.
CORE DETAILS:
| Core Principle | Cold mirror method (cooling mirror surface to condensation/frost, measuring dew point) or capacitive polymer sensing method (DRYCAP®), directly outputs dew point temperature and converts to ppm-level moisture content |
| Measurement Range | Dew point: -80°C to +20°C (covers extreme operating conditions of SF6 equipment) |
| Accuracy | ≤±0.5°C dew point, resolution 0.1°C, compliant with IEC 60480 and other standards |
| Response Time | +20°C to -20°C dew point ≤1 minute, suitable for rapid on-site detection |
| Interference Resistance | Resistant to SF6 decomposition product (SO₂, HF) contamination; select models feature automatic cleaning function |
APPLICATIONS:
1. New Gas Acceptance Testing
Purpose: To verify that SF₆ gas newly charged into equipment complies with international standards (e.g., IEC 60376, GB/T 12022). Typically requires a dew point ≤ -50°C (corresponding to moisture content ≤ 200 ppm).
Test Method: Direct dew point measurement of gas from cylinders or charging lines.
2. Periodic Monitoring of Operational Equipment
Purpose: To monitor humidity changes in operational SF₆ equipment, assess equipment condition, and identify potential risks. Operational gas dew point is generally required to be ≤ -20°C to -10°C (primarily based on equipment type and voltage level).
Two testing methods:
1. Online Monitoring: Some analyzers can be installed in equipment gas pipelines for real-time monitoring.
2. Offline sampling: Samples are taken through equipment sampling ports for analysis in laboratories or on-site.
3. Equipment Fault Diagnosis and Decomposition Product Correlation Analysis
Purpose: Combined with SF₆ decomposition product testing (e.g., SO₂, H₂S, CO), comprehensively assess internal equipment faults (e.g., partial discharge, arcing overheating). Elevated moisture may accelerate decomposition product generation or indicate poor sealing/adsorbent saturation.
4. Post-Installation/Maintenance Sealing Integrity and Dryness Verification
Purpose: Primarily ensures internal dryness compliance and absence of moisture ingress after equipment installation/maintenance.
Test Method: Measure dew point multiple times after gas charging and settling to confirm humidity stabilizes within acceptable limits.
5. Low-Temperature Environment Suitability Assessment
Purpose: Evaluate potential SF₆ gas liquefaction in low-temperature environments (liquefaction temperature correlates with pressure and humidity).
Method: Convert dew point to water vapor partial pressure and assess risk using SF₆ pressure-temperature curves.
6. Desiccant Performance Evaluation
Purpose: Detect saturation failure of internal desiccants (e.g., molecular sieves).
Method: Continuously monitor humidity changes; sustained humidity increases may indicate desiccant replacement is required.
