A Gas Chromatograph Tester is a core tool for monitoring the insulation condition and diagnosing faults in electrical equipment (especially power transformers). It works by detecting dissolved fault characteristic gases formed from the decomposition of insulating oil under electrical and thermal stress to identify potential issues within the equipment.
The key gases it detects are primarily divided into two categories:
I. Primary Fault Characteristic Gases (Core Diagnostic Indicators)
These five gases are the most critical for diagnosing the type and severity of a fault and are often called the "Five Key Characteristic Gases":
1.Hydrogen (H₂)
Source: Generated by partial discharge (corona), arcing, or the decomposition of water molecules in moist oil. It is a sensitive indicator of low-energy electrical discharges and moisture.
2.Methane (CH₄)
Source: Produced by the decomposition of insulating oil and solid insulating materials (like paperboard, wood) due to low-temperature overheating (typically <300°C).
3.Ethane (C₂H₆)
Source: Similar to methane, it is also a product of overheating faults, but it is typically generated at a slightly higher temperature range than methane, indicating medium-temperature overheating.
4.Ethylene (C₂H₄)
Source: This is a crucial key gas for identifying high-temperature overheating (typically >700°C). The production rate of ethylene increases dramatically with rising temperature. It is a vital indicator for determining the severity of overheating.
5.Acetylene (C₂H₂)
Source: This is the most representative characteristic gas of arcing (high-energy electrical discharges). It is generated rapidly from the cracking of oil molecules under the extreme heat of an electric arc (which can exceed 3000°C). The presence of any acetylene is a serious sign that requires immediate attention, as it indicates severe discharge activity. It is the critical indicator for determining the seriousness of a fault.
II. Other Important Gases (Auxiliary Diagnostic Indicators)
Besides the five key gases, the following gases also provide essential information:
6.Carbon Monoxide (CO)
Source: Primarily generated from the thermal decomposition of solid insulating materials (cellulose paper, paperboard). Its concentration and rate of increase directly reflect the aging and overheating of solid insulation. It is key to determining if a fault involves solid insulation.
7.Carbon Dioxide (CO₂)
Source: Also comes from the aging and oxidative decomposition of solid insulating materials, but its production is more general (including normal aging). It must be analyzed in conjunction with the CO content and the CO/CO₂ ratio.