DGA limits are not one size fits all. Utilities typically use guidance documents, then apply asset specific limits based on voltage class, design, and historical trends. Standards such as IEC 60599 focus on interpreting gas patterns for fault type, while utility guides also use caution and alarm thresholds for key gases and total dissolved combustible gas. The most practical approach is trending: sudden increases in hydrogen, acetylene, ethylene, methane, or carbon oxides often matter more than a single snapshot. Limits are paired with actions such as repeat sampling, online monitoring, inspection, or outage planning.
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