Blog

OLTC dissolved gas analysis is a discipline apart from main-tank DGA. Why IEEE C57.139-2015 governs tap-changer oil, and which readings are normal.

Hydrogen and oxygen are both invisible to optical DGA. Measuring them properly means not extracting them at all — here is the physics and the engineering.

One number, ±15%, is quoted worldwide — but IEC, ASTM, IEEE, Russian and Chinese standards each define accuracy differently. Here is what each one demands.

Hydrogen is invisible to photoacoustic spectroscopy — not a design flaw but molecular physics. Here is why, and why the hydrogen channel matters more than the gas count.

The ±15% figure everyone quotes is an acceptance target, not a detector spec. Here is where dissolved gas analysis error actually comes from, stage by stage.

A UHF partial discharge sensor most often enters the tank through an oil valve. What a live retrofit requires, where sensors go, and what to specify in the IED.

DGA gas ratios turn a nine-gas reading into a fault type. How the Rogers, Doernenburg and IEC 60599 schemes work, where they fail, and what machine learning adds.

PRPD and PRPS record partial discharge pulses phase-resolved. What the patterns show, how source localization works, and what to specify in an online PD system.

A transformer dissolved hydrogen sensor can alarm on air ingress, sampling error or sensor drift rather than a real fault. Here is how to rule each cause out.

Online partial discharge monitoring for transformers explained: what PD sensors measure, where UHF, HFCT, AE and RF sensors go, what to specify, and how PD complements DGA.