Offline PD testing re-measures a circuit, not just a transformer: coupling capacitance, measuring impedance and calibration decide the picocoulomb number you write down.
A 2026 study finds acetylene does not mix evenly inside a transformer, so the oil sampling point decides whether an online DGA monitor ever sees a developing fault.
An anonymized 220 kV field record: online DGA acetylene monitoring caught 0.29 µL/L at dawn, escalated through 1.93 and 2.55, and the laboratory confirmed 2.99 µL/L eleven hours later.
A fifty-transformer campaign is where the complaint \”PD testing system not portable\” turns into a schedule problem. Four field constraints decide what you can actually buy.
Reliability-based DGA ranks transformers by what a failure would cost, not by nameplate rating. That ranking decides how many units get continuous gas monitoring, and which gas each is watched for.
A handheld survey and a permanent transformer PD monitoring system answer different questions. Here are the four specifications that decide which one you are actually buying.
Three words appear on almost every DGA sensor datasheet — cross-sensitivity, selectivity and specificity — and only one of them is a number you can check.
A PRPD plot’s horizontal axis is phase, not time, and that makes the comparison across three phases the cheapest discriminator an analyst has. What each pattern means and what it costs to read them.
Both sensing elements read the same palladium-hydrogen reaction, but through different quantities. What a resistive thin film and a MOS junction are each good at, and how to buy Pd alloy online monitoring hardware that fits the duty.
A partial discharge alarm threshold copied from one pC figure compares quantities that were never comparable. How to baseline a unit and alarm on trend instead.
