Fact sheet · EN — Fact sheet for the SITRAM H2Guard Lite, Siemens Energy's online single-gas DGA monitor that continuously tracks dissolved hydrogen — the key indicator gas for abnormal transformer conditions — in the insulating liquid of power transformers. A solid-state thin-film alloy sensor (25–5000 ppm range, no consumables or reference gases) mounts on any suitable valve in the liquid or gas phase, runs stand-alone or feeds SCADA via RS-485 Modbus/DNP3.0, and is rated IP68 for -40 to +70 °C outdoor service.
Winding-related failures rank highest among the causes of transformer outages. When partial discharge ("sparking") occurs, the transformer liquid generates internal gases — and hydrogen is the key indicator gas for any abnormal condition inside a transformer.
Conventionally, the insulating liquid is sampled and tested offline by classical laboratory DGA (dissolved gas analysis). That manual procedure is not always trivial and delivers only a snapshot in time, which may explain part of the statistical failure-rate picture.
The SITRAM H2Guard Lite is Siemens Energy's online DGA answer: a versatile single-gas monitoring system dedicated to hydrogen measurement, making fleet-wide transformer monitoring practical.
The system lets asset managers check the hydrogen health condition of the transformer's insulating liquid continuously, enabling trending of hydrogen creation and evolution against historical and present operating conditions. This condition data supports thorough evaluation and can reveal developing equipment issues before they become a problem.
It operates as a stand-alone hydrogen data monitor or together with superior monitoring platforms, and integrates easily into existing SCADA landscapes through standard protocol communication interfaces.
The miniature sensing element sits in a sensor tube that installs on any suitable valve, in either the liquid phase or the gas phase (headspace) of a liquid-filled transformer tank or its pipe system.
Fleet-wide hydrogen gas monitoring with fast detection and reliable data output. The unit is easy to install and uninstall, very durable with minimum maintenance compared with other products, and offers interoperability with simple operation.
Continuous monitoring improves scheduling of maintenance work, downtimes, repairs and personnel support, and delivers price-attractive ownership with quick amortization versus classical assessment approaches.
Siemens Energy supplies a standard electrical and mechanical connection kit (individual mechanical connection kits on request), turnkey installation and communications services, expert analysis of monitoring data with customer support, on-site training courses for operation and maintenance, and the design, installation and commissioning of all necessary equipment.
The sensor uses a compact solid-state thin-film alloy design: molecular hydrogen is catalyzed into atoms, which the alloy mix picks up and binds into the metallic lattice inside the film. Binding hydrogen changes the bulk electrical properties of the alloy, and this change is used as the measurement basis.
The alloy design does not degrade over time and maintains its accuracy over the sensor's life expectancy. There is therefore no need for consumables such as the reference gases used in gas chromatography, and no sensor-element replacement — unlike the classical membranes of electrochemical fuel-cell sensors or thermal conductivity detection (TCD) approaches. Siemens Energy's global service network is available whenever support is needed.
Headline measurement performance as printed (for full detail the fact sheet refers to the system manual):
| Parameter | Value |
|---|---|
| Range | 25 – 5000 ppm |
| Accuracy | 20% of reading or 25 ppm, whichever is greater |
| Repeatability | 10% of reading or 15 ppm, whichever is greater |
| Response Time | < 60 min (90% of step change) |
| Cross-Sensitivity | < 2% to other gases CO, CO2, CH4, C2H2, C2H4, C2H6, C3H8, etc. |
Electrical, environmental, mechanical and communication ratings of the SITRAM H2Guard Lite:
| Characteristic | Specification |
|---|---|
| Supply Voltage / Power Consumption | 12-48 VDC, 10 W |
| Ambient Operating Conditions | -40°C…+70°C, indoor/outdoor also in harsh EMC areas, 5%...95% RH (non-condensing) for complete operating temperature |
| Operating Conditions | Pressure and vacuum withstanding; oil temperature / pressure: ≤ 105°C / ≤ 10 bar |
| Physical Dimensions and Weight | Tube > ¾" NPT / 3.5"; System > L:151 W:39.6 H:39.6 mm (L:5.9 W:1.6 H:1.6 inch), 387 grams |
| Ingress and Corrosion Protection | IP68 (IEC 60529); C5M (a.o. ISO 12944); weather and UV resistant powder coat (AAMA 2604); cast aluminum enclosure (UNS A03280) with stainless-steel probe tube (316 type) |
| Resistance to Shock and Vibration | Tested on basis of DIN EN 60068-2-6 (Shock and Vibration), DIN EN 60068-2-64 (Vibration Environmental Test), DIN EN 60068-2-27 (Shock Test for Transformer Environment); additional extended, aggressive vibration dwell at 50 and 60 Hz |
| Data Rate | Maximum 1 measurement value per second; self-calibration: 2 h every 12 h |
| Analogue I/O | Optional: 1 x output, standard 4-20 mA or 0-5 VDC |
| Communication | Serial RS-485; protocols: Modbus and DNP3.0 serial |
| Memory | 1 year data storage capability |
Click any figure to enlarge.