The trusted online DGA monitoring system for continuous transformer DGA analysis — detect incipient faults in transformer insulating oil weeks before failure. 7-gas DGA monitor with automated Duval Triangle, Three-Ratio, Rogers Ratio & Key Gas Method. Factory-direct DGA testing solution with ±5% accuracy.
CE · ISO 9001 · IEC 60599 · IEEE C57.104 · OEM / ODM Factory Direct
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Dissolved Gas Analysis (DGA) — also called transformer dissolved gas analysis, DGA gas analysis, or DGA of transformer oil — is the principal diagnostic method for assessing the internal condition of oil-immersed power transformers. When a transformer experiences thermal stress, partial discharge, or electrical arcing, the insulating oil and cellulose paper insulation decompose, releasing characteristic fault gases that dissolve into the surrounding oil. DGA testing measures the type and concentration of these dissolved gases to provide a reliable, early indication of the specific fault mechanism developing inside the transformer.
Traditional transformer DGA analysis relied on periodic offline oil sampling sent to an external laboratory, producing results days after collection. An online DGA monitoring system — a multi-gas DGA monitor installed directly on the transformer — continuously extracts and analyzes dissolved gases at the site, delivering real-time gas concentration data, trend analysis, and automated fault diagnosis without human intervention. This transition from periodic DGA testing to continuous DGA monitoring represents the most significant advance in transformer predictive maintenance over the past two decades.
The interpretation of dissolved gas analysis of transformer oil is governed by international standards including IEC 60599 and IEEE C57.104, which define typical gas concentration values, action levels for Total Dissolved Combustible Gas (TDCG), and diagnostic methods such as the Duval Triangle, Three-Ratio Method, Rogers Ratio Method, Doernenburg Ratio, and Key Gas Method used by utilities and asset managers worldwide for transformer condition monitoring.
Offline DGA testing is too slow. Laboratory dissolved gas analysis takes days to return results — by then, a developing fault may already be in an advanced stage requiring emergency action. Real-time DGA monitoring eliminates this latency and triggers configurable DGA alarms within a single measurement cycle.
Temperature sensors alone are insufficient. Thermal sensors cannot detect partial discharge, incipient arcing, or early paper insulation breakdown — all of which generate fault gases in DGA oil analysis well before any temperature anomaly appears. Only a dedicated DGA monitor can capture these early indicators.
Transformer failures are catastrophic in cost. A single unplanned failure at a critical substation can result in $500K–$2M+ in equipment replacement, emergency repair, and grid downtime costs. An online DGA monitoring system delivers ROI typically within 2–3 years for critical transformers.
Remote sites cannot support manual DGA testing. Offshore platforms, unmanned substations, and mountain installations make periodic manual transformer DGA oil sampling impractical — continuous online DGA monitoring is the only viable solution for these locations.
Transformer insulating oil circulates continuously through the DGA monitoring system via a dedicated connection to the transformer body. The sampled oil is fully representative of bulk oil condition — not a stagnant pocket — ensuring measurement accuracy reflects the actual transformer state for precise dissolved gas analysis of transformer oil.
The oil sample passes through a dynamic vacuum extraction chamber where dissolved fault gases are separated from the oil with high extraction efficiency. This vacuum degassing method reliably captures all seven target gases — including trace concentrations of H₂ and C₂H₂ at incipient fault levels — and outperforms headspace gas analysis for low-concentration DGA testing sensitivity.
The extracted gas mixture passes through a gas chromatography (GC) separation column where each of the seven gas components is separated by retention time and quantified by sensitive TCD + FID detectors. The full chromatogram is recorded and stored for every DGA analysis cycle, providing a verifiable audit trail of all transformer DGA analysis results.
Calculated gas concentrations and TDCG values are transmitted via RS485, IEC 61850, DNP3.0, or Ethernet to the backend platform. The Three-Ratio Method, Rogers Ratio, Doernenburg Ratio, Duval Triangle, and Key Gas Method are applied automatically every cycle — generating fault classification results and triggering configurable DGA alarms without manual interpretation.
Two competing detection technologies dominate the online DGA monitor market today. Understanding their differences helps you select the right multi-gas DGA analyzer for your transformer fleet and DGA testing requirements.
For utility-grade transformer monitoring where C₂H₂ detection sensitivity directly determines early arcing detection capability, gas chromatography remains the international reference method specified by IEC 60567 and used by all major laboratory dissolved gas analysis service providers.
The 7-gas DGA monitor continuously measures all IEC 60599 / IEEE C57.104 fault indicator gases — providing complete coverage of every major transformer fault mechanism.
Standard 7-gas DGA analysis covers all IEC 60599 fault gases. For special applications — OLTC-integrated transformers, reactors, high-moisture environments, or 9-gas configurations — we configure custom gas combinations, extended measurement ranges, and application-specific DGA alarm logic to match your exact asset and operating conditions.
The IEEE C57.104 standard defines four DGA alarm condition levels based on TDCG (Total Dissolved Combustible Gas) = H₂ + CO + CH₄ + C₂H₆ + C₂H₄ + C₂H₂ — the key metric in dissolved gas analysis of transformer oil. The INNO online DGA monitoring system calculates TDCG automatically every measurement cycle and applies these standard thresholds, with full user configurability for site-specific overrides.
| Gas (μL/L) — DGA Analysis Limits | Condition 1 Normal |
Condition 2 Caution |
Condition 3 Warning |
Condition 4 Critical DGA Alarm |
|---|---|---|---|---|
| Hydrogen (H₂) | ≤ 100 | 101 – 700 | 701 – 1800 | > 1800 |
| Methane (CH₄) | ≤ 120 | 121 – 400 | 401 – 1000 | > 1000 |
| Acetylene (C₂H₂) | ≤ 1 | 2 – 9 | 10 – 35 | > 35 |
| Ethylene (C₂H₄) | ≤ 50 | 51 – 100 | 101 – 200 | > 200 |
| Ethane (C₂H₆) | ≤ 65 | 66 – 100 | 101 – 150 | > 150 |
| Carbon Monoxide (CO) | ≤ 350 | 351 – 570 | 571 – 1400 | > 1400 |
| Carbon Dioxide (CO₂) | ≤ 2500 | 2501 – 4000 | 4001 – 10000 | > 10000 |
| TDCG (Total Combustible) — DGA Alarm Sum | ≤ 720 | 721 – 1920 | 1921 – 4630 | > 4630 |
Threshold values per IEEE C57.104-2019 for in-service oil-immersed power transformers. Gas generation rate of change (μL/L per day) is often a more reliable fault indicator than absolute concentration — the DGA monitoring system tracks both automatically.
Three distinct approaches exist for transformer dissolved gas analysis. Choosing the right approach depends on transformer criticality, site accessibility, and required response time to developing faults.
| Online DGA Monitor & Monitoring System | Portable DGA Analyzer | Offline Lab DGA Testing | |
|---|---|---|---|
| Monitoring Frequency | ✓ Continuous — every 2+ hours, 24/7 | On-site visit — typically monthly or quarterly | ✗ Weeks or months between DGA tests |
| Response to Developing Fault | ✓ Real-time DGA alarm within one cycle | Hours — only when operator is on-site | ✗ Days to weeks after DGA sampling |
| Gas Coverage | ✓ Full 7-gas DGA analysis + TDCG every cycle | Full 7-gas DGA per visit | Full 7-gas dissolved gas analysis per sample |
| Remote / Unmanned Sites | ✓ Fully automated — no site visits required | ✗ Requires personnel travel | ✗ Requires personnel travel |
| Fault Trend Analysis | ✓ Complete historical DGA monitoring trending | Discrete points — limited trending | ✗ Isolated data points only |
| Automated Fault Diagnosis | ✓ Auto Duval Triangle, Three-Ratio, Rogers Ratio, Key Gas | Manual interpretation post-visit | Manual interpretation by specialist |
| SCADA Integration | ✓ RS485, IEC 61850, DNP3.0, Ethernet | ✗ Data exported manually | ✗ Paper or spreadsheet reports only |
| DGA Alarm Capability | ✓ Automated multi-level DGA alarm thresholds | Manual threshold comparison on-site | ✗ No automated alarm capability |
| Best Suited For | Critical assets, EHV transformers, remote sites | Mid-sized fleets, scheduled DGA testing rounds | Small distribution transformers, routine baseline |
The DGA monitoring system automatically applies all major IEC 60599 and IEEE C57.104 DGA analysis methods every measurement cycle — Three-Ratio, Rogers Ratio, Doernenburg Ratio, Duval Triangle, and Key Gas Method — with no manual calculation required.
| Fault Type | Gas Ratio Signature | Class |
|---|---|---|
| Normal Aging | All ratios within baseline | Normal |
| Partial Discharge | CH₄/H₂ < 0.1 | PD |
| Low-Energy Discharge | C₂H₂/C₂H₄ > 3 | D1 |
| Thermal Fault <300°C | C₂H₄/C₂H₆ < 1 | T1/T2 |
| High-Temp Arcing >700°C | C₂H₂/C₂H₄ > 3, C₂H₄/C₂H₆ > 3 | D2 |
Plots the percentage share of CH₄, C₂H₄, and C₂H₂ within a triangular diagram divided into seven distinct fault zones. Each DGA analysis cycle automatically generates a plotted data point, visually classifying current fault state.
| Diagnostic Ratio | DGA Analysis Indication |
|---|---|
| CH₄/H₂ < 0.1 | Partial Discharge |
| C₂H₂/C₂H₄ > 0.75 | Arcing — DGA Alarm |
| C₂H₄/C₂H₆ between 1–3 | Thermal 300–700°C |
| C₂H₄/C₂H₆ > 3 | Thermal >700°C |
| DGA Analysis Gases | H₂, CO, CO₂, CH₄, C₂H₆, C₂H₄, C₂H₂ (7 gases) + TDCG |
| DGA Monitor Technology | Gas chromatography + vacuum extraction |
| DGA Testing Accuracy | ±5% F.S. (customizable) |
| Resolution | 0.1 ppm |
| Repeatability (RSD) | ≤3% |
| Min. DGA Analysis Cycle | ≥2 hours (configurable) |
| DGA Analysis Methods | Duval Triangle, Three-Ratio, Rogers Ratio, Doernenburg, Key Gas |
| Optional DGA Monitoring | H₂O moisture (1–100 μL/L), 9-gas DGA option |
| DGA Data Storage | ≥10 years onboard |
| Enclosure Dimensions | 650 × 500 × 1300 mm |
| Weight | ~110 kg |
| Protection Rating | IP55 |
| Ambient Temperature | −40°C to +65°C |
| Power Supply | AC 220V ±15%, 50Hz, ≤800VA |
| Communication | RS485/Modbus, Ethernet, IEC 61850, DNP3.0 |
| Wireless Option | 4G / 5G (optional) |
| Carrier Gas | N₂ ≥99.999% (cylinder or on-site generator) |
| Standards Compliance | IEC 60567, IEC 60599, IEEE C57.104 |
Detect developing transformer faults weeks before they become critical — continuous DGA monitoring captures partial discharge, overheating, and arcing before any temperature anomaly appears.
Replace fixed-interval DGA testing schedules with data-driven decisions based on actual transformer health. Maintenance resources are deployed only where genuine DGA alarm indicators are present.
Eliminate recurring laboratory DGA testing fees and unplanned emergency repair expenses. Continuous online DGA monitoring system deployment typically delivers positive ROI within 2–3 years.
Prevent unplanned outages at critical substations. Continuous transformer DGA analysis means scheduled maintenance replaces reactive emergency response.
Ten or more years of stored DGA monitoring data enables rate-of-change analysis. Gradual gas generation trends are identified long before absolute TDCG thresholds are reached.
Fully automated 24/7 DGA oil analysis eliminates manual DGA testing at remote, offshore, or difficult-to-access sites. SCADA integration provides real-time visibility from any operations center.
Standard serial communication for PLC, RTU, and legacy SCADA systems
Native substation automation protocol for modern digital substations
High-speed network communication for centralized DGA monitoring platforms
Utility automation protocol + wireless option for remote DGA monitor connectivity
Dissolved gas analysis of transformer oil reveals fault gases in insulating oil. Cross-validating transformer DGA analysis with winding temperature, partial discharge, and oil level data substantially increases diagnostic confidence and reduces false DGA alarms.
Direct hot-spot measurement inside oil-immersed transformer windings. ±1°C accuracy, 140kV dielectric withstand, 25+ year operating lifetime.
Multi-channel winding temperature monitoring system — 1 to 64 channels, IEC 61850 / Modbus output, scalable for substation-wide deployment.
Continuous PD detection inside transformer insulation — identifies dielectric defects before they generate significant gas volumes in DGA testing.
Magnetic coupling oil level indicator — local dial + 4–20mA remote output, IP55, alarm contacts for conservator tank monitoring.
INNO provides a full suite of online monitoring solutions covering every critical health parameter of oil-immersed power transformers — from insulating oil gas analysis to winding temperature, partial discharge, bushing condition, OLTC wear, and beyond.
Continuous 7-gas analysis of transformer insulating oil — detects partial discharge, thermal faults, and arcing weeks before failure. Automated Duval Triangle, Three-Ratio & Rogers Ratio fault diagnosis every ≥2 h cycle.
Fiber optic winding hotspot temperature measurement directly inside oil-immersed transformer windings. ±1°C accuracy, 140 kV dielectric withstand — the only technology capable of real winding hotspot detection per IEC 60076-7.
Continuous on-line PD detection inside transformer solid insulation — detects voids, delamination, and contamination before they generate measurable DGA gas volumes. UHF and acoustic emission sensors, compatible with all transformer types.
On-load tap changer condition monitoring — detects contact wear, oil contamination, and mechanical faults in the OLTC compartment before they escalate to transformer failure. Vibro-acoustic and dynamic resistance methods.
Continuous capacitance and tan δ (dissipation factor) monitoring of HV transformer bushings — identifies moisture ingress, insulation aging, and internal partial discharge in bushings, one of the most common causes of catastrophic transformer failure.
Continuous assessment of transformer oil dielectric health — moisture content, breakdown voltage trend, acidity, and color index — enabling data-driven oil replacement and drying decisions alongside DGA gas analysis results.
Monitoring of transformer core ground current, core temperature, and stray flux — detects inter-lamination shorts, core bolt insulation failures, and circulating currents that generate CO and CO₂ in DGA analysis before structural damage occurs.
Bespoke monitoring solutions for special transformer types — reactors, furnace transformers, phase-shifting transformers, traction units — combining any subset of INNO sensors and the DGA monitoring system into a single integrated platform.
Continuous DGA monitoring is deployed across every major transformer application — from EHV transmission to distribution transformers, GSU step-up transformers, and shunt reactors — where insulation health and operational continuity are critical.
110kV+ transmission and distribution transformers where continuous DGA monitoring system deployment is a grid reliability and asset management requirement.
Generator step-up transformers at thermal, hydro, nuclear, and renewable facilities where transformer DGA analysis outage directly impacts generation revenue.
Collector and grid-connection transformers operating under variable load cycles that accelerate insulation aging — requiring continuous DGA monitoring.
Traction transformers where DGA alarm capability directly affects passenger safety, scheduling, and infrastructure operator liability.
Critical process transformers in manufacturing, petrochemical, mining, and data center operations where online DGA monitoring prevents costly unplanned shutdowns.
Oil-filled shunt reactors on EHV transmission lines — DGA monitoring system identifies winding and core faults where manual DGA testing is impractical.
Transformers operating near rated capacity or beyond design life. Enhanced transformer DGA analysis supports risk-based lifetime extension decisions.
Data centers, hospitals, airports where continuous DGA monitoring prevents transformer failures with immediate consequences for operations or public safety.
Every online DGA monitoring system and DGA monitor is designed, manufactured, and calibrated in our own facility in Fuzhou, Fujian — with no distributor intermediaries, full traceability, and genuine engineering support.
Full in-house manufacturing, assembly, and calibration. Factory-direct pricing with no distributor markup and complete product traceability.
Proprietary gas chromatography modules and dynamic vacuum extraction technology developed by our own engineering team.
Field-proven DGA monitoring system in utility substations, power generation plants, industrial facilities, and rail transit systems across six continents.
Custom branding, modified communication interfaces, tailored enclosure designs, and dedicated technical support for system integrators and transformer OEM manufacturers.
Feedback from asset managers, maintenance engineers, and procurement teams across leading utilities and industrial operators who rely on INNO for transformer dissolved gas analysis.
We deployed INNO online DGA monitoring systems across 14 transmission substations. Within the first six months, the DGA monitor flagged a developing C₂H₂ trend on a 220kV autotransformer that our quarterly DGA testing had completely missed. We avoided a catastrophic failure. The IEC 61850 integration with our existing SCADA was seamless.
The accuracy of the 7-gas DGA analyzer matched our reference laboratory dissolved gas analysis results within acceptable margins right from commissioning. What impressed us most was the ±5% F.S. DGA testing performance even at -25°C ambient during our winter field trials. The OEM configuration support was excellent.
We needed a DGA monitoring solution for offshore wind farm collector transformers — locations where manual DGA testing is genuinely impractical. The 4G communication option and IP55 rating solved our problem completely. Three years of reliable DGA monitor operation with zero unplanned maintenance visits to the platform.
As a transformer OEM integrating third-party DGA monitoring systems, supply chain reliability and technical documentation quality are critical. INNO's private-label DGA monitor programme, timely delivery record, and detailed technical data have made them our preferred DGA monitoring supplier for the past four years.
We evaluated four DGA monitoring system suppliers on detection sensitivity, SCADA protocol support, and total cost of ownership. The INNO multi-gas DGA analyzer offered the best combination across all three criteria. The Duval Triangle and Rogers Ratio automatic DGA analysis have become core tools in our transformer health reporting.
Our industrial facility runs 24/7 process operations. The INNO DGA monitoring system integrated with our Modbus TCP DCS in under a day. Within weeks it detected rising CO and CO₂ trends indicating cellulose insulation degradation that guided a planned maintenance intervention rather than an emergency shutdown.
Answers to the most common technical, operational, and commercial questions about our online DGA monitoring system and transformer dissolved gas analysis solutions.
Share your transformer specifications and receive a custom DGA monitor and DGA monitoring system recommendation within 1 business day — completely free of charge.
