Transformer monitoring is not a one-size-fits-all approach due to the varied operational environments, transformer types, and specific needs of different power systems.
Dissolved gas is a leading indicator of the health of a transformer, and DGA monitoring helps determine the types of abnormal events that may be occurring within the main tank. This makes it an effective way to analyze partial discharge, arcing, excessive thermal conditions, and more.
But the choice between Key Gas and Multi gas depends on several factors including the criticality of the transformer, the type of load it handles, the environmental conditions, and the maintenance strategy of the utility or industrial operator.
In this article, we’ll be helping you understand why asset management requires DGA, and which of these two options is right for you. In order to keep the power grid stable and the lights on, it pays to know which condition based monitoring option is best.
What’s the Difference?
DGA testing is complex, and methods vary. Key Gas monitoring is a critical component in the maintenance and management of electrical transformers and other high-voltage equipment. This technique focuses on detecting specific gases dissolved in transformer oil, which are indicators of various types of faults or deteriorations within the equipment.
While Key Gas monitoring is valuable for initial fault detection and basic monitoring, it does not provide the detailed, comprehensive data required for in-depth diagnostics, fault differentiation, and predictive maintenance. Multi-gas analysis, by contrast, offers a fuller picture of the transformer’s condition, allowing for more accurate fault identification, early detection of potential issues, and informed maintenance planning.
Key Gas Monitoring and How to Improve It
Key gas monitoring enables the early detection of faults in transformers and other high-voltage equipment. By continuously or periodically measuring the concentration of specific gases such as hydrogen, carbon monoxide, and acetylene, it is possible to identify incipient faults before they escalate into serious problems. Early detection allows for timely maintenance and repair, preventing costly unplanned outages and catastrophic failures.
By focusing on hydrogen, which is a key indicator of many types of faults (such as overheating, arcing, and partial discharges), key gas monitoring can provide sufficient early warning with less complexity. Multi-gas monitoring, meanwhile, aims to detect a broader range of fault types, necessitating more comprehensive sensor arrays and monitoring systems.
Compared to comprehensive multi-gas monitoring systems, key gas monitoring is relatively cost-effective. It requires fewer sensors and less complex analytical equipment, making it an affordable option for continuous monitoring of critical assets.
Key gas monitors have fewer sensors and components because they track a limited number of gases, usually just hydrogen. This simplicity translates to fewer parts that can fail or require calibration.
With only one or a few sensors to manage, the calibration process is quicker and less frequent compared to multi-gas monitors, which have multiple sensors each requiring regular calibration to maintain accuracy.
Key gas monitoring also offers stable calibration compared to other methods. Hydrogen sensors, the primary component in key gas monitors, typically exhibit stable calibration over longer periods compared to the diverse range of sensors in multi-gas systems.
However, key gas monitoring, while useful for initial fault detection, often does not provide enough data to perform a comprehensive diagnostic analysis of a transformer’s condition.
Limited Fault Identification
Key gas monitoring typically focuses on one or a few specific gases, such as hydrogen or acetylene. While these gases are important indicators of certain types of faults (e.g., hydrogen for partial discharges, acetylene for arcing), they do not provide a complete picture of all potential fault conditions.
Lack of Fault Differentiation
Key gas monitoring cannot distinguish between different types of faults as effectively as multi-gas monitoring can. For instance, hydrogen can be produced by several different fault mechanisms, including partial discharges, thermal faults, and electrical arcing, making it difficult to pinpoint the exact nature of the problem.
Detailed diagnostics often require the analysis of the ratios between different gases. This ratio analysis helps in identifying the specific type of fault (e.g., thermal vs. electrical), its severity, and its location within the transformer.
Incomplete Condition Assessment
While Key gas monitoring provides a broad overview of the condition of the transformer, it lacks the granularity needed for a detailed assessment. Comprehensive diagnostics often require the analysis of multiple gases to understand the complete internal condition of the transformer, including the health of the insulation, oil, and other components.
For accurate lifecycle analysis and maintenance planning, a detailed understanding of all fault gases and their interactions is crucial. Key gas monitoring alone cannot provide this level of detail, but the hydrogen sensor can be paired with B100, E3 or C50 devices from Dynamic Ratings for more efficient monitoring.
Better Accuracy Throughout the B100
The B100 Series Electronic Temperature Monitor (ETM) is a complete monitoring solution for any distribution, transmission or generation transformer.
Pairing hydrogen sensors with B100 allows for highly sensitive and accurate detection of hydrogen, indicating transformer faults, such as partial discharges and overheating.
The B100 ETM is an analog gauge replacement that provides accurate indication of problems inside the transformer via fault gas detection. Additionally, a hydrogen sensor and/or moisture sensor provides an all-in-one, low-cost solution with remote notification of any problems detected, enabling preventive maintenance and avoiding catastrophic failures.
Comprehensive Monitoring with E3
The advanced analytics within the E3 monitoring system filters through the condition data to automatically identify issues requiring maintenance attention, allowing the Operations & Maintenance crews to focus on resolving problems rather than manually collecting data for offline condition assessment.
With online condition-based data, users receive alarms when problems first arise allowing early detection so that appropriate actions can be taken before problems escalate. Transformer failure can be catastrophic. Knowing the condition of assets allows users to reduce failure rates and unplanned outages.
E3 devices can offer real-time, continuous monitoring, leading to more proactive asset management and reducing the risk of unexpected failures.
C50 Provides Multi-Functional Monitoring
C50 devices often refer to high-end, multi-functional monitoring systems used in critical applications.
When paired with hydrogen sensors, C50 devices can provide extremely precise monitoring capabilities. This combination is particularly useful in high-value, critical infrastructure where reliability and accuracy are paramount.
The Dynamic Ratings C50’s ability to analyze a wide range of data, including hydrogen levels, enables advanced diagnostics. This helps in understanding not just the presence of faults but also their root causes and potential progression.
By leveraging the detailed insights provided by the C50 system along with hydrogen sensor data, utilities can implement predictive maintenance strategies, extending the life of their equipment and reducing downtime.
The Enhancements of Multi-Gas Monitoring
Multi gas monitoring, on the other hand, enhances the ability to detect, diagnose, and manage faults within the transformer, thereby improving reliability and reducing maintenance costs.
Multi gas testing monitors multiple gases such as hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide. Each of these gases can indicate specific types of faults, such as thermal overheating, electrical arcing, or insulation degradation. A Multi gas testing approach provides a detailed understanding of the transformer’s internal condition by analyzing various gases dissolved in the oil, each of which indicates different types of faults and stresses.
Multi gas DGA is a monitor capable of measuring diagnostic gasses saturated in oil in the ppm range, making for more precise measurements. These monitors are available in the following:
- Five-gas: hydrogen, methane, ethane, ethylene, and acetylene.
- Seven-gas: carbon monoxide, carbon dioxide, hydrogen, methane, ethane, ethylene, and acetylene.
- Nine-gas: oxygen, nitrogen, carbon monoxide, carbon dioxide, hydrogen, methane, ethane, ethylene, and acetylene.
Hydrogen, methane, ethane and acetylene are deemed to be the combustible gasses most crucial for thermal diagnostics of a transformer. (Carbon monoxide is also included in the combustible gas but is not related to a thermal value due to fault condition.)
These gasses provide an indication of the severity of a thermal defect due to the approximate thermal energy temperature at which they are produced.
Multi gas monitoring requires that oil be circulated through the monitor to ensure that a fresh
sample is being measured. This is required for the monitor to provide a DGA measurement that is representative of the transformer’s bulk oil.
Multi gas also provides fault recovery monitoring, meaning that during routine outages, transformers can cool down and later be subjected to inrush currents when re-energized. Multi gas testing helps in assessing the impact of these operational cycles by monitoring gas levels before, during, and after outages.
By detecting the presence and concentration of these gases, multi-gas testing provides early warning signs of various fault conditions, allowing for timely intervention before faults escalate, while also reducing overall downtime.
Which is the Right Tool for Your Needs?
Key Gas monitoring offers a cost-effective solution for early fault detection in less critical applications, while Multi Gas monitoring provides detailed diagnostics and is essential for critical transformers and those subject to variable loads.
Dynamic Ratings prides itself on finding the right asset health solution for you.
Tailoring the monitoring approach ensures that each transformer is effectively managed according to its importance and operational context, optimizing reliability and maintenance efficiency. Budgetary limitations can influence the choice of monitoring systems, as well. After all, while comprehensive systems offer extensive data, they are more expensive.
Different monitoring methods provide varying levels of detail and diagnostic capabilities. The choice depends on the precision needed for fault detection and analysis.
While hydrogen monitoring alone does not provide enough detail to perform any advanced analytics, it is very useful in the early detection of incipient faults. This is due to the manner which hydrogen generates when compared to the other hot metal gases.
Key gas monitors have fewer sensors and components because they track a limited number of gases, usually just hydrogen. This simplicity translates to fewer parts that can fail or require calibration.
Simpler set of sensor arrays and monitoring systems overall.
Multi-gas analysis, by contrast, offers a fuller picture of the transformer’s condition, allowing for more accurate fault identification, early detection of potential issues, and informed maintenance planning.
Multi-gas testing is ideal for critical transformers with heavy loading, load fluctuation, and routine outages due to its ability to provide comprehensive fault detection, monitor dynamic conditions, handle thermal and electrical stresses, and support proactive maintenance strategies. This testing approach enhances the reliability, safety, and performance of transformers, ensuring they can withstand the demanding conditions they operate under.
Get In Touch with Our Specialists
Successful asset management means more than just installing a monitor. At Dynamic Ratings, we work within our clients’ supply chain and lead times, learning their online transformer monitoring system inside and out, and we learn how the customer does their work.
And we follow their structure to manage multiple OEMs, creating standardization across new and old equipment.
If you’d like to learn more about DGA and other electrical usage monitoring or condition-based monitoring, get in touch today.
Author: Tyler Willis, Dynamic Ratings