A new era of maintenance-free, smart security maintenance for Takaoka Toko
Real-time diagnosis of transformer aging through online monitoring
Many developed countries are currently facing aging transformers. In Japan, over 40% of the approx. 16,000 transformers in operation were installed over 30 years ago. As the risk of transformer failure increases with age, there is a growing demand for monitoring and maintenance to prevent serious incidents from occurring due to failure. There are high expectations for the development of sophisticated diagnostic technology.
Conventionally, a manually collected sample of the insulating oil must be analyzed to check for the presence and amount of signature fault gases. However, this sort of manual sampling and analysis is understandably burdensome. Even worse, faults and issues can arise and develop during the periods when no sample testing is conducted.
Transformer aging and maintenance issues
Takaoka Toko Group, a leading electrical infrastructure company, has found a solution to the challenge of safe and efficient monitoring of aging transformers.
Its Power Equipment Division manufactures transformers, switchgear, and other power generation, transmission and distribution equipment. In recent years, the company has seized the opportunity presented by changes in the energy market to develop its technologies coupled with the range of emerging digital solutions now coming to market — known as digital transformation or DX.
The company has installed the Vaisala OPT100 Optimus™ DGA Monitor in its transformers and is conducting tests at several end-user sites.
Maximizing value for users
In order to reduce transformer technicians' maintenance burden and to ensure more stable operation, Takaoka Toko focused on automatically monitoring moisture changes in their transformers’ insulating oil as an alternative to manual sampling.
Water accelerates the deterioration of insulation paper. In addition, there is continuous moisture exchange between insulation paper and oil. Their theory was that if the oil temperature and the moisture content in the oil could continuously and accurately be measured, the degree of the insulation paper’s deterioration could be estimated.
"We understood from technical reports and engineers at other companies that Vaisala's sensors are highly regarded for their performance. We first focused our attention on the Moisture, Hydrogen and Temperature Transmitter MHT410, which incorporates the sensing functions necessary for the diagnostics we wanted to achieve," explains Mr. Kurihara, from the Technical Development Center, Strategic Technology Institute, of Takaoka Toko Co., Ltd.
His colleague, Mr. Idei continues, "The MHT410 moisture sensor performed very well, regarding both the detection of trace amounts of moisture and the tracking of moisture changes.”.
Online monitoring detects faults as they happen
The OPT100's accuracy and measurement consistency demonstrated the advantages of replacing conventional offline gas and transformer fault diagnosis with real-time online monitoring. The OPT100 supports constant measurement from the moment it is connected to the transformer's insulating oil line. Key data can be gathered and analyzed continuously over time so that changes in transformer conditions – including serious faults and other abnormalities – can be detected immediately.
"With conventional offline methods, transformer maintenance is performed only once every few years or so, and the condition of the equipment can be diagnosed only at that time. Early recognition of emerging value changes – as soon as abnormal values are detected – can help extend older transformers' lifetime. By using always-on sensors to monitor their condition, we can make more appropriate suggestions regarding when they should be replaced.", Mr. Idei explains.
The technology behind the OPT100
The OPT100 uses a vacuum extraction method for more complete gas separation, which increases measurement reliability even when the pressure of the total dissolved gases in the transformer’s insulating oil is very low.
The OPT100’s high-vacuum gas extraction method works for all fault gases, resulting in more accurate and reliable measurements. Another advantage over the fixed optical filters used in conventional DGA devices, the tunable filters in the OPT100 extend the infrared (IR) scanning range. When data for the final gas analysis can be collected using a wider range of IR wavelengths, it gives a more accurate measurement of the gas concentrations.
"The method the OPT100 uses to measure dissolved gases is suitable for permanent installation because it accurately captures changes in the amounts of gases. And its results are consistent with those of offline dissolved gas analysis. The method is particularly impressive in its ability to detect trace amounts of acetylene. Acetylene is produced when internal discharge is abnormal, so it is an item that should be detected in as small a quantity as possible. We were very surprised that an online monitor could perform detection with such high accuracy."
Mr. Kurihara explains: "Manufacturing companies usually have a high demand for electricity, making it problematic to shut down plant operations. Maintenance personnel are understandably concerned about the risk of any outages at their facilities. For this reason, we have received many requests to install an online monitoring device like the OPT100 on our own transformers."
A new era of maintenance-free "smart security maintenance"
In the three years since installation testing began, Takaoka Toko has continued to accumulate operational data and knowledge regarding the Vaisala OPT100. What is already clear is that remote monitoring of power transformers will increasingly become the standard for safety and efficiency in the industry.
Analysis of accumulated data in conjunction with AI will improve accuracy and expand its use even further. This will lead to the realization of many benefits, including a reduction in maintenance workload and costs, the proper operation of equipment, checks performed remotely in the cloud, and AI integration. Ultimately, this will contribute to the more efficient operation of power substations and their long-term stability.
Mr. Kurihara explains the positive impact on costs: "Improved and more efficient maintenance directly leads to more stable operation and lower operating costs for our customers' equipment. In addition, with the growing focus on condition-based maintenance (CBM) of facilities using advanced sensing combined with IoT, we are confident that this type of solution will be increasingly adopted for electric power facilities."
"Since the OPT100 circulates the oil, it can also be connected to older transformers that do not have a mounting port in the oil-flow area," he continues.
"Transformers are usually quite trouble-free and have a long lifespan, which demands extreme stability from the sensors. The maintenance-free nature of the OPT100 is very much appreciated. Traditionally, transformer maintenance and operation have required a lot of labor, so it is important to contribute significantly to efficiency without reducing the quality of maintenance. In addition, despite frequent transportation and re-installation of the equipment, it has operated stably. We trust it to keep doing so," Mr. Kurihara concludes.
