How the application of a 19th century curiosity brought DGA monitoring to the very edge of science and engineering today.

In 2003, the world’s first Dissolved Gas Analysis (DGA) transformer monitor based on Photo-Acoustic Spectroscopy technology (PAS) was installed in the United States.

Monitoring DGA within the transformer using PAS technologies was developed by a small group of engineers and scientists from Northern Ireland and Denmark. This revolutionary development was based on research from the 1980s on the photo-acoustic effect, a concept discovered by Alexander Graham Bell in the 19th Century. It was and still is today a game changer, bringing lab science to the field, removing the need for consumables and maintenance.

Continuous innovation, backed by years of science and industry expertise, led the very same group of people to develop the Camlin DGA monitoring system known worldwide today as TOTUS.

DGA: The Cornerstone of Transformer Diagnostics

Dissolved Gas Analysis (DGA) has been used to test for abnormal conditions in power transformers for well over 50 years. It is the “blood-test” of transformers and highlights the current condition of a transformer and if any further investigation is needed. Back in its infancy, DGA in transformers was limited to an offline laboratory environment due to its complexity. Specialist equipment was needed to extract and measure the gases taken from oil samples, which were often in exceptionally low quantities, as little as one part-per-million.

Gas Chromatography (GC) was an advancement on lab tests, removing the gases from the oil and injecting them into a gas chromatograph. Whilst being a very effective technology for monitoring DGA the approach is vulnerable to inconsistencies. GC systems are extremely sensitive and require expertise to function properly, with daily calibration to certified gas standards needed and a consumable carrier gas is required for operation. In carefully controlled laboratory environments GC testing can be very effective, although consistency remains difficult to achieve. But overall, GC gained acceptance as DGA became the mainstay of transformer monitoring.

Spectroscopy

Whilst spectroscopy in simple terms is about the absorption of light, there is much more to it. Different gases will absorb different wavelengths in the infra-red spectrum: for example methane gas will absorb wavelength A whereas acetylene absorbs wavelength B.

Think about it in this scenario: if you were to take a balloon that was filled with methane and you were to illuminate it with only wavelength B, you would get no signal. However, if your balloon was filled with a 50 / 50 mixture of methane and acetylene and you were to illuminate it with wavelength B you would only be able to ‘see / hear’ the acetylene.
Applying this understanding, if you know the correct wavelengths to a collection of gases you can then split up any mixture of gases and measure each separately. Other notable scientists did explore this concept but due to the lack of sensitive microphone technology, the analytical technique could not be used to measure the sound intensity reliably.

The Evolution of Photo Acoustic Spectroscopy:

1960 - 1980: The Early Days

Until the 1960s PAS was limited purely to R&D applications. The first commercially available PAS based detector was introduced by Bruel and Kjaer (B&K), launched to detect toxic and polluting gases in the air.

Despite the vast array of available techniques, infrared was preferred. Other spectroscopic methods could qualitatively and quantitatively measure the amount of light absorbed by a material. Where PAS differed was its fast response time, its enhanced sensitivity and vastly improved level of accuracy. There was also a benefit from reduced maintenance costs since no expendable materials were used.

1980 - 2000 PAS Goes into Space

Between 1980 and the early 2000s, a group of talented engineers and scientists who had worked at B&K continued their investigations in the field of photo acoustics. The team were able to take the basics of the PAS technique and apply their innovative design and electronic ingenuity to engineer a highly accurate system/instrument. Their first PAS-based system was used to measure the cardiac efficiency of astronauts on the International Space Station, by analysing their breath as they pedalled an exercise bike.

Celebrating 20 Years As The Pinnacle Of DGA Analysis

Prior to 2003, Photoacoustic Spectroscopy was completely unknown in our industry. The development team, subsequently the core team at Camlin Energy today, pioneered and championed this new industry-leading standard for DGA. Whilst many in the industry continued using gas chromatography for DGA analysis, Camlin continued to look to the future.

Today, 20 years on, monitoring products conducting DGA with PAS technology account for more than half of the world market. All the main DGA monitoring suppliers have tried to move to infrared-based technology, most of them successfully, due to significantly lower maintenance costs without affecting accuracy.

For the last 10 years, Camlin’s combined knowledge and experience of 20 years of research have been embodied in the TOTUS Transformer Monitor.

Now, when you look at a TOTUS in the field, or look up as the ISS slowly crosses the night sky, you can appreciate how Camlin brought a 19th century curiosity to the very edge of science and engineering.

To find out more about the TOTUS Transformer Monitor, click here or complete the Contact Us form below.