Transformers are being monitored for humidity using moisture sensors to detect when atmospheric ingress is degrading insulation.
Vaisala is working alongside DryKeep to enhance the moisture monitoring capabilities of its transformer dry-out system, through the installation of Vaisala’s HUMICAP MMT162 sensor. The partnership comes as DryKeep aims to meet increasing demand for installation of its transformer monitoring display systems across the USA.
The MMT162 is a capacitive thin-film polymer sensor, developed by Vaisala to provide moisture measurements in liquid hydrocarbons, including those used to insulate transformers. As DryKeep ramps up production of its SMART controller, which displays real-time moisture and temperature values for transformers, Vaisala will supply its MMT162 sensor as required on a project basis.
“Transformer technology is frequently being pushed to the limits in terms of how long it is expected to perform, and there is a greater need for up-to-the-minute information in order to meet this demand,” said Steven Jiroutek, Business Development Manager at Vaisala.
“Equipping DryKeep’s controller with our MMT162 sensor will allow it to accurately monitor moisture levels within transformers, and clearly communicate this information to site engineers and maintenance personnel – reducing the need for costly manual interventions.”
As load demands on aging substation power transformers increase worldwide, preventing catastrophic faults and breakdowns has become a key concern of asset owners and operators. Any disruption to transformers’ continuing performance can result in significant financial losses for asset owners, and one of the most persistent causes of such disruption is the presence of moisture in transformers.
The threat of moisture and its ability to take a power transformer offline lies in its ability to deteriorate the mechanical properties of the paper insulation and the dielectric properties of transformer’s insulation system. This threat exists regardless of how harsh or benign the regional climate is. Atmospheric conditions allow moisture to enter or it can seep in during transformer maintenance. Unfortunately, moisture is also a byproduct of aging transformer oil and insulation, ensuring that, even if the equipment is completely sealed from external sources, internal build-up of moisture will still occur.
Another important factor is the effect moisture has on the speed of degradation, as moisture increases the insulating materials degrade faster, producing yet more moisture, and setting up a vicious cycle of accelerating damage.
Assessing moisture levels has traditionally been a manual process, involving laboratory analysis of oil samples extracted by engineers. However, the DryKeep system allows continuous monitoring of moisture and temperature levels via a 7-inch, touch-operated LCD screen attached to the transformer itself.
By using Vaisala’s MMT162 sensors and proprietary algorithms, the DryKeep system calculates the percentage of moisture in the insulation paper before removing it. Vaisala has been providing this technology to DryKeep since 2013, upgrading the functionality to ensure high-quality, continuous moisture monitoring.
“The old way of doing things was good for the time because that’s all that was available, but by using reactive strategies they were not necessarily dealing with the actual problem,” said Ed Vance, Director at DryKeep. “They were fixing it temporarily, until the next time the moisture built up, and all the while the mechanical properties of the paper were deteriorating fast.
“The MMT162 sensor allows us to control the drying process and send historical data and trend analysis to the operator – and this can all be done without shutting down the transformer.”
The next opportunity to learn more about the MMT162, and Vaisala’s wider power industry offering will be at CIRED, the biannual international conference and exhibition for the electricity distribution community. This year’s event takes place in Glasgow, from 12-15 June, where Pasi Iisakkala, Product Area Manager at Vaisala, will be in attendance.