Most widely used for monitoring green energy resources around the world for more than 80 years



Moisture is one of the dominant factors that limit the lifetime of a power transformer. For effective transformer lifetime management, the moisture content of the insulation system, cellulose, and oil should be kept at a low level.

Moisture and heat provide an optimal environment for various compounds in the oil – such as acids and metal ions – to react with the cellulose molecules and break them down. This is important as when the water content in the paper doubles, it can cut the remaining life of the transformer in half.

Online monitoring gives a true and real-time picture of the moisture levels in all operating conditions. Online monitoring provides the operator with valuable information on oil moisture, enabling further analysis such as evaluation of the risk of moisture saturation and decreased dielectric strength, as well as input data for paper moisture evaluation. Online monitoring allows the operator to detect evolving moisture-related risks and other early signs of faults – and react appropriately


The Vaisala MMT330 Moisture and Temperature Transmitter measures transformer oil moisture online, providing an accurate real-time picture of the transformer’s condition. The transmitter monitors moisture levels in all ambient and operating conditions, and is compatible with all types of insulating oil. Installation is easy, and the device can be directly connected to the substation data collection system. Read more in the datasheet below…



The Vaisala MM70 Hand-held Moisture and Temperature Meter is a lightweight meter for spot checks to identify transformers with moisture issues. Because the probe can be inserted directly into the process through a ball valve, there’s no need to drain the oil or shut down the transformer. Read more in the datasheet below...

VAISALA Indigo 520

The Vaisala Indigo 520 transmitter with dual-probe and multi-parameter support is a host device for Vaisala Indigo-compatible, stand-alone smart probes. The transmitter offers many additional features to the Indigo probes. The Indigo-compatible smart probes include humidity probes (HMP3HMP4HMP5, HMP7HMP8 and HMP9), dew point probes (DMP5DMP6DMP7 and DMP8),  carbon dioxide probes (GMP251 and GMP252), moisture in oil probe (MMP8), temperature probe (TMP1), and vaporized hydrogen peroxide probes (HPP270). The Indigo 520 is also compatible with MHT410 Moisture, Hydrogen and Temperature Transmitter for power transformer online monitoring

The Indigo 520 transmitter can accommodate up to two probes simultaneously. The plug-and-play probes are easy to install and remove for calibration. Read more in the link below…