2 June 2020

From insulation expertise to monitoring know-how

Weidmann Electrical Technology is the world’s leader in the global transformer insulation market. With more than 140 years experience developing, manufacturing and delivering state-of-the-art products and services, Weidmann have a unique expertise in the area of insulation, along with a deep-rooted knowledge in the design, development and operation of transformers. Our core product, insulation, is without question a critical element linked directly to the life of a transformer. Monitoring this material is therefore key in determining transformers reliability.

Why is monitoring important? Deterioration in the condition of insulation can lead to the failure of a transformer. The objective of a monitor is to detect a change in the transformer and avoid the risk of failure. By conducting research into the possible reasons why transformers fail, Weidmann is taking steps beyond simple monitoring. Our unique knowledge has allowed us to develop the most accurate monitoring devices available in the market and award us the status of ‘preferred partner’ when working with our customers to overcome challenges.


Weidmann has carried out research into materials for many decades. Areas include cellulose and synthetic fibers, as well as research leading to the development of new materials. The fiber and board laboratory in Rapperswil, Switzerland, is our global technology center, conducting experiments into of different research groups fibers, board and paper. Applying the latest imaging examination technology involving micro x-ray tomography, allows us to visualize and explain the structure of material samples. The knowledge gained from our research is essential in understanding the impact of fiber quality, fiber combinations and process parameters, for example the use of hydraulic pressure and hot press temperature. Weidmann also monitor parameters such as fiber length, fiber orientation, conductivity and the pH of aqueous extract or tensile strength.

With this extensive know-how, Weidmann is regarded as an expert on the parameters that influence the characteristics of cellulose materials and the durability of the insulation.

Close-up of a fiber x-ray
Source: Weidmann Electrical Technology


Weidman have three high voltage laboratories located in Rapperswil, St Johnsbury and Malyn. These laboratories investigate electrical characteristics of the materials under different field conditions. They have the capability to conduct extensive testing on material samples and on models of assembled structures. Furthermore, in collaboration with Universities with high voltage departments (University of Graz in Austria, University of Manchester in United Kingdom and University of Schweinfurt in Germany) material or full-scale structures are tested in different operation modes and conditions. The results and their interpretation, combined with chemical and mechanical tests, are the foundation to understanding the behavior of the material and its limitations in the long-term operation of a transformer.

On a daily basis, Weidmann designers are laying out insulation structures for our customers. They are experts who understand the fabrication and application of insulation components and who are frequently involved in transformer testing on behalf of the utilities.


Over many years, Weidmann have established a broad database of insulation liquids that have been tested, such as mineral oil and ester, and are able to offer a range of diagnostic services. The experience derived from this body of work is a further significant step towards understanding the interaction of liquid and solid insulation. It has allowed us to formulate the necessary algorithms to evaluate transformer conditions in sensors and monitors. These are Weidmann proprietary algorithms.

It is the combined experience of these specialists in their fields of electro technology, paper making, chemistry and mechanical engineering that form the foundation of sensors and monitors.

Find out Weidmann’s monitoring devices portfolio

InsuLogix® B

Bushing relative power and operating voltage monitoring

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InsuLogix® H/M

Key fault gas (hydrogen concentration) and moisture in oil monitoring

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InsuLogix® T

Hot spot winding temperature monitoring and indication

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InsuLogix® RFM

Transformer internal fault detection and indication

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InsuLogix® Vault

Transformer health monitoring and cyber security control

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InsuLogix® SGS

Liquid oil and winding temperature monitoring

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InsuLogix® GIC

Monitoring of the geomagnetic current in the winding

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InsuLogix® DTM

Smart distribution transformer monitoring (pressure, current and temperature)

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