9 June 2020

Discover the InsuLogix® T: Weidmann’s solution to transformer winding hot spot temperature monitoring

Many factors influence the overall aging process of a transformer and if not checked regularly, some can lead to major failures. The objective of a monitoring device is to minimize this risk of failure. On average, a monitoring device reduces the annual cost of failure rate1 by half as the transformer is managed with greater efficiency, resulting in significant savings by avoiding unnecessary maintenance or premature replacement costs (See previous article: On-line monitoring solutions to detect potential transformer failures).
Transformer monitors alert operators and control centers in the event of an unusual change, allowing the necessary action(s) to be taken at an early stage and ensuring the continuous reliability of the transformer.

InsuLogix® T: transformer winding temperature monitoring by Weidmann Electrical

The InsuLogix® T provides monitoring capabilities which directly reduce the risk of transformer failure. It offers reliable fiber optic hot spot temperature monitoring, with the option to measure up to sixteen temperatures. Once installed, the InsuLogix® T continuously monitors winding temperatures, with no action required by the operators.


Glass fiber optic: safe and reliable

Designed, manufactured and tested in Dresden, Germany, our state-of-the-art monitoring system uses 200 μm (microns) PTFE coated fiberglass cables (2), allowing real-time and interference-free data transmission about the temperatures inside the transformer tank, specifically in the transformer windings. Installed inside the transformer tank, the fiber optic cables can withstand temperatures from -200°C to +300°C and are designed to exceed the lifetime of the transformer. The fiber optic-insulation component (Smart Spacer™) represents the safest, most technologically advanced solution existing in the market today.

State-of-the-art temperature sensors

The sensors of the InsuLogix® T are produced by Weidmann Technologies Deutschland GMBH, a world leading company in temperature measurement solutions owned by Weidmann Group.

The temperature probes are assembled in-house and consist of glass fiber and Gallium Arsenide (GaAs) crystal at the sensor tip. With the feed-through connector at the opposite end, the fiber optic probe is immune to RFI, EMI, NMR and microwave radiation. The fiber optic probes are also resistant to the transformer testing process conducted by the OEM, as well as to liquids, oil additives and other elements found in oil during the operation of the transformer.

Monitoring process: data collection and transmission

The InsuLogix® T utilizes the latest high-performance processor that increases power and stability to ensure maximum percentage uptime of the device. The monitor runs continuously and is configurable with one alarm relay per channel. All data collected is stored directly in the internal memory of the monitor and accessible on demand by connecting to the device.

Communication capabilities and integration with SCADA (3)

The InsuLogix® T features a comprehensive communication functionality required by transformer operators and is supplied with RS485 and Ethernet ports.

Communication protocols available are: Modbus, DNP3, IEC 61850 and IEC 60870-104.

The configuration software allows operators to define alarm logic schemes by combining temperature thresholds using and/or, in addition to mapping the output to specific relays.
The large 7“ TFT display allows direct access to the monitor configuration and real-time monitoring data. Compared to classic LCD displays, TFT provides a brighter display and sharper contrast to help avoid reading errors. The response and refreshing times are the best in the industry. Three LEDs are available on the front panel of the device to provide information on the operation of the monitoring system.

Data sheets



o Robust and reliable industrial design

o No drift and no re-calibration required

o 2 to 16 measuring channels

o Measuring range: [-200°C to +300°C]

o High accuracy : +/- 0.2°C

o Short response time:2s

o Large 7” TFT display and status LED

o Data recording in internal memory

o 4-20mA analog outputs (up to 8 channels)

o 4 programmable control relays

o Built-in USB interface

o RS485-Modbus RTU or Ethernet-Modbus TCP option

o Includes FOTEMP-ASSISTANT data logging software


o Provides assistance in transformer design and rating verification

o Safely maximizes loading and overloading

o Reduces overall physical stress on winding

o Prevents premature failure

o Prevents outages and catastrophic failures


o Better knowledge of operational condition assessment, load planning and asset management

o Reduces inspection and maintenance costs

o Reduces failure-related repair or replacement costs

o Improves real-time transformer loading capability

o Defers upgrade capital costs due to load growth

o Defers replacement capital costs due to equipment age or condition


About Weidmann Technologies Deutschland (WTD) GMBH: a member of the Weidmann Group of companies and headquartered in Dresden, Germany, WTD delivers high quality, innovative products and service solutions that meet the requirements of a diverse global customer base. In 2018, the company acquired Optocon AG, a leading developer of fiber optic temperature measurement solutions for over 25 years. With core knowledge in the design, development and manufacturing of complete systems, WTD is a leading provider of both ‘off-the-shelf’ and customized temperature measuring solutions.


(1) Annual cost of failure rate = failure rate x cost of transformer replacement.

(2) The fibers are available in 200 or 65.8 microns only. The 200 micron has the advantage of being less sensitive to breakage, therefore reducing the replacement cost.

(3) SCADA: supervisory control and data acquisition.