New LFT Insulation Offers Increased Overload, Reduced Size

3M introduces Liquid-Filled Transformer insulation offering thermal stability.

3M recently introduced their new Liquid-Filled Transformer Insulation (LFT insulation), designed to offer thermal stability, low moisture absorption, high thermal conductivity and long-term reliability.

The new LFT insulation combined with high-temperature insulation liquids and components will meet new standards for liquid-immersed power transformers, such as IEEE C57.154 and IEC 60076-14. It can also help to reduce the transformer’s size.

For example, a transformer coil design optimized for a higher thermal class with LFT insulation can be made using less conductor, less liquid and a smaller tank, and can potentially cost less overall.


Thermal Stability

In long-term thermal aging tests conducted in accordance with IEEE C57.100-2011 Annex A and B, LFT insulation has been assigned a 155 degrees Celsius Thermal Class rating in mineral oil — 35 degrees Celsius (95 degrees Fahrenheit) higher than thermally upgraded kraft insulation.

Low Moisture Absorption

LFT insulation typically achieves 1 percent moisture content by weight at 50 percent relative humidity, and less than 5 percent moisture content at 95 percent relative humidity. This can be up to seven times less than thermally upgraded kraft insulation.

This can reduce manufacturing energy costs, as the reduced moisture content of LFT insulation means less energy is required to dry transformer coils.

Higher Thermal Conductivity

LFT insulation provides higher thermal conductivity almost 10 percent greater than conventional cellulose insulation, which increases heat dissipation and may reduce coil hot spot temperatures.

Sustainability Requirements

LFT insulation can help transformer designers meet sustainability requirements with less environmental impact. Increasing thermal class and thermal conductivity means transformers can be designed smaller, with less material and lower subsequent lifecycle waste. LFT insulation is RoHS and REACH compliant.

Long-Term Reliability

LFT insulation resists degradation from exposure to moisture from water ingress, increasing long-term reliability. This is a key concern for liquid-filled transformers that must meet lifetime requirements of most global electrical utilities.

For more information, visit 3M’s LFT insulation page here.