Dielectric Insulating Fluid
Product Overview

Midel is an environmentally friendly alternative to conventional coolants. Midel meets the classification criteria as "non-water hazardous". (UBA No. 52330, data sheet 770 of the Federal Department of the Environment, Berlin).
Midel is supplied with a low dissolved gas content and moisture level.

Areas of application
MIDEL 7131 transformer fluid has a high Fire Point of 322°C and is therefore classified as a K-class liquid (fire point >300°C according to IEC 61100). This, coupled with a slow heating rate due to its high specific heat and thermal conductivity, gives the product its noted resistance to ignition.

Areas of use include:
- power transformers up to 150kV/ 110 MVA
- pole-type transformers
- distribution transformers in urban areas
- tapchangers
- thyristor cooling in power electronics

Properties
In addition to the properties set out in IEC 61099:1992, MIDEL 7131 is characterized by:

Ecological compatibility
- readily biodegradable (99% after 28 days)
- classified as "non-water hazardous" according to Umwelt Bundes Amt (UBA) in Germany
- low vapor pressure under operating conditions

Low acute and chronic toxicity
- non-toxic to aquatic life
- will not effect the degradation activity of activated sludge in biological sewage treatment plants
- not classified as hazardous.

Good thermal properties
- low thermal coefficient of expansion
- heat transfer properties comparable with mineral oil.

Excellent dielectric properties
- high breakdown strength
- low dependence of dielectric properties on the effects of moisture.

Excellent fire resistance
- high fire point (322°C)
- will not ignite in the event of a major electrical fault and transformer rupture.

MIDEL 7131 is further noted for its very good lubricating properties. MIDEL 7131 is compatible with all insulating materials used in conventional transformer construction.

Retrofilling
MIDEL 7131 is used to retrofill PCB and mineral oil filled transformers. Midel's thermal characteristics, cooling performance and electrical properties are equivalent to those of mineral oil. This ensures that there is no need to make any alterations to the design of the transformer or to downrate it when retrofilling with MIDEL 7131.
During retrofill, contamination with other insulating fluids has to be minimized to avoid lowering the fire point or endangering the “non-water hazardous“ classification.

Disposal
For disposal, it is recommended that used Midel or remains of the insulating fluid be burnt in a suitable installation. Waste disposal code 130309 applies (readily biodegradable insulating and heat transmission oils).

Regulations
Midel is not subject to the regulations for land, sea and air transport. It does not require labeling in accordance with the Dangerous Substances Regulations.

Characterization of type T1 transformer ester according to IEC 61099 and DIN VDE 0375
Physical properties according to IEC 61099
 

Chemical properties according to IEC 61099
 

Dielectrical properties according to IEC 61099
 

Data quoted above are typical values. It is the policy of M&I Materials Ltd to continually improve product quality. The published values above may be altered without notice and do not constitute a specification.