By nature
a fluid with a high fire point must have a minimum fire point of 300 ° e. On
their chemical properties, the dielectric liquids that actually fall into this
category can be classified into three categories. High molecular weight
Hydrocarbons (HMWH) are chemically similar to conventional Transformer Oil
based on minerals. They have higher molecular weight elements, however, and
hence hold even higher fire rates. They have excellent dielectrical and
lubricating properties and fair capacity to pass power. HMWI-based fluids were
used in transformers fitted with load interrupting devices such as load tap
changers (LTC). Specifically, silicone fluids or Polydimethyl Siloxanes (PDMS)
are one of the liquids used to substitute askarel due to their large fire
points. Such fluids exhibit appropriate electrical properties, and their heat
transfer properties are usually satisfactory. They were not extensively used
for applications involving mechanical switches, primarily due to poor lubricity
of the fluid.
Poly01 Esters are substances of organic origin. They have strong dielectric and heat transfer properties but have restricted their usage to specific transformer applications due to their fairly high costs. They usually have strong lubricating properties in several forms of synthetic lubricants and form the key part.
2=> Transformer insulating
oil:
The main duties of transformer
oil are to insulate and refrigerate a transformer. Hence, it must have strong
dielectric power, thermal conductivity, and chemical stability and must
preserve these properties for long times while kept at high temperatures.
The oil-filled tank will have
external radiators, from which the oil circulates through natural convection,
to boost the cooling of massive power transformers. Power transformers with
capacities of thousands of kVA can even have fans for cooling, oil pumps and
even heat exchangers for oil to gas.
Power
transformers experience extended drying cycles using electrical self-heating,
vacuum treatment, or both to insure that the transformer is fully free of water
vapor prior to the release of the insulating material. This helps avoid
under-burden corona development and resulting electrical breakdown.
Oil filled transformers may have a gas
detector relay (Buchholz relay) with a conservator (oil reservoir). Owing to
corona discharge, overheating, or an internal electric arc, these protective
systems sense gas accumulation within the transformer. These devices can trip a
protective circuit breaker to remove power from the transformer on a slow gas
accumulation or rapid pressure increase.
Transformers
without preservatives are usually equipped with sudden pressure relays that
perform a function similar to the Buchholz relay.
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