These types of transformers have an oil storage system that prevents the insulation oil from coming into contact with oxygen and moisture, which are the main causes of oil corruption and reduced electrical resistance.This will improve the operating conditions so there will be no need for maintenance during the life of the transformer. Hermetic transformers for installation in humid environments, cases where there are limited maintenance operations, transformers with aerial installation and limited spaces such as compact substations and packages are superior to conventional types.Hermetic three-phase oil-filled transformers have a distribution range of 25 to 5000 kW amps and a maximum system voltage of up to 36 kW.
Two main types of hermetic transformers:
1. Hermetic without gas cushion
Which has a closed structure, without gas cushion, completely full of oil, is a resilient promenade.
2. Hermetic with gas cushion
It has a closed structure without expansion source, with gas cushion (nitrogen gas), rigid tank walls and cooling radiators that can be detached or welded on the tank.
In completely oil-filled hermetic transformers, the expansion and contraction of the oil is done by its steel and elastic tank (tank design with variable volume), which creates only a fraction of the designed pressure tolerable at the maximum operating pressure.These transformers are always fully delivered and shipped full of oil and are sealed for life. In gas-cushioned hermetic transformers, the expansion and contraction of the oil is done by a nitrogen gas cushion located above the oil surface.These transformers generally have a rigid radiator tank (welded or expandable) and their LV, HV bushings are located on the longitudinal side of the tank. Ensure oil, especially in oil bushings.
Special hermetic equipment:
– Facade oil
– Hermetic protection relay
– Pressure breaker
– Indicator of pressure and vacuum
– Sudden pressure relay
– Gas injection valve
– Multi function relays
DMCR, DGPT2
Available brands:
IRAN TRANSFO-ABB- TAMINI ITALY- MR GERMANY – MESSKO GERMANY