Oil Filtration, Online/Offline
Protech PAS has several sizes of filtration machines, with a maximum of 6,000 litres per hour, and can be supplied with their own generator for remote location or where the transformer to be filtered is off-line and there is not an alternative power supply.
Oil filtration is critical to achieve the expected service life of a transformer.
Moisture kills years off the life of a transformer, creating lower dielectric strength, the formation of acid and the degradation of the cellular properties of the paper insulation.
Gas levels can become elevated above recommended limits due to factors such as internal faults and low oil level. Some gases are explosive and in sufficient concentrations can lead to catastrophic failure of the transformer.
Regular oil testing and trending of the results will give indicative levels of moisture and gas levels. This allows for timely maintenance outages to be scheduled, so that hot oil under vacuum filtering can be included in the maintenance works, allowing for the removal of excess moisture and gas to very low levels.
Filtering can be done on-line or off-line, depending on operational constraints. Off-line is the normal practice, where the oil filtration machine is connected to the Main Tank and the oil is circulated via top and bottom valves for several times the total volume of oil in the transformer. On-Line filtration is possible; however, steps must be taken to reduce the possibility that the transformer will trip off due to a disturbance via the Buckholz relay or the sudden pressure Qualitrol relay or another protective/monitoring device. The oil hose connections go into the Conservator Tank and out of the bottom valve. Usually On-Line filtering is conducted at a lower volume of litres per hour.
When filtering insulating oil, Protech PAS uses a Vokes Stream-Line C Range mobile oil filter which is capable of filtering 6000 litres of oil per hour.
The Vokes Stream-Line C Range utilises a high efficiency (98.7%@1µm) disposable Vokes Microfine filter cartridge, which has been specially developed for use with insulating fluids.
The C Range of plants are up to 30% more energy efficient than their SL equivalents, and still returns performance synonymous with the Stream-Line name – water contamination reduction from 50ppm to 5ppm, dissolved gases from 10% to 0.25% by volume all in a single pass.
The Vokes Stream-Line C Range is a compact, high efficiency, comprehensive solution for treating insulating fluid.