One of the benefits of dry-type transformers is the limited maintenance they need, which means considerable savings on costs and time for owners. Dry-type transformers also offer reliable performance over lengthy lifespans, with few of the risks and hazards associated with oil cooled transformers.
One of the benefits of dry-type transformers is that they need only limited maintenance.
David Claassen, Managing Director of dry-type transformer specialist Trafo Power Solutions, explains that because the units are air cooled, much of the limited servicing required relates to maintaining clear air channels, which can be compromised by the accumulation of dust layers.
“To allow for the transformer to cool effectively, it is important to check regularly that there is not an excessive build-up of dust on or around it. Depending on the ambient conditions, dust can build up in these confined spaces and start to impede the free flow of air.”
An accumulation of dust can be easily cleared using a leaf blower or similar appliance to remove the dust from the transformer. This method quickly disperses the dust, leaving the surfaces clean and allowing for more efficient heat transfer.
He highlights that a regular maintenance schedule is especially important in applications such as coal mines, where there are often high dust levels. Where dust layers prevent adequate cooling, the transformer could run at temperatures higher than its design parameters. This, in turn, degrades the insulation material faster and could significantly reduce the unit’s lifespan. Even where a completely sealed enclosure is used (≥ IP55), dust can enter the enclosure when the doors are opened, or if the doors are left open accidently.
“It is also important to check that the temperature probes are measuring accurately,” Claassen notes. “This, of course, ensures that any unexpected rise in temperature will trigger an alarm, and that the feed-in circuit breaker to the transformer is tripped in the event of overheating.”
Terminals on the transformer should also be checked, as it is possible for these connections to loosen over time due to vibrations or other factors. This is a simple process of checking the torque on the connection points, as any looseness could lead to partial discharge, heat build-up and further damage.
To guide the customer in maintenance planning, Trafo Power Solutions provides a maintenance manual with each installation. This details the required frequency of service interventions, which in a clean indoor environment is usually only once a year. Under dusty conditions that might be encountered outdoors, the maintenance should normally be conducted every six months.
“Beyond our standard requirements, we also provide our customers with site-specific servicing guidelines that suit the application and environment,” says Claassen. “We can provide the maintenance service too, should the customer require this, ensuring they have access to a detailed log of the maintenance results and recommended interventions.”
He explains that, although the maintenance tasks are generally straightforward, the transformer does need to be de-energised by a qualified technician before the work is conducted. This ensures compliance to regulations relating to medium voltage equipment, including procedures for lock-out and isolation.
“A key advantage of dry-type transformers is that the maintenance procedures are relatively quick and simple compared to those required for oil cooled transformers,” he says. “One difference in the servicing of these two technologies is that conventional oil cooled transformers require oil samples to be taken regularly and sent away for testing and analysis. This is a costly and time-consuming addition to the total cost of ownership.”
For more information visit: www.trafo.co.za
