When we talk about the aging of a high voltage machine, we are talking about the deterioration cycle of the insulating material. Basically 2 factors are the main agents that lead to this deterioration. The temperature and the partial discharges that act simultaneously over time and that destroy the covalent bonds of the insulating polymers. The loss of this material changes their dielectric properties.

In the insulating system of the coils we have the deterioration of the main phase x internal ground wall and the contact surfaces between coil x core or between coils of different phases in the region we call. The internal discharges are monitored through specific equipment, mainly measuring partial discharges. Surface discharges, on the other hand, can be monitored by equipment or also through visual inspections.

The coils, when manufactured, with the objective of avoiding these surface discharges, have a corona suppressor system in the grooves and in their exit region. The material applied in the groove is conductive and in the output a semi-conductive with specific characteristics that soften the rapid rise of the electric field when there is a loss of reference to ground. These 2 materials (conductive and semi-conductive) are electrically connected, a region called the corona sleeve.

Over time of operation and during routine maintenance it is a practice, when visually observing the appearance of corona in these regions, to correct these points of the corona suppressor system.

The tip and warning we want to leave is that this action must be done with great care, because it seems that it is only a dark “paint job” and only its repainting does not guarantee the success of the operation, on the contrary, it may even make it worse. As we have already pointed out, its function is electrical, and the premises of smoothing the electric field must be maintained to achieve the goal of avoiding discharges in this region.

Contact our team and clarify your doubts about corona suppressor system and make an evaluation of your case with us.