If you work with substation transformers, then it is your responsibility to ensure adequate maintenance of the devices. It is because progressive internal faults contribute, to a large extent, to unscheduled power interruptions and associated costly repairs. However, since substation transformers are exposed to external stresses, it can be challenging to pinpoint the exact causes of internal faults. Therefore, electrical engineers are forced to conduct lengthy tests to determine the cause of malfunctions in a substation transformer. Consequently, the professionals end up spending more time doing costly operational procedures. This article provides insight into the most difficult-to-detect substation transformer faults.
Faults in the Turns -- One of the most frequent but challenging transformer faults to detect occur between medium voltage turns. According to electrical engineers, failures occurring between a transformer's turns are primarily caused by thermal stresses. Consequently, it leads to slow deterioration of the insulation around the conductor. During the preliminary stages of the fault, a slight increase in the primary current occurs, which, unfortunately, is difficult to detect. Over time, the gradual increase in primary current causes a short circuit on the transformer turns and leads to the rapid deterioration of adjacent turns. The low primary current resulting from faults between transformer turns make it difficult to detect, primarily if you rely on monitoring the supply current. Nonetheless, monitoring of gaseous emissions in substation transformers is the most effective protective measure for this type of defect.
Faults in the Windings -- Unlike failures that occur between turns, those that occur on transformer windings are rare and often cause high currents. In turn, it leads to short-circuiting on the network, and this can cause devastating damage to a substation transformer. It is crucial to note that most faults in the windings affect medium-voltage (MV) windings. It is because the proximity of low-voltage (LV) windings to the magnetic transformer core provide a shield against damage. However, if there are multiple LV windings on a single magnetic core, then the chances of faults increase. As a result, the progression of damage to the substation transformer is fast.
Faults to Earthing Supply Network -- The type of failure is mostly attributed to overvoltage, which causes breakage in the insulation of the earthing. However, the fault can also result from mechanical defects and well as the slow progression of an electrical error. It becomes a challenge to detect transformer earthing faults if the supply network earthing arrangement is inadequate or improper. Besides, if the failure occurs outside of the earthing arrangement, then it will go undetected and eventually cause significant damage to the transformer.
Use these tips to keep transformers working well, and if you do find any of these faults, consult with a technician who repairs transformers.