What is the reason for the current transformer blast ?

Current transformer (CT) blasts or failures can occur due to various reasons, but one common cause is overcurrent conditions. When a CT is subjected to currents beyond its rated capacity for an extended period or experiences a sudden surge in current, it can lead to overheating of the windings and insulation breakdown. This overheating can cause the insulation materials to degrade or melt, resulting in internal short circuits or arcing within the CT. Such conditions can escalate rapidly, leading to a catastrophic failure known as a CT blast or explosion. Proper sizing and protection against overcurrent conditions are crucial to prevent CT failures.

CTs can blast due to internal faults such as insulation breakdown, manufacturing defects, or mechanical damage. Insulation breakdown can occur over time due to aging, exposure to moisture or contaminants, or thermal stress from excessive currents. Manufacturing defects like poor winding insulation or improper assembly can weaken the CT’s integrity, making it susceptible to failure under normal operating conditions. Mechanical damage, such as physical impacts or improper handling during installation or maintenance, can also compromise the CT’s structural integrity and lead to internal faults or short circuits.

Several factors contribute to CT failure, including thermal overload, overvoltage conditions, external short circuits, and environmental factors. Thermal overload happens when the CT operates beyond its rated capacity for an extended period, causing excessive heating of the windings and insulation. Overvoltage conditions, such as lightning strikes or voltage transients, can exceed the CT’s insulation withstand capability, leading to insulation breakdown and failure. External short circuits or faults in the connected circuit can impose excessive currents on the CT, causing mechanical stress, overheating, or damage. Environmental factors like moisture ingress, corrosion, and extreme temperatures can also degrade the CT’s components over time, compromising its performance and reliability.

A transformer explosion typically occurs due to internal faults that lead to a rapid buildup of gases and pressure within the transformer tank. One common cause is a fault in the winding insulation, which can result in a short circuit or arcing inside the transformer. This fault generates intense heat and gases, causing the transformer oil to vaporize and expand rapidly. The sudden increase in pressure inside the tank can exceed its design limits, leading to an explosion. Other causes include overloading, which can cause excessive heating and mechanical stress on the transformer’s components, as well as external factors like lightning strikes or equipment failures that induce high currents or voltages into the transformer.

Potential transformer (PT) failures can occur due to similar reasons as CTs, including overvoltage conditions, insulation breakdown, thermal overload, and external faults. Overvoltage conditions, such as lightning strikes or switching transients, can exceed the insulation withstand capability of the PT, leading to insulation failure and internal faults. Thermal overload occurs when the PT operates beyond its rated capacity, causing overheating and degradation of insulation materials. External faults in the connected circuit, such as short circuits or overcurrent conditions, can impose mechanical stress and damage on the PT’s windings and components. Regular maintenance, proper installation, and adequate protection measures are essential to mitigate the risk of PT failures in electrical systems.

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