Improper Workmanship

Apart from poor design, sub-standard execution of a good design also becomes a purpose for transformer failure. We now Shorty elaborates some such reasons.

• Improper alignment of HV windings: While a transformer is loaded, the primary and secondary ampere-turns act in magnetic opposition but are in full alignment along with respect to the core and coils. While current flows by the coils, magnetic field is set up around them that have a related magnetic flux. Even a little error in the alignment of either coil, i.e., an asymmetrical ampere-turn balancing, leads to production of cross magnetic fluxes. This output in lower impedance and thus mechanical failure of the coils.

• Improper clamping arrangement: Inadequate clamping arrangements of the HV coils lead to vibrations and movement of the coils during short circuit conditions resulting in failure of HV Coils.

• Improper connections: In several cases, the connecting delta leads to the bushing are not properly supported on the framework, resulting in breakage during trans-shipment or at the time of the first charge of transformer. Therefore, improper soldering of leads will give output in open circuit even at general full load conditions. Also, such transformers might fail although encountering the first fault or after a few faults.

• Inadequate tightening of core: Even along with proper fuse protection on the HV side, inadequate tightening will give output in failure of transformer because of collapse of the windings. The transformer could fail because of this fault even under minor fault condition in the LT distribution due to mechanical vibration within the core and windings.