What are the faults of current transformers？

Common faults in current transformers are primarily categorized into internal and external faults. Core faults can lead to inaccurate metering and protection misoperation, and in severe cases, may even cause equipment burnout or explosion.

1. Internal Failures (Core Risk Points)

Internal faults are often related to the structural design of the transformer body, characterized by strong concealment and significant hazards.

Winding faults: including inter-turn short circuits, phase-to-phase short circuits, or ground short circuits. These are often caused by insulation aging, moisture exposure, or manufacturing defects, leading to transformer heating, increased core losses, and abnormal output current.

Core Fault: Common issues include multi-point grounding, insulation damage, or excessive core loss. These faults can cause localized overheating of the core, severely damaging insulation and subsequently compromising the safety of the windings.

Internal moisture or water ingress: Poor sealing allows moisture to penetrate, which can reduce insulation performance, cause leakage or breakdown incidents, and accelerate corrosion of internal components.

II. External Faults (Easy to Diagnose)

External faults are mostly related to connections and accessories, making them relatively easy to detect and address.

Secondary circuit faults: These include secondary side open circuits, loose connections, or poor contact. Among these, secondary side open circuits are high-risk faults that can generate extremely high induced voltages, endangering both personnel and equipment safety while also causing the transformer core to overheat.

Ceramic bushing failure: Cracks, dirt, or flashovers in the ceramic bushing. Dirt can cause surface discharge, while cracks may lead to internal water ingress. Both can compromise insulation, resulting in grounding or short circuits.

Oil leakage (oil-immersed transformers): Aging of the tank sealing components causes oil leakage, which may lead to a drop in oil level, reduced insulation performance, and potential oxidation and corrosion of internal components.

To promptly detect faults, regular inspections of the oil level, insulation testing, and secondary circuit continuity tests for current transformers are required