Case Study: Low Oil Level Fault Alarm

Fault Description

The transformer issued a low oil level fault alarm, prompting the customer to contact VE Power for help.

Fault Analysis

1. Our field technicians were dispatched to the site to investigate.
• The oil level gauge was confirmed to be functioning properly, and no evidence of oil leakage was observed.

2. During the fault event, the feeder protection relay also indicated a ground fault, suggesting the transformer may have experienced an internal fault to ground.

3. A Dissolved Gas Analysis (DGA) was performed, and results showed elevated gas levels, consistent with internal electrical faults.

Site Activities & Findings:

Electrical diagnostic testing was conducted, including:

• Winding Resistance Test (WRT)
• Transformer Turns Ratio (TTR)
• Polarization Index (PI)

The test results indicated that the H1–H3 winding was exhibiting a ground fault condition.

Recommendations & Coordination

Following consultation with the transformer manufacturer, it was determined that the transformer should be replaced.

Corrective Actions Taken:

  • Our team performed a full transformer replacement.
  • We reconnected all instrumentation and verified proper operation.
  • Final electrical acceptance testing was completed per NETA standards to confirm the replacement unit’s integrity.