Problem Solving - oil level low fault alarm
Fault Description
The customer reported that the transformer triggered an oil level low fault alarm.
Site Assessment and Performance Summary
1. The 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 Assessment and Performance Summary - Continue
4. 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.
Site Assessment and Performance Summary - Continue
5. Following consultation with the transformer manufacturer, it was determined that the transformer should be replaced.
• Our team performed a full transformer replacement.
• All associated instrumentation was reconnected and verified for correct operation.
• Final electrical acceptance testing was conducted in accordance with NETA standards to validate the integrity of the replacement unit.
