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Internal inspection of transformer should be done at________
Every 6 months
Every 1 yr
Every 5 yrs
Every 3 months
Every 5 yrs
Internal inspection of a transformer involves opening the tank to check the condition of windings, insulation, core clamping, and connections. This procedure is generally recommended once every 5 years to ensure long-term reliability and assess the ageing of internal components.
Internal inspection of a transformer involves opening the tank to check the condition of windings, insulation, core clamping, and connections. This procedure is generally recommended once every 5 years to ensure long-term reliability and assess the ageing of internal components.
MaintenanceIntervalтИЭOperatingSeverity1тАЛ
PlossтАЛтЙИI2R тАФ monitoring internal connections helps minimize losses caused by high-resistance joints
The internal inspection is a preventive maintenance activity. It requires the transformer to be de-energized, drained of oil, and properly ventilated. This allows engineers to detect loose connections, signs of overheating (carbonization), insulation degradation, or sludge accumulation that cannot be diagnosed through external or oil-based analysis alone.
Internal inspection is a major maintenance task requiring transformer shutdown and oil handling.
Common tests performed during internal checks include winding resistance, insulation resistance (Megger), and visual inspection of clamping bolts.
The 5-year interval is standard for oil-filled distribution and power transformers under normal service conditions.
Always consult the manufacturer's O&M manual, as local environmental factors may necessitate more frequent checks.
Early detection of mechanical loosening in core and windings.
Assessment of insulation paper condition and aging.
High labor cost and extended downtime.
Risk of moisture ingress during the opening of the transformer tank.
Power transformers in grid substations
Industrial distribution transformers
Large liquid-filled units
External inspections (oil level, temperature, breathing apparatus check) are performed much more frequently (monthly or quarterly).
Option A (6 months) is usually for minor external maintenance, not major internal tank inspection.
Option B (1 year) is often reserved for annual preventative maintenance including oil testing (BDV/Dissolved Gas Analysis) rather than internal tank opening.
C is correct тАФ Internal inspection of a transformer is scheduled every 5 years as part of major maintenance to assess internal structural integrity.
For competitive exams, distinguish between 'Routine Maintenance' (oil sampling/external checks, done frequently) and 'Major Maintenance' (internal inspection/overhaul, done over years).