Determine maximum permissible load which a 15 MVA, ONAN cooled transformer to IS : 2026 can take for 6 hr, if the initial load on it was 12 MVA. The weighted ambient temperature is 20˚C. Assume the permissible load kVA as a fraction of rated kVA is 1.25.

• A. 18.75 MVA
• B. 15 MVA
• C. 9.6 MVA
• D. 12 MVA

Answer: (A)

Maximum permissible load = Rated MVA rating*fraction of rated kVA
Maximum permissible load = 15*1.25
Maximum permissible load = 18.75 MVA