System voltage i.e Nominal voltage = 11000 V
V1/V2 = N1/N2
98/V2 = 104
Primary = Turn ratio × Secondary voltage = 98 × 104 = 10192 V
Percentage of error is the Potential error
= (Nominal voltage − Primary voltage)/Primary voltage
(11000 − 10192)/10192
= 7.92%