Given:
Secondary voltage, V2 = 2000 V
Secondary current, I2 = 200 V/20 kVA = 10 A
Number of turns in secondary, N2 = 66

We know that the transformer is an ideal transformer, hence it can be assumed that there are no losses in the transformer.

Calculation:
We know that the voltage across the primary and secondary is the same. Hence, we can use the voltage equation to find the number of turns in the primary.

Voltage equation for an ideal transformer is V1/V2 = N1/N2

Substituting the values in the above equation, we get
V1/2000 = N1/66

V1 = 2000(N1/66)

We know that the transformer is rated for 20 kVA. Hence, we can use the power equation to find the primary current.

Power equation for an ideal transformer is V1I1 = V2I2

Substituting the values in the above equation, we get
V1I1 = 2000 x 10

I1 = (2000 x 10)/V1

Substituting the value of V1, we get
I1 = (2000 x 10)/(2000(N1/66))

Simplifying the above equation, we get
I1 = 660/N1

We know that the transformer is rated for 20 kVA. Hence, we can use the apparent power equation to find the primary current.

Apparent power equation for an ideal transformer is V1I1 = V2I2

Substituting the values in the above equation, we get
V1I1 = 20 kVA

Substituting the values of V1 and I1, we get
2000(N1/66) x (660/N1) = 20 kVA

Simplifying the above equation, we get
N1 = 660

Hence, the number of primary turns is 660.