Ok, Let us assume a real case. Assume switchgear with 2x 100 x 10 mm busbar (2000 A) and relevant current transformer as following characteristics: -Ratio: 2000/1 A – Rated Burden: 25 VA We will have a suitable path for flowing of 2000 A current if 2 meter of mentioned busbar is shorted according to figure in below. 
Assume we can produce 2000 A current in short circuited paths. In this case the primary short circuit drop voltage can be calculated as follows: V= (2 * 2000) / (56 * 2000) ~ 0.01 V And for consumption burden we can write: S= 0.01 * 2000 = 20 VA < 25 VA ( CT burden ) Is it possible? Can we produce 2000 A in primary side?