A high tension (HT) supply of say $6kv$ must have a very large internal resistance . Why ?

Question

$\begin{array}{1 1} \text{HT supply should have very large external resistance } \\ \text{HT supply should have very low external resistance } \\ \text{HT supply should have very low internal resistance } \\ \text{HT supply should have very high internal resistance } \end{array}$