Highest system voltage

Assuming it is an AC distribution system, which isn't explicit in the posting, one of the solutions is a step-up transformer. However, the difference in voltages is only 3/33 ≈ 9%, which is wholly understandable for a distribution system, and to be expected. So before investing in a substantial piece of equipment the question "why bother?" needs to be answered in a way that the investor will understand, and back with cash.

Another solution is to change the tapping on the sending transformer so that 36kV is received, assuming that the cabling downstream will withstand the increased voltage. If it isn't, then replacement of part of the network may be in the tea leaves.

The best bet is probably to hire a specialised consultant locally for detailed investigation and advice in the first instance. It may be cheaper in the long run.

Electrical distribution systems are designed to maintain voltage at nominal ± 10%. For your 33 KV system, the acceptable range is 29.7-33.3 KV. Most people round these values to 30-36 KV.