One and Half Breaker Scheme Protection CTs

Probably for protection of the entire GIS installation. Unfortunately your description is too vague for an accurate response, a SLD might help to remove any doubts.

Did you read your manual? Did you ring your supplier?

NEVER, EVER ask strangers to do your electrical design work for you.

You will surely kill someone with your lack of professionalism. Unfortunately, it probably won't be you.

Read this:

An electrical code is a set of regulations for electrical wiring. The intention of an electrical code is to provide standards to ensure electrical wiring systems that are safe and unlikely to produce either electric shock or fires. Ways in which electrical codes ensure safety include ways to prevent (or mitigate) short circuits, ground faults, and overheating from inadequate current-carrying capacity (ampacity). Appropriately rated fuses or circuit breakers are used to interrupt a circuit loop whose ampacity is exceeded to avoid overheating of wires or other fixtures. Electrical codes are usually devised by national or international technical organizations, and adopted as law to make them enforceable. Electrical codes differ based on geographic area. See the following:

Electrical Codes, Standards, Recommended Practices and ...