The functions of transformers are quite numerous but that of instrument transformer is very crucial. This is because the protective relays and other measuring and control devices relies so much on the current and potential transformers fo perform their duty. That is understandable when you consider that in high voltage system, the relays if built to measure directly will be somewhat bulky and expensive. The only way out is to get a proportionate voltage and current equivalent to the one being measured and this is achieved using instrument transformers. Thanks for sharing.