What kind of protections must be provided to 33kv electrical feeder?

Answer 1

Typical protection for a radial system would be overcurrent protection - a mixture of definite time, instantaneous time, and time overcurrent for positive sequence, negative sequence, and zero sequence is usually used (negative sequence isn't used very often, but there are times when it is needed). These overcurrent protective devices will trip a breaker, circuit switcher, or similar device.

When feeds become extremely long, sometimes in-line fusing is used part way down the line as a cheap alternate to a recloser or breaker. The drawback is if a fault occurs, someone has to go out and replace the fuse, and you are typically at the mercy of the customer calling in and complaining before you will know a fuse is blown.