Power fuses are a generally accepted means of protecting power transformers in distribution substations. The primary purpose of a power fuse is to provide interruption of permanent faults. Fusing is an economical alternative to circuit switcher or circuit breaker protection.
Fuse protection is generally limited to voltages from 34.5 kV through 69 kV, but has been applied for protection of 115-kV and 138-kV transformers.
Good explanation
Good explanation though, but does not state the full meaning of ‘J and P fuse’ which is the actual question.
Full meaning of j and p fuse