LV fuses are more suitable for Short circuit protection where speed of arc clearance is too small by the Circuit breakers or in other words Fuses are the only option when you want to limit the short circuit currents to not more than 1/2 cycles or even less. A typical example is given below
An electrical Power system employing 8 Alternators of 2000KVA @690V 3 Ph 60 Hz and Xd” of 20%. is required to feed electrical Variable speed drive. Unfortunately, the availability of drives in market is limited to a maximum KA of 65KA. Therefore it is not possible to feed VSD directly from 690V Switchboard (fed from 8 Alternators). How do we solve this problem.
1. By splitting the 690V bus in to two Sections, each supplied by 4 alternators
2. Bus coupling is achieved by employing a Short circuit limiter which limits the short circuit flow between two buses to 10KA
By employing above arrangement, we can limit the shirt circuit level of 690V bus.