i want to share and discuss the impact of using one medium voltage circuit breaker at 22KV to protect two series loads (transformer 22/6.6KV) and compressor motor 3MW at 6.6KV side.

Ok you start first. What's your design and be specific.

i received 22KV cable and having 2 transformers at 22KV side (22/0.4KV and 22/6.6KV)then one load at 6.6KV which is compressor motor 3MW with softstarter.

hmmm... as long as your MV CB (vacuum or SF6) has the right kAIC, AT, AF, etc. then there's nothing wrong with that (quality-wise)... but check the specifications of your two transformers, protection relay settings per load transformer and the specifications of your compressor drive motor so that your system is electrically protected... it would be better if you will install circuit breaker at HV and LV of per transformer for maintenance and protection sake (quantity-wise)...

You may use one main breaker and no other downstream breaker, but best to still have various protective relays and CT sets to do proper protection.

You then will lack selectivity but still have good protection and the cost for fitting your system with proper protection is much less than a breaker.

You may use one main breaker and no other downstream breaker, but best to still have various protective relays and CT sets to do proper protection.

You then will lack selectivity but still have good protection and the cost for fitting your system with proper protection is much less than a breaker.