Switch disconnector alignment

Protection for the switch disconnector (and the wiring to it) is assumed to have been installed at the distribution panel (or in a fused spur etc. en route).

Yes, I try to simplify. If you want the breaker to be repaired / serviced, you need not to go to Out-going of the up stream panel to isolate the panel, rather switch off the breaker, disconnect the isolator/ fuse link.

this is better in terms of engineering practice. In any case if you have selected the fuse & the breaker with type 2 co-ordination, the breaker trips in case of a fault within the range of kA rating of the breaker. Schneider uses a patented technology, thermal energy release to achieve this.

hope, I could answer your question.

A switch-disconnector does not have inherent protection. As defined in IEC, it is capable of making and breaking normal current, capable of carrying short-circuit current, but not able to break it. When open, it will provide isolating distance. So, upstream short-circuit protection is a must.

The breaker itself is quite often the withdrawable type, so that any maintenance on it can be carried out by withdrawing it from its cradle to the isolated position.

Thanks, i partially agree, normally switch disconnects are provided before MCCBs, these are not draw out type. by giving the term disconnector ( and not breaker) we try to explain that the device is meant for operation under no-load or normal operation. thus a short ckt. is an abnormal condition. In any case a up-stream protection should be always present for a device to make other feeder work with same breaking capacity in co-ordination.

Just curious ... MCCBs not being maintainable, what is the need for an upstream switch-disconnector? It is usual to have an appropriate ACB at the transformer end, and have the sub-circuits fed through MCCBs. Co-ordination between the ACB and subsequent MCCBs is important of course, whether discrimination or cascading is used.

Tricky.... Ha Ha, Type-2 Co-ordination or total discrimination asks for Protecting device & isolator. Normally manufacturers' do guarantee for co-ordination within the same switch board, not between an O/G ACB in PCC and an incoming MCCB in MCC.

I have seen ABB giving cascading through communication between these two but not electrically. Schneider guarantees the same electrically but at a higher cost.

By the way I thing the guest who raised the issue has not seen these at all, or has found his answer any way.

i am curious about Type 2. As far as i knew before, Type 2 coordination is in reference to motor starters and SCPD. The relay characteristics must not get changed after clearing the SC tests. i haven't come across Type 2 coord between isolators and breakers, would appreciate it if you can enlighten me a little on this...