The shorted cable has a dedicated MCB extended from the DB in house A and all the way to a birdhouse B. The cable shorted in between A and B.
Only realized cable shorted upon seeing a spark at the cable.
I did ask my electrician why there is no tripping but was told when live and neutral shorted, the MCB wouldn't trip but the main fuse blown instead. Can any sifu care to explain ?

Thank you sir,
These are the info that I can gether.
1) when cable A to B shorted, the was a big spark, main fuse blown off and house A and birdhouse B no electricity.
2) before knowing the actual cause of the problem. wireman came replaced the main fuse in the morning but evening fuse blown again.
3) wireman disconnected the birdhouse cable from MCB in the DB, no more blown fuse but birdhouse B no electricity.
4) upon checking no wiring problem inside birdhouse B, I asked wireman to reconnect the birdhouse cable to MCB.
5) it lasted for a few days before the main fuse blown again. Replaced the fuse again without disconnecting the MCB for the birdhouse for further investigation.
6) break through came when a spark happened before my every eyes. A and B is about 40-50m apart and the extension outdoor cable is supported by cable pole and trees. The spark happened at a tree.
7) wireman fixed the exposed cable and no more blown fuse ever since.

So which extension method in this case?

MCB function is just like a fuse.

Fuse blow, you need to change. MCB trip, just need to reset back.

So the MCB should be able to trip. Since the MCB is 20A max trip. While the fuse is 63A blow.

Should ask the electrician to test it out the MCB is function properly or not. Change it if problem.
I do have many experience some plug point short. and trip the MCB. Main fuse doesn't blow. it should be in this way.

Do have experience some rare case, where the main fuse blow only. Where the shortcircuit Amp instant short is too high.

Can't give a firm answer base on your experience. #1 happen because incoming fuse are blow. That affect House A & B.

If you happen to be in that house, just try trip the main house Master switch inside your house. Check if your birdhouse still have electric. This will confirm of the birdhouse is tap before or after the Master switch.  If is tap after the master switch, and your house master switch did not trip, you need to replace it as per ozak suggest. If is before the master switch that is normal behavior.

Thank you sirs.

I'm very sure if the master switch in house A tripped, the birdhouse no electricity also. Happened few times already.
Also, when wireman disconnected the birdhouse cable from the MCB inside the house A's DB, birdhouse house no electricity. When reconnected the cable to MCB, birdhouse got electricity.
The power supply of birdhouse is definitely tapped from DB of house A.

So in this case, the wireman was wrong to say that if live and neutral shorted (the cable between A and B), the MCB wouldn't trip but main fuse will blow instead ?

So in this case, the wireman was wrong to say that if live and neutral shorted (the cable between A and B), the MCB wouldn't trip but main fuse will blow instead ?

Thank you sirs.

I'm very sure if the master switch in house A tripped, the birdhouse no electricity also. Happened few times already.
Also, when wireman disconnected the birdhouse cable from the MCB inside the house A's DB, birdhouse house no electricity. When reconnected the cable to MCB, birdhouse got electricity.
The power supply of birdhouse is definitely tapped from DB of house A.

So in this case, the wireman was wrong to say that if live and neutral shorted (the cable between A and B), the MCB wouldn't trip but main fuse will blow instead ?

Yes, the wireman is wrong. If he know it, he will test it for you and recommend to change or not.

MCB Amp rating should be lower than the Fuse Amp rating. So the MCB will trip 1st.

Beter check your MCB any problem. Most of the time, I encounter the MCB is mechanical jam. 

Ignore my rare case. It is just some rare experience that I experience before. But it do happen.

Mechanical can jam if the house DB flooded before and not replace.

Not just that.

Some is aging. If you always put it at ON for thousand yrs, and never trip it before, the mechanical will stuck there.

Some is quality issue. You know nowadays this MCB source from where la. Cheap is the issue. What I know is ABB still produce MCB locally. In subang.

In some case, the contact fuse together. Prevent it from trip.

Some is broken contact joint to the tripping mechanical. Result no contact.

This are some case that I encounter before. Normally I will CSI inside to see what happen.

here is 1 of the MCB component. This is the fuse tripping coil from my customer.

ABB Subang, (facing Kesas) no longer produce MCB for residential and commercial. All the low voltage MCB are build in China for many years already. The Subang factor are producing larger scale switchboard, I know, because my previous company I go there often and into their factor too.

Current overload from outside or inside?

Last time already called TNB, but they asked me to get a technician because probably due to faulty appliance or bad wiring inside the house. But after it happened again this morning; I'm not sure it originated from the house.

This morning, I off MCB; and right when I insert the new fuse it blows.

since you mcb inside DB no trip means in between tnb supply to you db might be leak
to blow that 60a fuse the current must've flow to sumwhere.
most likely ground (thru anything i dunno) but it doesnt go thru ur DB since no mcb tripped.

infact i doubt your household will even draw 60a
this must be leak issue.

ABB Subang, (facing Kesas) no longer produce MCB for residential and commercial. All the low voltage MCB are build in China for many years already. The Subang factor are producing larger scale switchboard, I know, because my previous company I go there often and into their factor too.