Forgot to add, I have already replaced everything in the MCB box after it happened the second time.
I think its single phase. Nothing unusual switched on.

You're describing a direct short circuit (Live to Neutral).. If you're sure the DB isolator is off then the cable  fault is between the kWh meter to the DB..

Have you had any renovation work done recently? Or anyone drive nails into walls ??

They might have accidentally driven a nail into the Live/Neutral cables thus blowing out your fuse..

Yes; already off all MCB. When inserting the new fuse, sparks come out and the fuse blow.

I have no idea what you are talking about..  do you?

you're saying a slow thermal buildup short circuit as in the case of indirect conductivity (surface dust, liquid and conductive flesh)..
but Aeran typed "already off all MCB. When inserting the new fuse, sparks come out and the fuse blow" that describes an instantaneous short circuit..

Anyway the easiest way to check is to disconnect both ends of Live Neutral and check for continuity between the two.. 
If there's continuity then its a direct short..

Guys, finally can get electrician to come and see this morning. Will update later.

No; I'm not using any 'creative' wiring to bypass meter. Though previously I do notice the meter tend to spin a bit fast.

Update: Confirm wire between meter and MCB was shorted.

you are one cuckoo fella..  people say incoming live/neutral already confirm short blow fuse still say resistance short, talk voltage ?? Pls stop talking cock !!! 

Already blow fuse means no more supply !!  You talk what !!

Hi all,

Lately my house always suffer power trip randomly; e.g. not because of lightning or switch on appliance. Example; this morning around 4am power trip again.

MCB/ELCB did not trip; but the outside fuse near TNB meter blown. Always happened this way. Usually I replaced this fuse; but it will randomly happened again.

Any idea why it trip this way? And is it normal if I switch off MCB but TNB meter still show movement (very slow)?

Guys, finally can get electrician to come and see this morning. Will update later.

No; I'm not using any 'creative' wiring to bypass meter. Though previously I do notice the meter tend to spin a bit fast.

By right, the MCB should trip 1st.

Time to change the MCB.

Not TS case. But aeiou228 case.

MCB won't trip if the short circuit happen before the MCB incoming.

While aeiou228 case is after the MCB. Since the MCB have lower Amp rating than the fuse, it should trip 1st before the fuse.

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?

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.

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.