RCDs were the next jump up from a standard breaker. A standard breaker is there to stop the wiring in your property melting, and potentially catching fire. And RCD is there to protect you, as a living breathing being, from fatal electric shocks.

And we're fragile little things, you and I. Which is why an RCD can be so sensitive and prone to tripping. So sensitive, in fact, it could pick up on a current 200 times smaller than what would cause a lighting breaker to trip.

Let see what you might be experiencing and see if we can lend any ideas:

Fuse blowing with or without a bang / breaker tripping with or without a bang / RCD blowing with a bang

An audible bang is a good pointer to indicate the live is involved. It could be live to neutral or live to earth. 

You can also get a fuse / breaker / RCD tripping without a loud bang (or even a quiet one).

If an RCD is blowing with a bang, you likely would have noticed a particular fuse has popped or breaker has dropped. That will help narrow down what circuit your issue lies on. Try to keep that particular circuit off and reset the RCD. That will get some power back on whilst you investigate further.

RCD tripping, by itself, without a bang:

An RCD tripping without a bang, by itself, with no other breaker dropping nor fuse popping, could indicate a few potential issues:

You have an earth leakage fault (live to earth or could be caused by an appliance).

You have a neutral to earth fault. 

In these cases you will want to unplug everything totally from the plug sockets (don't just switch off at the plug, pull the plug out), for boilers and white goods, you may have fused spurs (dedicated switches nearby) you can switch off, and switch all of your lights off / take the bulbs out.

Fuse blowing without a bang:

You could be overloading the circuit (do you have all your white goods on as well as the kettle and toaster and iron by any chance?) Things that heat up are generally the juiciest things you'll have plugged in. Did you have a lot on at the same time?

You could have a slow-blow short. What we mean by that is - your electrics are experiencing a bit of a short but short isn't strong enough to blow it instantly. 

How can you tell which is which?

A fuse is re-wirable and you can physically pull it out of its fuse holder in the fuse box. These fuse boxes are generally brown in colour and will look old (too old in fact, get with the times!) When a fuse trips, you will lose only one circuit such as plug sockets or lights

A breaker is a thin rectangle with a little lever on it, generally pointing up when on, and down when tripped. They should each be labelled (lighting, sockets, kitchen, boiler, immersion, etc) when a breaker trips, you will lose only one circuit such as plug sockets or lights.

An RCD is usually twice the thickness of a breaker and it's biggest giveaway is the push button (push to test). And it'll likely have "30mA" or "100mA" written on it. If an RCD trips, you might be unlucky to find a mixture of circuits not working, such as your shower isn't working and neither are your lights.
 

If it's a very new fuse box (upgraded in the last 5 years) you may have RCBOs in it. RCBOs are the love child of a breaker and an RCD. They're slim like a breaker, and have a test button, too.

A bit of fault finding investigation - questions to ask yourself

This knowledge should put you onto the right circuit, then once you've hopefully honed in on your circuit, you've got to start wondering what has caused this to trip?

You can go quite far by asking yourself some simple questions. Questions us as electricians might be asking you is:

Does it trip instantly? Or regularly? Completely randomly? Is there any pattern you can match up to when it trips?

If it trips instantly you've got a good chance of finding it quickly. Can you narrow it down to something that is plugged in or a particular light? 
 

Do you have water getting into the electrics somewhere. Some causes and tell-tale incidents:

Has it rained heavily in the last few hours?
Has water managed to get out of the bath / shower / sink? (you'd be surprised how little amount of water can get into the smallest holes in the building)

Has anything been buzzing or flickering, turning off and on randomly by itself in the past few days/weeks/months?

Does it happen to only do it when the oven is on? Or when someone uses a kettle?

Does it happen to only do it when someone has recently used the bath or shower? You may have a leak coming from the silicone or the waste that drains the water away!

If you're wondering if its the oven that is tripping the electrics, turn it on til it trips. It may well have taken 5 minutes. reset the RCD and turn the oven back on. Did it trip in less time? And again, less time? It might well be the heating element on your oven, which gets worse as the oven warms up.

Is it happening at the same time every day? It may be something on a timer, such as an immersion heater on your water tank or electric underfloor heating.

Does it only happen when it's cold? It may be condensation collecting and pooling in the electrics, or it may be an electric heater or electric underfloor heating.

How to get by with loss of power

With the questions and ideas in mind, til a registered electrician can get to you, you may be able to have a little investigation yourself to help narrow the issue down and get the rest of the power back on. Heck, you may even be able to crack it by yourself!

Til then - some ideas (most of these are ideas for the short term!)

If you've lost your lights, get the torches out and candles on, do you still have your plug sockets on? Do you have any plug-in lights you can make use of?

If you've lost your internet and you have kids - get a game going on to keep them occupied. Do you have any board games? Can you make a competition with lego or arts & crafts?

If you've lost sockets in one part of the house but still have power from sockets elsewhere - can you run an extension lead to the crucial elements such as the fridge and the freezer? And for goodness sake, don't forget the internet router!

If the boiler is causing the problem, or your electric heaters, but you still have power at the plug sockets, do you have any plug top heaters you can make use of?

And remember, if all fails:

Turn all breakers off, and try each breaker one by one to see what breaker is causing the issue

Unplug everything totally from the plug sockets (don't just switch off at the plug, pull the plug out), for boilers and white goods, you may have fused spurs (dedicated switches nearby) you can switch off, switches for the boiler, immersion heater, isolator for your shower, isolator for your cooker, the lot, and switch all of your lights off / take the bulbs out, and trying powering them back up one by one.

And for all of the millennials out there (I am one by the way, so don't come at me bro), there was once upon a time, life on earth without internet! Shocking, I know!!

Take care, all of the best, 

Kev

Places we've solved tripping RCD issues:
Bluebell Hill, Chatham
Top of the Landway, Bearsted, Maidstone,
Bottom of the Landway, Bearsted, Maidstone
Near Castle Road, Allington,
High Street (Lower new road), Chatham,
a Cottage in Bearsted, Maidstone,