Plug insertion Sparks: 110 V versus 220 V

[rollingstein]

In the US, most residential power outlets never have a wall-switch controlling them whereas whenever I travel (say, on my frequent trips to India) every socket has a controlling switch.

First question: Is this because of the relative danger differential of 110 V versus 240 V? Or other reasons? Is live insertion of plugs into sockets routine all over the 110 V nations?

Second question: Some equipment seems to spark more / larger at the point and moment of insertion than others. What determines this? Eg. my cellphone charger never seems to spark on a live insertion but laptop chargers or my table lamp sparks livelier.

 

[mfb]

In the US, most residential power outlets never have a wall-switch controlling them whereas whenever I travel (say, on my frequent trips to India) every socket has a controlling switch.

First question: Is this because of the relative danger differential of 110 V versus 240 V? Or other reasons? Is live insertion of plugs into sockets routine all over the 110 V nations?

It is routine in many European countries with 230V (Germany, Switzerland, Austria, France, Italy, Spain, ...), so voltage cannot be the (only) reason.

 

[Windadct]

As far as the switch issue - probably some different safety standards ( ideas ) - that if there is a problem the outlet can be switched off, or it is safer to plug in and then turn on the power. Since these scenarios require human behavior - which is unreliable, the US thinking may be to make sure the components ( Socket, Plugs etc) can be handled while energized. -- Also think of child safety - here in the US now they are requiring sockets with shutters for new construction.
As far as the chargers - I have notice that the laptop chargers are probably the worst for creating a spark when plugging in. This indicated they have a large capacitor on the input - likely part of the filtering.

 

[Drmarshall]

As far as the switch issue - probably some different safety standards ( ideas ) - that if there is a problem the outlet can be switched off, or it is safer to plug in and then turn on the power. Since these scenarios require human behavior - which is unreliable, the US thinking may be to make sure the components ( Socket, Plugs etc) can be handled while energized. -- Also think of child safety - here in the US now they are requiring sockets with shutters for new construction.
As far as the chargers - I have notice that the laptop chargers are probably the worst for creating a spark when plugging in. This indicated they have a large capacitor on the input - likely part of the filtering.

Sparks.
Some equipment such as transformers and lamps take HUGE surge currents on switch-on
The lamp at 300K has 1/10th of its resistance at 3000K
The transformer core has ZERO flux on turn-on. So the current is limited by resistance and air-flux (leagage flux) until the core eddy curents and hysterisis allow time for flux build-up.
Especially if turn-on instant is at the peak of the ac waveform.

 

[rollingstein]

It is routine in many European countries with 230V (Germany, Switzerland, Austria, France, Italy, Spain, ...), so voltage cannot be the (only) reason.

More nations seem to use a switch than I originally thought.

This was interesting to see:

https://www.google.com/search?um=1&...56.434.0j3.3.0...0.0...1c.1.4.img.X7Cg1MsbofY

 

[mfb]

More nations seem to use a switch than I originally thought.

Where?

I posted a list of countries where those wall-switches are not common.

 

[0xDEADBEEF]

In Britain there is a wiring technique for homes called ring circuit. In most countries the power is distributed in a "hub and spoke" fashion, so a few rooms share one pair of wires, which end somewhere in the furthest location. One of these strings of sockets gets a circuit breaker, when it trips all connected sockets lose power.

During the war there was a copper shortage in Britain, and one tried to design such, that as little copper as possible was needed for the power distribution in the home. What people came up with is a ring of cable that connects as many sockets as possible and returns to the starting point. To every socket there are now two paths, so the wire can have half the cross section area. Additionally, every socket received its own fuse making longer wire loops feasible. The fuse is sitting on the phase wire for obvious reasons so the socket needs a means to turn off the socket, to be able to exchange the fuse without turning off the electricity of the whole house.

I wouldn't be surprised if many Commonwealth countries shared the design. South African and Indian power plugs have a British history, and maybe in some other countries it is just tradition to have a switch. Just like the Swiss all have the same light switches for no apparent reason.

 

[0xDEADBEEF]

I just saw that actually the plug seems to carry the fuse in Britain says wikipedia. The description of the ring circuit with the fuse comes from some other forum and it made sense to me, so I don't know what is actually happening... On second thought, if you don't have wire for the power distribution, then you don't have wire for the switches either. Maybe that is why they are in the sockets.

 

[e3belectrical]

Many buildings in the United States and Canada have both 240- and 110-volt electrical outlets, though most of the electronic devices use 110V plugs. In Europe and various other parts of the world, 110V plugs remain absent while 240V outlets and plugs prove quite plentiful. When compared, these two types of plugs have several important differences, most significantly with regard to installation cost and electrical capabilities.

 

[AlephZero]

I just saw that actually the plug seems to carry the fuse in Britain says wikipedia.

The British standard for house wiring changed some time between WWII and the present. The original system had round-pin plugs of different sizes for different current ratings (15A and 5A were the most common but 2A was sometimes used). I remember that system from where we lived when I was a kid. I don't remember the sockets having fuses, but they certainly had switches.

The current system uses ring mains rated at 30A, and a single size of plug rated at 13A. The fuse or circuit breaker for the ring main is in the main distribution box whcih can be completely isolated from the outside supply. However a 30A fuse is not sufficient to protect against fires in thin flexible cables for low-power devices, so each plug also has a fuse appropriate for the device it is powering. Common fuse ratings are 13A, 5A and 3A but even lower values are used.

Replacing the fuse in a plug does not require a switched socket, since it is impossible to access the fuse while the plug is in the socket (unless you do something that is obviosuly dangerous!)

The pins on the old-style round pin plugs were bare metal, and hence a shock hazard when partly plugged in. The modern UK plugs have partially insulated pins, and should not connect to the supply while there is any exposed bare metal showing. That might explain the fact that the old style sockets were switched, but new ones are often not.

AFAIK the system in India (and probably other Commonwealth countries) was based on the old "round pin" wiring.

EDIT: I think it was very unlkely that the round-pin sockets had a fuse in the socket, because in those days fuses would have been fuse wire and screw terminals, not the current style of cartridge fuses.

 

[d3mm]

There is no law or regulation in the UK that requires a switched socket. Indeed they still occasionally fit switchless sockets where things will not generally be unplugged, for example, a refridgerator socket. However, economies of supply and demand have pushed up the price of switchless sockets to the point where switched ones are cheaper (and "better" in that putting in switchless ones makes you look dodgy).

 

[AlephZero]

However, economies of supply and demand have pushed up the price of switchless sockets to the point where switched ones are cheaper (and "better" in that putting in switchless ones makes you look dodgy).

There is virtually no price difference at least from one major UK DIY chain. For example single soocket £2.79, with switch £2.98. (Both from the same big-brand-name manufacturer.)

But a switched socket plus a neon indicator lamp costs nearly 3 times as much. Go figure!

 

[rollingstein]

Just like the Swiss all have the same light switches for no apparent reason.

Hmmm...What's special about Swiss light switches?

 

[d3mm]

Screwfix has them at about 1.50 last time I checked. But I was thinking about the large firms that build blocks of flats. They aren't going buy sockets individually and they don't want to manage 2 different inventory items.