Thursday, January 14, 2010

Electric Meters

Who would be interested in the pictures of electric meters? I do not know either. However, electric meters are an important component in electrical installations. That is how the energy consumed by an installation is measured and recorded. With this record, the owner of a factory, as an example, can be charged for what he uses.

Picture 1 – Single phase house electric meter

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I set up this blog about three months ago. After one or two posts, I started having difficulties in allocating the time needed to accelerate its development progress into speed.

Only now I can start looking this blog again. So I will start rebuilding it with materials that I already have in my collections. I have lots of pictures. However, I do not want to dump them all here.

There should be a story to it, like a script so that the pictures will have more useful meanings to the readers who look at them.

Again, as I already said before, this blog is for beginners. Beginners do not necessarily mean young people or students.

Building managers who need to know a little bit about a few electrical things in order to solve a few management issues, or an accountant who desperately need to know how some electrical components look like because one of her client’s accounts shows a huge price tag for those components.

This blog is for these types of readers. How I arrange and present the materials here will have this type of audience as the main objective.

Now and then, the materials presented may get “heavy” or highly technical. Many times this cannot be avoided. Components like distance protection relays cannot be explained with descriptions anywhere resembling those for simple components such as 13A switched socket outlets, or the electric meters as in the title of this post.

However, for those readers who “desperately” need to know something but cannot find it here and do not know how to dig it out from the internet “jungle”, you can just leave a short comment on this blog.

You can get my assurance that I will answer your questions as soon as I can. That means two days the fastest, and one week at the worst case.

Now let us get back to the electric meter topic.

I am not going to talk too much on this component today because it is the first day I am back to this blog. I will update this post with additional information soon.

This electric meter is from a 3-bedroom medium-cost terrace house unit. This type of houses almost always uses a single phase supply. So this meter is a single phase meter.

You can see that the meter is mounted on a wooden panel. This is very conventional. The oldest meter panels that I have ever seen already uses this type of meter panels and they are still used even today.

However, nowadays a few other types of meter panels are in the market that are acceptable to the supply authorities. You will be able to see the other variations here in future.

The meter panel in the picture may look simple to some readers, but since we are on the topic, I would not want any reader leave this post without a basic understanding of how those things on the panel work.

I have explained a little bit about the meter itself.

However there are two more major components on the board: one you can see and the other you cannot see in this picture.

The Cut-out Fuse

The one you can see is a cutout fuse, which is the black component beside the meter. The cutout fuse is just a fuse. When the electric current flowing through the fuse exceed the rating of the fuse, then the fusing element inside the black casing will blow, cutting off the supply to the meter.

So the meter does not run when the house is without power.

Picture 2 below show a closer view of the meter and the cutout fuse.

Picture 2 – Closer view of cutout fuse

There are two parts of the cutout fuse, which you may see by closer observation of the picture. One is a top part, which is inserted into a lower part. The other is the fuse holder that forms the base that is screwed firmly onto the wooden panel. One of the incoming supply cables is connected to the cutout fuse and it is terminated at the lower part, the fuse holder.

The fusing element, which is a thin conductor wire that melts and breaks the path of electricity to the meter (and therefore to the house electric distribution panel), is actually installed inside the top part of the cutout fuse assembly, the “fuse carrier” as it is often called.

If the house occupant do not pay the electricity bill within the time as required by the electricity supply company, then the company may cut off the electric supply to the house.

This is where they cut off the supply, the cutout fuse. That is why it have been called that way, “ CUT OUT”. The supply company just pulls out the fuse carrier from the fuse holder and takes it back to their office.

The Neutral Link

The second component that is mounted on the meter beside the meter unit is called the neutral link. I am sorry you cannot see it here in this picture. I will upload another picture of a meter panel that will show this neutral link.

As you can see, there is a pair of incoming black cables to the meter panel. One of the black cables is connected to the cutout fuse as already described above.

The other cable is connected to the neutral link. This is the neutral cable, or also called “return cable”, or “return wire”. While the one connected to the cutout fuse is the “live wire”, or the “phase conductor”.

The neutral link is a connection method similar to the fuse, but its connection is without the fuse. It is done with a solid connection bar. Therefore, this side of the electric circuit cannot automatically break the circuit.

Then why is it provided there? This is for the purpose of maintenance and repair work. Sometimes, for safety reasons, a repair work necessitates that the house wiring is fully isolated from the supply company’s incoming circuit. In that case, both the cutout fuse and the neutral like is taken out, disconnecting the house wiring from both sides of the incoming supply cables.

The meter panel cabling

There are four cable connections to the meter panel.

1. The incoming phase conductor (one of the two incoming supply cables) connects to the cutout fuse terminal.

2. The second incoming cable is connected to the neutral link.

3. Phase cable from the meter unit outgoing phase terminal to the house distribution panel.

4. Neutral cable from the meter unit neutral outgoing terminal to the house distribution panel.

Within the meter panel itself, also four cable connections are needed with two other cables involved.

These are to link both the second terminals of cutout fuse and neutral link to the incoming meter panel terminals.

The cabling work that is visible from the front of the meter panel is basically incoming cables.

Other cables are hidden below the wooden panels as much as possible. That is why the panel is constructed with some hollow space underneath to contain the cabling work so it is hidden from view.

The mounting location

The height of the meter panel mounting is also decided so it is above the reach of access by hand. This arrangement is necessary for safety reasons. Anyone who wants to work on the panel needs a ladder of some kind.

This is necessary because most of the time the meter is located at the front of the house to facilitate the billing by the electric company. But this location can present a real shock hazard if the panel is not effectively placed out of reach.

Mounting height is only one method. Other means of placing it out of reach such as locking inside a small cabinet with glass window is also an acceptable by the supply authority.

That’s all the spare time I have today. I think I have covered most of the issues on the electric meter panels. If there is anything left, I will pick it up again in the next post. There are one or two more pictures on the electric meters that I need to upload also.

See you.

Jimmy Lee Wan Seng

Copyright Electric Meters


Anonymous said...

Thanks man, good blog,just what I needed to know.

Steven Brooks said...

Hi friends,

Electric meter is designed to accurately measure the amount of electricity your home is using. The electric meter on your home measures the number of kilowatt-hours of electricity you use each month to heat your home and power your lights, water heater, refrigerator, television, clock radio and other appliances. Your meter may be either a dial meter or a digital meter. Thanks...

Meter Probe