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[TAS] Free - CablePI Power Alarm from TasNetworks - Detects Supply Issues such as a Broken Neutral

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[TAS] Free - CablePI Power Alarm from TasNetworks - Detects Supply Issues such as a Broken Neutral
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Meowcat on 29/03/2016 - 20:01 tasnetworks.com.au (255 clicks)
Last edited 29/03/2016 - 20:16

CablePI is a device that detects a potentially life-threatening electrical fault known as a broken neutral (also detects out of tolerance voltage issues)

It offers a potential solution to a problem that has challenged the electricity industry worldwide for decades.

CablePI is free to Tasmanian residential and small businesses customers (though I managed to get mine delivered to a QLD Address, YLMV)

Broken neutrals are a serious problem and present a significant risk to the health and safety of you and your family.

A broken neutral is a relatively common but potentially life-threatening electrical fault that can affect households and businesses.

Power flows in and out of customers' premises from our distribution network, entering via the active cable and leaving via the neutral cable. Customers also have within their premises an earth connection. If there is a break in the neutral return path, electricity can still exit the premises via the customer’s earth connection. If there are problems with the neutral and earth, electricity may then travel by a different path. This may be via water pipes, stoves and metal taps or any other conductor of electricity. This situation can be very dangerous and customers may suffer serious electric shocks if they touch something where electricity is present.

Broken neutrals can be difficult to detect and in some instances may not be easily identified. Sometimes broken neutrals can be indicated by flickering lights or tingling taps. If you have flickering lights or tingly taps in your home, you may be at risk of serious injury or even death.

http://www.tasnetworks.com.au/safety/cablepi

Electrical & Electronics

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closed Comments

  • Clear on 29/03/2016 - 20:14
    +1

    These detect faults 100% of the time. The basslink is cut. No power.

  • furiousgeorge on 29/03/2016 - 20:14

    Elcb or rcd.

    • Russ on 29/03/2016 - 23:58

      No, it appears to be a undervoltage/overvoltage alarm, see here:
      http://www.tasnetworks.com.au/safety/cablepi/what-is-cablepi

      If that's all that it is, then this alarm won't necessarily warn you of a neutral failure. If your house's earth stake is properly placed, in conductive (damp) soil, then all of the house's current will flow through the earth stake, and there may not be enough of a voltage drop to set this alarm off.

      • llama on 30/03/2016 - 01:21

        No, the device ALSO includes an undervoltage/overvoltage alarm

        This is just a simple conductivity tester. They have been around for years.

        OK as a freebie.

        • Russ on 30/03/2016 - 10:35

          Not sure what you mean by "conductivity tester", perhaps you mean a mains wiring tester, for checking the wiring of power points? It isn't one of those.

          It's a two-terminal device with no earth connection, see the pictures here: http://www.tasnetworks.com.au/safety/cablepi/cablepi-recall

          As it's only connected to live and neutral, the only thing it can be is an overvoltage/undervoltage detector.

        • llama on 30/03/2016 - 18:38

          @Russ:

          AHHH - sorry, now I see! So that means that this "CablePi" is far more limited than the common testing devices that I was thinking of. I was talking about these things:

          Ebay Search

          These standard "Power Point Testers" check for FIVE kinds of faults, not just one…
          * Active/Neutral Reversed
          * Active/Earth Reversed
          * No Neutral, Live Earth
          * No Earth
          * No Active

          Plus they almost all have a pretty decent RCD tester as well, which is incredibly handy for home owners to test the effectiveness of their "safety switches".

          So yeah, with only 2 connections there is no way in the world the CablePi can detect the presence or lack of a Neutral back to the grid.

          Also, I cannot work out how a Bad Neutral (on it's own) might make a particular problem is any Aussie home that has a proper Earth. It certainly wouldn't make water taps go live… unless there is ALSO a poor Earth as well as a broken Neutral, AND the earth conductor was bonded to the water pipes (been illegal for a LONG time) AND gawd knows what other obtuse situation.

          It's even more alarming that there is absolutely zero information online about these things, except for a Safety Recall. So, as a freebie I guess these are OK, but it's not a gadget that I would be placing any trust in. But now I want to order one to crack it open and see the magical pixies inside.

        • Russ on 31/03/2016 - 00:28

          @llama:

          I can see three ways a bad neutral could be dangerous.

          • at lower-than-normal voltages, compressors in refrigerators often won't start. Then the motor gets hot, and the over-temperature safety cut-out activates until the motor cools. Sometimes the cut-outs fail and you end up with a fire. Might also happen with other motors too, universal motors draw their highest current when they are stalled, and their cooling fan won't be operating either.

          • I've had a look at the earth stake at my house, and the wire feeding it doesn't look like it's rated to 50A. I know the feed from the street is rated that high or higher, and the main fuse on the fusebox is 50A. So if your house is drawing 50A or close to it, the earth wire between the fuse box and the earth stake could get VERY hot, possibly hot enough to start a fire in a wooden house.

          • The earth stake isn't always a good ground return. You could possibly end up with the earth stake being tens of volts above the better-grounded water tap beside it, and when your skin is wet, that could be enough to kill you. Could also happen inside the house, e.g. in the kitchen, the stove body and refrigerator are earthed through the mains, while the sink is earthed through the plumbing. One hand on each could kill.

          To illustrate how variable an earth stake can be, I have relatives who live on a farm, which is powered by a single-wire-earth-return system. Basically a single wire distribution going to several farms at maybe 3.3kV. Each farm has its own transformer, and the single wire goes to one side of the primary winding. The other side of the primary winding goes to an earth stake at the base of the power pole. My relatives say that after an extended dry stretch, they notice the house lights seem a bit dim, so they put a garden sprinkler under the power pole to keep the ground moist. Then their lights go back to normal brightness!

        • llama on 31/03/2016 - 02:37

          @Russ:

          • at lower-than-normal voltages, compressors in refrigerators often won't start.

          Yes, however the home owner would notice such a problem (it wouldn't be "invisible").

          • I've had a look at the earth stake at my house, and the wire feeding it doesn't look like it's rated to 50A

          It'll normally be 16mm² cable. That's fine for a "normal" voltage drop at 80A or even more at the short length used between fusebox and earth stake.

          So if your house is drawing 50A or close to it, the earth wire between the fuse box and the earth stake could get VERY hot, possibly hot enough to start a fire in a wooden house.

          Nah. You'd need to be pulling thousands of amps to make it get that hot.

          • The earth stake isn't always a good ground return.

          Well, it will still be a better ground return than a human being.

          You could possibly end up with the earth stake being tens of volts above the better-grounded water tap beside it,

          Almost impossible, since the earth stake and the water pipes are Equipotentially Bonded. That is the technical term for "electrically connected together".

          To illustrate how variable an earth stake can be, I have relatives who live on a farm,

          Yep, and they are still alive :-)

        • Russ on 31/03/2016 - 04:02

          @llama:

          the earth stake and the water pipes are Equipotentially Bonded.

          That seems to disagree with your earlier comment

          the earth conductor was bonded to the water pipes (been illegal for a LONG time)

          In both of the houses I know well, there is no electrical link between the two. And on one of the houses the earth stake and the water pipe are on opposite sides of the house, so there could be a fairly large potential between them in a fault situation.

          Digging around the web suggests that up to 5 ohms is a typical value for the ground impedance, so ten amps flowing through the earth stake will give 50V rise compared to a distant stake - like the water pipes on the opposite side of the house.

        • llama on 31/03/2016 - 16:03

          @Russ:

          Yes, I inadvertently contradicted myself about the bonding. Reading back, I see that I explained it really badly - what I was actually trying to point out was that a number of faults would need to occur simultaneously in order for the "bad neutral" to become dangerous. In fact, the whole installation would need to be illegal, non-compliant and also faulty…

          The Australian Wiring Rules (AS/NZS3000) section 5.6 covers this stuff. For example:

          5.6.2.2 Conductive water piping
          Conductive water piping that is both—
          (a) installed and accessible within the building containing the electrical installation; and
          (b) continuously conductive from inside the building to a point of contact with the ground,
          shall be bonded to the earthing system of the electrical installation.

          The earliest copy of Standards that I can find on our server is from 2007, so I copied it from there. I doubt that it was introduced in 2007, since the risk of the 2 not being linked has always been present. In 2009 Amendment they made also it mandatory to also bond the reinforcing mesh within the floor slabs of the bathroom, etc.

          In both of the houses I know well, there is no electrical link between the two. And on one of the houses the earth stake and the water pipe are on opposite sides of the house, so there could be a fairly large potential between them in a fault situation.

          The bonding connection is at the switchboard. Since the water pipes will probably be a FAR better earth than the 1.2m long Earth Stake, in reality this means that the plumbing is usually the main earth and the stake is the backup.

          Anyway, what's more important is whether this gadget is of any use. And I am sceptical about what a 2-wire device could possibly detect.

  • Berek on 29/03/2016 - 20:14

    That's handy for Tassy people. Maybe it can detect cable faults too…

    • JetBombat on 29/03/2016 - 22:45

      Guess how they found it?

      • llama on 30/03/2016 - 01:22

        Guess how they found what?

        We cannot even guess what you are talking about LOL

  • Basslync on 30/03/2016 - 07:07

    Will be interested to know how this one works. Broken neutrals are dangerous. Thanks for sharing!

  • LaTerrible on 27/04/2016 - 14:51

    So ahhh, did anyone receive theirs yet?

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