A fault at the cutout could result in a current of several hundred amps, releasing as much energy every 10-20 seconds as a stick of dynamite.
inaccurate electric meter
- Thread starter uknokianut
- Start date
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And it is sealed. And its real dangerous if something goes wrong.
Meter guys wear stuff like this, just in case….
Although if you have an isolator after the meter, as in that picture, you can turn off the supply there and fit your own meter alongside your consumer unit easily enough,
Do I see correctly - guy working on cutout fuse with CU isolator closed so no guarantee that fuse isn't carrying current
That appears to be the case, although I suppose it's possible that the CU Main Switch is open. However, even if it is, I would personally still want to use that isolator!
In passing, I've watched a good few meter changes in my time and, despite what is meant to happen, I'm not sure that I can recall ever having seen any PPE used when the cutout was plastic!
Kind Regards, John
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It's probably an actor.
I've see promotional videos where an actor was removing a socket by turning the screws the wrong way.
I've see promotional videos where an actor was removing a socket by turning the screws the wrong way.
I have a couple of OWLs, they are not very accurate. They vary but are usually within a few hundred watts of each other. When I turn the kettle on and off the reading changes up and down, by an amount usually within a couple of hundred of 3000W.
You tell them what you think your voltage is, for them to calculate the watts used according to what the sensor thinks is the amps passing through the tails.
My clamp meter is much more accurate, but doesn't store the data.
As I look at them now, one reads 487W and one reads 521 (just changed to 487 and 504)
If you're buying an OWL, get a used CM160 for a few pounds on ebay. It will connect to your PC with a USB and do graphs by minute/hour/day/month/year and record the data. Other models do not have the USB function*
*Although there may be a newer model since I looked.
You tell them what you think your voltage is, for them to calculate the watts used according to what the sensor thinks is the amps passing through the tails.
My clamp meter is much more accurate, but doesn't store the data.
As I look at them now, one reads 487W and one reads 521 (just changed to 487 and 504)
If you're buying an OWL, get a used CM160 for a few pounds on ebay. It will connect to your PC with a USB and do graphs by minute/hour/day/month/year and record the data. Other models do not have the USB function*
*Although there may be a newer model since I looked.
Owls are not accurate as they only measure current and guess voltage. But the biggest error is assuming power factor is unity which is pretty rare. In my opinion they are not fit for purpose and should not be sold.
How accurate is the Owl, and down to what level?
With a pure resistive load at the voltage it's set to very accurate. With a pure capacitive load the reading is meaningless. With say a 0.5 PF load it will read double.
I've been looking at the instructions for a CM119, and it says "better than 5%" at 3A to 71A (though below 1A to 3A, it said, "better than 10%") and below 1A is not specified.
But it can only mean its measurement in Amps, because it doesn't know true voltage.
It is not a continuous record, I think it gets a pulse at about 30 second intervals.
By observing that my two meters usually show different readings, we can surmise that at least one of them is not very accurate. Each has its own sensor.
But it can only mean its measurement in Amps, because it doesn't know true voltage.
It is not a continuous record, I think it gets a pulse at about 30 second intervals.
By observing that my two meters usually show different readings, we can surmise that at least one of them is not very accurate. Each has its own sensor.
This video shows a 10kA fault for 1 second.
10kA is entirely possible on a single phase supply with a short L-N.
1 second is approximately how long it would take an 800A fuse to disconnect with a 10kA fault current.
230 ÷ 10000 = an order of magnitude smaller than the "conventional" Ze for a TN-C-S supply.....
What suppliers quote as a typical maximum impedance and what you get in reality are usually very different.
They also quote a 16kA PFC. https://www.ssepd.co.uk/ForContractors/
They also quote a 16kA PFC. https://www.ssepd.co.uk/ForContractors/
10kA is possible, but statistically unlikely, you'll only see it if you are right next door to the transformer.
I can't ever recall seeing it that high in a domestic property.
A 1MVA transformer will have a fault level of ~28KA for a fault involving all three phases (the spanner across the busbars situation). You can more or less halve this where only a single phase is available. A short length of the waveform street feeder will not add much attentuation. However add the 5m of 16mm² concentric under the driveway and into the meter box and we are down to ~8.5Ka.
There are going to be a very small percentage of houses where anywhere near 10kA is going to seen.
Its also bearing in mine that once you start getting much below about a tenth of an ohm, most loop testers are not very accurate, so one might perhaps see 10kA on the display when the real figure could be still reasonably high (say 6ka) but not as high as is being reported
I can't ever recall seeing it that high in a domestic property.
A 1MVA transformer will have a fault level of ~28KA for a fault involving all three phases (the spanner across the busbars situation). You can more or less halve this where only a single phase is available. A short length of the waveform street feeder will not add much attentuation. However add the 5m of 16mm² concentric under the driveway and into the meter box and we are down to ~8.5Ka.
There are going to be a very small percentage of houses where anywhere near 10kA is going to seen.
Its also bearing in mine that once you start getting much below about a tenth of an ohm, most loop testers are not very accurate, so one might perhaps see 10kA on the display when the real figure could be still reasonably high (say 6ka) but not as high as is being reported
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