Pulsed Outputs

[MDD]

Hi,

I am looking to configure pulsed outputs on an EDMI meter and was hoping someone could explain the difference between using a Primary / Secondary pulse constant?

I assume it has something to do with the CT/VT ratios but can't quite get my head around how they are different as in my head even if the meter is looking at Secondary current to determine the KWh and in turn when to pulse it must have an idea of the primary to calculate when a KWh has been used and when it should output a pulse.

 

[MDD]

Hi,

Anybody have any ideas on this? Would appreciate any guidance.

Thanks

MDD

 

[Manator]

Is there any instructions with the smart meter? The sttings will always depend on the tarriffs if that is my understanding.

Try this link http://www.bglobalplc.com/userfiles/file/PDFs/Read%20your%20meter/Mk10%20Booklet%20v1-4.pdf

 

[Marvo]

I'm not sure about the primary and secondary pulsed output, it doesn't make sense to me that the meter would have a pulsed output that corresponds somehow directly to the primary of the CT.

All the pulsed LED outputs I've seen on smaller metering systems are at a frequency of 1000 pulses per kilowatthour. As long as the CT ratio is correctly set in the meter program options this is flash rate / consumption. Some larger commercial meters have a slower flash rate but this would be stated in their documentation.

Maybe a link or an exact model number of the meter might help.

 

[MDD]

Thanks for the response Manator.

As I understand it the 'tariffs' only control which rate the meter is recording on, i.e, the tariff for an economy 7 meter may have rate 1 between 00:00-07:00 and Rate 2 between 07:00-00:00.

The pulsed output (in the form I want to use it) simply transmits a pulse when a particular volume of energy is measured. This is configurable in the software as a Wh/Kwh value per pulse but it also asks to specify whether the source is primary or secondary.

As I see it to work out Kwh using only the secondary current would only provide a nominal Kwh value as it would only take into account the max of 5 amps going to the meter and have no idea of the primary value to work out the genuine consumption. If primary in turn means that the CT ratio is being considered (I can't see what else it would mean as the primary current is only calculated via ratio and not actually measured) and the pulse will use this calculated energy then I don't see the point in the secondary setting..........unless of course this isn't what it means at all!

Think i'll ask EDMI on Monday!

 

[MDD]

Marvo,

Sorry just saw your post as I posted my previous.

In my mind the output should be linked to the primary, the reason being that if I fit the meter on a 100/5 CT set the number of pulses per second / minute etc would be far less than if it was fitted on an 800/5 set if both were operating at full load. The way I see it the 800/5 set would simply pulse too fast unless a different pulse to Kwh ratio was used. This logic seems ok when thinking about the primary current and in turn Kwh but with secondary currents, unless the ratios are applied I don't see how the pulse could be useful to monitor energy?

I think i'm going to go with primary and just check that an advance of 1 Kwh on the meters energy register corresponds to the right number of pulses. Assuming it does i'll know all is ok but still won't know what the software means by secondary!

P.S. The same meter (EDMI Mk10A) would be used on both a 100/5 or 800/5 LV CT set.

 

[Marvo]

but it also asks to specify whether the source is primary or secondary.

Maybe this refers the whether the supply goes directly through the meter which would be primary sensing or whether it's using a CT which would be secondary or indirect sensing.

 

[MDD]

Thanks for the help with this. I have now discussed this further at work and have an answer as below,

When set to secondary the pulse value is only looking at secondary values, i.e, 5 amps current and 230 volts on the LV CT meter and so regardless of the CT ratio there would only ever be 0.95 Kwh on the secondary. This is useful for the outputs linked to the LEDs on the front of the meter if different CT ratios need to be programmed into stock meters where the value printed on the front is always the same per model (in this case MK10A CT).

In this scenario the pulses are not actually useful for calculating energy unless you take the transformer ratios into account and the values used will be in wh/pulse.

Primary on the other hand looks at the energy values after the meter has performed it's calculations using the programmed ratios and will simply pulse when the specified energy volume is recorded by the meter and so more consideration would need to be given to the anticipated load when setting a value using primary.

Hope that makes sense!