Reading Power and Energy

Hi

I have an green application that needs to read power in KW and also accumulate total energy consumed over 4-5 seperate single phase 20A - 40A circuits (may need to be expanded at a later time). I will also need to display a some sort of chart of this information in real-time? Can someone point me in the right direction as to what Cbus hardware interfaces to use and how to program a homegate application that will do the monitoring and also be able to switch on/off certain appliance/loads when specific pre-set power or energy setpoints have been reached?

thanks

 

checkout: http://www.cbusforums.com/forums/showthread.php?t=5533

 

See the PICED help file for details of power meter support.

If you want energy values, you will need to write a bit of logic to accumulate the values.

Colour C-Touch, HomeGate and Schedule Plus can all graph data. Refer to the help file for details of graphs.

Use the Schneider EN40 pulse power meter or any power meter with an analogue output into a General Input Unit.

I am not aware of any existing examples of how to do this. If I get a chance, I will see if I can put something together in the next few days.

 

1. do we have requirements for pulse power meters?
2. we have ABB power meter which gives 100 pulses per 1kWh, is it OK to connect to bus coupler?

thank you

 

As an extra clarification to the above most pulse power meters put out a fixed 'mark' width marker pulse and then a variable 'space' time delay to the next pulse to achieve n pulses per KWHr. Typically the marker pulse is 10ms, 20ms or sometimes 50ms in duration so it's pretty short. Will a bus coupler always see pulses of this short width ?

K

 

By Default, a Bus Coupler de-bounces it's inputs so that any pulse needs to be 48ms long for it to be captured as an input. This is for de-bouncing of mechanical switches.

This is configurable in 16ms increments. If it is configured to 0ms in Toolkit, then the unit will check the inputs once every 16ms to see if a valid input is there. If you're using a pulse power meter that outputs 10ms-wide pulses, there is a chance that it will be missed.

 

Pulse Power/Energy Meters

Somehow, using pulse meters doesn't seem to stack up - has anyone been successful in this endeavour?

If the EN40 needs estimates of Voltage & PF then it cannot be called a true power meter as these variables are unknown in any particular installation and may vary considerably during the day especially in industrial/commercial situations?

If thats the case, the EN40 may not be any more accurate that the "CENT-A-METER" product?

And not being an accumulation meter means possible loss of meaningfull data?

Seems there are some doubts whether the Bus Coupler can do the job because of response times - so we may need to use more expensive Cbus interface?

Issues about safety/isolation may require other measures or Input devices?
Homegate programming development to provide energy displays, charts, histories and energy managment may be somewhat time consuming?
Costs may be significant if we want to monitor more than one load circuit?

Has anyone been successful in using pulse meters and can give us an idea of costs, performance and time involved?
From a systems integrator point, our margins are being constantly squeezed by competition and the high costs of Cbus components so the time required to do the job is very important.

 

yep.... There have been a number of studies that show if a homeowner can see their present power use, they will be inclined to switch things off. Having used the EN40 onto c-Bus and displaying on a touchscreen for the last 3 months (in test), I have found this to be true.

The EN40 is a class 1 meter. see http://www.schneider-electric.com/c...ew_kilowatt_hours_meters_en40_and_en_clic.xml

it is completely different to a cent-o meter

The EN40 is an accumulation meter... the C-Bus reading it is not

As stated, been using it for some months.... the doubts you speak of come from where?

If you use a 5504AUX in a switchboard with mains rated (240v rated fig 8) and segregation between the EN40 contacts, this shouldn't be an issue. There are quite a number of products on the market that require such connections in a s/bd

You might need to experiment as a lot of SI's do before subjecting customers to systems.

This is a solution for energy monitoring which is relatively low cost, and easy to configure. I used a graph on a C-Touch to show my historical data as well as a monitor to show the present power use... As I said, it's been very useful in highlighting to my family where power is wasted.

 

Cbus Power & Energy Monitoring

Thanks Nick,

We have been looking at providing Energy Monitoring solutions for our cbus automation projects for the last 12 months or more and this demand is coming from our builder/planning clients, mainly for apartment blocks.

Over the past six months I have put on hold about 4 projects that have requested Energy Monitoring (20 apartments).

I have played around with a pulse power meter, and they seem OK for basic power demand monitoring, but overall lacks a "complete solution" for home energy monitoring. You still got to do all the hard work with PICED programming and I can see that each solution will be different?

If the energy pulses are not accumulated properly and cannot be re-discovered by PICED or HomeGate (not possible with a pulse meter), then you have an irrecoverable loss of data. Even if PICED restores its own data after a break, you have to begin an entirely new record of energy consumption that is not related to the previous record (since you will have no knowledge) unless you add some predictive programming of sorts to "estimate" the energy loss over that period - which starts to get complicated?

Since hearing about the Syntek meter, have been pounding their door waiting for its release. I have seen the unit and how the software works and it looks great. The only Cbus configuration is to set the unit address with toolkit and the meter simply broadcasts its data over the Cbus Network.
The Syntek software does the rest with simple "fill in the form" details for specific site details like what each channel is monitoring, email addresses etc.
The bar graphs and line charts are impressive, and displays power,energy, carbon emissions, costs, gas, water etc.

From what I was told its a true Energy/Power meter with billing accuracy like an AMPY, it uses external CT's and has other features. The meter is a full accumulating meter, the energy readings are restored after a power interruption and the Syntek software logs all readings so can calculate power or energy between.

Some extra software features were un-finished when I saw the unit in December, these were to be finalized when they release for sale?
A drawback is that PICED and Homegate don't have direct support for this unit, it would be great if some kind of driver or interface was available to do this - they mentioned its something to do with application numbers?

My query was a result that Newman mentioned possible response time issues that some pulses may not be counted and also while playing around myself I had some incorrect readings (may have been my oversight) ?

I can see that the En40 does have its application, my other concern was/is that since it uses a bus coupler (or other Cbus input modules) over the cbus network to count the pulses in real-time, then there is always the possibility that some pulses will be missed and hence reduce overall accuracy since it will be counting over long periods of time then these errors will grow over time?

From my understanding you cannot guarantee whether the cbus transmission takes place within a specific time period (apart from input response time) - so another power pulse may arrive at the input before the previous one has been received and registered by PICED software - Is this possible?

Have you guys tested the pulse output of the EN40 with a digital counter and compared this count with that received by PICED over a cbus network that is running a typical cbus application with a touch screen and average cbus traffic over a period of say 30 - 90 days?

Generally, my enquiries want to be able to display energy and power usage over different periods of time, daily, weekly, monthly, quarterly, half-yearly.
Real time and historical charts are good for these but others also want a table printout of monthly energy usage and costs for sub-tenant sharing etc.

Power is probably more usable for quick displays since it is not time dependent and good for comparing different periods. When comparing energy costs and carbon emissions we need to use energy values to determine those quantities, accumulated energy is probably not that useful except for giving you an idea of what's been happening over longer periods of time and billing.

The other point is that most of my clients want to monitor more than just the main switchboard feed, they that want to segregate and monitor into several circuits (some want to do monitor all CB's) such as Light, Power and air-cond? This is where the En40 solution would begin to get relatively expensive?

The En40 is rated for around 40Amps, so a single En40 is not suitable for monitoring the full load of standard domestic switchboard - you either need more than one En40 or need to buy a larger model?

 

My comment was in response to your statement that some power meters have 10ms or 20ms output pulses. If you happen to use a pulse power meter that outputs only 10ms wide pulses, and the bus coupler only checks the inputs once every 16ms, then there's a chance that it will be missed. This is not a problem if you use the EN40.

 

If you want to monitor the whole switchboard power you will need to use the more costly ME1zr model - rated at 63A which still may not be quite high enough for heavy load periods - but also be warned the pulse resolution is 100 times lower than the EN40P so you won't get a good power/energy profile?
At 1 pulse per KWh you will probably only get 10 pulses per day in a typical apartment - which is hardly enough to see any trend, so you are better off using multiple EN40P's on each major load circuit if your budget allows.

Alternatively the ME4zrt unit can be used with external CT's. But if you use the ME1zr or ME4zrt models the power pulse resolution is 100 - 1000 times lower than the EN40P depending on CT and model used - it seems unlikely that these models will be good enough to show decent energy trends in apartments or homes?

 

I understand the 'low cost pulse' solution but wouldn't ModBus/TCP have been a more complete solution? Unfortunately that would require a H/W interface of some sorts, or a software interface to a user supplied gateway. In my case I have a PM9C and an EGX100 gateway but it's not integrated into CBus.

Ingo

 

Hey thanks for all the replies guys!

Wow - Looks like I have a bit of reading and investigating to do on this subject, I will look into the Synctek and the EN40P metering options.

The project I am currently looking at does need full energy monitoring features including logging of all energy consumption not just power.
I'm not an expert in PICED programming, and don't really want to make the energy monitoring aspect of my projects a major development or programming issue but do need to find a good reliable over all and easy solution.

thanks

 

The synctek energy meter also has modbus and ethernet interface options according to their website