Accurate monitoring and evaluation are the first steps toward improving energy efficiency for residential, commercial and industrial installations. Whether it is about tracking usage or evaluating distributions, monitoring load levels and the installation itself, the result is more precise billing and invoicing.
What is accuracy?
The largest allowable measurement error that exists under operating conditions is referred to as accuracy. The displayed measurement's accuracy is expressed as a percentage, and it shows how similar the displayed measurement is to the actual value of the signal measured.
Electricity metering accuracy is crucial to ensure the integrity of a billing system, with anomalies in measurements resulting in huge variations in the electricity bill. To assess whether the accuracy of the measurement is satisfactory, it is important to understand the accuracy class of the instrument. The higher the accuracy, the lower the error, allowing for a measured value that is more in line with actual consumption and ultimately reducing discrepancies in billing.
For example, if we consider an installation with an average demand of 100kW for approximately 2000 hours every year, depending on the measuring instrument used, the overall expenses of the installation will vary. An accuracy of 0.5% may lead to a difference between an actual and measured value in the range of ±1.000kWh, increasing to ±2.000kWh with 1% and to ±4.000kWh with 2% accuracy. Using measurement instruments with Class 0,5 accuracy instead of Class 2 instruments, could generate a saving of around 540€ on annual energy costs (based on an assumption of 0,18€/kWh).
That is why the standards governing the use of measuring instruments for billing applications prescribe the use of meters whose accuracy remains within a well-defined range.
What is the Measuring Instruments Directive (MID)?
The MID 2004/22/EC was introduced by the European Commission in 2004 to promote the free trade of measuring instruments throughout Europe and provide common rules for their usage. The directive was later updated by 2014/32/EU that came into force in April 2016. It applies to devices and systems with a measuring function, such as gas, electrical and heat meters as well as weighing instruments, taximeters and even the fill line of beer glasses.
MID is designed to guarantee a high and standardized level of accuracy of measuring instruments while providing assurance to all parties that the measurements and readings can be trusted.
How accurate is your class?
To reduce energy costs, it is important to understand the accuracy class instruments can offer and how accurate measured values will be. There are three accuracies methods to choose from including:
- Full scale accuracy (%FS) which has the poorest accuracy when measuring lower values
- Percentage of the reading (%RD) that has a constant and linear error of reading
- IEC-compliant accuracy that guarantees an accurate measurement in any conditions, aligned with performance classes defined in IEC 61557-12 (PMD) or IEC 62053-21,22 (electricity meters)
IEC compliance guarantees the most accurate measurement in any condition. On top of IEC requirements, to be in line with MID and ensure anti-tampering on the billed energy, there are some additional requirements that needs to be fulfilled for fiscal traceability. These include using tampering seals to prevent unauthorized access and using anti-tamper switches to trigger the meter if the case is opened.
How ABB measures up
ABB’s approach to optimizing energy usage is to provide products and solutions that provide a detailed picture of consumption in terms of quantity, quality and location. This allows building owners to identify areas for improvement and consequently take informed decisions to reduce costs.
The ABB offer covers a wide range of energy efficiency devices that can be used to monitor systems in different areas and with different levels of accuracies.
For example, CMS sensors can monitor single branches on both AC and DC currents with accuracy of 1 or 0,5%FS, depending on the open-core or solid-core shape.
ABB EQ Meters offer a comprehensive solution for sub-billing thanks to MID Certification and accuracy classes B or C, perfectly fit the sub-metering requirements.
Alternatively, M4M is the new generation of network analyzer for high level power monitoring and analysis with class 0,5S accuracy for active energy and a full set of IEC accuracy compliance including on power quality KPIs, such as unbalances and harmonics.
Accurate measurement is key to unlocking the potential for energy savings: to find out more about how ABB’s range of energy management tools could support your targets click here.
