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Category: PRI Excerpts From The Metering Essentials Handbook - An Introduction To Metering BasicsPRI The booklet is designed to be a basic introduction to the subject of electricity sub-metering and not a definitive guide to installing any specific meter. Tenant Billing Meters - Your ResponsibilitiesThis is a subject that seems to cause a great deal of confusion but the position is clear. In accordance with Schedule 7 of the 1989 Electricity Act, any reading used to bill a customer or tenant must be taken from a meter approved by Ofgem. According to Ofgem:“In the commercial environment, the landlord may take a supply as a
customer of an electricity supplier. Where the landlord installs a
sub-meter for re-supply to his tenants, he becomes the authorised
electricity supplier under Schedule 7(1)(10) of the Electricity Act. He
is authorised by exemption (Class B: Resale – schedule 4 of the
exemptions order, SI 3270/2001) and his tenants become his customers.
Generally, no meter shall be used for ascertaining the quantity of
electricity supplied by an authorised supplier to a customer unless the
meter is What are the Implications?This rules out almost all panel mounted sub-meters as very few have been
approved. CoP5 Meters (Code of Practice 5)All sites rated above 100kW but below 1MW will have a CoP5 meter installed for billing purposes. These are special meters that record and store 30 minute load survey data. This data is collected daily via a communications link by an approved data collector. The data is then used to create the customer bill and the charges the electricity suppliers have to pay for using the network to deliver the electricity. The data is owned by the supply company but the customer has the right to access and collect the data at no additional cost (some supply companies charge to provide the data in a convenient format). To access the data directly your Meter Operator will need to put a customer password into the meter and you will need agreement from your supplier. The meter manufacturer or a third-party will be able to supply suitable software to access the data but note that you are only allowed to collect the data between midday and midnight as the rest of the day is reserved for data collection for billing and settlement purposes. Above 1MW CoP3 meters are used and these operate in a very similar way to CoP5 meters. Elements of Sub-meteringThe term ‘secondary’ or ‘sub-meter’ usually refers to commercial or industrial applications downstream of the main billing meter. SafetyBecause of the dangerous voltages involved any invasive work must only be carried out by suitably qualified staff or contractors in accordance with current health and safety regulations. Wiring RegulationsBS7671 came into force on 1st April 2006 and covers harmonised colours and alphanumeric marking of cables, conductors and terminals in new electrical installations. It is now not permissible to install equipment or wiring in the UK using the ‘old’ colours (red, yellow & blue for phases, black for neutral). All conductors and terminals must be marked ‘L1’, ‘L2’, and ‘L3’. Conductors can be colour-coded either with ‘new’ colours (brown, black & grey for phases, blue for neutral), or brown for all phases, blue for neutral. Types, Characteristics & ApplicationsThere are three main designs of fixed electricity meter: surface-mounted
for fixing to a wall or on the front of an enclosure, panel-mounted for
installing in the front of an electrical panel and DIN-rail-mounted for
mounting in the back of a control panel. In addition to the mounting
format, meters may have differing characteristics, according to the
application: Accuracy & StandardsClass 1 accuracy is usually all that is required for sub-metering applications. Select a meter that meets a good international standard such as IEC/BS EN 61036 but more importantly buy your meter from a reputable manufacturer or supplier that can provide after-sales support for the life of the meter. For power quality meters use the international standard EN50160. Communication OptionsPulsed Output – as a minimum the meter should have a kWh pulsed output.
Meters that also offer a second output for kVAh or kvarh will allow
power factor and kVA or kvar Maximum Demand to be monitored. Electrical ConnectionsThe majority of sub meters sold in the UK are 230V, 3-phase, 4-wire, connected via current transformers for circuits above 100 A rating. In this configuration of three phases and a neutral, three CTs are required, one for each phase. If the meter has internal CTs the secondary lead from each CT can be commoned and earthed, reducing the amount of cabling needed. Not all low-voltage three-phase supplies have a neutral. Systems such as 400V 3-phase 3-wire motor controllers require only two CTs for accurate measurement. High-voltage systems are also 3-phase 3-wire but voltage transformers are used in addition to the current transformers, voltage transformers are used to reduce the voltage to 110V. Most industrial HV applications are 11kV although other voltages (33kV, 66kV etc) are still used on some sites. Building Regulations L2These new regulations came into effect in 2002 and are intended to
improve the monitoring of energy consumption within buildings with a
view to reducing carbon emissions. The regulations relate to new
buildings or major refurbishment.
All three phase supplies of 75A and above will need to be metered. For single phase supplies the current rating will need to be above 200A before metering is needed unless the supply is for chillers or pumps etc as detailed above. Energy Performance of Buildings Directive (EPBD)The European Union Energy Performance of Buildings Directive was
published in the Official Journal on the 4th January 2003. The overall
objective of the Directive is to: Enhanced Capital Allowances (ECA)As part of the Government’s commitment to reducing CO2 emissions, businesses investing in certain energy-saving technologies can benefit from a significant tax break (100% first year capital allowance). These technologies include electricity meters to IEC EN61036 or BS8431 when used as part of an Automatic Monitoring and Targeting system that meets the required criteria. For further information visit the ECA website at www.eca.gov.uk Other Sections Covered Include:Meter Accessories: Meter Installation: Specifying Sub Metering: Specifying PRI Meters:
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