Section S2 – Supplier Volume Allocation Rules 
Simple Guide 

Section S: Annex S2 sets out how the metered quantities for
Metering Systems are determined and allocated to
Supplier BM Units and
Secondary BM Units by the
Supplier Volume Allocation Agent (
SVAA).
The Supplier Meter Registration Services
Each Supplier Meter Registration Agent (SMRA) must have arrangements for the exchange of data with Suppliers, Licensed Distribution System Operators (LDSOs), Non Half Hourly Data Aggregators (NHHDAs), Half Hourly Data Aggregators (HHDAs) and the SVAA.
Half Hourly Data Collection and Aggregation
Each Supplier is required to ensure that the SVAA is given the total consumption in each Settlement Period for all Half Hourly Metering Systems or Unmetered Supplies (UMS) with Equivalent Metering for which the Supplier is responsible.
Half Hourly Data Collection
The Supplier is obliged to ensure that each of its Half Hourly Data Collectors (HHDCs) collects Metered Data for the Metering Systems for which it is appointed. Metered Data comprises the Supplier's Meter Register Consumption in kWh for each of the Settlement Registers within a Metering System, and may be collected by site visit or by remote means.
The HHDC sums these values for each
Metering System to give a
Supplier's
Metering System Metered Consumption. Energy flowing through a
Metering System can be allocated between two or more
Suppliers, which are referred to as the
Primary Supplier and the
Secondary Supplier(s) using one of the four Allocation Methods specified in
BSCP550.
BSCP550 sets out further rules for making a
Shared SVA Meter Arrangement.
Where such a Shared SVA Meter arrangement exists, the HHDC uses an Allocation Schedule, provided by the Primary Supplier, to determine each Supplier's Metering System Metered Consumptions for provision to the relevant HHDAs.
Half Hourly Data Aggregation
The Supplier is obliged to ensure that each of its HHDAs receive data from the relevant HHDCs and calculate BM Unit's Metered Consumptions (where the HHDA is Qualified for calculating consumption values for Base BM Units and Additional BM Units) or Supplier's Metered Consumption (where the HHDA is Qualified for calculating consumption for a Supplier Base BM Unit only). The HHDA allocates consumption to the appropriate BM Unit using the GSP Group identified assigned to each Supplier Metering System.
Aggregated Half Hourly consumption values are allocated to the appropriate Consumption Component Class (CCC), depending on whether the value is metered or unmetered, import or export, actual or estimated and whether the Supplier Metering System is mandatory half hourly (above 100kW maximum demand) or elective (below 100kW).
The HHDA calculates the estimated line loss value associated with the consumption value (using Line Loss Factors provided by LDSOs) and assigns these values to appropriate CCCs. The preloss adjusted consumption values and the associated loss estimates are allocated to separate CCCs.
Determination of Secondary BM Unit’s Metering System Metered Consumption
Each Supplier shall ensure that its HHDA provides half hourly metered consumption values for any Half Hourly Metering System for which it is appointed and is registered in a Secondary BM Unit in accordance with Section S11.
Determination of Metering System Delivered Volumes
Where a Virtual Lead Party (VLP) has provided an MSID Pair Delivered Volume for each MSID Pair in a Secondary BM Unit in accordance with Section S11, the SVAA shall determine the Metering System Delivered Volume for the Import and, where applicable, Export MSID comprising the MSID Pair.
Where an Asset Metering Virtual Lead Party (AMVLP) has provided an AMSID Pair Delivered Volume for each AMSID Pair in a Secondary BM Unit in accordance with Section S11, the SVAA shall determine the Metering System Delivered Volume for the Import and, where applicable, Export MSID comprising the AMSID Pair. Note that AMSID Pairs, registered by an AMVLP to Secondary BM Unit, can be used for both Asset Metering and Asset Differencing.
The SVAA will determine the Metering System Delivered Volume using the MSID/AMSID Pair Delivered Volume received from the VLP/AMVLP and the half hourly metered consumption values received from the HHDA.
The SVAA shall inform Elexon and the NETSO if the MSID/AMSID Pair Delivered Volume cannot not be allocated to MSIDs/AMSIDs.
Non Half Hourly Data Collection and Aggregation
For Non Half Hourly Metering Systems, the objective of Non Half Hourly Data Collection and Aggregation is to provide the data to the SVAA necessary for the profiling calculations that determine half hour by half hour consumption values.
These data are referred to as a Supplier Purchase Matrix, and Suppliers are obliged to provide the SVAA (via their appointed NHHDA) with a Supplier Purchase Matrix for each Settlement Day, comprising Annualised Advances (AAs), Estimated Annual Consumptions (EACs) and Unmetered Consumption, totalled for that Supplier but subdivided for each combination of Profile Class, Line Loss Factor Class, Standard Settlement Configuration and Time Pattern Regime (collectively known as a Settlement Class).
Non Half Hourly Data Collection
The
Supplier is obliged to ensure that each of its NHHDCs collect
Metered Data for the
Metering Systems for which it is appointed at intervals and in a manner described in
BSCP504. The
Metered Data comprises a reading in kWh for each of the
Settlement Registers within a
Metering System, and may be collected by site visit, by remote means or by customer reading.
When a new meter reading has been taken, the NHHDC then calculates, for each Settlement Register, the Meter Advance as being the difference since the previous reading, with the period between the two readings being known as the Meter Advance Period. Daily Profile Coefficients are supplied by the SVAA that describe the proportion of annual consumption expected on each particular Settlement Day, and the NHHDC uses these to calculate the Fraction of Yearly Consumption, which is the proportion of annual consumption that would be expected over the Meter Advance Period.
The Annualised Advance (AA) is then derived as the Meter Advance divided by the Fraction of Yearly Consumption, and represents an annual rate of consumption for the Metering System equivalent to the Meter Advance over the Meter Advance Period.
As well as calculating an AA for the period before a meter reading, the NHHDC produces an Estimated Annual Consumption (EAC), to apply to the period following the meter reading until such time as another meter reading is taken. The EAC is calculated as a weighted average of the AA for the Meter Advance Period just gone and the Previous Estimated Annual Consumption (PEAC) that had been previously calculated for that Meter Advance Period.
The relative weightings attached to the AA and PEAC depends on the length of the Meter Advance Period, such that the EAC is dependent on the AA alone when the Meter Advance Period exceeds around 6 months (although this time can be varied through the Panel's choice of the Smoothing Parameter). For a Long Term Vacant Metering System the EAC is set to zero.
Where the NHHDC has not been able to calculate a Meter Advance, despite making reasonable endeavours to do so, the NHHDC is required to (in some circumstances) or may (in other circumstances) define a Deemed Meter Advance Period, calculate a Deemed Meter Advance and calculate new AAs and EACs for each Settlement Register using these in place of a true Meter Advance and Meter Advance Period.
In specific circumstances, where an EAC has been calculated that does not reflect the likely generation/consumption of the Metering System, then this EAC can be replaced with an EAC that does reflect the likely consumption/generation of the Metering System.
Non Half Hourly Data Aggregation
The Supplier is obliged to ensure that each of its NHHDAs receives data from the relevant NHHDCs. For each Supplier and each Settlement Class, the NHHDA will calculate the total of all the AAs for meters that have been read since the Settlement Day and the total of all the EACs for meters that have not yet been read (but for which an EAC is available), together with the number of Metering Systems contributing to each of these totals.
There are also Non Half Hourly Unmetered Metering Systems. These are supplies that are neither metered nor have Equivalent Metering. Such Unmetered Supplies are regarded as notionally having Metering Systems for which the NHHDA determines a consumption value merely equal to the EAC (which was assigned by the LDSO). The NHHDA also takes the total Unmetered Consumption from Unmetered Supplies for each Supplier, together with the number of these Unmetered Metering Systems contributing to this total.
Where a Metering System has neither been read nor a value of EAC provided, a default consumption value, the Default Estimated Annual Consumption for Metered Metering Systems is calculated. Provided there are a sufficient number of Metering Systems with either AAs or EACs for the Supplier in the particular Settlement Class, then the default is equal to the average of those AAs or EACs. Where the number is insufficient a national average figure is used.
Similarly for Unmetered Metering Systems missing an EAC value, the Default Estimated Annual Consumption for Unmetered Metering Systems is calculated either as the average of consumption values for the Unmetered Metering Systems for the same Supplier in the same Settlement Class or as national average. The totals provided to the SVAA then include the relevant default consumption values and the numbers of Metering Systems comprising those totals.
If a
Supplier is notified in writing by an
LDSO that it requires the relevant NHHDA to provide it with EAC data and
Metering System details, each
Supplier shall ensure that its relevant NHHDA provides the EAC data and
Metering System details to each relevant
LDSO as is detailed in
BSCP505.
Supplier Volume Allocation Data Input
The SVAA receives various data from Suppliers and LDSOs in accordance with various BSC Procedures (BSCPs). It also calculates:
(a) a GSP Group Profile Class Default Estimated Annual Consumption for each GSP Group and Profile Class, used by HHDAs and NHHDAs in the determination of default EACs;
(b) a GSP Group Profile Class Average Estimated Annual Consumption for each GSP Group and Profile Class and Standard Settlement Configuration, which is provided to Suppliers for use by their appointed NHHDCs for new connections, where a Meter Advance has not yet been calculated;
(c) an Annual Fraction of Yearly Consumption for each combination of GSP Group, Profile Class, Standard Settlement Configuration and Time Pattern Regime. This represents the proportion of the annual consumption expected to be recorded by each of the registers of the Metering System.
For each calendar year, each
Supplier is required to assist the
Profile Administrator in providing NHH profiling information as required by
BSCP510.
This involves Suppliers annually recruiting new customers to address any shortfall or deficiency in the profiling sample. Suppliers will also be responsible for replacing these customers' existing NHH Settlement meters with Half Hourly (HH) capable meters, so that HH consumption data can be collected for profiling alongside the normal NHH data used in Settlement.
Suppliers have the choice to either use their own Party Agents to provide/install the necessary meters and collect the HH data (in which case they will be reimbursed for these costs), or to use the PrA's nominated agents free of charge for these services as well as normal NHH data collection.
Where a Change of Supplier occurs, no action is taken to retain the customer and the customer is lost from the profiling sample. The resulting shortfall in sample numbers is then taken into account in the following year's annual recruitment exercise, when a replacement customer will be recruited.
For each Metering System in a particular GSP Group, Profile Class and each combination of Standard Settlement Configuration and Time Pattern Regime, the SVAA derives a set of coefficients, one for each Settlement Period, which when multiplied by the corresponding AA or the EAC would give an estimate of the consumption through that Metering System.
Broadly, the algorithm is as follows. A set of coefficients, the Matrix of Regression Coefficients, is supplied by the Profile Administrator, and the SVAA selects the coefficients applicable to the relevant Season and Day Type (which specifies whether the day is a Weekday, Saturday, Sunday or Bank Holiday). The coefficients are applied to a number of variables:
(a) Noon Effective Temperature, which is a weighted average over the current and previous two Settlement Days, derived from data supplied to the SVAA by the Temperature Provider in respect of each GSP Group;
(b) Sunset Variable, being the sunset time in minutes after 18:00 hours Greenwich Mean Time procured from sources agreed by the Panel;
(c) the square of the Sunset Variable; and
(d) a number of variables that have the effect of modifying the profile if the Settlement Day is a Monday, Wednesday, Thursday or Friday (Tuesday being regarded as the standard weekday).
This produces, for each GSP Group, Profile Class and Settlement Period, the Estimated Regional Average Demand Per Customer for each Settlement Period in kW. This value is divided by the Group Average Annual Consumption (after converting MWh to kW, by multiplying by 2000, for each annual Settlement period) for SVA Customers in that GSP Group and Profile Class (also supplied by the Profile Administrator).
The result is the Basic Period Profile Coefficients which represent, for a given GSP Group and Profile Class, the proportions of a SVA Customer's Consumption in each Settlement Period.
However to accommodate the different Time Pattern Regimes within a Standard Settlement Configuration a number of extra steps are required. Each Time Pattern Regime has an Unadjusted Interval defined by an Unadjusted Interval Start Time and an Unadjusted Interval End Time and which defines the spot times for which the register associated with the Time Pattern Regime is recording.
Corresponding Adjusted Intervals, with Adjusted Interval Start Times and Adjusted Interval End Times, are derived to meet various criteria such as: recognising that the Unadjusted Interval Start Time of one Time Pattern Regime may be the Unadjusted Interval End Time of another, that there is no gap or overlap between the corresponding Adjusted Intervals; there are no Adjusted Intervals of zero duration, and minimising the sums of the squares of the differences between Adjusted and Unadjusted Interval Start and End Times.
For each Time Pattern Regime a Period Time Pattern State Indicator for each Settlement Period then specifies whether, according to Adjusted Interval Start and End Times, the register associated with the Time Pattern Regime is deemed to be "on" or "off" and hence whether there will be a value of Period Profile Class Coefficient for that Time Pattern Regime in that Standard Settlement Configuration for the particular GSP Group and Profile Class.
Period Profile Class Coefficients are then derived by dividing the ‘on’ settlement periods associated with the Time Pattern Regime by the appropriate Average Fraction of Annual Consumption. Daily Profile Coefficients are derived by summating the Period Profile Class Coefficients for each Time Pattern Regime across the Settlement Day.
Further provisions are required for switched loads. For switched loads, the associated Profile Class will specify both the Baseload Profile Coefficients that apply to the unswitched consumption and Switched Load Profile Coefficients that apply to the switched consumption. The Period Time Pattern State Indicator for the switched load then becomes a Switched Load State Indicator.
For those Settlement Periods in which the Switched Load State Indicator is zero then Normal Register Profile Coefficients are derived as being a combination of the Baseload Profile Coefficients and the Switched Load Profile Coefficients in the proportions of the Baseload Fraction and the Switched Fraction provided by the Profile Administrator.
The Baseload Profile Coefficients are derived for each Settlement Period directly from the Basic Profile Coefficients specified for the corresponding Settlement Periods for the Time Pattern Regime corresponding with the Baseload Profile. However, the Switched Load Profile Coefficients are derived as follows. The On Duration for a particular Time Pattern Regime is determined by identifying the number of Settlement Periods for which the Switched Load State Indicator is set to one.
The first n Basic Profile Coefficients for the Time Pattern Regime corresponding with the Switched Load Profile are selected, where n is the number of Settlement Periods corresponding to the On Duration, and these are assigned to the Switched Load Profile Coefficients in the Settlement Periods for which the Switched Load State Indicator is one. The Switched Load Profile Coefficients for the particular Standard Settlement Configuration is zero in all other Settlement Periods.
Half Hourly Metering System Consumption
The consumption and line loss values provided by HHDAs are allocated to the appropriate Supplier Base BM Unit or Additional BM Unit. Separate totals (either consumption or associated line losses) are calculated for each BM Unit, CCC and Settlement Period.
The SVAA calculates line loss values based on the half hourly metered volumes provided by HHDAs in respect of Metering Systems associated with Secondary BM Units. The SVAA reports half hourly metered volumes and associated line losses to the relevant ViLP/AMVLP. Separate totals (either consumption or associated line losses) are calculated for each Secondary BM Unit, CCC and Settlement Period.
The SVAA calculates line loss values based on the Secondary BM Unit Delivered Volumes provided by the VLP/AMVLP. The SVAA reports Secondary Half Hourly Delivered volumes (and associated line losses) to the relevant Supplier for each MSID, subject to customer consent for the MSID in question.
Non Half Hourly Metering System Consumption
From the Supplier Purchase Matrix submitted by each NHHDA (consisting of the AAs, EACs and Unmetered Consumption, totalled by Supplier and for each combination of Profile Class, Line Loss Factor Class, Time Pattern Regime and Standard Settlement Configuration), the SVAA will determine a BM Unit Purchase Matrix for each Supplier's Base BM Units and any Additional BM Units. This is achieved by selecting the data for the GSP Group, Profile Class, Line Loss Factor Class and Standard Settlement Configuration assigned to the particular BM Unit and summing across all NHHDAs.
The SVAA then multiplies these values by the Period Profile Class Coefficients for each combination of GSP Group, Profile Class, Standard Settlement Configuration/Time Pattern Regime and Settlement Period to give the BM Unit's Profiled Consumption for that Profile Class, Line Loss Factor Class, Standard Settlement Configuration/Time Pattern Regime and Settlement Period.
The SVAA then aggregates the profiled Supplier Purchase Matrix data by BMU Unit, CCC (NHH non losses only) and Settlement Period. The SVAA uses Line Loss Factors provided by LDSOs to calculate the line losses associated with the profiled Supplier Purchase Matrix data. The SVAA aggregates these losses by BM Unit, CCC (NHH losses) and Settlement Period.
For each GSP Group, CCC and Settlement Period, the SVAA calculates the total consumption of all BM Units as the GSP Group Half Hourly Consumption. The difference between the GSP Group Half Hourly Consumption and the GSP Group Take (supplied by the Central Data Collection Agent) is calculated as a proportion of GSP Group Half Hourly Consumption, and the proportion weighted by dividing by a GSP Group Correction Scaling Factor.
The GSP Group Correction Factor for each CCC is then calculated as one plus the weighted proportion. Finally, a Corrected Component is calculated by scaling each Half Hourly Consumption (Non Losses) and a Half Hourly Consumption (Losses) using the appropriate GSP Group Correction Factor.
The purpose of the GSP Group Correction Scaling Factor is to determine whether the particular CCC is corrected or whether the Corrected Component is merely equal to the uncorrected consumption.
Three aggregate quantities are derived:
(a) a
BM Unit Allocated
Metered Volume for each
BM Unit (including
Secondary BM Units) in each
Settlement Period is calculated as the sum of the
Corrected Components for each
BM Unit, CCC, and
Settlement Period, summed over all CCCs. This is used in
Section T for calculating
Trading Charges. In the case of
Secondary BM Units, the
SVAA also determines the
Secondary BM Unit Supplier Delivered Volume;
(b) a Supplier Deemed Take, being the total consumption for each Supplier in each GSP Group in each Settlement Period and which is calculated for reporting purposes; and
(c) a Corrected Correctable
Supplier Deemed Take, being that consumption for a
Supplier in each
GSP Group per
Settlement Period to which a
GSP Group Correction Factor is applied. This equates to the non half hourly consumption and is used for charging purposes in
Section D.
For each Settlement Period in each Settlement Day, the SVAA will determine or, in the case of Timetabled Reconciliation or AdHoc Volume Allocation Runs, redetermine the BM Unit Allocated Metered Demand. Note that in successive runs, the proportion of consumption covered by AAs compared to EACs should increase.
In the event that it fails to obtain BM Unit's Metered Consumption data or Supplier's Metered Consumption data from the relevant HHDAs or Suppliers, the SVAA derives the missing data from the previous run for that Settlement Day or, for the Initial Volume Allocation Run, from the Settlement Day that most nearly corresponds to the characteristics of the Settlement Day having missing data, or, if no such Settlement Day exists, performs the Volume Allocation Run without the missing data.
In the event that it believes that Non Half Hourly Aggregation data has not been determined correctly, the SVAA shall derive the data from the previous run of the same Settlement Day or, in the case of the Initial Allocation Run, data from the previous Settlement Day.
Should the SVAA fail to determine BM Unit Metered Volumes within the required timescales, Elexon determines the missing data using any available data from the SVAA where practicable.
Suppliers have an obligation to provide reasonable assistance to the SVAA and to Elexon to determine missing data.
In the event that an HHDA fails to provide half hourly metered data in respect of Half Hourly Metering Systems in Secondary BM Units, the SVAA shall derive the missing data from the previous run for that Settlement Day or, for the Initial Volume Allocation Run, shall perform the run without the missing data.
In the event that one or more VLP/AMVLP fails to provide half hourly metered data in respect of Half Hourly Metering Systems in Secondary BM Units, the SVAA shall perform the run without the missing data.
Estimation of Demand Disconnection Volumes
Each Supplier shall ensure that, for each Demand Control Impacted Settlement Period and each Half Hourly Metering System impacted by a Demand Disconnection, the Half Hourly Data Collector responsible for that Metering System shall estimate the Half Hourly Demand Disconnection Volume for each Settlement Period and provide this to the relevant HHDA.
For all Settlement Days that include at least one Demand Control Impacted Settlement Period, the SVAA shall send the relevant Period Profile Class Coefficients to all Non Half Hourly Data Collectors.
Each Supplier shall ensure that for each Settlement Day, GSP Group and valid combination of Profile Class, Standard Settlement Configuration and Time Pattern Regime, its Non Half Hourly Data Collector shall determine a Demand Disconnection Daily Profile Coefficient and calculate the Fraction of Yearly Consumption for the Meter Advance Period for each Settlement Register.
The Non Half Hourly Data Collector shall recalculate the Fraction of Yearly Consumption on receipt of a revised list of affected Metering Systems or new Demand Disconnection Daily Profile Coefficients.
Each Supplier shall ensure that, for each Settlement Day affected by a Demand Disconnection Event, its NHHDAs shall, for all Metering Systems and affected Settlement Days:
(a) aggregate annualised Consumption Data for Metering Systems which are subject to a Demand Disconnection Event, excluding any that have voluntarily reduced consumption at the request of the Demand Disconnection Impacted DSO; and
(b) provide the aggregated annualised Consumption Data to the SVAA in the form of a Supplier Disconnection Matrix.
For each Supplier's Demand Disconnection Volume, the SVAA shall determine the BM Unit's Demand Disconnection Volume by assigning the Supplier's Demand Disconnection Volume value to the Base BM Unit for the Supplier to which the value of Demand Disconnection Volume applies.
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