Metering dispensations and co-located generation |
Guidance Note |
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Section L sets out the obligations on BSC Parties who register
Metering Systems (
Registrants), for the purposes of
Settlement, in Primary Balancing Mechanism Units (BMUs) or
Asset Metering Systems, for the purposes of
Balancing Services, in Secondary BMUs.
Registrants must ensure that the
Metering Equipment, comprised within the
Metering System(s), for which they are responsible, is compliant with the relevant
Code of Practice (CoP) applicable at the time that
Metering System is first registered in
Settlement. They also need to ensure the
Metering Equipment is calibrated, commissioned, and tested in accordance the prevailing version of CoP4, in the case of
CVA Metering Systems and
SVA Metering Systems or CoP11, in the case of
Asset Metering Systems.
If, for practical and/or financial reasons, any Metering Equipment or Metering System does not meet the requirements set out in the relevant CoP, the Metering Equipment or Metering System may be the subject of an application for a Metering Dispensation from the requirement(s) of the relevant CoP.
BSC Procedure BSCP32 sets out the process to follow when applying for a
Metering Dispensation. For a site specific application, the
Registrant can apply for a
Metering Dispensation or, where a
Registrant has not been appointed yet, the Balancing and
Settlement Code Company (
BSCCo), Elexon, can apply, on behalf of a non-
Registrant.
The purpose of this document is to highlight, and add clarification to, the changes Modification Proposal P453 made to the requirements in CoPs 1, 2, 3, and 5, in relation to the Actual Metering Point (AMP) and the Defined Metering Point (DMP); and the amendments to the Metering Dispensation process in BSCP32, in relation to BSCCo (Elexon) approving applications in limited circumstance, instead of the BSC Panel. It also highlights situations in which Metering Equipment for a co-located generation site may need a Metering Dispensation and who can approve such Metering Dispensations (i.e. BSCCo (Elexon) or the BSC Panel).
These changes were approved by the BSC
Panel on 11 May 2023 and introduced on 2 November 2023 via
Modification Proposal P453.
Actual Metering Point / Defined Metering Point
The CoPs define the minimum requirements for the Metering Equipment required for the measurement and recording of electricity transfers occurring at a DMP. The location for the DMP is listed in Appendix A of CoPs 1, 2, 3, 5 and 10 for a number of different scenarios (e.g. for transfers between a Distribution System operated by a Licensed Distribution System Operator and Generating Plant, the DMP is the point of connection of the generating station to that Distribution System).
There are situations where the AMP cannot be at the exact point required and is different from the DMP. Whether a Metering Dispensation is required for this difference in location is dependent on how the overall accuracy (section 4.3.1 of the relevant CoP) is met at the DMP and if it requires compensation to be applied for power transformer and/or cable/line and/or busbar losses. P453 also clarified, in CoPs 1, 2, 3, 5 and 10, that the relevant CoP for an embedded circuit will be based on the rating (or demand) of the circuit to be metered, not the CoP that would be relevant if the Metering Equipment for that embedded circuit were located at the DMP.
Section 4.3.3 of CoPs 1, 2, 3 and 5 details the situations where the AMP does not coincide with the DMP and whether a Metering Dispensation is required or not. These situations are:
Where it is necessary to apply compensation for power transformer and/or cable/line and/or busbar losses, to ensure overall accuracy is met at the DMP, a Metering Dispensation is required;
Where it is not necessary to apply compensation for power transformer and/or cable/line and/or busbar losses, to ensure overall accuracy is met at the DMP, a Metering Dispensation is not required, provided that there is only a length of cable or line or busbar between the AMP and the DMP (i.e. no power transformer); and
Where Appendix A, paragraph 5(ii) applies, a Metering Dispensation is not required and accuracy compensation for power transformer and/or cable/line and/or busbar losses (for the purpose of Section K1.1.6 of the Code) shall, where necessary, be applied to meet the overall accuracy limits of error required at the DMP.
It should be noted that if compensation is only being applied for current transformers and/or voltage transformers errors (section 4.3.2 of CoPs 1, 2, 3 and 5) then a Metering Dispensation is not required. Where compensation is being applied for current transformers and voltage transformers errors, in addition to compensation for power transformer and/or cable/line and/or busbar losses then, a Metering Dispensation is required. Only the compensations for the power transformer and/or cable/line and/or busbar losses are validated under the BSCP32 process.
The Registrant of the Metering System is responsible for ensuring that it, or its appointed Meter Operator Agent (MOA), has completed an assessment of the overall accuracy and evidence of the calculation should be retained. Especially, to justify that no accuracy compensation is required where the AMP and DMP do not coincide. This should include evidence such as, where relevant:
Factory Acceptance Tests for power transformers between the AMP and the DMP showing:
No-load (iron) watt losses;
Full load (copper) watt losses;
% excitation current; and
% impedance.
Lengths of relevant sections of any cables, lines or busbar between the AMP and the DMP and the cable, line and/or busbar manufacturer technical specification/information sheets detailing resistance, impedance and capacitance.
Measurement transformer (current transformers and voltage transformers) manufacturer calibration test certificates, tested to the requirements of relevant standard and CoP4.
Meter manufacturer calibration test certificates, tested to the requirements of relevant standard and CoP4.
The CoPs require that this shall be available for inspection by the Panel or Technical Assurance Agent.
The examples which follow highlight different scenarios and whether a Metering Dispensation is required or not.
Starting with the ideal scenario, as can be seen in Figure 1, the Metering Equipment is located (AMP) at the point of connection (DMP).
Figure 1: AMP at point of connection (DMP)
The Metering Equipment is compliant with the CoPs in all respects and no compensation is required for power transformer and/or cable/line and/or busbar losses so, no Metering Dispensation is required.
If the AMP is now a distance (200m) from the DMP, where the point of connection is, as per the example in Figure 2.
Figure 2: AMP a distance from DMP
The Metering Equipment is compliant with the CoPs in all other respects and, following an assessment of the losses, compensation is not required for cable/line and/or busbar losses in order to ensure overall accuracy is met at the DMP, so, a Metering Dispensation is not required.
An assessment of the overall accuracy and evidence of the calculation should be retained to justify that no accuracy compensation needs to be applied in order to maintain accuracy at the DMP, in relation to each AMP.
Should the distance between AMP and DMP be greater and the losses for cable/line and/or busbar losses become material to the extent that compensation has to be applied then, a Metering Dispensation is required.
If the AMP is instead on the low voltage side of the power transformer, as per the example in Figure 3, with the DMP on the high voltage side of the power transformer, where the point of connection is.
Figure 3: AMP on low voltage side of power transformer
The Metering Equipment is compliant with the CoPs in all other respects and compensation is required for power transformer and/or cable/line and/or busbar losses in order to ensure overall accuracy is met at the DMP so, a Metering Dispensation is required.
In any of the examples, should there be anything not compliant with the CoPs (e.g. current transformers installed with an accuracy class that does not meet or exceed the minimum requirements of the relevant CoP) then, a Metering Dispensation would be required for that non-compliance.
For the assessment of overall accuracy, the site developer or Metering System Registrant, or their appointed MOA, must consider a variety of factors.
Where the Metering System is at the point of connection (DMP) the factors to be considered would be, where applicable:
Meter errors;
Current transformer ratio error and phase displacement;
Voltage transformer ratio error and phase displacement;
Connected burden to the secondary side of the measurement transformers; and
Secondary wiring losses.
This assessment requires the calibration test certificates for the individual items of Metering Equipment or, where a certificate including percentage errors at various load points is not available, the worst case error for the accuracy class would be used (i.e. for a class 1.0 Meter a value of +/-1% would be used in the assessment).
Should there be any changes to the Metering Equipment or connected burden the overall accuracy assessment must be performed again.
Where the Metering System is not located at the point of connection (DMP) some, a combination of, or all of the following factors to be considered would also include:
This assessment requires the factory acceptance test certificate for a power transformer and the technical specifications of the line and/or cable and/or busbar (including relevant lengths).
The limits of overall accuracy are specified in section 4.3.1 for
Active Energy and 4.3.2 for
Reactive Energy. If we take the
Active Energy limits specified in
CoP1 as an example:
Table 1: CoP1 overall accuracy limits of error (as at May 2023)
Condition | Limit of Errors at stated System Power Factor |
Current expresses as a percentage of Rated Measuring Current | Power Factor | Limits of Error |
120% to 10% inclusive | 1 | ± 0.5% |
Below 10% to 5% | 1 | ± 0.7% |
Below 5% to 1% | 1 | ± 1.5% |
120% to 10% inclusive | 0.5 lag and 0.8 lead | ± 1.0% |
The overall accuracy assessment must take into account all the required contributing factors and confirm that no compensation for power transformer and/or cable/line and/or busbar losses is required to meet the relevant CoP overall accuracy limits of error.
As an example, for a point in the 120% to 10% Rated Measuring Current range, at Unity Power Factor (i.e. power factor of 1), where the only factors to be considered are:
Current transformer error: +0.15%
Voltage transformer error: +0.35%
In this scenario, for a CoP1 Metering System, compensation would need to be applied to be compliant with the overall accuracy limits of error. As this compensation would be for the error introduced by the current transformer and voltage transformer, a Metering Dispensation would not be required.
Taking a second example, under the same conditions, but where an additional factor of cable losses needs to be considered:
Current transformer error: +0.15%
Voltage transformer error: +0.35%
In this scenario, for a CoP1 Metering System, compensation would need to be applied to be compliant with the overall accuracy limits of error. As this compensation would be for the error introduced by the largest contributing factors, in this case from the current transformer and voltage transformer a Metering Dispensation would not be required so long as no compensation was applied for the cable losses.
Taking a third example, under the same conditions, but where an additional factor of power transformer losses needs to be considered:
Current transformer error: +0.15%
Voltage transformer error: +0.35%
Power Transformer: Between +0.53% (at 10% Ir) to +0.26% (at 100% Ir)
Overall accuracy: +1.17% (at 10% Ir)
In this scenario, for a CoP1 Metering System, compensation would need to be applied to be compliant with the overall accuracy limits of error. As this compensation would be for the error introduced by the largest contributing factors, in this case from the power transformer loss and the error from the current transformer and voltage transformer, a Metering Dispensation would be required as compensation is applied for the power transformer losses.
Prior to the implementation of P453, only the BSC
Panel could approve an application for a
Metering Dispensation. The
Panel delegated this authority to the
Imbalance Settlement Group (ISG) and the
Supplier Volume Allocation Group (SVG), based on the ownership of the relevant CoP. Where a CoP is jointly owned it has to be presented for approval to both committees. The
BSC Baseline Statement details the ownership of the CoPs.
Following the implementation of P453, there is a scenario where the BSCCo (Elexon) can approve a Metering Dispensation. This scenario is where the AMP does not coincide with the DMP, compensation is being applied for power transformer and/or cable/line and/or busbar losses, and where two, or more, Metering Systems are to be, or are, registered separately sharing a single point of connection. The Metering Equipment must be compliant with the CoP in all other respects. Where there is a non-compliance then, the decision will be made by SVG/ISG, as applicable.
The following examples provide some scenarios on how the new Metering Dispensation approval process would work.
Taking a scenario, as can be seen in Figure 4, where the site is being split into two (i.e. each part registered with separate either Primary BMUs (i.e. Transmission System connected (‘T_’) or Embedded Generation (‘E_’) or under MPANs). The Metering Equipment is not located (AMP) at the point of connection (DMP) but no compensation is needed to be applied (for power transformer and/or cable/line and/or busbar losses) to meet the overall accuracy limits of error.
Figure 4: AMP not at DMP, site being registered in two parts and no compensation required
The Metering Equipment is compliant with the relevant CoP for the metered circuit in all other respects and, following an assessment of the losses, compensation is not required for cable/line and/or busbar losses so, a Metering Dispensation is not required.
An assessment of the overall accuracy and evidence of the calculation should be retained to justify that no accuracy compensation needs to be applied in order to maintain accuracy at the DMP, in relation to each AMP.
Taking a second scenario, as can be seen in Figure 5, where again the site is being split into two. The Metering Equipment is not located (AMP) at the point of connection (DMP) and compensation is required to be applied (for power transformer and/or cable/line and/or busbar losses) to meet the overall accuracy limits of error at the DMP.
Figure 5: AMP not at DMP, site being registered in two parts and compensation required
The Metering Equipment is compliant with the relevant CoP for the metered circuit in all other respects and, following an assessment of the losses, compensation is required for cable/line and/or busbar losses so, a Metering Dispensation is required. In this scenario BSCCo (Elexon) can consider the Metering Dispensation application.
If we take the same scenario in Figure 5 but this time the current transformers installed have an accuracy class that does not meet or exceed the minimum requirements of the relevant CoP then, the Metering Equipment is not compliant with the CoPs in all other respects so, the SVG and/or ISG must consider the Metering Dispensation application, as applicable.
Taking a scenario, as can be seen in Figure 6, where the site is being split into two and requires the use of difference metering (i.e. each part registered with separate either Primary BMUs (i.e. Transmission System connected (‘T_’) or Embedded Generation (‘E_’)) or under MPANs). The Metering Equipment related to Part 1 of the site is located at the DMP. The Metering Equipment for Part 2 of the site (i.e. the intermittent renewable generator) is not located (AMP) at the point of connection (DMP) but no compensation is needed to be applied (for power transformer and/or cable/line and/or busbar losses) to meet the overall accuracy limits of error at the DMP.
Figure 6: Difference metering used for AMP not at DMP for Part 2 of site, site being registered in two parts and no compensation required
The Metering Equipment is compliant with the relevant CoP for the metered circuit in all other respects and, following an assessment of the losses for the Metering System for Part 2 of the site not being at the DMP, compensation is not required for cable/line and/or busbar losses so, a Metering Dispensation is not required.
An assessment of the overall accuracy and evidence of the calculation should be retained to justify that no accuracy compensation needs to be applied in order to maintain accuracy at the DMP, in relation to each AMP
Taking a second scenario, as can be seen in Figure 7, where again the site is being split into two and difference metering is required. The Metering Equipment is not located (AMP) at the point of connection (DMP) for Part 2 of the site (i.e. the intermittent renewable generator) and compensation is required to be applied (for power transformer and/or cable/line and/or busbar losses) to meet the overall accuracy limits of error at the DMP.
Figure 7: Difference metering used for AMP not at DMP for Part 2 of site, site being registered in two parts and compensation required
The Metering Equipment is compliant with the relevant CoP for the metered circuit in all other respects and, following an assessment of the losses for the Metering System for Part 2 of the site not being at the DMP, compensation is required for cable/line and/or busbar losses so, a Metering Dispensation is required. In this scenario, BSCCo (Elexon) can consider the Metering Dispensation application.
If we take the same scenario in Figure 7 but this time the current transformers installed have an accuracy class that does not meet or exceed the minimum requirements of the relevant CoP then the Metering Equipment is not compliant with the CoPs in all other respects so, the SVG/ISG must consider the Metering Dispensation application, as applicable.
Where a differencing metering arrangement is being used, the aggregation rule used to perform the differencing calculation shall be created:
For Metering Systems registered in CMRS, this shall be done in accordance with BSCP75 ‘Registration of Meter Aggregation Rules for Volume Allocation Units’; or
For Metering Systems registered in SMRS, this shall be done in accordance with the Metering Operations Schedule of the Retail Energy Code (REC) and BSCP502 ‘Half Hourly Data Collection for SVA Metering Systems Registered in SMRS’, via a Complex Site Supplementary Information Form .
Only the last stage of the process of approval has been amended by P453. An applicant is still required to submit an application and consult with affected parties. Elexon will still consult with appropriate parties, for example:
National Electricity Transmission System Operator or Licensed Distribution System Operator (as appropriate);
Metering Dispensation Review Group;
Electrical Loss Validation Agent.
As part of the BSCCo (Elexon) review of the application we will determine whether the conditions for BSCCo (Elexon) to consider the application have been met. These conditions being:
the AMP does not coincide with the DMP;
compensation is being applied for power transformer and/or cable/line and/or busbar losses; and
two, or more, Metering Systems are to be, or are, registered separately sharing a single point of connection.
Where the conditions have been met, BSCCo (Elexon) will confirm to the applicant, taking into consideration the views of affected and appropriate parties and the opinion of the ELVA on the suitability of the compensation factors, whether we have approved or rejected the Metering Dispensation application. BSCCo (Elexon) cannot approve applications on a conditional basis.
Where the conditions have not been met BSCCo (Elexon) will prepare a paper for the next available meeting of the SVG/ISG, as applicable, and notify the applicant of the decision made by the relevant Panel Committee(s).
Where information comes to the attention of BSCCo (Elexon) about an additional non-compliance, the application will need to be updated. Where BSCCo (Elexon) has granted approval, or is in the process of assessing an application, the additional non-compliance must be presented to the SVG/ISG, as applicable, as the conditions for BSCCo (Elexon) approval are not met. If the original Metering Dispensation was approved by BSCCo (Elexon), it is rendered void and a new application will have to be submitted for consideration by the relevant Panel Committee(s).
For more information please contact the BSC Service Desk or call 0370 010 6950.
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