Metering Dispensations and Co-Located Generation

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Metering dispensations and co-located generation

Guidance Note

Introduction

Section L1 sets out the obligations on BSC Parties who register Metering Systems2 (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 Equipment3, 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 Settlement4, and is calibrated, commissioned, and tested in accordance the prevailing version of CoP45, 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 that relevant CoP.

BSC Procedure BSCP326 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-BSC Party.

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 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 Panel7 on 11 May 2023 and introduced on 2 November 2023 via Modification Proposal P4538.

Actual Metering Point / Defined Metering Point

Background

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 transformer9); 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 provided or 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 standard10 and CoP4.

    • Meter manufacturer calibration test certificates, tested to the requirements of relevant standard11 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.

Examples

Starting with the ideal scenario, as can be seen in Figure 1, the Metering Equipment is located (AMP) at the point of connection (DMP).

complex image of process

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.

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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.

Should the distance between AMP and DMP be far 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.

complex image of process

complex image of process

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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.

Overall Accuracy

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:

    • Power transformer load and no-load losses;

    • Line losses;

    • Cable losses; and

    • Busbar losses.

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).

More information on the overall accuracy assessment can be found in Code of Practice Four guidance document.

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 CoP112 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:

Meter error: +0.13%

Current transformer error: +0.15%

Voltage transformer error: +0.35%

Overall accuracy: +0.63%

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:

Meter error: +0.13%

Current transformer error: +0.15%

Voltage transformer error: +0.35%

Cable losses: +0.01%

Overall accuracy: +0.64%

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:

Meter error: +0.13%

Current transformer error: +0.15%

Voltage transformer error: +0.35%

Cable losses: +0.01%

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.

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Metering Dispensations

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.

Applications for a Metering Dispensation should be made to dispensations@elexon.co.uk

Examples

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 MPANs13. 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.

complex image of process

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.

complex image of process

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 metering14 (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.

complex image of process

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.

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.

complex image of process

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 will be created via:

    • For Metering Systems registered in CMRS this shall be done in accordance with BSCP75 ‘Registration of Meter Aggregation Rules for Volume Allocation Units15; 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 Form16 .

Process

Only the last stage of the process on 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).

Further Information

For more information please contact the BSC Service Desk or call 0370 010 6950.

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All other rights of the copyright owner not expressly dealt with above are reserved.

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1Metering’

2 For Central Volume Allocation (CVA) and Supplier Volume Allocation (SVA).

3 Metering Equipment means Meters, Asset Meters, measurement transformers (voltage, current or combination units), metering protection equipment including alarms, circuitry, associated Communications Equipment and Outstations and wiring.

4 Or, in the case of those Metering Systems which were registered under the Pooling and Settlement Agreement (P&SA) or Settlement Agreement for Scotland (SAS), the versions of the Code of Practice the Metering Equipment was required to comply with just before the Go-live Date or the BETTA Effective Date, respectively.

5Code of Practice for the calibration, testing and commissioning requirements of Metering Equipment for Settlement purposes’

6Metering Dispensations’

7 BSC Panel 338/03

8Metering Dispensation process improvements and clarification to the CoPs’

9 Due to the presence of any power transformer is it unlikely that overall accuracy can be maintained at the DMP without needing to apply loss compensation therefore a Metering Dispensation would be required.

10 IEC 61869-2 Instrument transformers - Part 2: Additional requirements for current transformers; 61869-3 Instrument transformers - Part 3: Additional requirements for inductive voltage transformers

11 For example, IEC 62063-22:2020 Electricity metering equipment - Particular requirements - Part 22: Static meters for AC active energy (classes 0,1S, 0,2S and 0,5S)

13 Where difference metering is being used via an aggregation rule both Metering Systems must be registered under the same option (i.e. either both Central Meter Registration Service or both Supplier Meter Registration Service)

14 The energy volumes for Part 1 of the site are derived by differencing off the readings recorded by the Meter associated with Part 2 of the site, from the readings recorded by the Meters associated with Part 1 of the site (i.e. the Boundary Point Meters).

15 BSCP75 ‘Registration of Meter Aggregation Rules for Volume Allocation Units

16 Refer to ‘Guide to Complex Sites’ section in BSCP502