Issue 1
Version 1.00
DATE Code Effective Date
CODE OF PRACTICE FOR THE METERING OF CIRCUITS WITH A RATED CAPACITY EXCEEDING 100MVA FOR SETTLEMENT PURPOSES
CODE OF PRACTICE FOR THE METERING OF CIRCUITS WITH A RATED CAPACITY EXCEEDING 100MVA FOR SETTLEMENT PURPOSES.
1. Reference is made to the Balancing and Settlement Code for the Electricity Industry in
England and Wales dated Code Effective Date, and in particular, to the definitions of
“Code of Practice” in Annex X-1 thereof.
2. This Code of Practice shall apply to Metering Systems comprising Metering Equipment that are subject to the requirements of Section L of the Balancing and Settlement Code.
3. This Code of Practice has been approved by the Panel.
________________________
For and on behalf of the Panel.
ISSUE | DATE | VERSION | CHANGES | AUTHOR | APPROVED |
Draft | 18/3/93 | 0.10 | Recommended to PEC | MSC | |
1 | 15/4/93 | 1.00 | Endorsed by PEC | CoP WG | |
1 | Code Effective Date | 1.00 | Re-badging of Code of Practice One for the implementation of the Balancing and Settlement Code | BSCCo | Panel 16/11/00 (Paper 07/003) |
CODE OF PRACTICE FOR THE METERING OF CIRCUITS WITH A RATED CAPACITY EXCEEDING 100MVA FOR SETTLEMENT PURPOSES.
CONTENTS | Page number |
| | |
FOREWORD | 6 |
1. | SCOPE | 7 |
2. | REFERENCES | 8 |
3. | DEFINITIONS AND INTERPRETATIONS | 9 |
4. | MEASUREMENT CRITERIA | 13 |
| 4.1 Measured Quantities and Demand Values | 13 |
| 4.1.1 Measured Quantities | 13 |
| 4.1.2 Demand Values | 13 |
| 4.2 Accuracy Requirements | 14 |
| 4.2.1 Overall Accuracy | 14 |
| 4.2.2 Compensation for Measurement Transformer Error | 15 |
| 4.2.3 Compensation for Power Transformer and Line Losses | 15 |
5. | METERING EQUIPMENT CRITERIA | 16 |
| 5.1 Measurement Transformers | 16 |
| 5.1.1 Current Transformers | 16 |
| 5.1.2 Voltage Transformers | 17 |
| 5.1.3 Measurement Transformers Installed on Existing Circuits | 17 |
| 5.2 Testing Facilities | 18 |
| 5.3 Meters | 19 |
| 5.4 Displays and Facilities for Registrant Information | 20 |
| 5.4.1 Displays | 20 |
| 5.4.2 Facilities | 20 |
| 5.5 Outstation | 21 |
| 5.5.1 Data Storage | 21 |
| 5.5.2 Time Keeping | 22 |
| 5.5.3 Monitoring Facilities | 24 |
| | |
| 5.6 Communication | 24 |
| 5.6.1 Local Interrogation | 24 |
| 5.6.2 Remote Interrogation | 25 |
| 5.7 Sealing | 25 |
6. | ASSOCIATED FACILITIES | 26 |
| 6.1 Interrogation Unit | 26 |
| 6.2 Additional Features | 26 |
7. | ACCESS TO DATA | 26 |
| | |
APPENDIX A | Defined Metering Points | 27 |
APPENDIX B | Labelling of Meters for Import and Export | 29 |
APPENDIX C | Non-Settlement Facilities for Registrant Information | 32 |
This Code of Practice defines the minimum requirements for the Metering Equipment required for the measurement and recording of electricity transfers at Defined Metering Points where the rated circuit capacity exceeds 100MVA.
For the purpose of this Code of Practice the rated circuit capacity in MVA shall be determined by the lowest rated primary plant (eg transformer rating, line rating, etc) of the circuit. The Metering Equipment provision and accuracy requirements shall anticipate any future up-rating consistent with the installed primary plant. The primary plant maximum continuous ratings shall be used in this assessment.
BSCCo shall retain copies of, inter alia, this Code of Practice together with copies of all documents referred to in it, in accordance with the provisions of the Balancing and Settlement Code (“the Code”).
This Code of Practice states the practices that shall be employed, and the facilities that shall be provided for the measurement and recording of the quantities required for Settlement purposes on each circuit where the rated capacity exceeds 100MVA.
It derives force from the Code, and in particular the metering provisions (Section L), to which reference should be made. It should also be read in conjunction with any relevant BSC Procedures.
This Code of Practice does not contain the calibration, testing and commissioning requirements for Metering Equipment used for Settlement purposes. These requirements are detailed in Code of Practice Four – “Code of Practice for Calibration, Testing and Commissioning Requirements for Metering Equipment for Settlement Purposes”.
Metering Dispensations from the requirements of this Code of Practice may be sought in accordance with the Code and BSC Procedure BSCP32.
In the event of an inconsistency between the provisions of this Code of Practice and the Code, the provisions of the Code shall prevail.
The following documents are referred to in the text:-
BS EN 60687 | AC Static Watthour Meters for Active Energy (Classes 0.2S and 0.5S) |
Draft IEC Standard 1030 | Alternating Current Static Var-Hour Meters for Reactive Energy (Classes 2 and 3) |
IEC Standard 44-3 | Instrument Transformers – Combined Transformers |
IEC Standard 185 | Current Transformers |
IEC Standard 186 | Voltage Transformers |
BS EN 61107 | Data Exchange for Meter Reading, Tariff and Load Control. Direct Local Exchange. |
Balancing and Settlement Code | Section X; Annex X-1 and Section L and BSC Procedures |
Code of Practice Four | Code of Practice for Calibration, Testing and Commissioning Requirements for Metering Equipment for Settlement Purposes |
| |
Electricity Act 1989 | Schedule 7 as amended by Schedule 1 to the Competition and Services (Utilities) Act 1992. |
3. DEFINITIONS AND INTERPRETATIONS
Save as otherwise expressly provided herein, words and expressions used in this Code of Practice shall have the meanings attributed to them in the Code.
The following definitions, which also apply, supplement or complement those in the Code and are included for the purpose of clarification.
Active Energy means the electrical energy produced, flowing or supplied by an electrical circuit during a time interval, and being the integral with respect to time of the instantaneous Active Power, measured in units of watt-hours or standard multiples thereof.
Active Power means the product of voltage and the in-phase component of alternating current measured in units of watts and standard multiples thereof, that is:-
3.3 Actual Metering Point
Actual Metering Point means the physical location at which electricity is metered.
Apparent Energy means the integral with respect to time of the Apparent Power.
Apparent Power means the product of voltage and current measured in units of voltamperes and standard multiples thereof, that is:-
3.6 Central Data Collection Agent (CDCA)
Central Data Collection Agent means the BSC Agent for Central Data Collection in accordance with Section E of the Code.
CTN means the Electricity Supply Industry (ESI) corporate telephone network.
CVA Customer means any customer, receiving electricity directly from the Transmission System, irrespective of from whom it is supplied.
3.9 Defined Metering Point
Defined Metering Point means the physical location at which the overall accuracy requirement as stated in this Code of Practice are to be met. The Defined Metering Points are identified in Appendix A and relate to Boundary Points and System Connection Points.
Demand Period means the period over which Active Energy, Reactive Energy or Apparent Energy are integrated to produce Demand Values. For Settlement purposes, unless the context requires otherwise, each Demand Period shall be of 30 minutes duration, one of which shall finish at 24:00 hours.
Demand Values means, expressed in kW, kvar or kVA, twice the value of kWh, kvarh or kVAh recorded during any Demand Period. The Demand Values are half hour demands and these are identified by the time of the end of the Demand Period.
“electricity” means Active Energy and Reactive Energy.
Export means, for the purposes of this Code of Practice, an electricity flow as indicated in Figure 1 of Appendix B.
Import means, for the purposes of this Code of Practice, an electricity flow as indicated in Figure 1 of Appendix B.
Interrogation Unit means a Hand Held Unit “HHU” (also known as Local Interrogation Unit “LIU”) or portable computer which can enter Metering Equipment parameters and extract information from the Metering Equipment and store this for later retrieval.
Meter means a device for measuring Active Energy and/or Reactive Energy.
Metering Equipment means meters, measurement transformers (voltage, current and combination units), metering protection equipment including alarms, circuitry, associated Communications Equipment and Outstation and wiring.
Meter Register means a device, normally associated with a Meter, from which it is possible to obtain a reading of the amount of Active Energy, or the amount of Reactive Energy that has been supplied by a circuit.
Outstation means equipment which receives and stores data from a Meter(s) for the purpose, inter-alia, of transfer of that metering data to the Central Data Collection Agent (CDCA) or a Data Collector as the case may be and which may perform some processing before such transfer and may be in one or more separate units or may be integral with the Meter.
Outstation System means one or more Outstations linked to a single communication line.
PSTN means the public switched telephone network.
3.21 Rated Measuring Current
Rated Measuring Current means the rated primary current of the current transformers in primary plant used for the purposes of measurement.
Reactive Energy means the integral with respect to time of the Reactive Power.
Reactive Power means the product of voltage and current and the sine of the phase angle between them, measured in units of voltamperes reactive and standard multiples thereof;
means, in relation to a Metering System, the person for the time being registered in CMRS or (as the case may be) SMRS in respect of that Metering System pursuant to Section K of the Balancing and Settlement Code.
3.25 Settlement Instation
Settlement Instation means a computer based system which collects or receives data on a routine basis from selected Outstation by the Central Data Collection Agent or (as the case may be) a relevant Data Collector.
means a person to whom electrical power is provided, whether or not that person is the provider of that electrical power; and where that electrical power is measured by a SVA Metering System.
4.1. Measured Quantities and Demand Values
4.1.1 Measured Quantities
For each separate circuit the following energy measurements are required for Settlement purposes:-
For each Demand Period for each circuit the following Demand Values shall be provided:-
4.2 Accuracy Requirements
The overall accuracy of the energy measurements at or referred to the Defined Metering Point shall at all times be within the limits of error as shown:-
CONDITION | LIMIT OF ERRORS AT STATED SYSTEM POWER FACTOR |
Current expressed as a percentage of Rated Measuring Current | Power Factor | Limits of Error |
120% to 10% inclusive Below 10% to 5% Below 5% to 1% * 120% to 10% inclusive | 1 1 1 0.5 lag and 0.8 lead | + 0.5% + 0.7% + 1.5% + 1.0% |
* This requirement shall only apply where the energy transfers to be measured by the Import Meter and/or the Export Meter during normal operating conditions is such that the Rated Measuring Current will be below 5% (excluding zero) for periods equivalent to 10% or greater per annum.
CONDITION | LIMIT OF ERRORS AT STATED SYSTEM POWER FACTOR |
Current expressed as a percentage of Rated Measuring Current | Power Factor | Limits of Error |
120% to 10% inclusive 120% to 20% inclusive | Zero 0.866 lag and 0.866 lead | + 4.0% + 5.0% |
These limits of error for both (i) and (ii) above shall apply at the Reference Conditions defined in the appropriate Meter specification.
Evidence to verify that these overall accuracy requirements are met shall be available for inspection by the Panel or Technical Assurance Agent.
4.2.2 Compensation for Measurement Transformer Error
To achieve the overall accuracy requirements it may be necessary to compensate Meters for the error of the measurement transformers and the associated leads to the meters. Values of the compensation shall be recorded and evidence to justify the compensation criteria, including wherever possible test certificates, shall be available for inspection by the Panel or Technical Assurance Agent.
4.2.3 Compensation for Power Transformer and Line Losses
Where the Actual Metering Point and the Defined Metering Point do not coincide then a Metering Dispensation shall be applied for and, where necessary, compensation for power transformer and/or line losses shall be provided to meet the overall accuracy at the Defined Metering Point.
The compensation may be achieved either within the Metering Equipment or within the Data Collector’s software.
Where compensation is applied the values used shall be recorded and supporting evidence to justify the compensation criteria shall be available for inspection by the Panel or Technical Assurance Agent.
5. METERING EQUIPMENT CRITERIA
Although for clarity this Code of Practice identifies separate items of equipment, nothing in it prevents such items being combined to perform the same task provided the requirements of this Code of Practice are met.
Metering Equipment other than outdoor measurement transformers, shall be accommodated in a clean and dry environment.
5.1 Measurement Transformers
The terms “current transformer” and “voltage transformer” used below in 5.1.1 and 5.1.2 do not preclude the use of other measuring techniques with a performance equal to that specified for such measurement transformers.
For each circuit current transformers (CT) and voltage transformers (VT) shall meet the requirements set out in clauses 5.1.1 and 5.1.2.
Additionally, where a combined unit measurement transformer (VT & CT) is provided the ‘Tests for Accuracy’ as covered in clause 8 of IEC Standard 44-3 covering mutual influence effects shall be met.
5.1.1. Current Transformers
Two sets of current transformers in accordance with IEC Standard 185 and with a minimum standard of accuracy class 0.2S (irrespective of the secondary current rating of the current transformers) shall be provided.
The current transformers supplying the main Meters shall be dedicated to that purpose.
The current transformers supplying the check Meters may be used for other purposes provided the overall accuracy requirements in paragraph 4.2.1 are met and evidence of the value of the additional burden is available for inspection by the Panel or Technical Assurance Agent. The additional burden shall not be modified without prior notification to the Panel, and the evidence of the value of the modified additional burden shall be available for inspection by the Panel or Technical Assurance Agent.
CT test certificates showing errors at the overall working burden or at burdens which enable the working burden errors to be calculated shall be available for inspection by the Panel or Technical Assurance Agent.
The total burden on each current transformer shall not exceed the rated burden of such CT.
5.1.2 Voltage Transformers
Two voltage transformers or one voltage transformer with two or more secondary winding sets in accordance with IEC Standard 186 and with a mininum standard of accuracy class 0.2 shall be provided.
The VT secondary winding supplying the main Meters shall be dedicated to that purpose.
The VT secondary winding supplying the check Meters may be used for other purposes provided the overall accuracy requirements in clause 4.2.1 are met and evidence of the value of the additional burden is available for inspection by the Panel or Technical Assurance Agent. The additional burden shall not be modified without prior notification to the Panel, and evidence of the value of the modified additional burden shall be available for inspection by the Panel or Technical Assurance Agent.
A VT test certificate(s) showing errors at the overall working burden(s) or at burdens which enable the working burden errors to be calculated shall be available for inspection by the Panel or Technical Assurance Agent.
The total burden on each secondary winding of a VT shall not exceed the rated burden of such secondary winding.
Separately fused VT supplies shall be provided for each of the following:-
the main Meter
the check Meter
any additional burden
Such fuses shall be located as close as practicable to the VT.
5.1.3 Measurement Transformers Installed on Existing Circuits
Where circuits, other than those newly installed, are to be metered to this Code of Practice and where the installed measurement transformers do not comply fully with clauses 5.1.1 & 5.1.2, then such measurement transformers may be used providing the following requirements and those in clause 4.2.1 are met.
the main Meters
the check Meters
any additional burden
Such fuses shall be located as close as practicable to the VT.
A VT failure alarm shall be produced at a manned point normally within 24 hours of the fault detection.
A spare channel on the Outstation or any other available means may be used to transmit the alarm.
Separate test terminal blocks or equivalent facilities shall be provided for the main Meters and for the check Meters of each circuit. The test facilities shall be nearby the Meters involved.
The quantities defined in clause 4.1.1 shall be measured by both main and check Meters.
Active Energy Meters shall meet the requirements of BS EN 60687 Class 0.2S.
Active Energy Meters shall be configured such that the number of measuring elements is equal to or one less than the number of primary system conductors. These include the neutral conductor, and/or the earth conductor where system configurations enable the flow of zero sequence energy.
Reactive Energy Meters shall meet the Class 2.0 requirements of the draft IEC Standard 1030.
All Meters shall be labelled or otherwise be readily identifiable in accordance with Appendix B.
All Meters shall include a non-volatile Meter Register of cumulative energy for each measured quantity. The Meter Register(s) shall not roll-over more than once within the normal Meter reading cycle.
Meters which provide data to separate Outstations shall for this purpose provide two outputs per measured quantity.
For Meters using electronic displays due account shall be taken of the obligations of the Central Data Collection Agent (CDCA) or other Data Collectors to obtain Meter readings.
5.4 Displays and Facilities for Registrant Information
Where requested by the Registrant, Metering Equipment shall have the ability to display some or all of the information as listed in Appendix C.
The Metering Equipment shall be capable of providing one voltage free pulsed output per measured quantity:-
Duplicate Outstation Systems shall be provided which can be interrogated by Settlement Instations using independent communication lines.
Where separate Outstations are provided these shall each store main and check Meter data for one or more circuits and where practicable shall be configured identically. Two or more such Outstations storing data from different circuits may be cascaded on to one communication line.
In the case of Meters with integral Outstation facilities (i.e. a main or check Meter storing its own data) the cascading on to one communication line shall be limited such that a communications failure is restricted to the loss of main or check Meter data from a maximum of four circuits.
The Outstation data shall be to a format and protocol specified by the Panel.
The Outstation shall have the ability to allow the metering data to be read by instations other than the Settlement Instation provided the requirements of Section 7 of this Code of Practice are satisfied.
Facilities shall be provided to select a relevant demand period from one of the following values:-
30, 20, 15, 10 and 5 minutes with in each case one demand period ending on the hour.
Normally metering data will be collected by the Settlement Instations by a daily interrogation, but repeat collections of metering data shall be possible throughout the Outstation data storage period.
A secure supply shall be provided to each Outstation System with separate fusing for each Outstation.
Where a separate modem associated with the Outstation System is used, then it shall be provided with a secure supply separately fused. Alternatively, line or battery powered modem types may be used.
The Outstations shall provide an alarm output signal at a manned point in the event of a supply failure.
Data storage facilities for metering data shall be provided as follows:-
(i) a storage capacity of 48 periods per day for a minimum of 10 days for all Demand Values
(ii) the stored Demand values shall be integer values of kW or kvar, or pulse counts, and have a resolution of better than +0.1% (at full load);
(iii) the accuracy of the energy values derived from Demand Values shall be within +0.1% (at full load) of the amount of energy measured by the associated Meter;
(iv) the value of any energy measured in a Demand Period but not stored in that Demand Period shall be carried forward to the next Demand Period;
(v) where a separate Outstation is used, cumulative register values shall be provided in the Outstation which can be set to match and increment with the Meter Registers;
(vi) in the event of an Outstation supply failure, the Outstation shall protect all data stored up to the time of the failure, and maintain the time accuracy in accordance with clause 5.5.2;
(vii) partial Demand Values, those in which an Outstation supply failure and/or restoration occurs, and zero Demand Values associated with an Outstation supply failure, shall be marked so that the Settlement Instation can identify them;
(viii) to cater for continuous supply failures, the clock, calendar and all data shall be supported for a period of 10 days without an external supply connected;
(ix) any “read” operation shall not delete or alter any stored metered data; and
(x) an Outstation shall provide any portion of the data stored upon request by an Instation.
(i) The Outstation time shall be set to the Universal Time Clock (UTC) also known as Greenwich Mean Time (GMT). No switching between UTC and British Summer Time (BST) shall occur.
(ii) Time synchronisation of the Outstation shall only be performed by communication with the Settlement Instation.
(iii) The overall limits of error for the time keeping allowing for a failure to communicate with the Outstation for an extended period of 10 days shall be:-
the completion of each Demand Period shall be at a time which is within + 10 seconds of UTC; and
the duration of each Demand period shall be within + 0.1%, except where time synchronisation has occurred in a Demand Period.
5.5.3 Monitoring Facilities
Monitoring facilities shall be provided for each of the following conditions and shall be reported, tagged wherever possible to the relevant Demand Period(s), via the local interrogation facility:-
In addition all of the above conditions shall be reported as, at minimum, a common alarm indication via the remote interrogation facility.
Outstation(s) shall accommodate both local and remote interrogation facilities, wherever possible, from separate ports.
The reprogramming of data shall only be possible through access at a suitable security level.
The reading of data shall only be possible through access at a suitable security level.
The following metering data shall be transferrable on request during the interrogation process:-
5.6.1 Local Interrogation
An interrogation port shall be provided for each Outstation which preferably shall be an opto port to BS EN 61107, and with a serial protocol such as BS EN 61107, for the following purposes:-
5.6.2 Remote Interrogation
Independent communication lines shall be provided to each Outstation System for remote interrogation.
Error checking facilities shall be provided for the communications between the Outstation and the Settlement Instation.
Interrogation of an Outstation shall be possible using one of the following media:-
(i) Switched telephone networks e.g. PSTN or CTN;
(ii) Public data networks e.g. PSN;
(iii) Radio data networks e.g. Paknet or any equivalent;
(iv) Customer own network;
(v) Mains signalling / power line carrier;
In addition any further media may be used as specified by the Panel.
The actual media employed shall be in accordance with the requirements of the CDCA for CVA Metering Systems and the Supplier for SVA Metering Systems.
The data shall be to a format and protocol specified by the Panel.
All Metering Equipment shall be capable of being sealed in accordance with BSC Procedure BSCP06.
The Operator may interrogate the Outstations using an Interrogation Unit (IU). The Interrogation Unit may be used for commissioning, maintenance/fault finding and when necessary the retrieval of stored metering data. The data retrieved by the Interrogation Unit shall be compatible with the Settlement Instation.
Additional features may be incorporated within or associated with the Metering Equipment provided but these shall not interfere with or endanger the operation of the Settlement process.
Access to metering data shall be in accordance with the provisions of the Code and the BSC Procedures referred to therein. Such access must not interfere with or endanger the security of the data or the collection process for Settlement purposes.
Access to stored metering data in Outstations shall also be the right of the Registrant and any party who has the permission of the Registrant.
For transfers of electricity between the following parties the Defined Metering Point (DMP) shall be at one of the following locations:-
1. For transfers between the Transmission Company and a single Public Distribution System Operator where no other Party(s) are connected to the busbar, the DMP shall be at the lower voltage side of the supergrid connected transformer.
2. For transfers between the Transmission Company and a single Public Distribution System Operator where other Party(s) are connected to the busbar, the DMP shall be at the circuit connections to that Public Distribution System Operator.
3. For transfers between the Transmission Company and more than one Public Distribution System Operator connected to the same busbar, the DMP shall be at the circuit connnections of each Public Distribution System Operator to such busbar.
4. For transfers between Public Distribution System Operators not including a connection to the Transmission System, the DMP shall be at the point of connection of the two Public Distribution System Operators.
5. For transfers between the Transmission Company and Generating Plant, the DMP shall be at the high voltage side of the generator transformers and station transformer(s).
6. For transfers between Public Distribution System Operators and Generating Plant, the DMP shall be at the point(s) of connection of the generating station to the Public Distribution System Operator.
7. For transfers between the Distribution System of a Public Distribution System Operator and a Customer, the DMP shall be at the point of connection to the Distribution System of the Public Distribution System Operator.
8. For transfers between the Transmission Company and a Customer, the DMP shall be at the point of connection to the Transmission Company.
9. For transfers between the Transmission Company and an Interconnector User the DMP shall be as follows:-
Harker 400 kV Substation
Harker 275 kV Substation
Harker 132 kV Substation
Stella 275 kV Substation
Stella 400 kV Substation
(ii) For the EdF link the busbar side of the busbar disconnectors at the Sellindge 400 kV Substation.
LABELLING OF METERS FOR IMPORT AND EXPORT
A standard method of labelling meters, test blocks, etc is necessary and based on the definitions for Import and Export the required labelling shall be as follows.
Meters or Meter Registers shall be labelled “Import” or “Export” according to the diagram “Figure 1”.
Within the context of this code the relationship between Active Energy and Reactive Energy can best be established by means of the power factor. The following table gives the relationship:-
Flow of Active Energy | Power Factor | Flow of Reactive Energy |
Import Import Import Export Export Export | Lagging Leading Unity Lagging Leading Unity | Import Export Zero Export Import Zero |
Meters or Meter Registers for registering Import Reactive Energy should be labelled “Import” and those for registering Export Reactive Energy should be labelled “Export”.
Non-Settlement Facilities for Registrant Information
MD shall be resettable at midnight of last day of charging period. Also resettable for part chargeable period demands. If a manual reset button is used then this shall be sealable.
Non-Settlement Facilities for Registrant Information continued
An output pulse which commences coincident with the end of each Demand Period and lasts for a duration of between 0.5 and 10 seconds.
The pulse shall be provided by voltage free outputs.
In additon to items (i) to (iv) in clause 5.6, the following metering data shall be transferrable on request during the interrogation process:-
(ii) multi-rate cumulative Active Energy as specified by Registrant.
