ANSI C12.20 and Proposed Field Testing Changes

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Understand contents of ANSI C12.20

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  • Blondel's theorem, named after its discoverer, French electrical engineer André Blondel, is the result of his attempt to simplify both the measurement of electrical energy and the validation of such measurements. The result is a simple rule that specifies the minimum number of watt-hour meters required to measure the consumption of energy in any system of electrical conductors. The theorem states that the power provided to a system of N conductors is equal to the algebraic sum of the power measured by N watt-meters. The N watt-meters are separately connected such that each one measures the current level in one of the N conductors and the potential level between that conductor and a common point. In a further simplification, if that common point is located on one of the conductors, that conductor's meter can be removed and only N-1 meters are required. An electrical energy meter is a watt-meter whose measurements are integrated over time, thus the theorem applies to watt-hour meters as well.[1] Blondel wrote a paper on his results that was delivered to the International Electric Congress held in Chicago in 1893. Although he was not present at the Congress, his paper is included in the published Proceedings.[2] Instead of using N-1 separate meters, the meters are combined into a single housing for commercial purposes such as measuring energy delivered to homes and businesses. Each pairing of a current measuring unit plus a potential measuring unit is then termed a stator or element. Thus, for example, a meter for a four wire service will include three elements. Blondel's Theorem simplifies the work of an electrical utility worker by specifying that an N wire service will be correctly measured by a N-1 element meter. Unfortunately, confusion arises for such workers due to the existence of meters that don't contain tidy pairings of single potential measuring units with single current measuring units. For example, a meter was previously used for four wire services containing two potential coils and three current coils and called a 2.5 element meter. Blondel Noncompliance [edit]Electric energy meters that meet the requirement of N-1 elements for an N wire service are often said to be Blondel Compliant. This label identifies the meter as one that will measure correctly under all conditions when correctly installed. However, a meter doesn't have to be Blondel compliant in order to provide suitably accurate measurements and industry practice often includes the use of such non compliant meters. The form 2S meter is extensively used in the metering of residential three wire services, despite being non compliant in such services. This common residential service consists of two 120 volt wires and one neutral wire. A Blondel compliant meter for such a service would need two elements (and a five jaw socket to accept such a meter), but the 2S meter is a single element meter. The 2S meter includes one potential measuring device (a coil or a voltmeter) and two current measuring devices. The current measuring devices provide a measurement equal to one half of the actual current value. The combination of a single potential coil and two so called half coils provides highly accurate metering under most conditions. The meter has been used since the early days of the electrical industry. The advantages were the lower cost of a single potential coil and the avoidance of interference between two elements driving a single disc in an induction meter. For line to line loads, the meter is Blondel compliant. Such loads are two wire loads and a single element meter suffices. The non compliance of the meter occurs in measuring line to neutral loads. The meter design approximates a two element measurement by combining a half current value with the potential value of the line to line connection. The line to line potential is exactly twice the line to neutral connection if the two line to neutral connections are exactly balanced. Twice the potential times half the current then approximates the actual power value with equality under balanced potential. In the case of line to line loads, two times the half current value times the potential value equals the actual power. Error is introduced if the two line to line potentials are not balanced and if the line to neutral loads are not equally distributed. That error is given by 0.5(V1-V2)(I1-I2) where V1 and I1 are the potential and current connected between one line and neutral and V2 and I2 are those connected between the other line and neutral.[1] Since the industry typically maintains five percent accuracy in potential, the error will be acceptably low if the loads aren't heavily unbalanced. This same meter has been modified or installed in modified sockets and used for two wire, 120 volt services (relabeled as 2W on the meter face). The modification places the two half coils in series such that a full coil is created. In such installations, the single element meter is Blondel compliant. There is also a three wire 240/480 volt version that is not Blondel compliant. Also in use are three phase meters that are not Blondel compliant, such as forms 14S and 15S, but they can be easily replaced by modern meters and can be considered obsolete.
  • Blondel's theorem, named after its discoverer, French electrical engineer André Blondel, is the result of his attempt to simplify both the measurement of electrical energy and the validation of such measurements. The result is a simple rule that specifies the minimum number of watt-hour meters required to measure the consumption of energy in any system of electrical conductors. The theorem states that the power provided to a system of N conductors is equal to the algebraic sum of the power measured by N watt-meters. The N watt-meters are separately connected such that each one measures the current level in one of the N conductors and the potential level between that conductor and a common point. In a further simplification, if that common point is located on one of the conductors, that conductor's meter can be removed and only N-1 meters are required. An electrical energy meter is a watt-meter whose measurements are integrated over time, thus the theorem applies to watt-hour meters as well.[1] Blondel wrote a paper on his results that was delivered to the International Electric Congress held in Chicago in 1893. Although he was not present at the Congress, his paper is included in the published Proceedings.[2] Instead of using N-1 separate meters, the meters are combined into a single housing for commercial purposes such as measuring energy delivered to homes and businesses. Each pairing of a current measuring unit plus a potential measuring unit is then termed a stator or element. Thus, for example, a meter for a four wire service will include three elements. Blondel's Theorem simplifies the work of an electrical utility worker by specifying that an N wire service will be correctly measured by a N-1 element meter. Unfortunately, confusion arises for such workers due to the existence of meters that don't contain tidy pairings of single potential measuring units with single current measuring units. For example, a meter was previously used for four wire services containing two potential coils and three current coils and called a 2.5 element meter. Blondel Noncompliance [edit]Electric energy meters that meet the requirement of N-1 elements for an N wire service are often said to be Blondel Compliant. This label identifies the meter as one that will measure correctly under all conditions when correctly installed. However, a meter doesn't have to be Blondel compliant in order to provide suitably accurate measurements and industry practice often includes the use of such non compliant meters. The form 2S meter is extensively used in the metering of residential three wire services, despite being non compliant in such services. This common residential service consists of two 120 volt wires and one neutral wire. A Blondel compliant meter for such a service would need two elements (and a five jaw socket to accept such a meter), but the 2S meter is a single element meter. The 2S meter includes one potential measuring device (a coil or a voltmeter) and two current measuring devices. The current measuring devices provide a measurement equal to one half of the actual current value. The combination of a single potential coil and two so called half coils provides highly accurate metering under most conditions. The meter has been used since the early days of the electrical industry. The advantages were the lower cost of a single potential coil and the avoidance of interference between two elements driving a single disc in an induction meter. For line to line loads, the meter is Blondel compliant. Such loads are two wire loads and a single element meter suffices. The non compliance of the meter occurs in measuring line to neutral loads. The meter design approximates a two element measurement by combining a half current value with the potential value of the line to line connection. The line to line potential is exactly twice the line to neutral connection if the two line to neutral connections are exactly balanced. Twice the potential times half the current then approximates the actual power value with equality under balanced potential. In the case of line to line loads, two times the half current value times the potential value equals the actual power. Error is introduced if the two line to line potentials are not balanced and if the line to neutral loads are not equally distributed. That error is given by 0.5(V1-V2)(I1-I2) where V1 and I1 are the potential and current connected between one line and neutral and V2 and I2 are those connected between the other line and neutral.[1] Since the industry typically maintains five percent accuracy in potential, the error will be acceptably low if the loads aren't heavily unbalanced. This same meter has been modified or installed in modified sockets and used for two wire, 120 volt services (relabeled as 2W on the meter face). The modification places the two half coils in series such that a full coil is created. In such installations, the single element meter is Blondel compliant. There is also a three wire 240/480 volt version that is not Blondel compliant. Also in use are three phase meters that are not Blondel compliant, such as forms 14S and 15S, but they can be easily replaced by modern meters and can be considered obsolete.
  • Blondel's theorem, named after its discoverer, French electrical engineer André Blondel, is the result of his attempt to simplify both the measurement of electrical energy and the validation of such measurements. The result is a simple rule that specifies the minimum number of watt-hour meters required to measure the consumption of energy in any system of electrical conductors. The theorem states that the power provided to a system of N conductors is equal to the algebraic sum of the power measured by N watt-meters. The N watt-meters are separately connected such that each one measures the current level in one of the N conductors and the potential level between that conductor and a common point. In a further simplification, if that common point is located on one of the conductors, that conductor's meter can be removed and only N-1 meters are required. An electrical energy meter is a watt-meter whose measurements are integrated over time, thus the theorem applies to watt-hour meters as well.[1] Blondel wrote a paper on his results that was delivered to the International Electric Congress held in Chicago in 1893. Although he was not present at the Congress, his paper is included in the published Proceedings.[2] Instead of using N-1 separate meters, the meters are combined into a single housing for commercial purposes such as measuring energy delivered to homes and businesses. Each pairing of a current measuring unit plus a potential measuring unit is then termed a stator or element. Thus, for example, a meter for a four wire service will include three elements. Blondel's Theorem simplifies the work of an electrical utility worker by specifying that an N wire service will be correctly measured by a N-1 element meter. Unfortunately, confusion arises for such workers due to the existence of meters that don't contain tidy pairings of single potential measuring units with single current measuring units. For example, a meter was previously used for four wire services containing two potential coils and three current coils and called a 2.5 element meter. Blondel Noncompliance [edit]Electric energy meters that meet the requirement of N-1 elements for an N wire service are often said to be Blondel Compliant. This label identifies the meter as one that will measure correctly under all conditions when correctly installed. However, a meter doesn't have to be Blondel compliant in order to provide suitably accurate measurements and industry practice often includes the use of such non compliant meters. The form 2S meter is extensively used in the metering of residential three wire services, despite being non compliant in such services. This common residential service consists of two 120 volt wires and one neutral wire. A Blondel compliant meter for such a service would need two elements (and a five jaw socket to accept such a meter), but the 2S meter is a single element meter. The 2S meter includes one potential measuring device (a coil or a voltmeter) and two current measuring devices. The current measuring devices provide a measurement equal to one half of the actual current value. The combination of a single potential coil and two so called half coils provides highly accurate metering under most conditions. The meter has been used since the early days of the electrical industry. The advantages were the lower cost of a single potential coil and the avoidance of interference between two elements driving a single disc in an induction meter. For line to line loads, the meter is Blondel compliant. Such loads are two wire loads and a single element meter suffices. The non compliance of the meter occurs in measuring line to neutral loads. The meter design approximates a two element measurement by combining a half current value with the potential value of the line to line connection. The line to line potential is exactly twice the line to neutral connection if the two line to neutral connections are exactly balanced. Twice the potential times half the current then approximates the actual power value with equality under balanced potential. In the case of line to line loads, two times the half current value times the potential value equals the actual power. Error is introduced if the two line to line potentials are not balanced and if the line to neutral loads are not equally distributed. That error is given by 0.5(V1-V2)(I1-I2) where V1 and I1 are the potential and current connected between one line and neutral and V2 and I2 are those connected between the other line and neutral.[1] Since the industry typically maintains five percent accuracy in potential, the error will be acceptably low if the loads aren't heavily unbalanced. This same meter has been modified or installed in modified sockets and used for two wire, 120 volt services (relabeled as 2W on the meter face). The modification places the two half coils in series such that a full coil is created. In such installations, the single element meter is Blondel compliant. There is also a three wire 240/480 volt version that is not Blondel compliant. Also in use are three phase meters that are not Blondel compliant, such as forms 14S and 15S, but they can be easily replaced by modern meters and can be considered obsolete.
  • ANSI C12.20 and Proposed Field Testing Changes

    1. 1. 110/02/2012 Slide 1ANSI C12.20 andProposed Field TESTINGChangesPrepared by Tom Lawton, TESCOThe Eastern Specialty Companyfor the Midwest Energy Association (MEA)May 15, 2013
    2. 2. 2Session Objectives• Understand contents of ANSI C12.20-2010 for0.2 and 0.5 Accuracy Class Meters• Understand the Relationship of C12.20 to C12.1• Understand ANSI C12.20 Changes Planned for2015 Edition and ANSI C12.1 changes plannedfor 2013• Understand new ANSI C12.29 for Field Testingand potential time frame• Discuss – Will this affect how we test in thefield?
    3. 3. 3Current Meter Testing StandardsMeter Testing for new and in-service kilowatthour meters,both electronic and electromechanical is specified in ANSIC12.1-2008, American National Standard for Electric Meters,Code for Electricity Metering. Most utility commissions usethis Standard as a reference or the basis for their metertesting requirements.ANSI C12.20-2010, American National Standard forElectricity Meters, 0.2 and 0.5 Accuracy Classes, providesdifferent test tolerances and a few different or modified testsfor higher accuracy meters. There is no reference made inC12.20 to field testing. The only mention of in-service testingrefers back to Section 5 of C12.1.
    4. 4. 4Current ANSI C12.20 Requirements•ANSI C12.20 establishes aspects andacceptable performance criteria for 0.2and 0.5 percent accuracy class metersmeeting Blondel’s Theorem. Thismeans that C12.20 is not applicable for2S meters.•Where there are differences betweenC12.20 and C12.1, ANSI StandardC12.20 takes precedence.
    5. 5. 5Current ANSI C12.20 Contents•Meter Requirements•Acceptable Performance of New Types of ElectricityMetering Devices and Associated Equipment•Refers back to C12.1 Section 4•Also has additional (and modified) tests specific tohigher accuracy class meters•Standards for In-Service Performance (refers toC12.1 Section 5)•No mention of Field Testing in ANSI C12.20 – 2010•The 2010 revision of the standard was broadenedtoallow three phase current and voltage sources as anoptional test method to the single phase, series,parallel method
    6. 6. 6Current ANSI Field Testing Standards•In ANSI C12.1–2008 there is no mention of fieldtesting•The In-Service section 5 of this standard was deemedin need of strengthening and ANSI C12 maincommittee decided there was a need to look at fieldtesting.•A draft of ANSI C12.1 – 2013 with a new section 5 isready for approval.•A Field Test Working Group was established tocreate a new ANSI standard focusing on FieldTesting (ANSI C12.29)•Both C12.1 and C12.20 will refer to this standard forfield testing
    7. 7. 7Current ANSI C12.1 TestingRequirements
    8. 8. 8Current ANSI C12.20 TestingRequirements
    9. 9. 9Current Meter Testing to Standards• Many State Utility Commissions require that new higher accuracyclass electric meters meet ANSI C12.1 and C12.20 requirements.• New meters are tested using all or a group of tests specified in ANSIC12.1 and C12.20. These tests are typically performed by the metervendors.• Meter vendors have different interpretations of certain ANSI testsand even what “ANSI qualified” means.• Meter vendors often perform ANSI testing early in the developmentof a meter and certify future modifications to the meter by stating theupdated design is similar to the old design in form and function.
    10. 10. 10ANSI C12.1 – 2013 Section 5Proposed Changes• More options for statistical models to use• More options for what to do if a group starts toperform poorly• Addresses the type of statistical testing available forancillary devices (e.g. disconnect switches;communication devices).• Addresses the need to use statistical methods todetermine as far in advance as possible the potentialfailure modes and life expectancies of any newtechnology being deployed to the field.
    11. 11. 11• The revised Section 5 for ANSI C12.1 will not specify any new field tests.The in-service testing required can be done in the field or in the meter shopas long as the basic requirements of the tests are met.• The revised Section 5 tries to include ancillary devices includingdisconnect switches included with the meter and external CT’s and PT’s.• This portion of the Standard focuses on the performance of the device as agroup and not the specfics of the test being performed.• ANSI C12 Main Committee has decided that this aspect of testing has beenoverlooked and has created a working group to address the “how-to” offield testing. A new standard, ANSI C12.29 is anticipated to be be draftedby this working group and presented to the main committee of C12 forapproval.• This working group has no time table to complete their work, but they arehoping to have a draft ready for the Spring 2014 ANSI meeting (The maincommittee meets every 6 months in conjunction with the EEI TD&Mconference.What do these Changes Mean forField Testing?
    12. 12. 12New ANSI C12.29 for Field TestingMetering DevicesANSI C12.29 will establish recommendedfield testing for metering devices and shouldeventually be referenced in C12.1 and C12.20.The new standard is expected to have threeSections:• Meter Testing• Instrument Transformer Testing• Site Wiring and Auxiliary Devices
    13. 13. 13New ANSI C12.29 for Field TestingMetering DevicesMeter Testing will be divided into threecategories based on where current andvoltage is supplied:• Using Customer Potential with CurrentSupplied by the Test Equipment• Using Customer Potential and CustomerSupplied Current• Using Potential and Current Supplied byTest Equipment
    14. 14. 14New ANSI C12.29 for Field TestingMetering DevicesInstrument Transformer testing is anticipatedto focus on:• Burden Testing. The theory and practicalapplication in the field• Ratio Testing. Practical application in thefield• Visual inspection of the CT’s and PT’s
    15. 15. 15New ANSI C12.29 for Field TestingMetering DevicesSite Wiring and Auxiliary devices isanticipated to focus on:• Visual inspection• Continuity testing• Service Ground testing• Communication testing• disconnect testing• Additional device testing
    16. 16. 16New ANSI C12.29 for Field TestingMetering DevicesWhat the new Standard is not expected to do:• Mandate a new test or tests• Mandate the “right way” to do this test• Mandate the use of any equipment orspecific processesThis Standard is anticipated to be a “bestPractices” type of document and not a newSet of requirements for Utility Metering Groups.
    17. 17. 17New ANSI C12.29 for Field TestingMetering DevicesGiven the early stages for this Working Groupthis is all personal opinion and could changebefore the new Standard is completed.There is also no mandate that this Standardever has to come into existence. If theCommittee never presents a draft or if theANSI C12 main committee rejects the draftthere will be no C12.9 in the near future, andif approved, C12.1 and C12.20 do not haveto reference the new Standard
    18. 18. 18Site Verification…The NewField TestingWhere are ANSI and the voting members heading?Toward more comprehensive field testing that focuses on far more thanjust accuracy testing. The members vision for the future of field testing isthat utilities will perform the following checks when checking a meteringinstallation in the field;• Meter Accuracy testing• Meter Communications Performance• Software and firmware verification• Setting verification• Functional testing• Disconnect/reconnect Functionalityand as left setting• Tamper Verification• Site Audits appropriate to the typeof meter
    19. 19. 19Questions and DiscussionTom LawtonTESCO – The Eastern Specialty CompanyBristol, PA1-800-762-8211This presentation can also be found under MeterConferences and Schools on the TESCO website: www.tesco-advent.com

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