Recommendations of the VA Joint Working Group

Report to Measurement Canada for Consideration

Final recommendations achieved in consensus with EPAC


Table of Contents


Background

In 2005 Measurement Canada developed a discussion paper which identified concerns and issues relating to the existence of potential inequities in the measurement of the legal unit of measure (LUM) known as volt-ampere (VA). It was identified that there are possible inequities resulting from the fact that there are a number of different VA calculation methods that potentially yield significantly different readings under the same load.

In the fall of 2005, the VA Joint Working Group (JWG) was launched to further review and discuss the issues associated with the establishment of methodologies pertaining to the determination of VA demand and VA-hour energy. The mandate of the JWG was to identify and study the factors which contribute to the potential inequity, and to make recommendations which would minimize or eliminate the inequities found. Standard algorithms will need to be identified for each of the demand units of measurement: watt, var, and volt-ampere (VA). The respective algorithms and any associated provisions for their use will be included within the Electricity and Gas Inspection Regulations established for this purpose.

To put into perspective the factors which contribute to the potential inequities, the following context is presented. In a simple direct current environment the unit VA is in fact a defined unit of measurement which is simply the amount of voltage across a load multiplied by the amount of current through the load. In terms of measurement, there is no other definition that would lead to differing values of VA given the same load conditions.

The question then is, from the perspective of trade measurement, what is the definition of VA in an alternating current, polyphase environment which includes harmonic distortions and reactive power, (both leading and lagging)? This is a complex question of which, prior to these recommendations, there was no one answer because there is no unified definition of VA in that electricity environment. In addition, because there are multiple methods of responding to a varying load, (demand response characteristics), this creates even greater disparity among measured values of the legal unit of measurement called VA demand. This situation would be completely unacceptable to regulators, measurement professionals and consumers in any other field of trade metrology such as mass or volume. In Canada, a kilogram is a kilogram is a kilogram, regardless of location, type of customer, or who the seller is.

Summary

The VA JWG gathered substantial data, developed analysis tools, and performed evaluations of all the identified factors which contribute to variation of VA demand and energy measurement. The results of that work formed the basis for the draft recommendations which were presented for public consultation in September 2007. After completion of the consultation, the JWG reconvened with the goals of reviewing comments received, determining if modifications were warranted, and establishing a final set of recommendations, including implementation plan and next steps.

The majority of comments received during the consultation related strictly to aspects of implementation such as time frames, and grandfathering issues. More specifically concerns were expressed regarding the cost impact of large scale reconfiguration and of retiring meters earlier than expected.

Of the technical comments received, in virtually all cases they related to the potential impact on current practices of measurement being performed outside a meter. The mandate of the JWG did not pertain specifically to measurement being performed either inside or outside of a meter. The JWG mandate centered upon defining what exactly is a unit of VA in the legal metrology context, similar to defining what exactly is a kilogram, or litre or watt, (all of which are defined as, or based on, SI units). In that regard, the VA JWG refers comments relating specifically to measurement methods performed outside of a meter to the LUM JWG as such comments pertain specifically to their mandate.

That said, the VA JWG contends that its recommendations pertain simply to measurement of VA/VA-h and the methods used in calculating VA, and that the principles should apply regardless of what method or what device is performing the measurement. It will be the responsibility of the LUM JWG to determine if there are technical or metrological considerations specific to performing VA calculation outside of a meter which can impact on the ability of meter owners and users to comply with the measurement principles recommended in this document.

There were virtually no objections to the technical or metrological principles of the JWG's recommendations. In fact there was generally strong support for many of the recommendations including the elimination of thermal and exponential demand, standardizing on vectorial addition and direct calculation of VA through incremental measurement of watts and vars, and eliminating the inclusion of Q-h and distortion power as factors in VA determination. Subsequent to consultation, only one recommendation was modified, and an exemption for a certain customer class was provided for another. But even both of those adjustments related to concerns pertaining to "current practices for measurement outside a meter", and not metrological concerns with the principle of the recommendation. This is a good indicator that the JWG did excellent work in fulfilling it's technical mandate of developing a standard method of VA measurement (energy and demand) that is fair, accurate, consistent and equitable for the Canadian electricity trade marketplace.

It was clear to the JWG that there is a divide within the electricity industry with some organizations strongly supporting standardization and others unwilling to do so based on reasons such as: "this is the way we do or have always done something", "there is a cost to change", "rate structures are based on the current system of measurement". This caused great difficulty for the JWG as its mandate was to make recommendations based on sound metrological principles and to standardize, to the extent possible, on a definition of VA for the context of legal metrology.

It is recognized by the JWG that rate structures and supporting infrastructure have been established around a system of measurement that is inconsistent in it's definition of the units of VA/VA-h and in particular VA demand. From a purely technical/metrological perspective, the JWG has difficulty accepting arguments against standardization which appear to be analogous to suggesting that "the calibration of a scale should be adjusted to reflect a rate" rather than that "the rates of charge (per unit) should be adjusted to reflect the standard measurement". The only rationale given for such arguments appears to be based on the difficulty to adjust established rates. In any other field of trade measurement, it is the measurement that is consistent and the rates which may vary depending on the location, type of customer, or who the seller is.

However, the JWG does accept that a certain amount of time is required for the market to adjust to utilizing a definition of a legal unit of measurement which is standard and equitable across the nation. The JWG reluctantly even made exceptions to certain technical recommendations in order to satisfy the implementation concerns of certain stakeholders.

Final Recommendations

1.0 Demand Response

1.1 New thermal demand meters no longer be approved in Canada

1.2 Exponential demand function no longer be approved in Canada.

1.3 Demand meters shall use a 15 minute integration period with 3 updates of 5 minutes, (sliding window). (This recommendation was modified from that which was originally proposed as a result of consultation comments. While the consultation comments on this specific recommendation generally pertained to current practices of measurement being performed outside a meter, the JWG nevertheless decided that modifying the recommendation would ease concerns expressed and would facilitate the LUM JWG in adopting this recommendation in regards of measurement performed outside a meter. We suggest that the LUM JWG carefully consider a definition for "load profile" which respects the principles of this recommendation).

Note: From a purely technical/metrological perspective, the JWG maintains that demand meters should use a 15 minute integration period with 5 updates of 3 minutes. In that regard the JWG recommends that a sliding window consisting of 5 updates of 3 minutes be considered in the future.

1.4 High Intervention Customers - Demand meters shall only use a 15 minute demand interval.

1.5 Low Intervention Customers - Demand meters may use a 15, 30 or 60 minute demand interval (Block or sliding window).

Note: As stated in the Summary, there appeared to be a wide disparity among stakeholders with regards to both the original proposed demand interval of 15 minutes, and the five sub-intervals of 3 minutes. The JWG had difficulty in dealing with this disparity given our mandate of standardization and equity. The JWG concluded that the technical recommendation could be dependant on customer class (high intervention vs. low intervention). The JWG however felt that it's expertise was in the realm of technical metrology and was not qualified nor had a mandate to unilaterally establish parameters for which types of consumers would constitute low intervention, and which would constitute high intervention. Many defining parameters were discussed including: 1) load size, 2) connectivity (transmission system vs. distribution system), or 3) as defined by Provincial regulatory authorities. The JWG concluded that it was the responsibility of the electricity measurement industry to define low vs. high intervention, and in that regard, deferred that decision to EPAC.

EPAC has indicated that a new JWG will be created comprising of representatives from utility rates departments and/or Provincial energy regulators. This JWG will be mandated with defining the parameters and criteria for customer classes which would be subject to the various levels of MC intervention.

In addition, the JWG recommends that a standard demand interval length of 15 minutes for all customers regardless of class be considered in the future.

2.0 VA measurement/calculation methodology

2.1 Demand meters shall calculate VA from source data on a continuous interval basis. The time interval for VA source data for demand calculation is to be as short as possible, but shall not exceed one minute.

2.2 Q/Q-hr metering shall not be used in determination of VA/VAh or var/varh.

2.3 Polyphase meters shall calculate total VA/VA-h of a load by the vectorial addition of coincidental incremental values of watts/watt-h and vars/var-h per phase.

2.4 Vars/var-h shall be measured directly and not calculated.

2.5 Vector Apparent Power shall be determined based on Budeanu's Reactive Power (IEEE 1459 section 3.1.2.7). Vector Apparent Power shall be determined excluding Distortion Power. Therefore, for the purpose of legal metrology in Canada, the sinusoidal definition in IEEE 1459 section 3.2.2.6 shall apply to both sinusoidal and non-sinusoidal conditions.

Note: The JWG would prefer to recommend measurement based on fundamental frequency only (excluding harmonic power), however, low-cost metering capable of performing that is not widely available today. The JWG recommends that measurement based strictly on fundamental frequency be considered in the future.

2.6 VA/VA-hrs shall be determined based on continuous accumulation of instantaneous or incremental values. This will result in a consistent methodology of determining VA regardless of the quadrant in which vars occur. This recommendation does not preclude electricity distributors from using var/var-h measured values in establishing the basis for a charge or credit for that particular LUM. Where vars are measured, the registration shall indicate the quadrant (or direction) in which the vars exist. Where an electricity distributor wants to establish a charge or a credit for reactive energy, the JWG recommends that it be done on the basis of measured values of reactive energy and not based on measured values of VA demand.

Exception: Where the VA determination is based on the totalization of measurements from more than one meter, it is not possible to perform totalization directly based on continuous accumulation of instantaneous or incremental values of VA-h. Nevertheless, the principles of VA/VAh measurement that the JWG recommends in this document should be applied to totalized quantities as the purpose of totalization is to measure the LUM of two or more separate meters, and combine those quantities in a manner that is representative of the LUM that would be measured if the loads were measured by a single meter. Where var and watt measurement are used for purposes of totalization, an identification shall be made to identify in which quadrant the var/var-h have occurred. This will require independent registers by quadrant, ie) a register for Q1 vars and a register for Q4 vars. This is effectively an issue specific to the LUM JWG as totalization is a process that occurs outside an approved meter. It is important for the LUM JWG to consider this recommendation and establish implementation parameters and time frames as that JWG sees fit, if different from those of the general principles proposed by the VA JWG.

3.0 Terminology and Equations

See Annex A

Implementation Plan

General Principles

As stated in the Summary, the VA JWG contends that our recommendations pertain simply to measurement of VA, and that the principles should apply regardless of what method or what device is performing the measurement. In general, the JWG recommends that measurement of VA/VA-h be performed in a manner compliant with the recommendations established herein by January 1, 2012.

An implementation plan pertaining to the approval and grandfathering of meters is identified below. The implementation plan for both new meter approvals and grandfathering of existing meters in service have been modified from those which were originally proposed. In effect, the modified implementation plan identifies dates pertaining to new meter approvals which will align with dates proposed by the LUM JWG. Additionally it will allow for all existing meters in service to be "grandfathered"for the duration of their usable life.

The JWG recognizes that it may not be possible to implement some of the principles of these recommendations (where pertaining to measurement outside a meter) within that time frame due to external factors (such as provincial regulatory processes or rate restructuring issues) beyond the control of meter owners and users. For those situations the JWG recommends that a meter owner or user be allowed to present a formal request to Measurement Canada for an extension including a justification for the extension and a revised proposal for date of implementation.

New Meter Approvals

1.1 Effective January 1, 2012.

1.2 Effective January 1, 2012.

1.3 Effective January 1, 2012.

1.4 Effective January 1, 2012. Footnote 1

1.5 Effective January 1, 2012. Footnote 1

2.1 Effective January 1, 2012.

2.2 Not applicable - There is no impact on actual meters. This is for all intents and purposes a recommendation that pertains to the determination of VA/VA-hr outside of a traditional meter.

It is important for the LUM JWG to consider this recommendation and establish implementation parameters and time frames as that JWG sees fit, if different from those of the general principles proposed by the VA JWG.

2.3 Effective January 1, 2012.

2.4 Effective January 1, 2012.

2.5 Effective January 1, 2012.

2.6 Effective January 1, 2012.

Grandfathering of Meters In-service

1.1 Effective January 1, 2012, no new meters of this type will be eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods.

1.2 Effective January 1, 2012 no new meters of this type will be eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

1.3, 1.4 and 1.5 Effective January 1, 2012 new meters which do not conform to the recommendation will not be eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

Note: For recommendations 1.2 to 1.5: All meters (including sample meters that represent a homogeneous lot of meters) which are returned to a verification facility for reverification shall be reprogrammed to perform demand measurement in the manner established in recommendations 1.3 and 1.4 (or 1.5 as applicable) before being reverified and returned to service. This means that the sample meters will have to be excluded from their lot subsequent to inspection and testing. The installed meters of the lot may remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

2.1, 2.4 and 2.5 Effective January 1, 2012 new meters which do not conform to the recommendation will be not eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

2.2 Not applicable - There is no impact on actual meters. This is for all intents and purposes a recommendation that pertains to the determination of VA/VA-hr outside of a traditional meter.

It is important for the LUM JWG to consider this recommendation and establish implementation parameters and time frames as that JWG sees fit, if different from those of the general principles proposed by the VA JWG.

2.3 Effective January 1, 2012 new meters which do not conform to the recommendation will be not eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

The VA JWG strongly recommends that existing 2-element meters which do not comply with this recommendation be voluntarily withdrawn from service as soon as practicable due to the high potential for inequity and inaccuracy which increases as load becomes more unbalanced.

2.6 Effective January 1, 2012 new meters which do not conform to the recommendation will be not eligible for verification. Meters currently in service at that time will be allowed to remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension). It is important for the LUM JWG to consider this recommendation where pertaining to measurement performed outside a meter and establish implementation parameters and time frames as that JWG sees fit, if different from those of the general principles proposed by the VA JWG.

Note: For recommendations 2.1, and 2.3 to 2.6: All meters (including sample meters that represent a homogeneous lot of meters) which are returned to a verification facility for reverification shall be reprogrammed to perform VA determination in the manner established in these recommendations before being reverified and returned to service. This means that sample meters will have to be excluded from their lot subsequent to inspection and testing. The installed meters of the lot may remain in service until the end of their current and subsequent reverification periods, (including subsequent reverification periods established through seal extension).

Key Performance Indicators

The VA JWG suggests using the following indicators to measure the rate of progress at which the percentage of meters in service comply with these recommendations. These KPI's make use of existing programs and available processes for data gathering.

  1. Manufacturers to provide sales data. This will provide and indication of the number of compliant meters coming in to service and can be expressed as a percentage of total population.
  2. Use MC Marketplace Monitoring targeted inspections to determine which VA / Demand meters (of those inspected) are compliant, again providing a ratio.
  3. Use MC dispute investigations to determine which VA / Demand meters (of those inspected) are compliant, again providing a ratio.

Review Cycle

The VA JWG suggests that these recommendations be reviewed in 5 years from date of acceptance by MC.

Completed Steps

  1. VA draft recommendations developed and public consultation performed.
  2. VA JWG Report submitted to EPAC for consideration.
  3. Consolidation of consultation comments and JWG response prepared and translated.
  4. Final report for MC consideration prepared subsequent to public consultation as well as discussion and direction from EPAC.

Next Steps

  1. Publication of consolidated consultation comments and JWG response. (To be done in conjunction with publication of same from LUM JWG).
  2. Publication of recommendations and implementation plan upon acceptance by MC.
  3. Identify changes required to existing MC Specifications pertaining to meter approval, verification/reverification, installation, and use.
  4. Identify if any new test equipment is required in regards of approval of meters and verification of meters. (The JWG discussed this throughout various meetings and it was generally confirmed that MC ELSD has, or will have, the capability to assess meters for compliance with these recommendations).
  5. Effectuate changes to Specifications where required and publish.

Conclusions

The JWG believes that it has achieved the best possible recommendations in regards of its mandate to develop a standard method of VA measurement (energy and demand) that is fair, accurate, consistent and equitable for the Canadian electricity trade marketplace.

It was recognized early on in the JWG's work that the factors pertaining to VA demand in fact pertain to VA-h energy units as well. It was also recognized that many of the factors pertaining to VA would in fact relate to Watts and Vars as well. This is particularly evidenced in the recommendations concerning demand response characteristics as demand applies to each of those legal units of measurement.

The recommendations pertaining to VA/VA-h measurement/calculation methodology effectively amount to "defining" what is a unit of VA in the legal metrology context (not the scientific or purely theoretical context). Should MC accept these recommendations and move forward with implementation, it would be prudent to recognize that the units Watt/Watt-h and Var/Var-h also be more specifically defined in a similar manner.

Final Report prepared by:

Mike Abraham
Chairperson VA JWG
Senior Program Officer - Electricity
Measurement Canada

VA JWG members:

  • Adnan Rashid - Measurement Canada
  • Jean Joly - Hydro Quebec
  • Subhas Chandra - Itron
  • Jeff Richardson - Elster Metering
  • (Brent Hughes - BC Hydro) ** Brent was a contributing member for the duration of the committee with the exception of the final meeting which resulted in these final recommendations.
  • (Luc Tessier) ** Luc chaired the committee during Mike's absence.

Annex A

Terminology

The Workgroup established a terminology listing to ensure that consistent terms and interpretations were being used. It is recommended that Measurement Canada (MC) type approval, verification, and installation and use specifications be amended to include the following terminology as applicable:

Arithmetic sum of VA:

Obtained by using a formula to determine the individual VA values in each phase, and subsequently arithmetically adding each phase value.

Block interval demand meter:

Block interval demand meters averages the power over a specified period of time. The time intervals (usually 15 minutes), follow each other continuously and consecutively (i.e.: when one interval concludes, the next one begins).

Budeanu's Reactive Power definition:

Refer to IEEE 1459, section 3.1.2.7

Buchholz definition of apparent power:

Refer to IEEE 1459, section 3.2.2.8

Calculation Frequency:

In general frequency is defined as the measurement of the number of occurrences of a repeated event per unit of time. In the context of this document Calculation Frequency means the frequency used by the meter to calculate the values that serve to establish the demand. As an example it could be calculate every pre-determined period such once per second, once per cycle, or at every sample that the technology of the meter can measure.

Demand Interval (of an integrating demand meter or of a pulse recorder):

The specified overall interval of time on which a demand measurement is based. Usually 15 minutes.

Demand meter:

An electricity meter intended to measure demand or maximum demand or both, where demand is the rate at which electrical energy is supplied to a load and which displays and stores the demand(s).

Distortion power:

Budeanu's Distortion Power is defined in IEEE 1459 section 3.1.2.16.

Exponential demand:

Represents the emulation of the thermal demand measurement in an electronic meter.

Fundamental Active Power:

Refer to IEEE 1459, section 3.1.2.4

P1 = (1÷kT) ∫(t; t + kT) V1i1dt = V1i1cosθ
Fundamental Apparent Power:

Refer to IEEE 1459, section 3.1.2.9

S1 = V1 × I1 S1^2 = P1^2 + Q1^2
Fundamental Reactive Power:

Refer to IEEE 1459, section 3.1.2.6

Q1 = (ω1 ÷ kT) ∫(t; t + kT) V1i1dt = V1i1sinθ
Harmonic:

A part of a signal that has a frequency that is an integer number multiple of the fundamental frequency of the signal. The fundamental frequency is generally the reference frequency (fref), generally 60 hertz for electric power.

Harmonic Distortion:

Refer to IEEE 1459, section 3.1.2.1

Harmonic Power:

The sum of power determined from all like order harmonics of voltage and current.

IEEE:

Institute of Electrical and Electronics Engineers

JWG:

Joint working Group

LUM:

Legal Unit of Measure

Peak splitting:

Achieved by synchronising the electricity consumption with the demand interval of a meter to reduce the registered value of the peak demand. E.g. Applying a block load of 100kVA for 15 minutes, beginning at the mid point of the first demand interval and ending at the mid point of the next demand interval, will lead to a registration of two successive 50kVA peak demand on a block interval meter.

Power Factor:

the cosine of the phase angle between voltage V and current I.

Q meter:

An electricity meter that measures a quantity (referred to as "Q" or "Q hour") that may be obtained by effectively lagging the applied voltage to a watt-hour meter by 60º. It is limited to PF range of 60º lag to 30º lead. The quantity "Q hour" was intended to facilitate VA measurement in electromechanical technology.

Reactive power:

Refer to IEEE 1459, section 3.1.1.3

Sliding window demand:

Sliding window integrating demand meters follow the same measurement principle as block interval however the intervals are not independent of each other, but are established through a series of sub-intervals. Demand is calculated by averaging the load recorded over contiguous sub-intervals which combine in time to equal the demand interval. Successive intervals are shifted in time by the length of the sub-intervals.

Sub-interval:

A series of equally sized intervals that make up the demand interval used in determining a sliding window demand value (e.g. 5 sub-intervals of 3 minutes, in a demand interval of 15 minutes).

Thermal demand meter:

An electromechanical meter which uses the principles of thermal response to loads in order to provide a demand registration. These devices operate based on the expansion of metals when heated, and on an electrical conductor's heat loss as a result of current passing through it. A bimetallic coil strip is used to produce predictable deflection of a demand pointer proportional to the power in the circuit.

Vector Apparent Power:

Refer to IEEE 1459, section 3.2.2.6

Sv = √(P^2 + Q^2) Sv = | Pa + Pb + Pc = j(Qa + Qb + Qc) | = | P + jQ |

Equations

(numbered by recommendation identified in final report)

1.3

Block Demand: BD(int) = ∫(t = 0; 3) Energy(Wh, varh, VAh) (t= time in minutes)

Block Demand (15 minute with 3 minute sliding window): BD = BD(int)1 + BD(int)2 + … BD(int)5

2.2

Volt-ampere (VA)vectorial VA = √(Watt^2 + Var^2)

2.3

Watts (W): W = V × I cosθ

Polyphase Watts: W(p) = Va × Ia cosθ + Vb × Ib cosθ + Vc × Ic cosθ

Vars (var): Var = V × I sinθ

Polyphase Vars: Var(p) = Va × Ia sinθ + Vb × Ib sinθ + Vc × Ic sinθ

Volt-ampere (VA) vectorial: VAvectorial = √(W^2 + Var^2)

Polyphase Volt-ampere (VA) vectorial: VA(p)vectorial = √(Wp^2 + Varp^2)

2.4

Vars (var): Var = V × I sinθ

Polyphase Vars: Var(p) = Va × Ia sinθ + Vb × Ib sinθ + Vc × Ic sinθ

2.5

Watts (Wh) including harmonics: Wh = V1 × I1(cosθ) + V2 × I2(cosθ) + … + V23 × I23(cosθ)

Vars (Varh) including harmonics: Varh = V1 × I1 (sinθ) + V2 × I2 (sinθ) + … + V23 × I23 (sinθ)

Volt-ampere (VAh) including harmonics: VAh = √(Wh^2 + Varh^2)

Footnotes

Footnote 1

Demand meters will be assessed for compliance with accuracy requirements for both of these recommendations as MC cannot distinguish between customer classes at the approval stage.

Return to footnote 1 referrer

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