Learning meter forms is as easy as 1S-2S-3S! You’ll learn the most common metering forms and how they are used. This presentation also dives into Blondel’s Theorem and how it is used to determine what type of meter to install at different services.
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TESCO Tuesday: Metering Testing by Form
1. Today’s session will begin shortly
@tescometering
@TESCO_Metering
TESCO -The Eastern Specialty Company
TESCO -The Eastern Specialty Company
TESCO
Tuesdays
2. Meter Testing
by Form
Prepared by John Williams, TESCO
The Eastern Specialty Company
For TESCO Tuesday
Tuesday, February 8, 2021
11:00 a.m. – 12:00 p.m.
3. Introduction
Today we are going to review how testing is performed on various
meter forms and why.
We will discuss the following:
• Background on meter testing – Phantom loads, Voltage and Current
Generation
• Self-Contained vs Transformer-Rated meters
• Single Phase vs Series Parallel vs “True” 3 phase testers
• Applications of testers to different meter forms
…but first, let’s learn about polyphase metering and Blondel’s Theorem
3
4. Three Phase Power
Blondel’s Theorem
The theory of polyphase watthour metering was first set forth on a scientific
basis in 1893 by Andre E. Blondel, engineer and mathematician. His theorem
applies to the measurement of real power in a polyphase system of any
number of wires. The theorem is as follows:
- If energy is supplied to any system of conductors
through N wires, the total power in the system is given
by the algebraic sum of the readings of N wattmeters, so
arranged that each of the N wires contains one current
coil, the corresponding voltage coil being connected
between that wire and some common point. If this
common point is on one of the N wires, the
measurement may be made by the use of N-1
wattmeters.
4
5. Three Phase Power
Blondel’s Theorem
• Simply – We can measure the power in a
N wire system by measuring the power in
N-1 conductors.
• For example, in a 4-wire, 3-phase system
we need to measure the power in 3
circuits.
5
6. Three Phase Power
Blondel’s Theorem
• If a meter installation meets Blondel’s
Theorem then we will get accurate power
measurements under all circumstances.
• If a metering system does not meet
Blondel’s Theorem then we will only get
accurate measurements if certain
assumptions are met.
6
7. Blondel’s Theorem
• Three wires
• Two voltage measurements with
one side common to Line 2
• Current measurements on lines
1 & 3.
This satisfies Blondel’s
Theorem.
7
8. Blondel’s Theorem
• Four wires
• Two voltage measurements to
neutral
• Current measurements on lines 1 &
3. How about line 2?
This DOES NOT satisfy Blondel’s
Theorem.
8
9. Blondel’s Theorem
• In the previous example:
– What are the “ASSUMPTIONS”?
– When do we get errors?
• What would the “Right Answer” be?
• What did we measure?
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cos(
)
cos(
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cos(
)
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[ b
b
c
c
c
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sys I
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9
10. Blondel’s Theorem
• Phase B power would be:
– P = Vb Ib cosθ
• But we aren’t measuring Vb
• What we are measuring is:
– IbVacos(60- θ) + IbVccos(60+ θ)
• cos(α + β) = cos(α)cos(β) - sin(α)sin(β)
• cos(α - β) = cos(α)cos(β) + sin(α)sin(β)
• So
10
12. Blondel’s Theorem
• If Va ≠ Vb ≠ Vc then the error is
• %Error =
-Ib{(Va+Vc)/(2Vb) - (Va-Vc) 0.866sin(θ)/(Vbcos(θ))
How big is this in reality? If
Va=117, Vb=120, Vc=119, PF=1 then E=-1.67%
Va=117, Vb=116, Vc=119, PF=.866 then E=-1.67%
12
14. Phantom Power
• In order to test a revenue grade meter to ANSI C12 specifications,
the test board will have to power each of the voltage and current
elements of the meter at rated test voltage (TV) and rated test
current (TA).
• Let’s take a typical form 1S meter, for instance. It’s TV is 120V and
TA is 10A. Without employing phantom loading, the test board would
have to consume at least 1200W. Using phantom power, the test
board would only consume about 150W
• Phantom Power separates the voltage and the current into two
separate sources; High voltage @ low current and high current @
low voltage.
• From the meter’s point of view, it doesn’t know the difference, but
the test board will consume far less energy over the course of a
year.
14
15. Phantom Power
• Voltage and Current Generation:
– In most modern meter board equipment, the phantom potential and
current start with a processor that creates a micro-stepped low-level
sine-wave output.
– That output is fed into an amplifier circuit that is the first stage in the
amplification.
– The output of the amplifier is then fed into a step-up transformer that
takes the amplitude to the level that is seen by the meter.
15
16. Phantom Power
• SeriesParallel Phantom power:
– This term refers to the application of single phase power to polyphase
meters
– The potential is wired in parallel to each voltage coil in the meter
– The current is wired in series through the primaries of the current
transformers.
16
41. Questions and Discussion
John Williams
john.williams@tescometering.com
TESCO – The Eastern Specialty Company
Bristol, PA
215-228-0500
www.tescometering.com
42. Thanks for tuning in!
See you at the next session.
Upcoming Session:
Metering Configurations
February 2, 2021 | 11:00 AM Eastern
**TESCO Users Group: July 18-21, 2021**
Presentation Date
Test Switch Operations and Hot Sockets 2/16
Meter Testing in the Field 2/23
Transformer-Rated Testing Using Pickups and Probes 3/2
Traditional Ratio, Burden, Admittance and Demag Testing – Part 1 3/9
Traditional Ratio, Burden, Admittance and Demag Testing – Part 2 3/16
Realizing Your Investment in Technology Through Analytics 3/23
Shop Testing 3/30
Preparing for AMI Deployment 4/6
Communication Equipment 4/13
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