11/7/2012
Metering Applications
Course 310
Irvin Lane II
Manager, Electric Metering
OUC – The Reliable One
SEMA 2012
Basic Terms
Mentioned in This Presentation
•
Meter Form #
•
Voltage & Current Coil
•
A, S, and K base
•
Self-contained
•
Transformer-rated
•
Current & Voltage Transformers (CT & PT)
•
Blondel’s Theorem
Basic Meter Definition:
• The basic watthour meter is comprised of voltage coils
and current coils (elements), the number and
arrangement of which depend on the particular
application. The current passing through the current
coils and the voltage applied across the voltage coils
produce a magnetic flux which, in turn, produces torque
on the meter disk. The torque and resulting rotational
speed are proportional to the power measured.
• Blondel’s Theorem: Given a service with “N” number of
wires, the number of meter elements “X” necessary to
accurately meter the service is represented by the
equation: X = N - 1
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Meter “Forms”
• Specifies the internal wiring and terminals
• Implies how the meter is wired into the service
• Self-contained meters connect directly to service
wires
• Transformer-rated connect indirectly to service
through instrument transformers
• Defines how meters are installed: A, S, and K
• Meters always have form printed on nameplate
ANSI C12.10
Form Designation Stators (elements)
Current Circuits
1S
One
One
External Wires
Two
2S
One
Two
Three
3S
One
One
Two
4S
One
Two
Three
5S
Two
Two
Three
6S
Two
Three
Four (wye)
7S
Two
Three
Four (y alt)
8S
Two
Three
Four (delta)
9S
Three
Three
Four
12S
Two
Two
Three
14S
Two
Three
Four (wye)
15S
Two
Three
Four (delta)
16S
Three
Three
Four (wye)
Many Sources of Information
• ABB’s “All In One Guide
• Landis + Gyr’s
“Meterman’s Notebook
• GE’s guide for installing
meters
• Ugly’s Electrical
Reference
• EEI’s “Handbook for
Electricity Metering”
• Meter schools across the
country
• Internet search engines
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• Initial “house” services
had just two wires. A
120v line and a neutral.
• Due to increasing
electricity demands, an
additional 120v line was
added. With 240v
“phase-to-phase”, stove
and water heaters could
efficiently be electric.
• Polyphase - mostly
commercial/
manufacturing
• Motor loads – delta
voltages and transformer
configurations
• “Lighting” loads had to be
fed from another
service/meter.
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• Polyphase, 4 wire
services combined every
aspect of previous
configurations into one
transformer and meter
configuration.
• “Simple” addition of
another element
transforms a form 2 meter
to a 3 phase application
• Commercial services with
more emphasis on
lighting and light motor
loads (A/C).
• Loads can be more
evenly balanced.
• Single phase service off a
wye bank.
• Note: this is a true 2
element meter unlike the
form 2 meter shown
previously.
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Factors That Go Into Current and
Voltage Transformer Selection
• PT’s (VT’s) allow standardization of meters by providing
standard voltages
• CT’s and PT’s provide for remote location of the meter
and isolation/insulation.
• Typically choose voltage transformer for 120v secondary
• Typically choose current transformer that drives meter
into it’s best accuracy range without exceeding the meter
class rating
What is a Transformer?
Transformer Examples
• Core of magnetic material
• Primary winding – N turns
• Secondary winding – N
turns
• Steps up/down
Volts/Amps
• True 3 phase – 3 element
meter for a 4 wire – 3
phase service.
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APPENDIX
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