Single Phase Meter Components, Constants, and Ratios · Single Phase Meter Components, Constants, and Ratios Presented by Scott Sutton Northwest Electric Meter School North Seattle

WATT-HOUR METER BASICS 1

Single Phase Meter Components, Constants, and RatiosPresented by Scott Sutton

Northwest Electric Meter School

North Seattle Community College

Group 1

Purpose of this class:• What is an electro-mechanical Watt-hour

meter

• The basic parts of the meter

• Electronic vs Electromechanical meters

• Meter types – Examples – Q & A


The Watt-hour meter

• Measures energy used -• Power is a rate at which energy flows

– Power X Time = Energy

Relate the Watt-hour meter to the speedometer and odometer of an automobile

– Miles per hour = Watts being used -Disk speed

– Miles driven = Kilowatt hours -Register Read

• 30 MPH for 2 hours = 60 miles driven

• 30 kW for 2 hours = 60 kWh


Today’s Electromechanical kWh meter’s are basically the same design as the ones manufactured 100+ years ago. • Much less expensive

• Light weight

• Highly accurate

• Maintenance free device

• Provide many years of reliable service

Today's meters are vastly improved:

• They are highly accurate and have a very flat accuracy curve over extreme loads and environmental conditions. Single phase self contained meter’s are so well calibrated from the manufacture that many utilities do not test new meters . They may perform a BAR-X,(sigma) or Sample Test


Basic Parts:• Name Plate

• Base

• Cover

• Frame & magnets

• Stator - potential coil and current coil

• Rotor(disk) and bearings

• Register

Basic Parts: Nameplate• The most important part of meter

• Form Number - Indicates the internal connections of the meter. ANSI Stds.

• Voltage - Design or test voltage of potential coil

• CL or Class - Maximum current capacity.– CL10, CL20, CL100, CL200, CL320-


Basic Parts: Nameplate (continued)• T.A. - Test Amps, (100% Full Load – 10% Light Load)

• Wire - (2w, 3w, 4w)

• Kh - Watt-hour Constant

• Multiplier (CT’s, VT’s, internal meter multi)

• Number of stators or potential coils

• Company ID number and MFR. Type


Basic Parts: Base

• Earlier meter bases were made of cast iron, metal alloys and cast aluminum

• Today’s bases are made of high impact strength plastic

• Base configurations - Socket type, A base type & Bolt In type (K base)

Basic Parts: Base (continued)

• Test Link - used to disconnect or isolate one side of the potential circuit from the current circuit when testing

• Screened vents - To prevent insects and dust from getting into meter and allows ventilation to minimize condensation


Basic Parts: Base (continued)• Lightning Arrestor - To protect meter

from High Surge Currents– an air gap between the current coil and

ground that will “Flash Over” between 5000 & 6500 volts

• Gasket - Provides a seal between the base & cover

• Hanger - Storage

• Sealing Provision - Security

Basic Parts: Cover• Purpose - To protect the meter

components from weather and dust while providing a means to read the register and inspect meter

• Security - Makes it difficult to tamper with or to conceal tampering


Basic Parts: Cover (continued)

• Glass - Special stress relieved glass

• Rim - Aluminum or stainless steel

• Plastic - Lexan® (Poly-Carbonate)

• Special metal Covers protection from vandals

• Demand Resets, Optical ports

Basic Parts: Frame

• Composition - Iron for older meters, Die cast aluminum for new

• Purpose - Mounting & supporting of meter components in an accurate and stable relationship. All meter components are machined to a tolerance of +/- 0.002 inch for precise fit & positioning.


Basic Parts: Magnets• Composition - ALNICO alloy: Aluminum,

nickel, cobalt & iron

• Purpose - to control the speed of the disk

• The magnet can withstand a surge of 20,000 amps with only 1/2 of 1% change in meter accuracy. Older meters with chrome steel magnets can only withstand 10,000 amps resulting in a change in meter accuracy of 4% or greater.

Basic Parts: Stator • Electromagnetic element

• The potential coil is connected across the line terminals– 2400 turns of #29AWG for 120v– 5700 turns of #32AWG for 240v– 9600 turns of #35AWG for 480v

• Fine wire wound on a silicone laminated plate steel core


Basic Parts: Stator

• The potential coil is compensated so that the meter is accurate from 50% to 120% of the rated or nominal voltage (name plate)

• The potential coil is highly reactive (inductive) in relation to the current coils & use only about 2 watts of power

• Purpose: to convert applied voltage into a magnetic field or flux which is proportional to the line voltage

Basic Parts: Stator

• The stator also facilitates or provides– Light load adjustment– Power factor adjustment


Basic Parts: Current coil

• The current coils of a meter are always connected in series with the load

• Purpose: Converts the load current into a magnetic field or flux which is proportional to the load current

Basic Parts: Current coil (continued)

• Self contained 200A meter coils are 2 or 4 turns of 30,000 Circular Mils wire (#6AWG)

• Insulated with epoxy resin

• In a form 2S meter two current coils are located beneath the disk and one of the current coils is wound in reverse of the other


Basic Parts: Rotor or Disk

• Two parts - Disk and the shaft

• Composition - Pure aluminum– Good conductivity– Light weight

• Disk is stippled for mechanical strength or stiffness

Basic Parts: Rotor or Disk (continued)• Graduations painted on the disk for

testing

• Edge is serrated for testing at the factory

• Two holes in disk are called Anti-Creep holes– these prevent disk rotation when only

potential is applied - no load current

• On the shaft a worm gear is cut


Break Time

• 10 minutes

Basic Parts: Bearings

• Two types of bearings - Mechanical and Magnetic

• Mechanical Bearings – no longer used– Pivot type: Hardened tip which rides on a

sapphire cup– Ball type: Ball bearing rides between two

sapphire cups


Basic Parts: Bearings (continued)

• Magnetic Bearings– Mutual attraction at top of disk shaft or– Repulsion at bottom of disk shaft– Vertical alignment by stainless steel guide

pins in the magnets to the top and bottom of the disk shaft

• Mechanical bearing required much more maintenance than magnetic bearings

Basic Parts: Register

• A system of gears, dials and pointers designed to count or accumulate the number revolutions of the disk

• The disk rotates at a design speed proportional to the load watts

• Each revolution represents a definite number of watts delivered to the load during the time required for that revolution


Basic Parts: Register (continued)

• Revolutions made by the disk are communicated to the register by a set of gears– Worm gear on the disk shaft– First gear - gear at the back of the register

• The register reads in kWh so there must be a relationship between the disk revolutions and the register ratio and watt-hours used

Kh or Watt-Hour Constant

• The number of watt-hours represented by one revolution of the disk– Symbol Kh

– also known as the Disk Constant


Basic Parts: Register: Shaft Reduction

• Definition - The number of revolutions of the disk for one revolution of the first gear on the register which meshes with the worm gear of the disk shaft

• Typical shaft reductions are 50 or 100 teeth on the First Gear

• Symbol - Rs

Basic Parts: Register: Register Ratio

• Definition - The number of revolutions of the first gear for one revolution of the first or right dial pointer

• Symbol - RR

• Basic Register Ratio Formula -10,000 = Kh X RR X Rs


Register Ratio

Basic Parts: Register: Register Constant

• Definition - The factor by which the register reading is multiplied to obtain total registration or KWH used

• Also know as - Dial constant, Dial Multiplier or Reading Multiplier


Basic Parts: Register: Register Constant (continued)

• When considering register constant we have to consider instrument constants:– CTR Current Transformer Ratio

• Most metering current transformers (CT’s) are labeled :5, reflecting the amount of current in the primary that will produce 5 amps in the secondary. Examples: 400:5 or 80:1

– VTR Voltage Transformer Ratio• Most metering voltage transformers are

labeled as to the primary and secondary


• cont- voltages reflecting the turns ratio of the transformer. Examples would be 7200:60 or 60:1 or 480:120 or 4:1

• By definition, one revolution of the right hand dial on the register is equal to 10 kilowatt hours or 10,000 watt hours

Therefore,

Kr = Kh x Rr x Rs x CTR x VTR

10,000



Find the Kr• A single phase meter, form 1S, 120v, Class 100

has a Kh of 1.8, Rr of 55 5/9, Rs of 100. No instrument transformers are used.

Kr = Kh x Rr x Rs x CTR x VTR / 10,000

Kr = 1.8 x 55 5/9 x 100 x 1 x 1 / 10,000



Find the Rr• You want the Kr to be 1, Kh = 1.8, Rs = 50,

Kr = Kh x Rr x Rs x CTR x VTR / 10,000

1= 1.8 x Rr x 50 x 1 x 1 / 10,000

Rr = 10,000

1.8 x 50

Rr = 111.1111111111 or 111 1/9

Meter Calibration and Adjustments

• Disk Adjustment

• Register Mesh

• Full Load Adjustment

• Light Load Adjustment

• Lag Adjustment


Meter Calibration -Disk Adjustment and Register Mesh• Disk Adjustment

– Using upper and lower bearings center disk in air gap

• Register Mesh– If equipped adjust gear/shaft mesh for a

30% to 50% mesh between first gear of the register and worm gear of disk shaft

TOPPED GEARS


Meter Calibration -Full Load Adjustment and Light Load AdjustmentFULL LOAD• Purpose - Adjusts speed of the disk @ rated

voltage and Test Amps

LIGHT LOAD• Purpose - Adjusts speed of the disk @ rated

voltage and at 10 % of Test Amps

Meter Calibration -Lag or Power Factor Adjustment• Purpose - Adjusts the phase angle of the

potential coil flux to lag the applied voltage by 90 degrees


Meter Compensations

• Voltage

• Overload

• Temperature Class I

• Temperature Class II

• Frequency

Break Time

• 10 minutes


Solid State VS Electromechanical

• Benefits– Weight– Cost– Accuracy– Programmability and additional functions

• Drawbacks– Customer concerns– Half life– Adjustability

Types of Solid State Meters

• Current Sensing (CT)– GE - KV2C and I-210– Landis and Gyr - Alf – ABB - A1D

• Hall Effect– Itron - C1S– Icon Sensus - iSO1 & iSA1


Current Sensing (CT) Meters

• Perhaps the easiest to understand in terms of an electronic meter. Current sensing meters work on the same principle as a transformer rated service. Current passed through the current coil or primary side is reduced based on the multiplier relationship established by the manufacturer to the output or secondary side of the CT.

Current Sensing (CT) Meters (continued)

• This measured (secondary) current is then sent to the microprocessor to be calculated with the voltage and service type. The corresponding load, KW, KWh, and any other requested measurements are produced and sent to the readout for display.


Current Sensing (CT) Meter Internal Example

Hall Effect• A Hall-effect meter is an electronic device

that provides a digital readout of the magnetic field strength in gauss or tesla units. The meters use a very small conductor or semiconductor element at the tip of the probe. Electric current is passed through the conductor. In a magnetic field, a force is exerted on the moving electrons which tends to push them to one side of the conductor.


Hall Effect (continued)

• A buildup of charge at the sides of the conductors will balance this magnetic influence, producing a measurable voltage between the two sides of the conductor. The presence of this measurable transverse voltage is called the Hall-effect after Edwin H. Hall, who discovered it in 1879

Hall Effect


Hall Effect (continued)

• Vh = I B Rh / b

• Where:Vh is the voltage generated.I is the applied direct current.B is the component of the magnetic field that is at a right angle to the direct current in the Hall element.Rh is the Hall Coefficient of the Hall element.b is the thickness of the Hall element.

Hall Effect Meter Internal Example


Hall Effect Meter Internal Example

Solid State VS Electromechanical Types


Solid State Examples

Electromechanical Types






Questions & Answers

• Hands on

• Thank you for your time!

8/3/2019

1

CUSTOMER PREMISE

PURPOSE OF THIS CLASS

• Detail how best to professionally handle yourself on a customer’s premise

• How to go about your work in a safe, workman like fashion

• Examples of OH and UG service entrance

• How to do a disconnect/reconnect safely, and a review of the PPE necessary

8/3/2019

2

QUESTIONS BEFORE WE START

• Why are we here?

• Is it safe to do our work?

• Where is the meter located?

• Do I have the necessary information for the job? ( billing history or meter history)

• Have you informed the customer? What needs to be included in the conversation?

PROFESSIONALISM

• Reason for visit

• Usage

• Privacy

• Proper language

• Customer knowledge

• Expected outcome

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3

SAFETY

• Federal requirements and Utility requirements

• Different problems exist if it is a new service versus an existing service

• Environmental concerns

• PPE

• Examples

SERVICE DROP

• What is a service drop?

• Normally defined as the conductors that connect the power company to the customer’s system:

• Underground

• Overhead

• Who owns it?

• Typically the serving utility

• Company standards

• Wire size

• Installation particulars

8/3/2019

4

SERVICE TYPES: OH VS. UG

NEW SERVICE

• Does it meet company standards (ESR)?

• NEC

• Meter location

• Meter connection

• Correct meter socket

• Bypass required

• Type of sealing ring

• Voltage check

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5

SOCKET TYPES

SOCKET TYPES WITH BYPASS

8/3/2019

6

OLD SERVICE

• Safety

• Look at weatherhead/riser

• Meter cover style and condition- see example

• Seal

• Verify socket and voltage are correct

• Verify wires and lugs are safe

OLD SERVICE

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7

SERVICE PROBLEMS

• Type of service: single phase vs. three phase

• Voltage check +/- (depends on your utility)

• Correct meter application

• Meter location/height

• Meter seals

• Missing, cut, tampered

DISCONNECT

• Verify paperwork and make sure you’re at right meter

• Inform customer

• Refrain from confrontation, swearing, or giving too much information

• Businesses

• Proceed with disconnect and call in immediately

• Customer could be making payment as you’re doing disconnect

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8

RECONNECT

• Verify paperwork and meter

• Check seal to see if any tampering

• If tampering call meterman or take appropriate cautionary steps

• Remove meter

• Check voltage, backfeed, and shorts in meterbase

• Proceed to replace and seal meter appropriately

• Call in to update system

PPE

• What is PPE?

• Federal Requirements

• Utility Requirements

• Recommendations

• Examples

8/3/2019

9

QUESTIONS?????

Documents

Single Phase Meter Components, Constants, and Ratios · Single Phase Meter Components, Constants, and Ratios Presented by Scott Sutton Northwest Electric Meter School North Seattle