Single Phase Meter Components

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The basic parts of the meter The function of these parts» Adjustments for

1 NWEMS Single Phase Meter Components August 21, 2017 Track A Scott Sutton, Snohomish County PUD PURPOSE of this class:» What is an electro mechanical Watt hour meter» The basic parts of the meter The function of these parts» Adjustments for calibrations» Compensations» Electronic vs Electromechanical meters» Meter types Examples Q & A 1

2 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 2

3 Today s Electromechanical kwh meter s are basically the same design as the ones manufactured 105 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 3

4 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 4

5 Basic Parts: Nameplate (continued)» T.A. Test Amps, (100% Full Load 10% Light Load)» Wire (2w, 3w, 4w, 5w)» Kh Watt hour Constant» Multiplier (CT s, VT s, internal meter multi)» Number of stators or potential coils» Company ID number and MFR. Type Meter Nameplates Service Application Manufacture Frequency HZ Voltage # of Stators Class Company Name and Number Manufacturer s Serial # 10 Register Ratio Manufacturer Type Form Wires Test Amps Disk Constant or Kh 5

6 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 6

7 Basic Parts:Base (continued)» Lightening 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 7

8 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 +/ inch for precise fit & positioning. 8

9 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 9

10 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 Compensations Overload 10

11 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 11

12 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 12

13 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 13

14 Break Time» 10 minutes 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 14

15 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 15

16 How do we determine Kh?» The design speed Kh of the meter is determined by engineers based on different factors Minimum Light load speed Damping magnet cost performance characteristics Bearing wear Kh continued» Nominal values are 7.2, 1.8, 0.6, 21.6» For example, a single phase 2S house meter is designed to turn 1000 revolutions per hour with 240 volts and 30 amps applied. 240 x 30 = 7200 watts 7200/1000 revs p/hour = 7.2 watthours p/rev 32 16

17 For Modern 1 ø meters the Design Speed is 16 2/3 RPM» With this we can figure the Kh & Register ratio of a meter designed for 240V & 30A» Rated Voltage X Test Amps = Test Watts 240V X 30A = 7200 watts» 7200 watts for 1 hour = 7200w X 1 Hr = 7200 watt hours» At design speed, test amps & rated voltage the disk rotational speed is 16 2/3 RPM» At 16 2/3 RPM = 50/3 RPM X 60 min = 1000 Revolutions» Therefore the number of watt hours per disk revolution is: 7200 watt hours/ 1000 Rev = 7.2 watt hours/rev 17

18 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 18

19 Register Ratio 37 Basic Parts: Register: Register Ratio (continued)» We know that one disk revolution = 7.2 watthours Rs Shaft reduction = 100» With 100 revolutions of the disk we have 100 rev X 7.2 watt hours/rev = 720 watthours» We want 10,000 watt hours on our register: 10,000 watt hours/720watt hours = 125/9 =13 8/9 = RR 19

20 Basic Parts: Register: Gear Ratio» Definition The number of revolutions of the disk needed to cause the first pointer to make one complete revolution» Symbol RG» Gear Ratio Formula RR X RS = RG 13 8/9 X 100Revs = /9 Revs 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 20

41 Basic Parts: Register: Register Constant (continued)» When considering register constant we have to consider instrument constants: CTR Current Transformer Ratio Most metering current transformers

21 41 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 42 21

22 Basic Parts: Register: Register Constant (continued) 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, Basic Parts: Register: Register Constant (continued) 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,

23 Basic Parts: Register: Register Constant (continued) 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, x 50 Rr = or 111 1/9 45 Basic Parts: Register: Register Constant (continued) Last one Find the Kr Kh = 1.8, Rr = 166 2/3, Rs = 50, CTR = 50:5, VTR = 7200:120 Kr = Kh x Rr x Rs x CTR x VTR / 10,000 Kr = 1.8 x 166 2/3 x 50 x 10 x 60 / 10,000 Kr =????? 46 23

24 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 24

screw moves a shunt across the permanent magnet which lets more or less

25 TOPPED GEARS 49 Meter Calibration Full Load Adjustment» Purpose Adjusts speed of the rated voltage and Test Amps» Description An adjusting screw moves a shunt across the permanent magnet which lets more or less rotation flux to cut across the disk and the disk slows down or speeds up 25

26 Meter Calibration Light Load Adjustment» Purpose Adjusts speed of the rated voltage and at 10 % of Test Amps» Description A rectangular plate (brass or copper) is mounted so that its adjusting motion is at a right angle to the disk radius. The main air gap potential flux passes through the plate and adjusts for shading and to overcome low load friction. 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» Description The Lag adjustment is a metal plate attached to the potential coil core. The resistance of the plate adjusts the power factor. This adjustment is set at the factory and normally does not need any further adjustment 26

27 Break Time» 10 minutes Meter Compensations» Voltage» Overload» Temperature Class I» Temperature Class II» Frequency 27

28 Meter Compensations Voltage» Modern electromechanical watt hour meters will operate accurately between 50% & 120% of rated voltage» A section of the potential coil core cross sectional area is reduced and shunted. At rated voltage the iron is operating at saturation, as the applied voltage increases the increased flux is shunted across the air gap and does not affect the meters accuracy. Meter Compensations Overload» Modern watt hour meters will operate accurately between.33% & 667% of Test Amperes or (once starting watts are overcome; about 24 watts)» A current shunt is across the current poles, when there is a overload the shunt saturates and allows more flux on the disk 28

29 Meter Compensations Temperature Class I» Class I compensations effect all loads and power factor equally, it is considered equivalent to changes in the strength of the retarding magnet affected by ambient temperatures.» A shunt across the permanent magnet carries a large amount of flux at low temperature and very little flux at high temperatures. This characteristic is opposite of the permanent magnet which gets stronger as the temperature decreases and weaker as the temperature increases thus compensating for changes in temperature Meter Compensations Temperature Class II» This compensation corrects changes in the resistance of the potential coil and lag plate as the temperature varies. Class II compensation consists of a reactor attached to the lag plate. As the temperature varies the resistance of the reactor changes opposite to the resistance of the lag plate 29

30 Meter Compensations Frequency» Because of frequency stability of modern electrical systems, variations in meter accuracy due to frequency variations are negligible Solid State VS Electromechanical» Benefits Weight Cost Accuracy Programmability and additional functions» Drawbacks Customer concerns Half life Adjustability 60 30

31 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 61 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.

32 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. 63 Current Sensing (CT) Meter Internal Example 64 32

33 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. 65 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

34 Hall Effect 67 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

35 Hall Effect (continued) 69 Hall Effect Meter Internal Example 70 35

36 Hall Effect Meter Internal Example 71 Solid State VS Electromechanical Types 72 36

37 Solid State Examples 73 Electromechanical Types 74 37

38 Solid State Examples 75 Solid State Examples 76 38

39 Solid State Examples 77 Questions & Answers» Hands on» Thank You for your time! 39

Introduction to 3-Phase Meters. Northwest Electric Meter School August 21,2017 Adam Schwab ~ Meter/Relay Tech. Grant County PUD

Introduction to 3-Phase Meters Northwest Electric Meter School August 21,2017 Adam Schwab ~ Meter/Relay Tech. Grant County PUD 1 Meter Pulling device Objectives Provide a brief overview of polyphase meters