Course #135 Metering Terminology

Transcription

1 Course #135 Metering Terminology Kimberly Clarke Meter Foreman JEA 135 Metering Terminology I like to call it Meter Speak There are fundamental terms that need to be defined for effective communications. The terms will be given and defined. Please feel free to ask questions at any time. 135 Metering Terminology Self Contained Transformer Rated Voltamperes (VA) Kilos and Megas Power Factor Watts Demand Kilowatthour Instrument Transformers Transformation Ratio Meter Multipliers Types of Circuits 1

2 Kinds of Meters Self Contained Stands alone Transformer Rated Requires additional equipment to meter VA or Voltamperes (Apparent Power) Voltamperes are the product of volts and the total current which flows because of the voltage. VA = Volts X Amps 240 volts X 10 amps = 2,400 VA Kilos and Megas Kilos = 1,000 Megas = 1,000,000 2

3 KVA and MVA Kilovoltamp and Megavoltamp KVA 1,000 VA = 1 KVA 2,400 VA = 2.4 KVA MVA 1,000,000 VA = 1,000 KVA = 1MVA 2,400 VA = 2.4 KVA =.0024 MVA VA, KVA and MVA are instantaneous values that vary with changes in volts or amps. Power Factor The ratio of the active power (KW) to the apparent power (KVA). Phase shift is caused by capacitive or inductive loads Power factor is either 1.0 or less than 1. Example 0.97, 0.86 Watts (Active Power) The practical unit of active power which is defined as the rate at which energy is delivered to a circuit. Watts = Volts X Amps X Power Factor or Watts = 240 X 10 X 1 = 2,400 If the power factor was 0.5 the calculated VA and Watts would be different. Watts = 240 X 10 X 0.5 = 1,200 VA = 240 X 10 = 2,400 NOTE: The VA is the same regardless of power factor. 3

4 KW and MW Kilowatt and Megawatt KW 1,000 Watts = 1 KW 2,400 Watts = 2.4 KW Mw 1,000,000 Watts = 1,000 KW = 1 MW 2,400 Watts = 2.4 KW =.0024 MW Watts, KW and MW are instantaneous values that vary with changes in volts, amps or power factor. DEMAND The average value of power or related quantity over a specified interval of time. Demand is expressed in KW (kilowatts), KVA (kilovoltamperes), KVAR (kilovars) or other suitable units Demand can be either instantaneous or average over a certain time period called Demand Interval. The demand interval is utility specific and is defined in minutes up to and including 60 minutes. DEMAND Block Demand is a set block of minutes Example: 15 minute block. Rolling Demand is a set of minutes updating every X minutes Example:15 minute interval updating every 5 minutes. Peak (MAX) Demand the highest average demand in a period of time. Although this is normally a month it can be any desired period of time. 4

5 Kilowatthour The practical unit of electric energy which is expended in one hour when the average power during the hour is one watt. This is the unit that all electric meters measure. Example: If a demand is 1 KW and is constant After one hour KWH = 1 After two hours KWH = 2 Instrument Transformers Instrument Transformer A transformer that reproduces in its secondary circuit in a definite and known proportion, the voltage or current of its primary circuit with the phase relation substantially preserved. These are CT s (current transformers) VT s (voltage transformers) The CT s and VT s 1. Lower the current and voltage to levels that are safe for meter personnel 2. Physically possible to build a meter VT CT 5

6 CTVT Ratio or Transformation Ratio Example transformers from previous page VT ratio 480:120 = VT 4:1 CT ratio of 300:5 = CT 60:1 CTVT = 4 X 60 = 240 In this example the meter readings must be multiplied by 240. CTVT Ratio or Transformation Ratio NOT ALL METERS REQUIRE CT S OR VT S. Meters that need CT s and VT s are called instrument rated. These meters use the CT/VT ratio of the transformers. Meters that do not need CT s and VT s are called self contained. These meters do not have CT s or VT s and use X1. Meter Multiplier Meter multiplier is the number the display of the meter must be multiplied to show total registration The meter multiplier can be but isn t always the CTVT ratio If it is different the meter is Scaled to a different value. Example: Scaled to X10, X100, X 1,000, 10,000 Meter Multipliers can be: X 1 - The normal residential and some commercial meters X CTVT ratio X240 X Scaled value X 1,000 6

7 Questions about terminology? Next is Meter Styles, Meter Forms, Meter Features, and a few circuit examples. Meter Styles A-base Wired Bottom connected meters Socket Type Plugged K-base Bolted Meter Forms Meter designs are referenced by a form number. Although many look the same from the outside, meters are designed differently for different circuits. 7

8 Meter Features Data Plate Form Test Amps (TA) Voltage Register Types Dial Cyclometer Digital Form 1A 8

9 Form 2S Network Form 5S 9

10 Form 6S Form 9S Form 8S 10

11 Questions?? 11