ASME 19.6:2018 pdf download

ASME 19.6:2018 pdf download.Electrical Power Measurements
2-2 DEFINITIONS
accuracy: closeness of agreement between a measured value and the true value. accuracy class: guaranteed worst-case accuracy for all devices ofa particular type, model, or design over their intended operatingrange. Usuallyrefers to meters and instrumenttransformers. Accuracyofindividual units maybe much better than the class accuracy, but testing is required to discover the actual value. activepower[expressedin watts(W)]:amountofpowerdelivered to theresistive componentofaload. Activepoweris the only power that can perform useful work. In a DC circuit, active power is volts multiplied by amps. In an AC circuit with sinusoidal waveforms, active poweris RMS volts multiplied byRMS amps and the cosine ofthe phase difference between them. (See apparent power and reactive power.) apparentpower[expressedin volt-amperes(VA)]: total powerthatis delivered to a circuitthatcontains both resistive and reactive loads. Apparentpower is the square rootofthe sum ofthe squares ofthe active and reactive powers. (See active power and reactive power.) burden (instrumenttransformer):loadconnectedto thesecondarywindingofaninstrumenttransformerthatdetermines the active and reactive power atthe secondary terminals. The burden is expressed either as total ohms impedance with the effective resistance and reactance components or as the total volt-amperes and power factor atthe specified value of current or voltage and frequency. calibration:process ofcomparingthe response ofaninstrumentto astandardinstrumentoversome measurementrange and adjusting the instrument to match the standard, if appropriate. Data gathered during calibration may be used to establish correction or uncertainty factors. Alternately, for an instrument, the development ofdocumentation that will show the difference between the Code and the instrument and the uncertainty of doing the comparison. instrument transformer: transformer that is intended to reproduce in its secondary circuit, in a definite and known proportion, the currentor voltage ofits primary circuitwith the phase relations substantially preserved. An instrument transformer is used to convert potentially dangerous voltage or current levels to a safer level suitable for a measuring instrument. marked ratio: ratio of a transformer’s rated primary value to the rated secondary value as stated on the nameplate. phase-angle correction factor (PACF): ratio of the true power factor to the measured power factor. The phase-angle correction factor corrects for the phase displacementofthe secondarycurrentor voltage, or both, due to the instrument transformer phase angle(s). phaseangleofan instrumenttransformer(PA):phasedisplacement, inminutes ofarcorradians,betweentheprimaryand secondary values. The phase angle ofa current transformer is designated by the Greek letter β and is positive when the current leaving the identified secondary terminal leads the current entering the identified primary terminal. The phase angle ofa voltage transformer is designated by the Greek letter γ and is positive when the secondary voltage leads the corresponding primary voltage.
primarywinding (instrumenttransformer): transformerwindingintended forconnection to the circuitto be measured or controlled. randomerror:theportionoftotalerrorthatvariesrandomlyinrepeatedmeasurementsofthetruevaluethroughoutatest process. ratiocorrection factor(RCF):ratioofthetrueratiotothemarkedratioonaninstrumenttransformer.Theprimarycurrent or voltage is equal to the secondary current or voltage multiplied by the marked ratio times the ratio correction factor. reactive power[expressedin volt-amperesreactive (var)]: amountofpower delivered to the reactive componentofa load. Reactive components cause a phase shift between voltage and current in an AC circuit. In an AC circuit with sinusoidal waveforms, reactive power is RMS volts multiplied by RMS amps and the sine ofthe phase shift. (See active power and apparent power.) secondarywinding (instrumenttransformer): winding ofa transformer thatis intended for connection to the measuring, protection, or control device. traceable: records are available demonstrating that an instrument’s calibration has been performed against an ultimate reference maintained by the National Institute for Standards and Technology (NIST) or against a standard that is trace- able to an NIST reference. transformercorrection factor(TCF): ratio ofthe true watts orwatt-hours to the measured secondarywatts orwatt-hours divided by the marked ratio. NOTE: The transformer correction factor for a current or voltage transformer is the ratio correction factor multiplied by the phase- anglecorrectionfactorforaspecifiedprimarycircuitpowerfactor. Thetrueprimarywattsorwatt-hoursareequaltothewattsorwatt- hours measured multiplied by the transformer correction factor and the marked ratio. The true primary watts or watt-hours, when measured using both currentand voltage transformers, are equal to the currenttransformer ratio correction factor m