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Note for Electrical and Electronics Instrumentation - EEI By JNTU Heroes

  • Electrical and Electronics Instrumentation - EEI
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Text from page-2

DISCRIPTION: THE MAIN CLASIFICATIONS OF VOLTMETER AND AMMETER IN POWER SYSTEM ARE DEPENDING ON SUPPLY PROVIDED I.E HENECE THE CLASSIFICATION IS MC AND MI INSTRUMENTS, WHERE MC USED TO MEASURE DC QUANTITIES AND MI TO MEASURE AC QUANTITIES. THEREFORE IN THE PRECEEDING TOPICS WE SHALL DISCUSS ABOUT THE CONSTRUCTION AND OPERATION OF MC INSTRUMENTS, THEIR ADVANTAGES AND DISADVANTAGES , DIFFERENT TYPES OF ERRORS WHICH EFFECTS THE MEASUREMENT USING MC INSTRUMENTS, DIFFERENT METHODS TO EXTEND THE RANGE OF MC METERS AND SUGGESTING THE BEST METHOD FOR MEASUREMENT. LATER WE SHALL DISCUSS ABOUT THE CONSTRUCTION AND OPERATION OF MI INSTRUMENTS, THEIR ADVANTAGES AND DISADVANTAGES , DIFFERENT TYPES OF ERRORS WHICH EFFECTS THE MEASUREMENT USING MI INSTRUMENTS, DIFFERENT METHODS TO EXTEND THE RANGE OF MI METERS AND SUGGESTING THE BEST METHOD FOR MEASUREMENT. THE EXPRESSIONS FOR THE DEFLECTION TORQUE OF MC AND MI INSTRUMENTS ARE DERIVED, THEIR THE NATURE OF SCALE CAN BE DECIDED. IMPORTANT NOTE: ONE CANT USE THE VOLTMETER AS THEIR LIKE TO MEASUREMENT, IT IS NECESSARY TO IDENTIFY WHETHER THE GIVEN CIRCUIT IS LOW RESISTIVE OR HIGH RESISTIVE . THIS METHOD OF CHOOSING VOLTMETER DEPENDS ON ITS SENSITIVITY WHICH IS CALLED AS LOADING EFFECT. ELECTRO-STATIC VOLTMETERS: THE INSTRUMENT WHICH WORKS ON THE PRINCIPLE OF ELECTRO-STATIC IS VOLTMETER. LET US SEE THE CLSSIFICATION OF ELECTRO-STATIC VOLTMETERS, THEIR CONSTRUCTION AND OPERATION , THEIR ADVANTAGES AND DISADVANTAGES , DIFFERENT TYPES OF ERRORS WHICH EFFECTS THE MEASUREMENT USING ELECTRO-STATIC VOLTMETER INSTRUMENTS, DIFFERENT METHODS TO EXTEND THE RANGE OF THESE METERS AND SUGGESTING THE BEST METHOD FOR MEASUREMENT. CONCLUSION: BY THE END OF THIS UNIT ONE CAN BE ABLE IDENTIFY THE TYPE IF ELECTRICAL INSTRUEMNT, THE IMPORTANCE OF MC, MI AND ELECTROSTATIC INSTRUMENTS IN POWER SYSTEMS

Text from page-3

UNIT 2 INTRODUCTION: TILL NOW WE KNOW THAT TRANSFORMER IS A DEVICE USED FOR TRANSFORMATION OF ENERGY, BUT IN PRACTICE TRANSFORMER IS ALSO USED AS PROTECTIVE DEVICE AND ALSO AS MEASURING DEVICE. HERE IN THIS UNIT WE SHALL STUDY AN TRANSFORMER IN POWER SYSTEM AS A MEASURING DEVICE CALLED AS INSTRUMENT TRANSFORMER. DEFINATION OF INSTRUMENT TRANSFORMER, ITS SIGNIFICANCE IN POWER SYSTEM AND RATIOS ASSOCIATED WITH IT . THE APPLICATIONS OF INSTRUMENT TRANSFORMER ARE DISCUSSED. DISCRIPTION: LATER THE MAIN CLASSIFICATION OF INSTRUMENT TRANSFORMER IS DONE, THE CONSTRUCTION AND OPERATION OF POTENTIAL AND CURRENT TRANSFORMERS ARE DISCUSSED. THE POTENTIAL TRANSFORMER IS USED TO MEASURE VOLTAGE IN HIGH VOLTAGE CIRCUITS AND THE CURRENT TRANSFORMER IS USED TO MEASURE CURRENT IN HIGH CURRENT CIRCUITS. THE MEASUREMENT OF VOLTAGE AND CURRENT USING INTRUMENT TRANSFORMERS ARE EFFECTED BY RATIO AND PHASE ANGLE ERROR. THE EXPRESSIONS FOR FOR RATIO AND PHASE ANGLE ERRORS ARE DERIVED FROM WHICH CHARACTERISTICS OF INSTRUEMNT TRANSFORMER ARE STUDIED. THE KNOWLEDGE OF PHASOR DIAGRAM OF INSTRUMENT IS VERY IMPORTANT TO CHARACTERISE THEM . THE LIMTATION OF INSTRUMENT TRANSFORMERS IS IMPORATANT BEFORE TAKING THEM INTO SERVICE. COMPARE THE POTENTIAL AND CURRENT TRANSFORMER FOR BETTER UNDERSTAND IN GENERAL TO DETERMINE THE POWER FACTOR OF CIRCUIT THE METHDO WE KNOW IS VOLTMETER –AMMETER METHOD, BUT THIS METHOD OF MEASUREMENT MAY NOT LEAD TO PRECISION VALUE. THEREFORE AN NEW DEVICE INTRODUCED INTO THE CIRCUIT CALLED AS POWER FACTOR METER. POWER FACTOR METER WORKS ON THE PRINCIPLE OF MAGENTIC EFFECT AND MOTORING OPERATION. IN THE CONSTRUCTION OF POWER FACTOR METER IT GOT UNIQUE PROPERTY THAT CONTROL TORQUE IS NOT PROVIDED. DEPENIDING ON NATURE OF SUPPLY THEY ARE CLASSIFIED AS 1-PH AND 3-PH POWER FACTOR METER. IN INDIA NATURAL FREQUENCY IS 50 HZ AND MANY OF THE POWER SYSTEM CIRCUITS ARE MONITORED AT THIS FREQUENCY, HENEC IT IS NECESSARY TO CONTINUOUSLY CHECK THE

Text from page-4

FREQUENCY OF SUPPLY. FREQUENCY IN DEFINATION NUMBER OF CYCLES MABE Y WAVE FORM IN ONE SECOND, IT IS ALSO GIVEN AS RECIPROCAL OF TIME. THE DEVICE USED TO MEASURE FREQUENCY IS CALLED AS FREQUENCY METER. DEPENDING ON MEACHANICAL AND ELECTRICAL RESONANCE THE FREQUENCY METERS ARE CLASSIFIED. LATER THE CONSTRUCTION AND OPERATION OF FREQUENCY METERS ARE STUDIED. THE SYNCHROSCOPE IS A DEVICE WHICH IS USED TO DETERMINE THE CORRECT INSTANT TO CLOSE THE SWITCH SUCH THAT INCOMING GENERATOR AND BUS BAR ARE SYNCHRONISED. THIS PPROCESS OF CLOSING SWITCH IS CALLED AS SYNCHRONIZATION. THE CONDITIONS FOR SYNCHRONIZATION OF ALTERNATOR AND BUS BAR ARE--- VOLTAGES MUST BE SAME.  FREQUENCY MUST BE SAME.  PHASE SEQUENCE MUST BE SAME.  PHASE MUST BE SAME. IN THE PRECEEDING THE ADVANTAGES AND DISADVANTAGES OF POWER FACTORMETER, FREQUENCY METER AND SYNCHROSCOPE ARE STUDIED. CONCLUSION: IN THE POWER SYSTEMS THE INSTRUEMENT TRANSFOEMERS, FREQUENCY METER AND SYNCHROSCOPE GOT THEIR OWN IMPORATNCE, HENCE IT IS NECESSARY FOR EVERY ELECTRICAL ENGINEER TO HAVE THE KNOWLEDGE OF THESE INSTRUMENTS.

Text from page-5

UNIT 3 INTRODUCTION: THE WORD POWER GOT VERY IMPORTANCE IN ELECTRICAL WORLD. GENERALLY POWER IN ELECTRICAL CIRCUITS IS GIVEN AS PRODUCT OF VOLTAGE AND CURRENT. BUT DEPENDING ON THE NATURE OF SUPPLY THE DC POWER IS GIVEN AS V*I AND AC POWER IS V*I*COSINE OF PHASE BETWEEN V AND I. IN THE POWER SYSTEM WE COME ACROSS THREE TYPES OF POWER ACTIVE POWER, REACTIVE POWER AND APPARENT POWER. HERE IN THIS UNIT WE SHALL DISCUSS ABOUT MEASUREMENT OF ACTIVE AND REACTIVE POWER . DISCRIPTION: MEASUREMENT OF POWER IN DC AND AC CIRCUITS. TO MEASURE THE POWER IN DC CIRCUITS THE BEST METHOD IS VOLT-AMP METHODS. THERE ARE TWO CONNECTIONS OF VOLT-AMP METHOD FOR MEASUREMENT OF POWER. BUT THESE TWO CONNECTIONS MAY NOT LEAD TO THE EXACT POWER MEASUREMENT CONSUMED BY LOAD. BUT THERE IS NO OTHER ALTERNATIVE METHOD TO MEASURE POWER IN DC CIRCUITS, HENCE IT IS NECESSARY TO CALCULATE ERROR IN THE MEASUREMENT USING THIS METHOD. TO MEASURE THE POWER IN AC CIRCUITS A DEVICE CALLED WATTMETER IS CAME INTO EXISTENCE. THIS WATTMETER IS MAINLY MEANT TO MEASURE USEFULL POWER ONLY.IN THE CONSTRUCTION OF WATTMETER IT CONSISTS OF PRESSURE COIL AND CURRENT COIL, WHERE THE PRESSURE IS EXITED BY VOLTAGE TO BE MEASURED AND CURRENT COIL BY CURRENT TO BE MEASURED. THE UNIQUENESS OF CURRENT COIL IS IT IS HIGHLY RESISTIVE AND PRESSURE COIL AND CURRENT COIL IS COMBINELY CALLED AS ELEMENT. AN DOUBLE ELEMENT WATTMETER IS USED TO MEASURE POWER IN POLY PHASE CIRCUIT. MEASUREMENT OF POWER IN POLY PHASE CIRCUIT IS GIVEN BY STATEMENT NAMED BLONDEL’S THEOREM. THE BLONDEL’S THEOREM IS PROVED FOR--1) 2) 3) 4) 5) 3 PHASE 3 WIRE SYSTEM. 3 PHASE 4 WIRE SYSTEM.. SINGLE WATTMETER METHOD . TWO WATTMETER METHOD. THREE WATTMETER METHOD.

Lecture Notes