DIGITAL MEASUREMENT TECHNIQUES IN POWER SYSTEMS

CONTENTS

1. Digital power system2. Digital measurements of power systems3. Power line frequency measurement4. Relaying5. Accelerated Life Testing6. Benefits7. Conclusion

System of high tension cables by which power is distributed throughout a region

POWER SYSTEM

DIGITAL POWER SYSTEM

The power system configuration, control and monitoring and fault detection are implemented with digital techniques.

CMOS digital technology provides digital processing with high density , negligible power dissipation and low cost

DIGITAL MEASUREMENTS OF POWER SYSTEMS

Frequency measurementEffective voltageApparent , active and reactive powerPhase measurementPower factor

POWER LINE FREQUENCY MEASUREMENT

Frequency meter is used to measure power line signal frequency and to calculate other important parameters of power line signal

FREQUENCY MEASUREMENT PROCEDURE

Fig : Energy power meter system on chip

SIGMA DELTA CURRENT

A/D CONVERTER

Analog inputs SINC AND FIR

FILTERS

HILBERT FILTER

SINC AND FIR

FILTERS

I

V DIGITAL SIGNAL

PROCESSOR

Vp

O/PSIGMA DELTA

VOLTAGE A/D

CONVERTER

FREQUENCY MEASUREMENT PROCEDURE

Fig : parts of DSP

SERIALCOMMUNICATiON BLOCK

64 BIT*24 BIT RAM

DSP PORT FOR PULSE COUNTING

DSP PORT FOR Ieff,Veff P ,Q ,S,POWER FACTOR

DSP PORT FOR FILTERING, MULTIPLY

AND ACCUMULATE

CONTROLLER

24 BIT DATA BUS

Fig: Signals relevant for frequency measurement

FREQUENCY MEASUREMENT PROCEDURE

Fig : Counting circuitry

FREQUENCY MEASUREMENT PROCEDURE

LS393

LS393

COMBINATIONAL LOGIC

TRI STATE BUFFER

SIGN

TIME BASE

CP

CP

q

q

voltage periods

frequency

reset

reset

Pulse input

Time base

OE

Beside frequency, DSP calculates other values suchas effective current and voltage, active, reactive and apparentpower and power factor.

Fig:Block of Ieff, Veff, P,Q,S, cos(ϕ) and Frequency calculation

RELAYING

•Power system relaying functions could be performed with a digital computer.

•Digital relays offer best economic and technical solution to the protection problems

FROM SUBSTATION SWITCH YARDCURRENTS AND VOLTAGES CONTACT INPUTS(D/I) CONTACT OUTPUTS(D/O) (COMMUNICATIONS)

SURGE FILTER

SIGNAL CONDITIONING

SAMPLING CLOCK

A/D

SURGE FILTER

SIGNAL CONDITIONING

PROCESSORSSERIAL PORT

PARALLEL PORT

RAM ROM PROM EPROM MASS

MEMORY

SIGNAL CONDITIONING

DIGITAL O/P

Power System Verification During Accelerated Life Testing

•Stresses are applied in a controlled and incremental manner to determine the root cause of hardware

•Time stamped voltages , currents and temperature conditions that existed just prior to the fault are recorded in digital system

ECIRCUIT BOARDFPGA

POWER C

POWER B

POWER A

CIRCUIT BOARD

ENCLOSED CHASSIS

SEALED ENVIRONMENTAL TESTING CHAMBER

Laptop Data Loggerand Test Controller

Digital Control Evolution of power systems resulted in

•Improved Digital Bandwidth•Improved Signal Resolution•Reduced Power Consumption•Reduced Cost•Effective protection techniques

BENEFITS

CONCLUSION

The efforts spent by the digital technology on the status monitoring are justified by•The reduction of the fault occurrence •Elimination of consequent losses due to disruption of electric power, •Preventing damage to equipment,•Reduction of emergency equipment replacement costs.

REFERENCES

[1] Rockefeller, G. D. (1969) Fault protection with a digital computer, IEEE Transactions on Power Apparatus and Systems , vol. 88

[2] J. Giddings, M. Simmons, and D. Hilder, “Practical experience on partialdischarge measurement and location on power cables,” in Proc. IEE Int.Conf. Partial Discharge, 1993, pp. 103–104.

[3] M. Tsutsui, H. Tsuchihashi, K. Satoh, M. Mukaida, H. Watanabe,S. Mori, Y. Kojima, and S. Yokoyama, “Manipulator system forconstructing overhead distribution lines,” IEEE Trans. Power Delivery,vol. 4, pp. 1904–1909, July 1989.

THANK YOU