Simulation and Measurement of Power Waveform Distortions using LabVIEW

The increased requirements on supervision, control, and performance in modern power systems make power quality monitoring a common practice for utilities. Power quality is the set of parameters defining the properties of power supply delivered to the users in normal operating conditions in terms of continuity of supply and characteristics of voltage (magnitude, frequency, symmetry, waveform etc.). Current electronic devices, such as microprocessors, micro-controllers, sensitive computerized equipment or telecommunications equipment etc. use ground as the reference for all their internal operations and connect throughout the plant. This makes them susceptible to ground differences and to power quality problems. Power disturbances compromise product quality, increase downtime, and reduce customer satisfaction. Power signal waveforms are not clean 50 Hz sine waves. Waveform distortion is an important aspect of power quality. In a power system, harmonics, transient impulses and noise are mainly responsible for waveform distortion. Harmonic analysis is an important part of power quality monitoring system. Waveform harmonics related power quality problems are usually caused by equipments which draw nonlinear currents. Modern electrical equipment such as computerized equipment and telecommunication equipment often use switching mode power supplies to "step up" or "step down" the voltage. This introduces a non sinusoidal load which pulls current in short pulses during every cycle. Other nonlinear devices such as digital/electronic/power electronic components and arching devices like fluorescent lamps can cause abnormal waveforms and serious decreases in power quality. By knowing the exact amount of harmonics, transient impulses and noise distortion in the system, it is possible to take appropriate actions to reduce their harmful effects. In the present study, graphical programming of LABVIEW has been utilized to simulate and measure different harmonics, noise and impulsive transients in the sinusoidal voltage waveforms. Results have been displayed on instrument like front panels on a computer screen, called virtual instruments. With virtual instrumentation, engineers and scientists can reduce development time, design higher quality products, lower their design costs, and keep close watch on waveforms. This helps in efficient use of electric power, and system reliability is also improved at the same time.