power_quality_4 Seminar

[born_for seminars]

Abstract
The subject power quality engineering truly en compasses most areas of electrical engineering from generation to utilization. Power quality problems due to mainly two reasons. One is the characteristic of the power supply voltage and the electrical system that effect the performance of the load and the other is the characteristics of the load that affect the electrical system or other loads.
The presentation starts with the necessity of quality in electrical power by pointing the causes and consequences that isolates the electrical power from its quality on demand like VOLTAGE SAGS and SWELLS, HARMONICS.Various solutions from the innovative technology those packs the power with its at most quality are presented. Not only various guidelines to maintain the power quality but also the analysis and monitoring of power quality are vividly highlighted.
INTRODUCTION
Power supply quality issues and resulting problems are consequences of the increasing use of solid state switching devices, nonlinear and power electronically switched loads, electronic type loads .the advent and wide spread of high power semiconductor switches at utilization, distribution and transmission leaves have non sinusoidal currents. The electronic type load causes voltage distortions, harmonics and distortion. Power quality problems can cause system equipment mal function, computer data loss and memory mal function of the sensitive equipment such as computer, programmable logic devices [plc] controls, and protection and relaying equipment.
Voltage sags are most wide spread power quality issue affecting distribution systems, especially industries. Where involved losses can reach very high values. Short and shallow voltage sag can produce dropout of a whole industry. In general, it is possible to consider voltage sags as the origin of 10 to 90% power quality problems. The main causes of voltage sags are faults and short circuits, lightning strokes, and inrush currents. In overhead distribution systems lightning is main cause of Voltage sag, with an approximate incidence of about 50% of the cases. An important% of voltage sags is repetitive such as lightning and re closer circuit breakers operations. The ability of SE to with stand Voltage sags without dropout is known as ride-through capability. Ride through capability guidelines are given by CBEMA (computer business equipment manufactures association). The curves are most important tool for the manufacturer user and system designer. Single- line to ground faults and lightning on the utility distribution or transmission system is often the cause of voltage sags. Power quality is a two-pronged issue, with electronic equipment playing both villain and victim. Most new electronic equipment, while more efficient than its mechanical predecessors, consumes electricity differently than traditional mechanical appliances. While older devices like incandescent bulbs use power as it is supplied by the utility, electronic devices draw currents in bursts, altering the electricity that flows through them, so that what comes out the other side and returns to the grid is distorted. This "dirty" power underutilizes utility equipment and increases line losses. Thus, some of the efficiency gained through improvements in appliances is lost in the transportation of the electricity that runs them. Additionally, utilities must invest in filters and capacitors to "clean" this dirty power. Poor-quality power also causes transformers, cables and other transmission equipment to burn out morequickly, thus increasing utility equipment costs.In general, the moresophisticated equipment is, the more sensitive it is to variations in power quality. Household appliances that were once simple mechanicaldevices--like furnaces, air conditioners and heat pumps--are goingelectronic. And the home electronics revolution has made video recorders personal computers, microwave ovens and digital clocks--all sensitive topower distortions--commonplace in American homes. As computers getsmaller and faster, they become increasingly sensitive to power qualityproblems. Efficiency improvements on the horizon for refrigerators includeelectronic motors, which will also make them prey to the same powerdisturbances that leave the VCR clock blinking at us dumbly when we walkin the front door.

Why power quality is so important?
Power quality is an increasingly important issue for all businesses. Problems with powering and grounding can cause data and processing errors that affect production and service quality.
 Lost production: Each time production is interrupted, your business loses the margin on the product that is not manufactured and sold.
 Damaged product: Interruptions can damage a partially complete product, cause the items to be rerun or scrapped.
 Maintenance: Reacting to a voltage disruption can involve restoring production, diagnosing and correcting the problem, clean up and repair, disposing of damaged products and, in some cases, environment costs.
 Hidden costs: If the impact of voltage sag is a control error, a product defect may be discovered after customer delivery. The costs of losing repeat sales, product recalls and negative public relations can be significant and hard to quantify.
A recent study by IBM showed that power quality problems cost U.S. businesses more than $15 billion a year. That’s an average of $79,000 for each company!
The good quality of power can be specified as: -
 The supply voltage should be with in guaranteed tolerance of declared value.in India the specifications related to power quality are _+10% variation in voltage and _+2%of frequency
 The wave should be a pure sine wave within allowable limits for distortion.
 Voltage should be balanced in all 3 phases.
 Supply should be reliable
 The earthing system should serve its purpose properly
Causes and consequences: -
The causes and consequences of power quality problems can be traced to a specific type of electrical disturbance. By analyzing the waveform of the disturbance, power quality engineers can determine what problems your facility has and what the optimal solution is.
For comparison purposes, a normal voltage waveform is 50 cycles per second - at most plus or minus ten percent of nominal voltage.
Power disturbances can be classified into five categories, each varying in effect, duration and intensity.