P Quality Prob Wiyh Dg

Improving Power Quality by Distributed Generation Prof.Mrs. P.R.Khatri,Member,IEEE, Prof.Mrs. V.S.Jape, Member,IEEE, Prof.Mrs. N.M.Lokhande,Member,IEEE Prof.Mrs. B.S.Motling,Member,IEEE Abstract - This paper highlights the case studies of steel plant and Municipal Corporation taking into consideration the power quality improvements. The main reason we are interested in Power Quality is economic value. The increasing application of electronic equipment and Distributed Generation has heightened the interest in Power Quality in recent years and this has been accompanied by special development of special terminology to describe the phenomena. Meeting customer’s expectations and maintaining customer confidence are the strong motivators behind maintaining the Power Quality. Distributed Generation has started gaining importance in our country and can become the answer for increasing the power failure. Power failure leads power interruption leading to insecure and unreliable Power System.

A. Why are we concerned about power quality? The ultimate reason why we are interested in power quality is economic value. There are economic impacts on utilities their customers and suppliers of load equipment. The power quality can have direct impact on many industrial consumers. Principal phenomenon causing electromagnetic disturbances leading to failure of power quality are: 1) Conducted low frequency phenomenon. 2) Radiated low frequency phenomenon. 3) Unidirectional transients. 4) Oscillatory transients.

Index Terms - Distributed Generation, Power Quality, Harmonic Distortion, Voltage fluctuations, Reliability, Flicker.

I. INTRODUCTION The sensitive customer loads has the need to define the quality of electricity provided in a common and succinct manner that can be evaluated by the electricity supplier as well as by consumers or equipments suppliers. One of the basic problems in solving power quality problems is that disturbances in the electrical power system are not restricted by the legal boundaries. Power suppliers, power consumers, and equipment suppliers all must work together in solving the problem. The utility services connected to the power system always have a complaint about the quality of the power they receive. Power quality, therefore is a consumer driven issue and the end user’s point of reference takes precedence. So we can define it as any power problem manifested in voltage, current or frequency deviations that results in failure or mal operation of consumer equipment. In addition to real power quality problems, there are also perceived power quality problems related to hardware, software or control system malfunctions. Power quality like quality in other goods and services, is difficult to quantify. But it is generally taken that when the power received cannot fulfill the needs of maintaining proper voltage and frequency than the “quality” is lacking. Affilitation footnotes: Mrs.P R Khatri is with the Department of Electrical Engineering, PVG College of Engg and Technology, Pune,Maharashtra INDIA. ( email : [email protected]) Mrs V S Jape is with the Department of Electrical Engineering, Modern College of Engg , Pune,Maharashtra INDIA( email :[email protected]) Mrs N M Lokhande is with the Department of Electrical Engineering, Modern College of Engg , Pune,Maharashtra INDIA. (email : [email protected])

5) Electrostatic discharge phenomenon. 6) Nuclear electromagnetic pulse. B. The Main Power Quality Issues affected by Distributed Generation 1. Sustained Interruption: This is the traditional reliability area. Many generators are designed to provide backup power to the load in case of power interruption. However, Distributed Generation has the potential to increase the number of interruptions in some cases. 2. Voltage Regulation: This is often the most limiting factor for how much Distributed Generation (DG) can be accommodated on a distribution feeder without making changes. 3. Harmonics: There are harmonics concerns with both rotating machines and inverters, although concern with inverters is less with modern technologies. 4. Voltage Sag: The most common power quality problem is the voltage sag, but the ability of DG to help II. STEPS INVOLVED IN POWER QUALITY PROBLEMS Before actually dealing with power quality solutions it is necessary to understand the electrical environment in which end use equipment operates. This is necessary to reduce the long term economic impact of inevitable power quality variations and to identify system improvements that can mitigate power quality problems. Electric power research institute (EPRI) has defined sets of power quality to solve problems related to this. The power quality indices are used to evaluate compatibility of the voltage as delivered by electric utility and the sensitivity of the end user’s equipment.

Keeping in pace with this electric utilities throughout the world are going for the concept of benchmarking service quality. Utilities now have realized that the levels of the service provided through out their distribution systems should be understood and analysed, and if the levels provided are appropriate or not has to be determined. Power quality problem takes into account a wide range of different phenomenon. The steps involved are: 1. Identify the problem category whether it is related to voltage and frequency unbalance, harmonic distortion or transients. 2. Characterize the problem and search for the causes. 3. Identify the range of solutions. 4. Evaluate technical alternatives by modeling, simulation or by procedure analysis

III. INTERFACING TO THE UTILITY SYSTEM While the energy conversion technology may play some role in the power quality most power quality issues relates to the type of electrical system interface. However some notable exceptions are : 1. The power variation from renewable sources such as wind and solar can cause voltage fluctuations. 2. Some fuel cells and micro turbines do not follow step changes in load and must be supplemented with battery or flywheel storage to achieve improved reliability. 3. Misfiring of the engine sets can lead to persistent and irritating type of flicker which is more prominent when magnified by the response of power system.

5. Evaluate the economics of possible solutions.

The main type of electrical system interfaces however are

To overcome the problems created by the increasing power demands by the end consumers and to improve the quality of the power the Distributed Generation is the only answer. The norms for the electric power industry has been to generate power in large or bulk in a centralized generating station and to distribute the power to end users through transformers, transmission lines and distribution lines. This system can create problems with power delivery when the incoming load increases. DG can help in solving the problems of power system reliability by acting as either a back up unit or the main unit. C. Advantages of Distributed Generation

1) Synchronous machine.

We can analyze the advantages from three different perspectives. 1. End-user perspective: End users who place a high value on electric power can generally benefit greatly by having back up generation to provide improved reliability. There are also substantial benefits in high efficiency applications, such as combined heat and power, where the total energy bill is reduced. End users may also be able to receive compensation for making their generation capacity available to the power systems in area where there are potential power shortages. 2. Distribution utility perspective: The distribution utility is interested in selling power to end users through its existing network of lines and substation. It can be used for transmission and distribution capacity relief. Thus it can also serve as a hedge against uncertain load growth and high price hikes on the power market, if permitted by regulatory agencies. 3. Commercial power producer perspective: Those looking at DG from this perspective are mainly interested in selling power in the power market. Commercial aggregators will bid the capacities of the units generated by them. The DG then can be directly interconnected into the grid or simply serve the load off- grid. However the perspectives on interconnected DG of typical utility distribution are very conservative in their approach to planning and operation.

2) Asynchronous or Induction machine. 3) Electronic power inverters. Though the synchronous machines are most commonly used technology and are well understood. The machine can follow any load within its designed capability. It is possible for such machine which is large enough relative to the capacity of the system at the PCC to regulate the utility system voltage which can be a power quality advantage in certain weak systems. Generators should be sized or designed considerably larger than the load to achieve satisfactory power quality in isolated operation. Though it is very simple to interface induction machine to the utility system as no special synchronizing equipment is necessary. The chief issue however is that a simple induction generator requires reactive power to excite the machine from the power where it is connected. Another problem that is prominent in such machines is that the capacitor bank yields resonance that coincides with the harmonics produced. Most of the DG technologies nowadays have to use electronic power inverter to interface with the electrical power system. However to achieve better control and to avoid harmonics problems the inverter technology has changed to switched , pulse – width modulated technologies. IV. CASE STUDY OF DISTRIBUTED GENERATION Distribution generation has started gaining importance in our country and can become the answer for increasing power failure. Power failure leads power interruption leading to insecure and unreliable power system. D. Case I In this paper a case study of a small township of Maharashtra (India) called Khopoli is considered. The total population

of this township is a meager 65000 but it has around 150 small and large scale industries in and around. The municipal council here had to face the problem of managing the waste generated. So along with BARC Mumbai, they have started a biomass conversion plant that generates electric power enough to illuminate the street lights. The daily generation of waste in Khopoli is about 300 to 400 kg minimum.The waste collected is in the form of garbage, silts recovered from drains and streets.Various sources of waste are household waste, hotel and restaurant waste, market wastes, silt removal from drain and waste rotten vegetables.The waste is collected by using curb system of collection and is finally disposed off to a large open field situated 8 km away from the main township. The plant is then filled with water in which animal waste, dirty drain water and rotten compost are added. The material is then charged into the digester after 10 days of decomposition. The waste is stirred and digested keeping the temperature at desired level. The regular feeding and stirring schedule is then followed regularly. The plant is located in open space having sufficient sunlight as the temperature is to be maintained between 15c to 30c to have optimum gas generation .It is been experimentally checked that methanogenic bacteria grows the best at temperature of 33c –40c.and the rate of gas generation approximately doubles for every 10c rise ion temperature. The gas thus released is then given to a gas turbine which is coupled to a generator that converts the bio energy to electrical energy and is used by the municipality load. Experiments are also going on to use this gas as alternate fuel by municipal transports. Some precautional measures are also taken by them such as : 1) Temperature of the digester is maintained constant. 2) A minimum gradient of 1% is maintained for conveying the gas. 3) The plant cover is not opened all of a sudden. 4) Khopoli has a long monsoon season so care is taken to see that monsoon water is not mixed up with the slurry. 5) Plastic canopy creating ‘green house’ effect is used to maintain the temperature. E. Case II A steel factory called Bhushan Steel and Strips Pvt. Ltd. Which is just 8 kms away from the main township of Khopoli has started power generation by heat recovery method. The thermal energy which is wasted in its furnace is recovered and used for producing steam and generate power. The basic point in power generation is by using the heat released by the liquid fuel i.e. the furnace oil. They have used two diesel generator set to generate power. Each set can produce 12 MW and the reserve capacity is 12.6 MW. The efficiency of the two sets are 97% .The system have only one drawback that is the power factor is very low only about 0.7.Both the sets are electrically synchronized and are operated in parallel. The load sharing is done both in manual and auto mode. Approximately200 gm of fuel is consumed per kWh but it varies as per the fuel quality and the energy to be generated.

The exhaust gas which is generated is also used for making steam which in turn is used for different media such as air, fascinating chemicals etc. The energy generated is sufficient to fulfill their energy demands and make them self- sufficient. They are also planning to sell the extra power to nearby industries. This type of power generation is most commonly applied technology nowadays and is readily available. Utilities currently favor this type of mobile generator sets mounted on trailers so that they can be moved to sites where they6 are needed. Diesel generator sets are quite popular with end users for back up power. But one of the serious disadvantages of this technology is high emission of NOx and SOx .This severely limits the number of hours of operation and the units generated. Thus they are popular only in combined heat and power cogeneration. V. CONCLUSION The two case studies that we have seen above are just two examples of distributed generation. Due to regulatory act that prevailed before it was not possible for anyone to produce power to meet their own demands. But with power deregulation it is now possible for us to fulfill our own demands. We in India are still at a early stage of accepting Distributed generation commercially. But we have already initialized it by starting it as a part of cogeneration. Most of the sugar factories of western Maharashtra (India) , the steel factories and even the municipal corporations are encouraged to initiate the ventures. Though we are progressing at a very slow pace but we are definitely moving forward .We just require some reforms in the regulatory acts which are prevailing at present. The power growth has been tremendous in the last decade. So it has become increasingly difficult to fulfill the growing demands of power. Consequently the first criteria of power engineering, that is to supply uninterrupted power supply is not been fulfilled. This also affects the voltage profile of the power system leading to poor power quality. So distributed generation either from non conventional sources or in the form of cogeneration should be used to improve the power reliability. The value of DG to the power delivery system is very much dependent on time and location. It must be available when needed and must be where it is needed. The obvious choice for a location is a substation where there are sufficient space and communication facilities. Also it is necessary some or the other non conventional sources should be used. Such generation will certainly relieve capacity constraints on transmission and power supply along with improvement in power quality. The generation might be leased for peak load period and the load profile can be improved also. As the steel plant and municipality citied above is generating its own power so there is power saving and this power which is saved can be wheeled towards the other consumers. This venture will not only save power but also will improve the power quality and the power reliability

VI. REFERENCES [1]

An assessment of distribution system power quality. statistical summary report,EPRI TR – 106294 –V2. [2] IEEE recommended practice on monitoring electric power, IEEE standards 1159- 1995. [3] Dugan, McGranahan, Santoso and Beaty, Electrical power system quality. [4] McGranahan, Kennedy, Power quality standards and specifications workbook. [6] Wills, Scott and Dekker, Distributed power generation planning and evaluation. [7] Samples collected and analysed during case study.

VII . BIOGRAPHIES 1.

Prof Mrs P R Khatri (M’2003) born in Nagpur, Maharashtra (India),June 17, 1969.Graduated from Nagpur University and completed Post Graduation from Pune University.Currently working with PVG’s College of Engg and Technology,Pune.The areas of interest include power systems,microprocessor,control systems.

2.

Prof Mrs V S Jape (M’2003) born in Nagpur, Maharashtra (India),Dec 18,1973.Graduated from Nagpur University and completed Post Graduation from Pune University.Currently working with Modern College of Engg,Pune.The areas of interest include power systems.

3.

Prof .Mrs N M Lokhande (M’ 2004) born in Kolhapur, Maharashtra (India),on June 17,1975. Graduated from Karnataka University and completed Post Graduation from Pune University. Currently working with Modern College of Engg, Pune.The areas of interest include power electronics, power systems,signal processing