Author: Arupananda Pradhan, Lecturer, Department of Electrical Engineering

College: Ajay Binay Institute of Technology, Cuttack

ABSTRACT – Distributed Generation (DG) is expected to become more important in the future generation system. In recent years, distributed generation, as Clean natural energy, generation and co-generation system of High thermal efficiency has increased due to problems of Global warming and exhaustion of fossil fuels. Many of the distributed generations are set up in the vicinity of the Customer, with the advantage that this decreases transmission losses. However, Output power generated from natural energy, such as wind power, Photo Voltaic, etc. which is distributed generation, is influenced by meteorological conditions. Therefore, when the distributed generation increases by conventional control techniques, it is expected that the voltage change of each node becomes a problem. This paper discusses the relevant issues and aims at Reliability operation of customer operated distributed generation in competitive Electricity markets.

KEY WORDS –Distributed Generation, Dispersed Generation, Distribution System.

In recent times, due to the increasing interest on renewable sources, such as ; Hydro, Wind, Solar, Geothermal, Biomass and Ocean energy, all over the world, the number of studies on integration of Distributed Resources to grid have rapidly increased. The DG is typically defined as small generators, typically less than 10 MW, that are connected to the substation, distribution feeder or Customer load level. Although there are many DG technologies that utilize renewable energy, this paper focuses on technologies that utilize a continuous fuel sources. (e.g. reciprocating engines, micro turbines, fuel cells). The Generator using fossil fuels produce Electrical Power of desired quantities at any moment. These technologies are much less expensive and dominate the DG Market for many years. The Techniques used in reliability evaluation of Power system generally be divided into the categories of analytical and Monte – Carlo simulation (MCS) method. Both methods are also used to calculate the reliability indices of a distribution system containing DGS. DG affects the flow of Power and Voltage conditions at Customers and Utility equipment. These impacts may manifest themselves either positively or negatively depending on the distribution system operating characteristics and the DG Characteristics. Positive impacts are generally called “System support benefits”, and include Voltage Support and improved Power quality; Loss reduction; transmission and distribution capacity release; improved Utility system reliability. On account of achieving the above benefits, the DG must be reliable, dispatch able, of the proper size and at the proper locations. Energy cost of distributed resources as compared to fossil resources is generally high where at the factors of Social and environmental benefits could not be included in cost account.

This paper considers two categories: the standby Power DG and the peak shaving DG.
The applications for DG include combined heat and power, standby power, peak shaving, grid support and stand alone (grid isolated). A standby Power DG means a unit that is operated to supply Power at interrupted customers. The customers have come to expect uninterrupted electric service throughout the year. But outages do occur and to maintain high reliability, the DGS are installed to supply power until utility service is restored. The installation of stand by generators is an economic choice based on extremely high interruption cost for specified customers.
A Peak shaving DG means a unit that is operated during peak load. The cost of utility power varies hourly depending on the demand and the availability of generation assets incorporated transmission systems. On the strategy is to use DG during periods of peak load when utility power is likely to be higher priced. The Utilization of DG is cheaper than the purchase of utility peak power for much of the year.

On site Power generation investments and installation trends are accelerating for industrial, commercial and residential consumers. Cambridge Research Associates reported that on site generation provides 35% of total US industrial electric power demand. A recent EPRI study concluded by 2013, 25% of new generation would be distributed. However, the Natural Gas foundation indicated that this figure could reach 30%. This Onsite power generation could provide their customers with cheap electricity and increase their reliability. Distributed Generation, as a new version of onsite power generation, is not a new concept but it is a new approach of installing small power generation at or near to the load being served. Customer – operated Distributed Generation (CDG) have been used for several years for supplying power in rural areas and as backup, stand by, energy storage, etc. to provide electricity to their facilities at a reasonable price and to ensure electric power continuity.

Under the new developed DG technologies, depending on the DG technology used, several benefits can be provided to customers by owning DGS such as reduced emissions, utilization of waste heat, implementation of combined heat and power (CHP), improved Power quality and increased reliability. The Excessive trend of owning CDG in the distribution system increases the Local Distribution companies (LDC) Network operation complexity. Distributed Generation also referred as cogeneration. Cogeneration of heat and electricity can be deal within two ways:-Topping Cycle & Bottoming CycleIn the topping cycle mode, fuel is burn to generate electric power and the discharged heat from the turbine is supplied as process heat. In Bottoming cycle, fuel is consumed to produce process heat and waste heat is then utilized to generate power.
The efficiency of a cogeneration plant is given by:
nco = (E + ∆ HS) / QA
Where E = Electric Energy generated.
∆ HS = Heat energy utilized from process steam (hot water)
QA = Heat added to plant.

For Separate generation of electricity and process steam, the heat added per unit of total energy out put is
Where, e = electric fraction of total energy output.
e = E / (E+∆ HS)
ne = efficiency of electric plant.
nb = efficiency of process steam generation plant.

The Overall efficiency of separate generation of electricity and process heat is given by:
Cogeneration is economical only if the efficiency of the cogeneration plant exceeds that of the overall efficiency of separate generating plants for electricity and heat dispersed power and Distributed Generation is cleaner, Greener power and energy that ends ; Power Problems, electric grid problem and black – out ; increases : profits through decreased energy expenses ; improves : Air quality through significantly reduced emissions ; conserves : Natural resources ; Reduces : Dependence on Foreign Oil.The National Electricity Policy notified on February’ 12, 2005 mentions under the Rural Electrification Component.
* That to provide a reliable Rural Electrification Distribution Backbone be established by extending the transmission lines.
* It directs that decentralized distributed Generation facilities (using conventional or non – conventional sources of energy) together with Local distribution network be provided.

This study presents and evaluates about Reliability operation of Customer operated Distributed Generation. In this paper, Distributed Generation is defined as installation and operation of small modular power generating technologies that can be combined with energy Management and Storage system. It is used to improve the operations of the Electricity delivery systems at or near the end user. These systems may or may not be connected to the Electric grid.

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