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EEET 426
ELECTRICAL DISTRIBUTION TECHNOLOGY
Dr.A.Arunagiri
Distribution System Planning
Chapter 1
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Chapter Outline
Introduction
Factors affecting distribution system planning
Present distribution system planning techniques
Distribution system planning models
Computer central role in distribution planning
Impact of dispersed storage and generation
Renewable resources of generation
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Introduction
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The electrical power system is very complex system.
Distribution is about 50% of the capital cost of the power system.
The power system consists of three main parts Generation plants,
Transmission and Distribution.
The electrical distribution system is a part of the system between
the transmission and the consumer service point.
The electrical distribution system is divided into primary and secondary
distribution.
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Typical Electrical Power System
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The electrical distribution systems consists of:
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1.Sub transmission
2.Distribution substation
3.Primary feeders
4.Distribution transformers
5.Secondary circuits
6.Service drops
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Distribution System
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Sub-transmission
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The sub-transmission is an electrical network designed to supply the
electrical power from the bulk power source (Transmission line) to the
distribution sub-station at a voltage ranging from 33 to 220 kV. May be over
head or underground cables.
There are six types of sub-transmission are:
•Radial system.
•Primary Loop System.
•Primary Selective.
•Secondary selective
•Spot Network
•Grid Network
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Radial Systems
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Primary Loop System
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Primary Selective System
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Secondary Selective System
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Spot Network
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Grid Network
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Electrical Power System
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(b)Single Wire Earth Return (SWER)
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Types of Distribution System (a) Single Phase
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(C ) Three phase Three Wire
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(d) Three Phase four Wire
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Basic Distribution Systems
• Radial
• Primary Loop
• Primary Selective
• Secondary Selective
• Spot Network
• Grid Network
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Factors Affecting Distribution System Planning
Load demand and load characteristics
Voltage level at the customer point
Type of secondary circuits
Size and location of distribution transformer
Types of primary distribution system
Loads at primary distribution level
Size and location of distribution substation
Routing and capacity of associated sub-transmission lines
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Factors Affecting Distribution System Planning…….
Restrictions such as Permissible voltage deviations
Voltage dip and flicker
Service continuity and reliability
Types of protection to be employed
Choice of circuit breakers, reclosers and sectionalizers
Requirement of capacitors for power factor correction and loss minimization
Requirement of voltage regulators
Types of transformers and availability of space for transformers
Insulation levels
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Distribution system Planning Technique
Load flow programs Radial or loop load flow
programs Short-circuit programs Voltage drop calculation
programs Total system impedance
calculation programs
Load forecasting programs Voltage regulation and
regulator setting programs Capacitor planning
programs Substation optimal sitting
and sizing programs Reliability programs
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However, in general, the overall concept of automatically using output of each program as input for the next program is not in use. Engineering judgment and trial and error method are used in system planning. In this chapter, we shall discuss some of the distribution planning and operation techniques.
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Future Distribution System Planning
Components
Vision:
A clear vision for the future
communicates a sense of the kind of
organization, power utility needs to become, and outlines the kind of
results it must achieve. The vision provides a continuing focus and
constantly reminds the employees and consumers of what the company
trying to change.
Mission: For particular task there can be a
mission statement such as Electricity for all KSA by the end of next decade
Values:
The power utility leadership must create values such as consumer satisfaction, environmental responsibility.
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Distribution system planning models
Traditional-Least cost model:
It is a process by which utilities
minimize the cost of supplying a
given amount of power. The
existing system inadequacies are
identified as:
• Poor voltage regulation
• Higher system loss
• Higher equipment
failure/breakdown
• Bad quality of power supply
• No scope for future growth.
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The initial system improvement can be very cost effective in
removing the above system inadequacies as compared to the other
alternatives of laying a new extended system.
Thus there are two options:
System improvement
Expansion of the existing network
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(a) System Improvement
Augmentation and strengthening of the existing system
Improving the reliability and quality of supply
Reduction of commercial and technical loss and / or
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b)Expansion of the existing network
When augmentation and strengthening of existing system are
involved the benefits of saving in losses (kw and energy), net
revenue increase due to additional sale of power and energy
after adjusting the expenditure incurred on generation of the
additional energy must be maximized.
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2. Demand Side Planning(DSP)
It is the process by which power utilities quantify and assess the
programmes to alter the load pattern and level of their consumer’s
demand for electricity.
This is planning at the consumer level and often has a long planning
period, much longer than distribution system planning. It can take years
of slow progress to obtain meaningful levels of participation.
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The low cost demand side option can be :
Implementing energy conservation programmes
Providing vigilance and detection of theft.
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DSM programmes generally fall into three main categories: 1 Conservation programmes Reduce energy use with programmes to improve the efficiency of the equipments (like lighting and motors), buildings and industrial processes as per the energy conservation act.
2 load management programmes: Redistribute energy demands to spread it more evenly throughout the day. Some way of doing this are:
Load shifting programmes ( shifting some of the loads during peak period to off peak period) Time -of –use ( Charging more for electricity during peak demand) Interruptible rates( providing rate discounts in exchange for the right to reduce consumers electricity allocation each year during few hours when electricity demand is the highest
Types of DSM
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3. Strategic load growth programmes:
Increase energy use during some periods, (Encourage cost effective electrical technologies that operate primarily during periods of low electricity demand.)
The following approaches can be used.
General information programmes to inform consumers about generic energy efficient options Site – specific information programmes that provide information about specific DSM measures appropriate for a particular industry , agriculture or home. Financing programmes to assist consumers to pay for DSM measures including loans, rebates, and shared savings programmes
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Direct installation programmes that provide complete services to design, finance and install a package of efficiency measures. Alternative tariff programmes including time-of-use tariff, interruptible tariff, and load shifting tariff. ( These programmes usually do not save energy but they are effective ways to shift loads to off peak periods. Bidding programmes in which utility solicits bids from consumers and energy service companies. Load limiters are effective in demand side management , as they limit the maximum power that the consumer draws from the supply.
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The process of designing and implementing DSM programmes generally consists of the following steps. Identifying the sectors, end -uses and efficiency measures to target Developing programme design Conducting cost-effective screening Preparing an implementation plan Implementing programmes and Evaluating programmes.
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Benefits of DSM
• Reduces consumers energy bills
• Reduces the need for the new plant, transmission and distribution construction
• Stimulates economic development
• Creates long time jobs that benefits the economy
• Increases the competitiveness of the local enterprises
• Can reduce maintenance and equipment replacement cost
• Reduces local air pollution
• Reduces emission s that contribute to national and international environmental problems such as acid rain and global warming
• Enhances national security by easing dependence on foreign energy sources
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Computer central role in distribution planning
Software needs: generally is selected on the basis of the
least life cycle cost or least ownership costs (hiring or purchase + training + maintenance costs). The software must be.
– Best overall performance – Best solution – Best open architecture system
Analysis of the system computer aided power flow studies in
improving the performance of the existing sub-transmission and distribution systems and proposed expansion of network up to the meter point (Consumers). Studies will provide
– Active and reactive power flows as well as the locations of capacitors
– Voltage variation (at each node or bus, percent variation)
– Peak power losses and energy losses – Computation of commercial losses of
feeder – Overloading of transformers
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Computer central role in distribution planning
Data: success of any information
technology system is highly
dependent on the accurate, up to
date field data for improvement in
the network and system.
Information must be clear and up-
dated on:
Nodes Single line diagram Distribution substation Primary feeder Distribution transformer
and secondary feeder Consumer data Load data
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Elements of the distribution system
Distribution Transformer
Primary distribution feeder
Secondary distribution feeder
Protection devices and instrumentation
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Dispersed Generation
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Impact of dispersed storage and generation
• This is When the generating plant is connected to a distribution
network capable of supplying power to the consumer load directly .
• This enhances the reliability and the quality of power supply.
• The expectations of the reliability especially for data centers, call
centers, computer controlled critical process/businesses, continuous
process industries, petro chemical refineries are four nines
(99.99%).
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Impact of dispersed generation….
For dispersed generations line losses will be nominal since there is
no transmission system is required.
Dispersed generation with local radial distribution network will
play an important role in the 21st century.
Dispersed generation is generally from local renewable sources.
This saves environment degradation compared to conventional
thermal generation.
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Renewable resources of generation
Fuel cells Solar photovoltaic Wind energy Tidal wave energy from
ocean
Small hydro (up to 25 MW
capacity, pumped storage)
Geo-thermal Bio-mass Municipal and industrial
west
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Net Metering
The kilo watt hour meter(import – export meter) can be used to
accurately register the flow of electricity in either direction. This
means the ‘netting’ process associated with net metering happens
automatically
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Assignment 1
Q.1 Draw the one line diagram of the electrical power system available in KSA.. Indicate the voltage levels for Generation Transmission Sub transmission Primary Feeder Secondary Feeder
Q2 Mention and discuss the different types of the renewable resources of generation available in the KSA.
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