The document provides an overview of electrical distribution system planning and reliability. It discusses the planning process, criteria, standards, economics, mapping, and load characteristics. The planning process involves defining problems, finding alternatives, evaluating options, and selecting the best plan. Criteria and standards are used to evaluate alternatives and ensure compatible equipment. Economics analyses determine the lowest cost plan, while mapping creates a geographic database of distribution assets. Load characteristics such as demand, load factor, and plant factor are also defined.

1. Electrical Distribution System
Name of the Faculty : Adithya Ballaji
School of Electrical and Electronics Engineering
Unit 3: System Planning and Reliability
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University

2. Syllabus
• Planning process, planning criteria, system developers, dispersed generation, distribution systems,
economics and finance, mapping. Load Characteristics - Basic definition, relation between load
and load factor, load growth.
• Reliability-Basic reliability concept –Cost verses system Reliability –Reliability planning
procedure–Mathematical concept.
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3. Introduction
• Planning is the process of taking careful decision. The main input in planning
is quality and systematic thought.
• It involves selecting the first a vision, values, mission and objective and deciding what should be
done to attain them.
• The main objective of distribution planning is to provide satisfactory service at lowest possible
cost.
• In power utility, the planning process is used to identify the best schedule of future resources and
actions to achieve the utility goal.
• Planning is driven by two inputs:
1. Future Needs
2. Time needed to fulfil these needs with defined master plan.
• Long term planning (5-10 years) determines the power energy forecasts and optimum network
arrangements.
• A short term planning involves the planning for current year and next year annual plans, and
subsequent years.
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4. Steps involved in Planning Process
• Feasibility studies are carried out to identify, evaluate and finalize the best plan.
1. Define the problem
2. Find the alternative
3. Evaluate the alternative
4. Select the best one
• Project report for long, medium, short term works along with the action plan/pert chart/bar chart
for each activity/ work is prepared and dates are set for milestones.
• Final approval is taken after financial and economic appraisal.
• Once the best plan is selected the next stage of process is inititated.
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5. Flow chart of Planning Process
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6. Planning Actions
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7. Planning Criteria and Standards
• Criteria and standards together form a set of requirements against which the planning process can
compare alternatives in the evaluation and final choice.
• A distribution plan must provided with least cost and also satisfy various criteria and standards.
• Criteria are rules or procedures.
• Standards are specifications to ensure that the system is built with compatible equipment that will
fit and function together when installed and maintained in an economical manner.
• Standards and criteria and their application to the planning process depends upon vision, mission
and the value system of the utility.
• Criteria and standards convey direction in the master plan.
• Planning standards exists for reasons of efficiency and to achieve the reduced investment
• The system may use various Indian standards, Indian Electricity Rules, Rural Electrification
Corporation Standards, IEC, ISO and electricity act 2003.
• These criteria and standards are used for better and improved power utility their by to achieve its
objective.
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8. Typical Criteria for Planning
The following are the typical criteria for planning:
• A prospective plan for the next 15 years to meet the anticipated load growth and forecast load
centers.
• The plan should be reviewed yearly on the basis of annual plans with respect to the targets
achieved.
• Detailed project reports be framed to identify the system strengthening works on long term and
short term bases.
• Demand side management projects reports be prepared to achieve tangible reduction in demand
and energy consumption on the planned year.
• Security of supply is one of the important factors for planning, for example, In industrial cities
supply to be provide using sub transmission open circuit of 33 or 66 or 132 or 220kV, 11kV open
ring main circuit for all urban area, and separate independent feeders to be provided for major
industrial consumers and rural areas.
• Power utility needs to use and create load research facilities to study and identify load profiles in
the particular area.
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9. Typical Criteria for Planning
• The number of 11kV outgoing feeders at distribution station should not exceed 15.
• The length of 11kV outgoing feeder emanating from substation up-to tail end not to be more than
12km.
• Improved metering, that is to provide electronic meters to all the consumers.
• Total harmonic distortion at any voltage level should be within 5 per cent.
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10. Types of planning standards
• Development of standard cost structure for material and labour rates for different voltages
to be used in the estimation.
• Use of standard system voltages as per Indian standards and voltage regulation as per IE Rules.
• The load growth of at least 10 years will considered to prepare new or system improvement
schemes.
• Shunt capacitor fixed / switched type shall be installed in distribution system to improve the power
factor and voltage profile there by reducing transmission and distribution losses.
• Fixed LT capacitor should be installed on the distribution transformers.
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11. Distribution system Economics and Finance
• Economic analysis is carried out to determine the lo cost plan among various alternatives.
• Financial analysis determines the rate of return and risk involved on the investment to be made on
the plan.
• The investment to carry out a planned distribution is either:
1. Annual expenses : Obtained from operating revenue
2. Capital expenditure : obtained from financing, reinvested reserve etc.
3. Both annual expenses and capital expenditure
Following methods are used for Investment decision :
1. Minimum Revenue Requirement
• Time value money
• Revenue Requirement of Investment
2. Financial Method
• Benefit/Cost Ration
• Internal Rate of Return( IRR)
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12. Minimum Revenue Requirement
• In this type of method choice is made on the basis of the present value of all future
annual costs.
• The economic choice is made based on the one with lowest present value of all the future cost.
• The economic comparison is done based on two steps:
1. Estimating the annual cost of each year
2. If the annual costs are not uniform, calculate their present value.
Time Value Money:
• Here money has time value and interest on its use has to be paid. The rate of interest is determined
by the reserve Bank of India according to economic condition at the time.
• There is a similar mechanism to determine the interest rate at the international level also.
• The process of taking money and finding its equivalent value at some future date is called future
value calculation.
• The process of finding the equivalent value at some earlier time is called present value
calculation.
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13. Minimum Revenue Requirement
Revenue Requirement of Investment:
• The total revenue requirement of investment is the sim of the annual charges extending over
the service life.
It includes:
1. Return on investment
2. Depreciation
3. Insurance expenses
4. Operating and Maintenance expenses
5. Interest on loan capital and working capital
6. Taxes etc.
The above charges can be conveniently estimated as a percentage of original investment. And three
methods to calculate the present value are:
1. Cumulative present worth method
2. Levelised Annual Cost Method
3. Uniform series present worth Method
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14. Financial Analysis
It can be classified into :
1. Benefit / cost ratio
2. Internal Rate of Return ( IRR)
Benefit / cost ratio
• This method ranks a project by the ratio of the present value of revenue and benefits earned to the
present value of the costs incurred.
• System improvement works are generally evaluated on a benefit – cost basis by the rural
electrification corporation of India.
• The central Electricity Authority (CEA) also uses this method for such schemes, based on lifecycle
(25-30 year period) cost benefits.
• The works proposed for strengthening, upgradation and improvement of sub- transmission and
distribution helps in reducing technical and commercial losses by the year.
• The financial analysis is usually done for the for lifetime of projects considering the year wise
costs including interest, depreciation, operation and maintenance charges.
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15. Financial Analysis
Internal Rate of Return ( IRR)
• The design and sustainability of the project should take into account the level of incentive for
undertaking and maintaining a project investment.
• The financial incentive takes the form of increased income that the investment generates with the
execution of the project.
• This method calculates the rate of interest needed for the present value of the returns to be the same
as the present value of the investment needed.
• Rural Electrification Corporation specifies the IRR as 15 percent while sanctioning short term
( seven year repayment) loan scheme.
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16. Mapping
• Creating a geodatabase containing relevant information about assets in existing electrical
distribution system.
• Types of Mapping:
• Global Positioning System (GPS)
1. Back ground Maps
2. Digital Mapping
3. Automated Mapping (AM)/ Facilities Management (FM)/ Geographical Information System
(GIS)
4. Enterprise Resource Planning (ERP)
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17. Mapping
Global Positioning System (GPS)
• GPS is a system in which earth orbiting satellites provide precise information on time and position
enabling GPS receiving devices to compute position on earth.
• Signals must be received from at least three satellites in order to establish the latitude and longitude
of receiver position.
• A fourth satellite is required to calculate the altitude.
• GPS technology is used to locate tap-off points, transformers and other facilities of power
distribution networks and consequently to map the system with an accuracy of up to one meter.
• GPS can be used to capture data for 11kV and above voltage level distribution/sub transmission
lines and substations/distribution transformer for mapping.
• For LT network each distribution transformer geographical maps on paper can be drawn based on
judgment and eye approximately.
• The length of the feeder is generally fixed, based on estimates and pole to pole standard distances.
• These maps can be prepared on survey of India sheets
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18. Mapping
Digital Mapping
• Digital mapping software can be used to create an integrated and automated facilities model
in which paper maps are first digitized and then suitably linked.
• A digitizer board is used for digitizing nodes with respect to a reference point pre-fixed on the map.
• One person can read co-ordinates on the digitized board and other can feed it into a computer.
• Once digitization is complete, the software numbers the nodes, draws the network diagram and
calculates the lengths.
• Network drawn with a computer then undergo field verification.
• A computer processing centre will then issue a prescribed format to obtain electrical loading data
of feeders, transformer capacity, size/type of feeder for the concerned area.
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19. Digital Mapping
The following steps should be taken to prepare the maps:
1. The complete area should be covered and duplication avoided.
2. The 132-33kV system be digitized first then followed by 11kV and finally the 400kV network.
3. Devices like GPS and VHF sets may be required for dense urban areas to capture attributes
accurately and ensuring high frequency digitized maps.
4. Oracle RDBMS is suitable for data storage. Digital mapping process is shown below:
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20. Automated Mapping (AM) / Facilities Management (FM)/
Geographical Information System (GIS)
• Every transaction whether it is a work order, billing, operation, system improvements or
maintenance is tied to a location.
• AM and FM provide an integrated tool to create an automated facilities model and help to convert
paper maps to a digital environment where the system details and its changes are fed and stored in
a graphic and tabular database.
• The graphic data is representation of the network and is the backbone of an AM/FM/GIS system
and the driving force for all the application.
• FM software links the graphic network map to tabular and non-graphic data associated with the
databases, work order drawing etc.
• GIS establishes the connection to these databases through a record server and provides the best
characteristics of AM and FM system to provide an integrated information system.
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21. Role of Geographical Information System (GIS) and
its application
• GIS is a system of mapping of complete electrical network including low voltage system
and consumer meter.
• Database plays a central role in the operation of planning, where analysis programme form a part
of system supported by a database management system which stores, retrieves and modifies
various data on the distribution system.
• The main role of GIS is to integrate the dynamic side of the operation with the relatively static side
of the utility facility record for effective utilization by all functional departments and personnel.
• The various roles include:
1. Detailed space representation of the facilities and network linked to the related data.
2. Integrated facility database and its management with multi user access.
3. Management of different stages of the facility’s life cycle.
4. Optimum data for facility application.
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22. Role of Geographical Information System (GIS) and
its application
• Applications:
1. The planning department will be needing field data of land records, load growth based on
population growth and demand, existing network layout.
2. The data is required for feeder layout/routing and network planning, load flow analysis,
protective devices locations.
3. Estimation and Costing
4. Management reports
5. Design / operational logistics
6. Maintenance
7. Troubleshooting School of Electrical and Electronics Engineering, REVA
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23. Load Characteristics
Basic Definitions
Demand
• The demand of an installation or system is the load at the receiving terminals averaged over a
specified interval of time. Here the load may be given in kilowatts, kilovars, kilovolt amperes, kilo
amperes or amperes
Demand interval
• It is the period over which the load is averaged. This selected ∆t period may be 15min, 30min or
even longer.
Maximum Demand
• The maximum demand of an installation or system is the greatest of all demands which have
occurred during the specified period of time. The maximum demand statement should also express
the demand interval used to measure it. For example, the specific demand might be the maximum
of all demands such as daily, weekly, monthly or annual.
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24. Daily Demand variation curve
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25. Basic Definitions
Utilization Factor
• It is the ratio of maximum demand of the system to the rated capacity of the system. Thus
utilization factor is denoted as 𝑭 𝒖
𝑭 𝒖 =
𝑴𝒂𝒙𝒊𝒎𝒖𝒎 𝑫𝒆𝒎𝒂𝒏𝒅
𝑹𝒂𝒕𝒆𝒅 𝑺𝒚𝒔𝒕𝒆𝒎 𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒚
Plant Factor
• It is the ratio of the total actual energy produced or served over a designated period of time to the
energy that would have been produced or served of the plant had operated continuously at
maximum rating. It is also known as capacity factor or use factor.
𝑷𝒍𝒂𝒏𝒕 𝑭𝒂𝒄𝒕𝒐𝒓 =
𝑨𝒄𝒕𝒖𝒂𝒍 𝒆𝒏𝒆𝒓𝒈𝒚 𝒑𝒓𝒐𝒅𝒖𝒄𝒆𝒅 𝒐𝒓 𝒔𝒆𝒓𝒗𝒆𝒅 × 𝑻
𝑴𝒂𝒙𝒊𝒎𝒖𝒎 𝑷𝒍𝒂𝒏𝒕 𝒓𝒂𝒕𝒊𝒏𝒈 × 𝑻
Where T is the time in days, weeks, months or years.
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26. Basic Definitions
Load Factor
• It is the ratio of the average load over a designated period of time to the peak load occurring on that
period. Therefore load factor FLD
𝑭 𝑳𝑫 =
𝑨𝒗𝒆𝒓𝒂𝒈𝒆 𝑳𝒐𝒂𝒅
𝑷𝒆𝒂𝒌 𝑳𝒐𝒂𝒅
𝑭 𝑳𝑫 =
𝑨𝒗𝒆𝒓𝒂𝒈𝒆 𝑳𝒐𝒂𝒅 × 𝑻
𝑷𝒆𝒂𝒌 𝑳𝒐𝒂𝒅 × 𝑻
=
𝑼𝒏𝒊𝒕𝒔 𝒔𝒆𝒓𝒗𝒆𝒅
𝑷𝒆𝒂𝒌 𝒍𝒐𝒂𝒅 × 𝑻
Where T is the time in days, weeks, months or years.
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27. Problem
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• Assume that the Yelahanka distribution substation of KPTCL supplying to Vinayakanagar, a small place,
• experiences an annual peak load of 3500 Kw. The total annual energy supplied to the primary feeder
• circuits is 10,000,000 kWh. The peak demand occurs in July or august and is due to air – conditioning load.
(i) Find the annual average power demand.
(ii) Find the annual load factor
Assume the monthly load curve as shown below:

28. Solution
(i) The annual average power demand is
𝐴𝑛𝑛𝑢𝑎𝑙 𝑃𝑎𝑣 =
𝑇𝑜𝑡𝑎𝑙 𝑎𝑛𝑛𝑢𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦
𝑌𝑒𝑎𝑟
=
107 𝑘𝑊ℎ/𝑦𝑒𝑎𝑟
8760ℎ/𝑦𝑒𝑎𝑟
= 1141kW
(II) Annual load factor is given by,
𝐹𝐿𝐷 =
𝐴𝑛𝑛𝑢𝑎𝑙 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐿𝑜𝑎𝑑
𝐴𝑛𝑛𝑢𝑎𝑙 𝑃𝑒𝑎𝑘 𝐷𝑒𝑚𝑎𝑛𝑑
=
1141𝑘𝑊
3500𝑘𝑊
= 0.326
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29. Distribution System Reliability
• Reliability is the probability of a device or system performing its purpose adequately for the period
of time intended under the operating conditions encountered.
• A measure of the ability of the system to perform its intended function
Basic Definition
Outage
• Describes the state of a component when it is not available to perform its intended function due to
some event directly associated with that component. An outage may or may not cause an
interruption of service to consumers depending on the system.
• Types of outages:
1. Forced Outage
2. Scheduled Outage
3. Partial Outage
4. Transient Forced Outage
5. Persistent forced Outage School of Electrical and Electronics Engineering, REVA
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30. Basic Definitions
Forced Outage
• An outage caused by emergency conditions directly associated with a component that require the
component to be taken out of service immediately, either automatically or as soon as switching
operations can be performed, or an outage caused by improper operation of equipment or human
error.
Scheduled error
• An outage that results when a component is deliberately taken out of service at a selected time,
usually for the purpose of construction, preventive maintenance or repair.
Partial Outage
• Describes an component state where the capacity of the component toperform its function is
reduced but not completely eliminated.
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31. Basic Definitions
Transient Forced Outage
• A component outage where the cause or the reason for outage is immediately self clearing so that
the affected component can be restored to service either automatically or as soon as a switch or
circuit breaker can be reclosed or a fuse is replaced.
For example: Outage due to lightning flash over
Persistent forced Outage
• A component outage where the cause or the reason for outage is not immediately self clearing but
must be cleared by eliminating the hazard or by repairing or replacing the effected line or
component before the line can be energized.
For example: a lightning flashover which shatters the insulators there by disabling the component
until it is replaced.
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32. Cost vs Reliability
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• By increasing the reliability level, leads to new investments for the utility, while
the economic consequences for the customers decreases.
• The opposite happens if the utilities decreases the system reliability level, which leads to fewer
investments, and thereby a reduced cost.
• But this will on the other hand increase the economic consequences for the customers, which might
be unsatisfactory.
• A global minimum at the total cost curve exists, which may be the aim for utilities, in order to
keep the costs and satisfied customers at a certain level

33. Thank You
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