This document discusses future trends in electrical distribution system planning. It predicts that distribution planning will rely heavily on computer tools to optimize network design based on multiple criteria. Load management will also impact distribution by altering load patterns, requiring systems to be designed differently. New automated tools like network editors are expected to enable trial network designs that can be simulated to ensure performance and accommodate load growth. The central role of databases and management systems in supporting these new planning tools is also highlighted.

1. Future Nature of Distribution Planning
Central Role of the Computer in Distribution Planning
Load characteristics.
ELECRTICAL DISTRIBUTION SYSTEMS
IV B.TECH II SEMESTER EEE
S K B PRADEEPKUMAR CH
ASSISTANT PROFESSOR
EEE

2. Future Nature of Distribution Planning
Increasing Importance of Good Planning
Impacts of Load Management (or Demand-Side Management)
Cost/Benefit Ratio for Innovation
New Planning Tools

3. Predictions about the future methods for distribution planning must necessarily be
extrapolations of present methods. Basic algorithms for network analysis have been known
for years and are not likely to be improved upon in the near future. However, the
superstructure that supports these algorithms and the problem-solving environment used by
the system designer is expected to change significantly to take advantage of new methods
that technology has made possible. Before giving a detailed discussion of these expected
changes, the changing role of distribution planning needs to be examined
Future Nature of Distribution Planning

4. For the economic reasons listed earlier, distribution systems will become more expensive to
build, expand, and modify. Thus, it is particularly important that each distribution system
design be as cost effective as possible. This means that the system must be optimal from many
points of view over the time period from the 1st day of operation to the planning-time horizon.
In addition to the accurate load growth estimates, components must be phased in and out of the
system so as to minimize capital expenditure, meet performance goals, and minimize losses.
These requirements need to be met at a time when demographic trends are veering away from
what have been their norms for many years in the past and when distribution systems are
becoming more complex in design due to the appearance of more active components (e.g., fuel
cells) instead of the conventional passive ones.
Increasing Importance of Good Planning

5. In the past, the power utility companies of this nation supplied electric energy to meet all
customer demands when demands occurred. Recently, however, because of the financial
constraints (i.e., high cost of labor, materials, and interest rates), environmental concerns,
and the recent shortage (or high cost) of fuels, this basic philosophy has been reexamined
and customer load management investigated as an alternative to capacity expansion. Load
management’s benefits are system wide. Alteration of the electric energy use patterns will
not only affect the demands on system generating equipment but also alter the loading of
distribution equipment. The load management (or demand-side management) may be used
to reduce or balance loads on marginal substations and circuits, thus even extending their
lives. Therefore, in the future, the implementation of load management policies may
drastically affect the distribution of load, in
Impacts of Load Management (or Demand-Side Management)

6. time and in location, on the distribution system, sub transmission system, and the bulk power
system. Since distribution systems have been designed to interface with controlled load
patterns, the systems of the future will necessarily be designed somewhat differently to benefit
from the altered conditions. However, the benefits of load management (or demand-side
management) cannot be fully realized unless the system planners have the tools required to
adequately plan incorporation into the evolving electric energy system. The evolution of the
system in response to changing requirements and under changing constraints is a process
involving considerable uncertainty.

7. 1. It must be able to reduce demand during critical system load periods.
2. It must result in a reduction in new generation requirements, purchased power, and/or fuel
costs.
3. It must have an acceptable cost/benefit ratio.
4. Its operation must be compatible with system design and operation.
5. It must operate at an acceptable reliability level.
6. It must have an acceptable level of customer convenience.
7. It must provide a benefit to the customer in the form of reduced rates or other incentives.
The requirements of a successful load management program are specified by
Delgado as follows:

8. In the utility industry, the most powerful force shaping the future is that of economics.
Therefore, any new innovations are not likely to be adopted for their own sake but will be
adopted only if they reduce the cost of some activity or provide something of economic value,
which previously had been unavailable for comparable costs. In predicting that certain
practices or tools will replace current ones, it is necessary that one judge their acceptance on
this basis. The expected innovations that satisfy these criteria are planning tools implemented
on a digital computer that deals with distribution systems in network terms. One might be
tempted to conclude that these planning tools would be adequate for industry use throughout
the 1980s. That this is not likely to be the case may be seen by considering the trends judged to
be dominant during this period with those that held sway over the period in which the tools
were developed.
Cost/Benefit Ratio for Innovation

9. Tools to be considered fall into two categories: network design tools and network analysis
tools. The analysis tools may become more efficient but are not expected to undergo any major
changes, although the environment in which they are used will change significantly. This
environment will be discussed in the next section. The design tools, however, are expected to
show the greatest development since better planning could have a significant impact on the
utility industry.
New Planning Tools

10. The results of this development will show the following characteristics:
1. Network design will be optimized with respect to many criteria by using programming
methods of operations research.
2. Network design will be only one facet of distribution system management directed by
human engineers using a computer system designed for such management functions.
3. So-called network editors will be available for designing trial networks; these designs in
digital form will be passed to extensive simulation programs, which will determine if the
proposed network satisfies performance and load growth criteria.

11. Central Role of the Computer in Distribution Planning
System Approach
Database Concept
New Automated Tools

12. Central Role of the Computer in Distribution Planning
As is well known, distribution system planners have used computers for many years to
perform the tedious calculations necessary for system analysis. However, it has only been
in the past few years that technology has provided the means for planners to truly take a
system approach to the total design and analysis. It is the central thesis of this book that
the development of such an approach will occupy planners in the future and will
significantly contribute to their meeting the challenges previously discussed.

13. System Approach
A collection of computer programs to solve the analysis problems of a designer necessarily
constitutes neither an efficient problem-solving system nor such a collection even when the
output of one can be used as the input of another. The system approach to the design of a
useful tool for the designer begins by examining the types of information required and its
sources. The view taken is that this information generates decisions and additional
information that pass from one stage of the design process to another. At certain points, it is
noted that the human engineer must evaluate the information generated and add his or her
input. Finally, the results must be displayed for use and stored for later reference. With this
conception of the planning process, the system approach seeks to automate as much of the
process as possible, ensuring in the process that the various transformations of information
are made as efficiently as possible. One representation of this information flow is shown in
Figure 1.10, where the outer circle represents the interface between the engineer and the
system.

14. Analysis programs forming part of the system are supported by a database management
system (DBMS) that stores, retrieves, and modifies various data on distribution systems.
Database Concept
As suggested in Figure 1.10, the database plays a central role in the operation of such a
system. It is in this area that technology has made some significant strides in the past 5
years so that not only is it possible to store vast quantities of data economically, but it is
also possible to retrieve desired data with access times on the order of seconds. The DBMS
provides the interface between the process that requires access to the data and the data
themselves. The particular organization that is likely to emerge as the dominant one in the
near future is based on the idea of a relation. Operations on the database are performed by
the DBMS.

16. In addition to the database management program and the network analysis programs, it is
expected that some new tools will emerge to assist the designer in arriving at the optimal
design. One such new tool that has appeared in the literature is known as a network editor.
The network consists of a graph whose vertices are network components, such as transformers
and loads, and edges that represent connections among the components. The features of the
network editor may include network objects, for example, feeder line sections, secondary line
sections, distribution transformers, or variable or fixed capacitors, control mechanisms, and
command functions. A primitive network object comprises a name, an object class
description, and a connection list. The control mechanisms may provide the planner with
natural tools for correct network construction and modification.
New Automated Tools

17. LOAD CHARACTERISTICS
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, kilovoltamperes, kiloamperes, or amperes.
Demand interval: It is the period over which the load is averaged. This selected Δt period
may be 15 min, 30 min, 1 h, or even longer. Of course, there may be situations where the 15
and 30 min demands are identical
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.

18. )is
Diversified demand (or coincident demand): It is the demand of the composite group,
as a whole, of somewhat unrelated loads over a specified period of time. Here, the
maximum diversified demand has an importance. It is the maximum sum of the
contributions of the individual demands to the diversified demand over a specific time
interval.
Utilization factor: It is “the ratio of the maximum demand of a system to the rated
capacity of the system”. Therefore, the utilization factor (Fu) is
Load: electrical power needed in KW or KVA

19. 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 if the plant (or unit)
had operated continuously at maximum rating. It is also known as the capacity factor or the
use factor.

20. 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, the load factor Fld is average load

21. Diversity factor: It is “the ratio of the sum of the individual maximum demands of the
various subdivisions of a system to the maximum demand of the whole system”.
Therefore, the diversity factor (FD) is
is the maximum demand of load i, disregarding time of occurrence
where
coincident maximum demand of group of loads

22. Coincidence factor: It is “the ratio of the maximum coincident total demand of a group of
consumers to the sum of the maximum power demands of individual consumers comprising
the group both taken at the same point of supply for the same time”. Therefore, the
coincidence factor (Fc) is

23. Load diversity: It is “the difference between the sum of the peaks of two or more
individual loads and the peak of the combined load”. Therefore, the load diversity (LD)
is
Contribution factor: Manning defines ci as “the contribution factor of the ith load to the
group maximum demand.” It is given in per unit of the individual maximum demand of the
ith load. Therefore,

24. Coincidence factor is
That is, the coincidence factor is equal to the contribution factor.
Loss factor: It is “the ratio of the average power loss to the peak-load power loss during a
specified period of time”. Therefore, the loss factor (FLS) is
Note: is applicable for the copper losses of the system but not for the iron losses.

25. Load Curve
Definition: Load curve or chronological curve is the graphical representation of load
(in kW or MW) in proper time sequence and the time in hours. It shows the variation of
load on the power station. When the load curve is plotted for 24 hours a day, then it is
called daily load curve. If the one year is considered then, it is called annual load curve.
The load curve of the power system is not same all the day. It differs from day to day
and season to season. The load curve is mainly classified into two types, i.e., the
summer load curve and the winter load curve.

26. Information Obtained From Load Curve
The following are the information obtained from load curves.
•Load duration curve determines the load variation during different hours of the day.
•It indicates the peak load which determines the maximum demand on the power station.
•The area under the load curve gives the total energy generated in the period under
consideration.
•The area under the curve divided by the total numbers of hours gives the load.
•The ratio of the area under the load curve of the total area of the rectangle in which it is
contained gives the load factor.
•The ideal load curve is flat, but practically it is far from flat. For a flat load curve, the load
factor will be higher. Higher load factor means the more uniform load pattern with fewer
variations in load.

28. Utility of Load Curve
The following are the utility of the load curve.
•Load curve decides the installed capacity of a power station.
• It is helpful in choosing the most economical sizes of the various generating units.
•The load curve estimates the generating cost.
•It decides the operating schedules of the power station, i.e., the sequence in which the
different generating units should run.

29. Definition: The load duration curve is defined as the curve between the load and time in
which the ordinates representing the load, plotted in the order of decreasing magnitude,
i.e., with the greatest load at the left, lesser loads towards the rights and the lowest loads
at the time extreme right. The load duration curve is shown in the figure below.
Load Duration Curve

30. This curve represents the same data as that of the load curve. The load duration curve is
constructed by selecting the maximum peak points and connecting them by a curve. The
load duration curve plotting for 24 hours of a day is called the daily load duration curve.
Similarly, the load duration curve plotted for a year is called the annual load curve.

31. Procedure for Plotting the Load Duration Curve
•From the data available from the load curve determines the maximum load and the
duration for which it occurs.
•Now take the next load and the total time during which this and the previous load
occurs.
•Plots the loads against the time during which it occurs.
•The load duration curves can be drawn for any duration of time, for example, a day or a
month or a year. The whole duration is taken as 100%.
Ex: Consider the daily load curve data of the power system

32. Time Load in MW
6.00 am to 8.00am 8
8.00 am to 1.00 noon 20
1.00 noon to 2.00
noon
5
2.00noon to 6.00 pm 30
6.00 pm to 6.00 am 8
Load in MW
Hours in a
day
Time in
percentage
30 4 4/5×100=16.
67%
20 4+5 9/24×100=3
7.5%
8 2+4+5+12
=23
23/24×100=
95.83%
5 4+5+2+12+1
= 24
24/24×100=
100%

33. information Available Form Load Duration Curve
The load duration curve gives the minimum load present throughout the specified
period.
It authorises the selection of base load and peak load power plants.
Any point on the load duration curve represents the total duration in hours for the
corresponding load and all loads of greater values.
The area under the load duration curve represents the energy associated with the
load duration curve.
The average demand during some specified time periods such as a day or a month
can be obtained from the load duration curve.