Microsoft Power Point - Distribution Planning Lecture 1 2010[1]

8/8/2019 Microsoft Power Point - Distribution Planning Lecture 1 2010[1]

1/13

OVERVIEW

MV AND LV DISTRIBUTION

PLANNING AND DESIGN


2/13

INTRODUCTION TO

DISTRIBUTION PLANNING ANDDESIGN It is estimated that about 70% of the population in

sub-Saharan Africa have no access to electricity New Connections and Rural Electrification Projects

are being done in the sub-continent by many utilities

in different ways

In Namibia Rural Electrification Master Plan is the

Policy Document by the Ministry of Mines andEnergy

The financial burden of electrification process is

huge and hence there is always a need to ensureReturn of Investment


3/13

A VIEW FROM THE HEAVENS! Extend of World Electrification- Night View


4/13

Engineering Planning and Design

The process of engineering planning and design isbased on models of the system and its responses.

These models are usually mathematical in nature and

are derived from data ,experience and scientifictheory.

In essence the physical criteria that need to be met inthe distribution design process are supplying

electrical power to the customers at a prescribed

standard of quality and at least cost. These requirements are generally conflicting in

nature and usually a balance has to be struck i.e an

optimum solution must be sought.


5/13

Distribution Design Criteria

The quality of supply is determined by the range of

the supply voltage at the customer's terminals under

all conditions of load. The design criteria is subject to physical limitations

within the network components such as:

The thermal capacity of conductors and

transformers

The Ohmic Voltage Drop in conductors( most

important in LV Distribution)

The level of the Supply Voltage available at the

input side of the network

The fault withstand capacity of the conductors


6/13

Distribution Design Approaches The objective of a distribution design process is the

lowest project Lifetime Cost (Initial Investment +

Running Cost). The cost of the ohmic losses in the feeders

contribute to the overall cost of the system.

Difficulty in achieving the objective in the design

process arises from uncertainties

How big is the load?How far along the feeder is the load?

How does the load change or vary?

How will the load vary over the expected lifetime

of the installed equipment?


7/13

Engineering Design ProcessEngineering Design is a process with well defined stages or steps

STEP 1: IDENTIFY THE PROBLEMe.g Design an overhead line to meet certain transferrequirements

STEP 2: RESEARCH ON THE PROBLEMe.g Literature Review, Load Forecasting and DesignSpecification

STEP 3: DEVELOP SOLUTIONS TO THE PROBLEM

e.g explore alternative designs or solutionsSTEP 4: SELECT THE BEST/OPTIMUM SOLUTIONe.g What is the project objectivity?

STEP 5: SIMULATE/CONSTRUCT A PROTOTYPESTEP 6: EVALUATE THE SOLUTION (PROTOTYPE)

STEP 7: REVIEW/SHARE THE SOLUTION

e.g Document the findingsSTEP 8: RE-DESIGN?e. Have the initial ob ectives been met?


8/13

Distribution Planning

Distribution Planning focuses on:

Loading of Equipment e,g Transformers andLines

Transfer Limits on lines not applicable

Voltage Levels (mainly Low voltage problemsas capacitive effects on lines and cables arenot that high)

Only AC systems

Planning Horizon :Variable but usually short-

medium term, usually 5-10 years.


9/13

3 Distribution Design Methods

There are 3 approaches that may be taken fordistribution system design,- each with someadvantages and disadvantages:

Apply Ohm's Law using an average loadwith empirical factors added to make

allowance for uncertainties.

(Deterministic Method)

Use a Simulation Technique to derive a large

set of possible results from which a decisionmay be taken.( Simulation Method)

Apply a statistical approach using either

probability or fuzzy set theory(Statistical Method)


10/13

DISTRIBUTION DESIGNMETHODS

INPUTS APPROACH TECHNIQUES MODEL

Certain Deterministic Algebraic Exact

Uncertai

Probabilistic

Statistical Probability Distribution Factors

Simulation Monte Carlo

Fuzzy Number

Triangular

TrapezoidalPossibilistic


11/13

Deterministic Method Traditional procedures for designing low voltage networks

In some cases and for a variety of reasons these methods

have proved to be inadequate

When all inputs can be specified with certainty thedeterministic approach can be used.

Input data in some cases may be precise. The DC

resistance of a feeder conductor of given length andoperating at a given temp can be specified with good

accuracy.

However the same may not be said for the expectedcombined load current of a group of customers from a

predicted community.

Although Ohm's Law is applied ,the precision of thecalculated voltage drop may be suspect due to the


12/13

Probabilistic Methods

These includes the use of Statistical methods

and/or Simulation methods. When one or more of the inputs are subject to

uncertainty the outputs are no longer exact.

The probabilistic approach is applicable when

sufficient sampled data regarding the parameter

with uncertainty is available. In such a case an analytical technique based on

statistical theory using probability distributions can

be used or simulation techniques such as MonteCarlo Method.


13/13

Possibilistic Methods

Due to uncertainty in one or more of the input

parameters to design calculation problem, theoutputs can no longer be exact.

If very little information is available for the

description of the uncertainty parameter, thepossibilistic method may be taken.

This involves the use of fuzzy number theory usingeither a triangular or trapezoidal model.

Documents

Microsoft Power Point - Distribution Planning Lecture 1 2010[1]