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Introduction

Electrical power generated in power stations reaches the end users through a large &

complex networks.

The power system networks comprise tranformers, overhead lines,cables & otherequipments to facilitate

the transfer of electricity to consumers. Hard fact about the supply of electric energy

is that the

units generated do not match with the units distributed to the consumers. Some

percentage of the units is always lost in the network. This difference in the generated

& distributed units is known as energy loss.

Losses can be divided:

A. Permanent technical losses:

corona,

leakage,

dielectric losses,

open-circuit losses,

losses caused by continuous load of measuring elements,

losses caused by continuous load of control elements.

B. Variable technical losses

joule losses in lines in each voltage level,

impedance losses,

losses caused by contact resistance,

joule losses in protection components.

Energy losses minimization

There are two directions, how to minimise losses.

Investments

o Higher voltage 110 V -> 230 V, 6 kV 22 kV,

o PF correction (compensation)

o Replace lines (higher diameter)o Replace old lines with new lines

o To use better materials in machines

o Power quality improvement

Without investments

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o Advisable distribution of reactive power

o Advisable load of lines

o Transformer group control to lower losses, replacement

o Network configuration

o Decrease peak power

o Balance networko Voltage control

o Service

But these days can be seen different approaches in energy losses minimisation:

- on-line energy measurement

- recloser usage

2.5 On-line measurement

This direction do not directly minimise technical losses, but offers possibilities of

costs and losses

minimisation, mainly service and illegal consumption. Usually, it consists of a tightly

integrated set of components that together provide the infrastructure to deliver

networked energy services to your utility. Intelligent, communicating digital

electricity meters; powerful IP-connected data concentrators; and scalable system

software form its elegant system architecture.

It is possible to upgrade system online without any personal. It offers advanced

metering functionality, this means, it is possible to decrease logistical expenses,

realize multiple utility services at minimal costs (at even no cost).

Recloser usage

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Distribution networks, mainly in villages and towns are usually radial. But, if this

radial network is transformed to ring type of network, it is necessary to maintain

reliability. Therefore, there can be used reclosers. The main function is to switch, but

also to switch off fault. Reliability is maintained, because a new network is protected

by this recloser and in a case of fault in line, only part of the supplying line will be

disconnected.Fig. 2. New network, closed network

And, there is another factor we have to consider, the losses minimisation. In this case

currents will change.

Therefore it is necessary to investigate energy losses change for this type of

reconfiguration.

Recloser 22 kV

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7% of the energy is lost in the network

The world average loss in the electric network system is 8.8%. However, this figure

includes countries like India and Brazil, where the losses are high due to so-called

non-technical losses electricity which could not be invoiced and is mainly lost via

illegal network connections.

How can network losses be reduced?

A few basic rules exist to minimise network losses. The first rule is to design the

network system in such a way that power lines to large consumers are as direct as

possible. The second basic rule is to reduce the number of transformation steps,

since transformers account for almost half of network losses. For the same reason,

high efficiency distribution transformers can make a large difference. Not all

losses are controllable and not every loss reduction is justifiable. The higher the loadon a power line, the higher its variable losses. It has been suggested that the optimal

average utilizations rate of distribution network cables should be as low as 30%

if the cost of losses is taken into account. A similar reasoning accounts for the cross-

section of lines and cables: the higher the cross-section, the lower the losses. An

optimum balance between investment cost and network losses should be aimed for.

2. Energy Losses Balance

The EEL are classified as two types;

Technical Losses

Defined as the "physical" losses corresponding to "Joule effect" or heat losses,

affected by the flow of the current in the ES equipment. (Transformers, transmission

lines, circuit breakers etc.). No-load losses - Corona and core transformer losses,

these are mainly a function of the line operating voltage. For a certain load level, the

higher the line voltage the lower the line losses.

Our own analysis indicates the following sources of losses:

Mains EHV 12%

Mains HV 16%

Mains LV 29%

Transformers - S stem17%

Transformers - HV/LV

15%

Other Engineering 3%

Non-technical 8%

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This shows that approximately 92% of losses are technical (fixed and variable) and

that approximately 8% are non-technical (measurement errors, unmetered supplies,etc).

Whilst it appears that the greatest scope for reducing losses is to reduce technical

losses, such an ambition would, as discussed above, require a major replacement of

distribution network assets. Bearing in mind that DNOs typically work on

approximately 1% of their networks each year, it would take decades to achieve a

significant impact on technical losses. Similarly, changes to design policies for

extensions to the network would take also decades to feed through as a noticeable

reduction in average losses.

Whilst our investment strategies include environmental drivers these generally relate

to visual amenity, noise and oil spillage protection measures (i.e. bunding). The

replacement of plant solely due to losses is not a key driver in our investment

programmed and efficient investment decisions could actually put upward pressure on

losses. However, losses are considered in the investment appraisal of the type of plant

we buy when weighed against the current incentives for loss reduction.

Technical Losses Reasons and Remedies

The major amount of losses in a power system is in primary and secondary

distribution lines; while transmission and sub-transmission lines account for onlyabout 30% of the total losses. Therefore the primary and secondary distribution

systems must be properly planned to ensure within acceptable limits.

The factors contributing to the increase in the lines losses in the primary and

secondary systems:

1. Lengthy Distribution lines:

In practice, 11 KV and 415 volts lines, in rural areas are hurriedly extended over long

distances to feed loads scattered over large areas. Thus the primary and secondary

distribution lines in rural areas; by and large radially laid, usually extend over longdistances. This results in high line resistance and therefore high 2R losses in the line.

2. Inadequate Size of Conductors:

As stated above, rural loads are usually scattered and generally fed by radial feeders.

The conductor size of these feeders should be adequate. The size of the conductors

should be selected on the basis of KVA X KM capacity of standard conductor for a

required voltage regulation.

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3. Distribution Transformers not located at Load center on the Secondary DistributionSystem:

Often DTs are not located centrally with respect to consumers. Consequently, the farthest

consumers obtain an extremity low voltage even though a reasonably good voltage levels

maintained at the transformers secondaries. This again leads to a higher line losses. (The

reason for the line losses increasing as a result of decreased voltage at the consumers

terminally are explained in para-5) Therefore in order to reduce the voltage drop in the

line to the farthest consumers, the distribution transformer should be located at the load

center to keep voltage drop within permissible limits.

6. Lower Power Factor:

In most LT distribution circuits, it is found that the PF ranges from 0.65 to 0.75. A

low PF contributes towards high distribution losses. For a given load, if the PF is low,

the current drawn in high. Consequently, the losses proportional to square of the

current will be more. Thus, line losses owing to the poor PF can be reduced by

improving the PF. This can be done by application of shunt capacitors.

Shunt capacitors can be connected in the following ways:

i) Shunt capacitors are connected on the secondary side (11 KV side) of the

33/11 KV power transformers.

ii). Line losses in LT distribution lines may also be considerably reduced by

installing shunt capacitors of optimum rating at vantage points.

The optimum rating of capacitor banks for a distribution system is 2/3 rd of the average

KVAR requirement of that distribution system. The vantage point is at 2/3rd the

length of the main distributor from the transformer.

iii) A more appropriate manner of improving this PF of the distribution system and

thereby reduce the line losses is to connect capacitors across the terminals of the

consumers having inductive loads. The extent of reduction of line losses in this

manner depends mainly on the extent to which the PF of consumers is

improved. In this case, the capacitor is connected in parallel to the terminals,

the capacitors being switched on and off together with the equipment itself.

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Many electricity supply authorities are modifying their tariff conditions to make it

compulsory for the consumers to provide capacitors for all types of installations

with connected loads of 5 HP and above.

By connecting the capacitors across individual loads, the line loss is reduced from 4-

9% depending upon the extent of PF improvement.

7. Bad Workmanship Resulting in Poor Contacts at Joints and Connections:

Bad Workmanship contributes significantly towards increasing distribution losses.

Efforts should, therefore, be made to have the best possible workmanship. In this

context

the following points should be borne in mind.

i) Joints are a source of power loss. Therefore the number of joints should be kept

to a minimum. Proper jointing techniques should be used to ensure firm

connections.

ii) Connections to the transformer bushing-stem, drop out fuse, isolator, and LT

switch etc. should be periodically inspected and proper pressure maintained to

avoid sparking and heating of contacts.

iii). Replacement of deteriorated wires and services should also be made timely to

avoid any cause of leaking and loss of power.

Conclusion:

From above paper, we studied the various types of technical as well as non-technical

losses in power system network and their effects on performance of system.Also; we

studied the remedies over it.