Electrical Power Substations

7/27/2019 Electrical Power Substations

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Contents1.0 INTRODUCTION ..............................................................................................................2

2.0 ELECTRICAL POWER SUBSTATIONS ..................................... 5

Transmission substation ....................................................................... 6

Distribution substation ......................................................................... 6

Collector substation ............................................................................. 6

Converter substations ........................................................................... 6

Switching substation ............................................................................ 6

3.0 DISCUSSION ............................................................................ 12

4.0 CONCLUSION.....11

5.0 REFERENCES..........12


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1.0 INTRODUCTION

1.1WHAT IS SUBSTATION?A substation is a part of an electrical generation, transmission and disrtibution system.

Substations transform voltage from high to low, or the reverse, or perform any of several

other important functions. Between the generating station and consumer, electric power mayflow through several substations at different voltage levels.

Substations may be owned and operated by an electrical utility, or may be owned by a large

industrial or commercial customer. Generally substations are unattended, relying

on SCADA for remote supervision and control.

A substation may include transfomer to change voltage levels between high transmission

voltages and lower distribution voltages, or at the interconnection of two different

transmission voltages. The word substation comes from the days before the distribution

system became a grid. As central generation stations became larger, smaller generating plants

were converted to distribution stations, receiving their energy supply from a larger plant

instead of using their own generators. The first substations were connected to only one powerstation, where the generators were housed, and were subsidiaries of that power station.

Substations are installations in a Transmission and Distribution System which are involved in

the connection of different sections of the transmission and distribution system, usually with

the transfer of electrical power from one voltage level to another. Substations play a vital role

in integrating the generating, transmitting and distributing parts of an electrical system.

A substation is generally located in an open area. The substation contains of numerous

equipments such as transformers, breakers, capacitors, measuring and protection devices and

so on.

Substations may be described by their voltage class, their applications within the power

system, the method used to insulate most connections, and by the style and materials of the

structures used. These categories are not disjointed, to solve a particular problem, a

transmission substation may include significant distribution functions, for example.

There are several type of substations which is Trasmision Substation, Distribution

Substation, Collector Substation, Converter Substation, Switching Substation and others.

Substations are classified based on the service, location, function and type of apparatus they

use.


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1.2ELEMENT OF SUBSTATIONSubstations generally have switching, protection and control equipment, and transformers. In

a large substation,circuit breakers are used to interrupt any short circuits or overload currents

that may occur on the network. Smaller distribution stations may use recloser circuit breaker

or fuses for protection of distribution circuits. Substations themselves do not usually havegenerators, although a power plan may have a substation nearby. Other devices such as

capacitors and voltage regulators may also be located at a substation.

Substations may be on the surface in fenced enclosures, underground, or located in special-

purpose buildings. High-rise buildings may have several indoor substations. Indoor

substations are usually found in urban areas to reduce the noise from the transformers, for

reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.

Where a substation has a metallic fence, it must be properly grounded to protect people from

high voltages that may occur during a fault in the network. Earth faults at a substation can

cause a ground potential rise. Currents flowing in the Earth's surface during a fault can cause

metal objects to have a significantly different voltage than the ground under a person's feet,this touch potential presents a hazard of electrocution.

Figure 1.2.1 : Element of Substation

Based on figure above:

1.Primary power lines

2.Ground wire

3.Overhead lines

4.Transformer for measurement of electric voltage

5.Disconnect switch

6.Circuit breaker

7.Current transformer

8.Lightning arrester

9.Main transformer

10.Control building

11.Security fence

12.Secondary power lines


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1.3 OBJECTIVES

Upon completion of this assignment, the student will be able to do the following:

1. To describe the functions performed by various substations.2.

To expose the students to the actual substations functions.3. To enhance and supplement the knowledge and skills of the students.

4. To develop the students in term of ability, competence, and interpersonalrelationship.

5. To generate knowledge, expose and familiarize the students to the type ofsubstations.

6. To develop the spirit of teamwork among the students and other working groupmembers.


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2.0 ELECTRICAL POWER SUBSTATIONS

Substations form an important part of the electricity network, providing power to you

every time a light switch or appliance is turned on. Substations 'step' or 'convert' power voltage

up or down so that electricity can be delivered from power generators or very high voltages

through to your home, workplace and community which has very low voltages.In a state that is

continuing to develop and grow there is an increasing demand to provide electricity across the

power network. As homes continue to use more and more power, and industry, communities and

businesses continue to grow, more substations will be required.

An Electrical Power Substation receives electric power from generating station via

transmission lines and delivers power via the outgoing transmission lines. Substations are

integral parts of a power system and form important links between the generating stations,

transmission systems, distribution systems and the load points. Various power substations

located in generating stations, transmission and distribution systems have similar layout and

similar electrical components. Electrical power substation basically consists of number of

incoming circuit connections and number of outgoing circuit connections connected to the

busbars. Busbars are conducting bars to which number of circuit connections is connected. Each

circuit has certain number of electrical components such as circuit breakers, Isolators, earth

switches, current transformers, voltage transformers, and other.

In a Power Substation there are various indoor and outdoor switchgear and equipment.

Transformers are necessary in a substation for stepping up and stepping down of a.c voltage.

Besides the transformers, the several other equipment include busbars, circuit breakers, isolators,

surge arresters, Substation Earthing System, Shunt reactors, Shunt Capacitors etc . Each

equipment has certain functional requirement. The equipment are either indoor or outdoor

depending upon the voltage rating and local conditions.

In a large power System large number of Generating stations, Electrical Power

Substations and load centers are interconnected. This large internetwork is controlled from load

dispatch center. Digital and voice signals are transmitted over the transmission lines via the

Power substations. The substations are interlinked with the load control centers via Power Line

Carrier Systems (PLCC). Modern Power System is controlled with the help of several automatic,


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semi - automatic equipment. Digital Computers and microprocessors are installed in the control

rooms of large substations, generating stations and load control centers for data collection, data

monitoring, automatic protection and control.

2.1 DIFFERENCES BETWEEN SUBSTATIONS

Substations may be described by their voltage class, their applications within the power

system, the method used to insulate most connections, and by the style and materials of the

structures used. These categories are not disjointed; to solve a particular problem, a transmission

substation may include significant distribution functions, for example.

Transmission

substation

Distribution

substation

Collector

substation

Converter

substations

Switching

substation

connects two ormore

transmission

lines

can range from

simple to

complex

transfers powerfrom the

transmission

system to thedistribution

system of an area

at least two

transmission orsubtransmission

lines

resembles adistribution

substation

although powerflow is in the

opposite

direction

Collectorsubstations also

exist wheremultiple thermal

or hydroelectric

power plants ofcomparable

output power are

in proximity

contain powerelectronic

devices to

change thefrequency of

current

a substationwithout

transformers and

operating only ata single voltage

level

commonly

located directlyadjacent to or

nearby a powerstation


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2.1.1 Transmission SubstationA transmission substation connects two or more transmission lines. The simplest case is

where all transmission lines have the same voltage. In such cases, substation contains high-

voltage switches that allow lines to be connected or isolated for fault clearance or maintenance.

A transmission station may havetransformers to convert between two transmission

voltages,voltage control/power factor correction devices such as capacitors, reactors orstatic

VAR compensators and equipment such asphase shifting transformers to control power flow

between two adjacent power systems.

Transmission substations can range from simple to complex. A small "switching station"

may be little more than abusplus somecircuit breakers.The largest transmission substations can

cover a large area with multiple voltage levels, many circuit breakers and a large amount of

protection and control equipment such as voltage and

currenttransformers,relays andSCADA systems. Modern substations may be implemented

using international standards such asIEC Standard 61850.

Figure 2.1.1(1)

Figure 2.1.1(2)

Figure 2.1.1(1) and Figure 2.1.1(2) show the example of transmission substation
http://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Voltage_compensationhttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Static_VAR_compensatorhttp://en.wikipedia.org/wiki/Static_VAR_compensatorhttp://en.wikipedia.org/wiki/Quadrature_boosterhttp://en.wikipedia.org/wiki/Busbarhttp://en.wikipedia.org/wiki/Circuit_breaker#High-voltage_circuit_breakershttp://en.wikipedia.org/wiki/Transformer#Instrument_transformershttp://en.wikipedia.org/wiki/Digital_protective_relayhttp://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/IEC61850http://en.wikipedia.org/wiki/IEC61850http://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/Digital_protective_relayhttp://en.wikipedia.org/wiki/Transformer#Instrument_transformershttp://en.wikipedia.org/wiki/Circuit_breaker#High-voltage_circuit_breakershttp://en.wikipedia.org/wiki/Busbarhttp://en.wikipedia.org/wiki/Quadrature_boosterhttp://en.wikipedia.org/wiki/Static_VAR_compensatorhttp://en.wikipedia.org/wiki/Static_VAR_compensatorhttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Voltage_compensationhttp://en.wikipedia.org/wiki/Transformer


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2.1.2 Distributor SubstationA distribution substation transfers power from the transmission system to the distribution

system of an area. It is uneconomical to directly connect electricity consumers to the main

transmission network, unless they use large amounts of power, so the distribution station reduces

voltage to a level suitable for local distribution.

The input for a distribution substation is typically at least two transmission or

subtransmission lines. Input voltage may be, for example, 115 kV, or whatever is common in the

area. The output is a number of feeders. Distribution voltages are typically medium voltage,

between 2.4 kV and 33 kV depending on the size of the area served and the practices of the local

utility. The feeders run along streets overhead or underground, in some cases and power the

distribution transformers at or near the customer premises.

In addition to transforming voltage, distribution substations also isolate faults in either

the transmission or distribution systems. Distribution substations are typically the points

ofvoltage regulation, although on long distribution circuits of several kilometer, voltage

regulation equipment may also be installed along the line.

The downtown areas of large cities feature complicated distribution substations, with

high-voltage switching, and switching and backup systems on the low-voltage side. More typical

distribution substations have a switch, one transformer, and minimal facilities on the low-voltage

side.

Figure 2.1.2

Figure 2.1.2 shows the distribution substation in electrical power station
http://en.wikipedia.org/wiki/Voltage_regulationhttp://en.wikipedia.org/wiki/Voltage_regulation


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2.1.3 Collector SubstationIndistributed generationprojects such as awind farm,a collector substation may be required.

It resembles a distribution substation although power flow is in the opposite direction, from

manywind turbines up into the transmission grid. Usually for economy of construction the

collector system operates around 35 kV, and the collector substation steps up voltage to a

transmission voltage for the grid. The collector substation can also providepower factor

correction if it is needed, metering and control of the wind farm. In some special cases a

collector substation can also contain an HVDC converter station.

Collector substations also exist where multiple thermal or hydroelectric power plants of

comparable output power are in proximity. Examples for such substations areBrauweiler in

Germany andHradec in the Czech Republic, where power is collected from nearby lignite-fired

power plants. If no transformers are required for increase of voltage to transmission level, the

substation is a switching station.

Figure 2.1.3 (1)

Figure 2.1.3 (2)

Figure 2.1.3(1) and Figure 2.1.3(2) show the example of collector transmission
http://en.wikipedia.org/wiki/Distributed_generationhttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Brauweilerhttp://en.wikipedia.org/wiki/Hradec_substationhttp://en.wikipedia.org/wiki/Hradec_substationhttp://en.wikipedia.org/wiki/Brauweilerhttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Distributed_generation


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2.1.4 Converter SubstationSubstations may be associated withHVDC converter plants,traction current, or

interconnected non-synchronous networks. These stations contain power electronic devices to

change the frequency of current, or else convert from alternating to direct current or the reverse.

Formerlyrotary converters changed frequency to interconnect two systems; such substations

today are rare.

Figure 2.1.4 shows the converter station is located between transmission line
http://en.wikipedia.org/wiki/High-voltage_direct_currenthttp://en.wikipedia.org/wiki/Traction_currenthttp://en.wikipedia.org/wiki/Rotary_converterhttp://en.wikipedia.org/wiki/Rotary_converterhttp://en.wikipedia.org/wiki/Traction_currenthttp://en.wikipedia.org/wiki/High-voltage_direct_current


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2.1.5 Switching SubstationA switching substation is a substation without transformers and operating only at a single

voltage level. Switching substations are sometimes used as collector and distribution stations.

Sometimes they are used for switching the current to back-up lines or for parallelizing circuits in

case of failure. An example is the switching stations for theHVDC IngaShaba transmission

line.

A switching substation may also be known as a switchyard, and these are commonly located

directly adjacent to or nearby apower station.In this case the generators from the power station

supply their power into the yard onto the Generator Bus on one side of the yard, and the

transmission lines take their power from a Feeder Bus on the other side of the yard.

Figure 2.1.5

Figure 2.1.5 shows the example of switching substation in electrical power station
http://en.wikipedia.org/wiki/Inga%E2%80%93Shabahttp://en.wikipedia.org/wiki/Inga%E2%80%93Shabahttp://en.wikipedia.org/wiki/Inga%E2%80%93Shabahttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Power_stationhttp://en.wikipedia.org/wiki/Inga%E2%80%93Shaba


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3.0 DISCUSSION

Substations take the electricity from power plants and from the transmission lines and

transform it from high to lower voltage. They distribute electricity to consumers and superviseand protect the distribution network to keep it working safely and efficiently and continuously.

Other than that, the function of substations are to supply of electricity power within specified

voltage limits and frequent limits, shortest possible fault duration, and to supply electrical energy

to the consumer at the lower cost. Electrical lines can be overhead or underground. The

construction of overhead lines costs less, but outages are more common than on underground

lines due to bad weather, lightning strikes or accidents.

4.0 CONCLUSION

As a conclusions, an electrical power substation receives electric power from generating

station via transmission lines and delivers power via the outgoing transmission lines. Substations

are integral parts of a power system and form important links between the generating stations,

transmission systems, distribution systems and the load points.


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5.0 REFERENCES

http://www.electrotechnik.net/2009/10/substation-introduction-and-types.html http://my.safaribooksonline.com/book/electrical-engineering/9789332503410/13-

substations

http://www.ustudy.in/node/6350 http://en.wikipedia.org/wiki/Electrical_substation http://en.wikipedia.org/wiki/File:Electrical_substation_model_(side-view).PNG

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Electrical Power Substations