Ch1 Electric Power Systems

Ch.I Electric Power Systems1.1 Introduction

1.2 Smart Grids

1.3 Brief History of Turkish National Electric Power System

1.4 Power System Communications

Requirements

Communication media

Metallic Cable Pairs

Power Line Carriers

RF/Microwave Communications

Fiber Optic Cables

Satellite Communication Systems

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1.1 IntroductionElectrical energy is the most convenient form of energy from the point of

generation,

transformation,

transmission,

consumption,

control and

environmental aspects.

On the other hand, storage impossibilities of electric energy is the most important disadvantage of electrical energy. That is why, it requires an excellent balance between the generation and the consumption.

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1.1 IntroductionAn interconnected power system is a complex enterprise that may be subdivided into the following major subsystems:

Generation Subsystem

Transmission and Subtransmission Subsystem

Distribution Subsystem

Consumption (Load) Subsystem

In addition, there are auxiliary monitoring and control systems.

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1.1 Introduction

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1.1 Introduction-Generation Subsystem Generation subsystem includes generators and

transformers.

Bulk generation plants produce electrical energy from another form of energy such as fossil fuels, nuclear fuels or hydropower. Typically, a prime mover turns an alternator that generates voltage between 10 kV and 30 kV. The step-up transformer increases the voltage level so that to minimize the power losses.

There are also other means of electric power generation, such as renewables.

Generation policy depends on several technologic, social and politic aspects. Present trends indicate that most of the countries try to shift away from a dependence on the direct use of fossil fuels.

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1.1 Introduction-Transmission Subsystem They transport bulk power over long distances without

overheating or jeopardizing system stability.

Transmission voltage level depends on the size of the country and the amount of energy to be transported. Typical transmission voltage levels are in the range of AC 66 kV-765 kV and DC 750-1500 kV.

In turkey we use 154 kV and 380 kV transmission voltage levels. We also have 66 kV sub-transmission system and 220 kV tie-lines with

Transmission/sub-transmission lines terminate at switching stations. Power transformers and the switching equipment are the major components of a switching station.

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1.1 Introduction-Distribution Subsystem They deliver power from bulk power systems (switching

stations) to retail customers. To do this, distribution substations receive power from transmission/ subtransmission lines and step down voltages with power transformers.

In turkey we use 6 kV, 10 kV, 15 kV and 36 kV level for distribution systems. Cable systems and overhead lines are generally used for urban areas and rural areas, respectively.

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1.1 Introduction-Consumption SubsystemLoads are the last subsystems of the chain and are divided into

industrial,

commercial and

residential.

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1.1 Introduction

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1.1 Introduction-Control

Power System Control Involves:

Data Collection: Sensors, PMUs, etc.

Decision Making: Controllers

Actuators: Circuit Breakers, etc.

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1.1 Introduction-Vertical MonopolyIn the past, it was generally accepted that electric energy generation, transmission, and distribution required either public or regulated private ownership because the industry constituted a natural monopoly.

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Conventional Power System-Vertical

Monopoly

1.1 IntroductionLater, it has been recognized that the vertical monopolies were inefficient. The followings are seemed to be the most important drawbacks of vertical monopolies:

No incentive to operate efficiently

Costs are higher than they could be

No penalty for mistakes

Unnecessary investments

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1.1 IntroductionAfter 1980s that the perception of the electric power industry as a “natural vertical monopoly'' began to change, and competition in the industry was seriously entertained. There were three major reasons for this.

1. Economies of scale in generation began to point downward, i.e., smaller plants became more economically attractive. (distributed generation)

2. Public approval of government involvement in daily affairs began to decline, whether that involvement was as an industry owner and operator or only as a regulator. This public sentiment resulted in deregulation or privatization of seeral types of industries.

3. Spot pricing, by which electric energy could be supplied and purchased in a real time fashion at marginal costs, and those costs tracked at each network node.

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1.1 IntroductionCurrent industry structure generally requires separating the functions associated with selling and buying electric energy, the generation and distribution (or consumption), from transmission.

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1.2 Smart GridIt is obvious that the new power system can not be controlled in the real time with the existing hardware. All the components of the grid should be aware (communicate) of the status of other components. Therefore, traditional power system needed to be improved with communication and decision making facilities.

A smart grid is an improved power network having some monitoring, analysis, control, and communication capabilities. It can intelligently integrate the behavior and actions of all users connected to it - generators, consumers and those that do both – in order to efficiently deliver sustainable, economic and secure electricity supplies.

A Smart Grid involves Merging Two Infrastructures: Electrical Infrastructure and Intelligence Infrastructure.

Smart Grid = IT + Electric Grid15

1.2 Smart Grid-Traditional P.S. vs Smart Grid

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1.2 Smart Grid

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1.2 Smart Grid

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1.2 Smart Grid-Anticipated Benefits1. Improving Power Reliability and Quality

– Better monitoring using sensor networks and communications

– Better and faster balancing of supply and demand

2. Minimizing the Need to Construct Back-up (Peak Load) Power Plants

– Better demand side management

– The use of advanced metering infrastructures

3. Enhancing the capacity and efficiency of existing electric grid


– Consequently, better control and resource management in real-time

4. Improving Resilience to Disruption and Being Self-Healing


– Distributed grid management and control

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1.2 Smart Grid-Anticipated Benefits5. Expanding Deployment of Renewable and Distributed Energy Sources


– Consequently, better control and resource management in real-time

– Better demand side Management

– Better renewable energy forecasting models

– Providing the infrastructure / incentives

6. Automating maintenance and operation


– Distributed grid management and control

7. Reducing greenhouse gas emissions

– Supporting / encouraging the use of electric vehicles

– Renewable power generation with low carbon footprint

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1.2 Smart Grid-Anticipated Benefits8. Reducing oil consumption

– Supporting / encouraging the use of electric vehicles

– Renewable power generation with low carbon footprint

9. Enabling transition to plug-in electric vehicles

– Can also provide new storage opportunities

10. Increasing consumer choice

– The use of advanced metering infrastructures

– Home automation

– Energy smart appliances

– Better demand side Management

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1.2 Smart Grid- Priority Areas1. Demand Response and Consumer Energy Efficiency

2. Wide‐Area Situational Awareness

3. Energy Storage

4. Electric Transportation

5. Advanced Metering Infrastructure

6. Distribution Grid Management

7. Cyber Security

8. Network Communications

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1.2 Smart Grid- Communications

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Interactions across 7 Smart Grid Domains

1.2 Smart Grid- Communications

There are two questions to answer:

• How can different smart grid entities exchange messages (information)?

• What kind of messages (information) (and why) should they exchange?

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The first power generation in Turkey had been from a 2 kW dynamo connected to water-mill in Tarsus-MERSİN, in 1902.

In 1913, coal-fired Silahtarağa Power Plant (3*6 MW) was put into service.

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Operating the power industry under the leadership of State was started upon the establishment of Etibank in 1935.

Turkish Electricity Authority (TEK) was founded in1970 aiming at the rendering of generation, transmission, distribution and trade of electricity services needed by the country as per the general energy and economy policies of the State.

TEK was later (1990) split into two separate state economic enterprises namely:

Turkish Electricity Generation Transmission Co. (TEAŞ): Responsible from power generation, transmission, and

Turkish Electricity Distribution Co. (TEDAŞ) .

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Main tasks of “Program for Economic Stability and Fighting Against Inflation” implemented by the Government in 2001were;

Restructuring of the power sector,

Transition into a free electricity market ensuring free competition,

Setting up of separate companies for generation, transmission, wholesale and distribution of electricity and

Privatization of the all public entities other than that of transmission.

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TEAŞ has been restructured in three separate state economic enterprises

Electricity Generation Co. (EÜAŞ) partly privatized

Turkish Electricity Transmission Co. (TEİAŞ) and

Turkish Electricity Contracting and Trading Co. (TETAŞ)

Turkish Electricity Distribution Co. (TEDAŞ) partly privatized

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1.3 Brief History of Turkish National Electric Power System – Generation System

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0

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1990 1995 2000 2005 2010 2015 2020

GWhMW

Year

Peak Load [MW]

Installed Capacity [MW]

Consumed Energy [GWh]


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Installed Capacity and Annual Generation -2011

GENERATION INSTALLED CAPACITY

ANNUAL GENERATION

[MW] % [GWh] %LIGNITE 8274 15.6 39729 17.3COAL+ASPHALTIT 690 1.3 2992 1.3IMPORTED COAL 3881 7.3 20230 8.8NATURAL GAS 19024 36.0 108228 47.0GEOTHERMAL 114 0.2 605 0.3

FUEL OIL 1706 3.2 6957 3.0

DIESEL 26 0.0 112 0.0

NUCLEAR 0 0.0 0 0.0

OTHER THERMAL 215 0.4 1062 0.5

BIOGAS+WASTE 115 0.2 606 0.3

HYDRO 17137 32.4 45174 19.6

WIND 1729 3.3 4606 2.0

TOTAL 52911 100 230300 100


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GENERATION 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021

LIGNITE 15,6 14,7 14,2 13,4 12,8 12,9 12,5 11,9 11,8 11,6 11,4

COAL+ASPHALTIT 1,3 1,2 1,2 1,1 1,4 1,3 1,3 1,2 1,2 1,2 1,2

IMPORTED COAL 7,3 6,9 6,6 6,2 5,8 6,2 6,0 7,2 7,1 7,0 6,9

NATURAL GAS 36,0 35,9 35,2 35,3 34,6 33,1 31,9 30,6 30,1 29,7 29,3

GEOTHERMAL 0,2 0,2 0,3 0,3 0,3 0,3 0,3 0,3 0,2 0,2 0,2

FUEL OIL 3,2 2,5 2,4 2,2 2,1 1,9 1,9 1,8 1,8 1,7 1,7

DIESEL 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0

NUCLEAR 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 1,5 3,0 4,4

OTHER THERMAL 0,4 0,4 0,4 0,3 0,3 0,3 0,3 0,3 0,3 0,3 0,3

BIOGAS+WASTE 0,2 0,3 0,3 0,3 0,3 0,3 0,2 0,2 0,2 0,2 0,2

HYDRO 32,4 34,8 35,8 36,9 38,5 40,1 42,1 43,0 42,4 41,8 41,2

WIND 3,3 3,2 3,6 3,8 3,9 3,6 3,5 3,4 3,3 3,3 3,2

TOTAL 100 100 100 100 100 100 100 100 100 100 100

Installed Capacity [%]

1.3 Brief History of Turkish National Electric Power System – Transmission System

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Transmission system is the group of facilities starting from generation units to distribution network. Components of transmission system are:

• Transmission lines and cables

380 kV EHV transmission lines/cables

154 kV HV transmission lines/cables

220 kV Interconnection lines connecting Turkish system to Georgia, to Armenia, to Bulgaria and to Greece,

66 kV HV sub-transmission lines

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Transmission system is the group of facilities starting from generation units to distribution network. Components of transmission system are:

• Transmission Substations and Switching Centers

380/154 kV Autotransformers,

380 kV/ MV and 154/MV step down substations,

Serial and shunt capacitors.

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Turkish generation and transmission system is managed via 9 regional dispatching centers and coordinated by the National Dispatching Center.

Power system operation is controlled by SCADA2 and Energy Management System EMS3 software.

SCADA system includes 380 kV lines and power plants greater than 50 MW. System operator can manage every kind of system studies necessary for more quality, daily operating programs and system frequency control.

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Number of Transformers and Capacities [MW]

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YEAR 380 kV 154 kV < 66 kV TOTAL

Number Capacity Number Capacity Number Capacity Number Capacity

2002 111 18910 882 45447 62 777 1055 65134

2003 116 20110 893 46240 63 734 1072 67085

2004 121 21290 905 46917 63 734 1089 68942

2005 132 24240 899 46979 57 678 1088 71897

2006 151 28015 923 49385 56 662 1130 78062

2007 153 28715 963 52669 57 672 1173 82056

2008 174 33220 1010 55584 57 672 1241 89476

2009 184 35020 1034 58015 54 637 1272 93672

2010 197 37870 1067 61365 53 617 1317 99852

2011 203 39620 1105 64470 49 568 1357 104658


Transmission Line Lengths [km]

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YEAR 380 kV 220 kV 154 kV 66 kV TOTAL

2002 13625.5 84.5 28506.0 549.3 42765.3

2003 13958.1 84.5 30961.7 718.9 45723.2

2004 13970.4 84.5 31005.7 718.9 45779.5

2005 13976.9 84.5 31030.0 718.9 45810.3

2006 14307.3 84.5 31163.4 477.4 46032.6

2007 14338.4 84.5 31383.0 477.4 46283.3

2008 14420.4 84.5 31653.9 508.5 46667.3

2009 14622.9 84.5 31931.7 508.5 47147.6

2010 15559.2 84.5 32607.8 508.5 48760.0

2011 15978.4 84.5 32878.4 509.4 49450.7

Cables 35.9 184.0 3.2 223.1

1.3 Brief History of Turkish National Electric Power System – Distribution System

Distribution system is fed by Transmission system and it consumes the costumers. However, there are also distributed generation facilities.

Lengths of distibution lines as 2010 [km].

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TYPE 33 kV 15.8 kV 10.5 kV 6.3 kV Other TOTAL LV – 0.4 kV

Tr.Line 348281 26244 421 5094 0 380041 522928

Cable 27079 3853 3479 1391 90 35892 48784

Total 375359 30097 3900 6486 91 415933 571711

1.4 Power System Communications-Requirements

Two way communications between electric utilities and customers:

Reduce meter reading costs,

Provide easy access to the meter,

Enable load monitoring and demand side management.

Provide demand control,

Provide remote tariff management,

Provide dynamic Pricing

Enable tokenless pre-payment,

Enable remote meter setting

Provide outage detection and instant reporting,

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System topology for automatic meter reading


Home automation,

Power system relaying and signaling,

Distribution management,

Automatic generation control,

Energy management,

Automatic mapping/facilities, management,

Power system control,

Sub-station automation,

Rail-way signaling,

AMR

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1.4 Power System Communications-Communication Media

There are five basic alternatives.


Power Line Carriers (PLCs)

Radio Frequency/Microwave Communications

Fiber Optic Cables

Satellite Communications Systems

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1.4 Power System Communications-Communication Media - Metallic Cable Pairs


The most widely used communications media is metallic cables consisting of twisted pair conductors or coaxial cables.

They have involved little new technology, and one such a pair can be used for simplex and half-duplex transmission at a speed up to 2400 bps.

They can only be used for the applications requiring cables run under one mile (1.6 km), such as in sub-stations and power plants, for economic reasons.

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Coaxial Cable

Twisted cable


Advantages

No licensing requirement,

Existing pole structure can be used,

Economical for short distances

Relatively high channel capacity (up to 1.54 MHz) for short distances

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Disadvantages

Right-of-way clearance required for buried cable

Subject to breakage and water ingress

Subject to ground potential rise due to power faults and lightning strokes (Coaxial types are more immune)

Failures may be difficult to pinpoint

Inflexible network configuration

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1.4 Power System Communications-Communication Media - Power Line Carriers

Power Line Carrier (PLC) Communication, is an approach to utilize the existing power lines for the transmission of information. That is, PLC carries data on a conductor that is also used simultaneously for electric power transmission or electric power distribution to consumers.

On the other hand, in today’s world every house and building has properly installed electricity lines. By using the existing AC power lines as a medium to transfer the information, it becomes easy to connect the houses with a high speed network access point without installing new wirings.

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1.4 Power System Communications-Communication Media - Power Line Carrier

PLC has been used since 1950, mainly used by the grid stations to transmit information at high speed. Today this technology is finding wide use in building/home automation as it avoids the need of extra wiring. The data collected from different sensors is transmitted on these power lines thereby also reducing the maintenance cost of the additional wiring.

PLC technology can be deployed into different types of applications in order to provide economic networking solutions. Hence merging with other technologies it proves useful in different areas.

These are few key areas where PLC communications are utilized:

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a) Transmission & Distribution Network: PLC was first adopted in the electrical TD system to transmit information at a fast rate.

b) Home control and Automation: It can reduce the resources as well as efforts for activities like power management, energy conservation, etc.

c) Entertainment: PLC is used to distribute the multimedia content throughout the home.

d) Telecommunication: Data transmission for different types of communications like telephonic communication, audio, video communication can be made with the use of PLC technology.

e) Security Systems: In monitoring houses or businesses through surveillance cameras, PLC technology is far useful.

f) Automatic Meter Reading – AMR applications use the PLC technology to send the data from home meters to Host Central Station.

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A basic plc system consists of three parts:

The terminal assemblies (transmitters, receivers, associated components),

Coupling and tuning equipment,

Power system itself which must provide a suitable path for transmission of high frequency energy between the terminals.

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Operating principle:

A proper coupler device superimposes a high frequency signal (1.6 to 30 MHz) at low energy levels over the 50 Hz electrical signal.

This high frequency signal is transmitted over the power line

It is received (decoupled) and decoded remotely. Thus the PLC signal is received by any PLC receiver located on the same electrical network.

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Typical PLC communication through a transmission line

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Typical PLC communication through a transmission line

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Three classes of PLC Technologies:

Broadband (BB) - Narrowband (NB) - Ultra Narrowband (UNB)

1. Broadband (BB):

• Operating at 1.8 – 250 MHz.

• Data Rate: Up to 200 Mbps

• Initial Application: Residential Internet Access

• Short Communication Range (few kilometers)

• Good for AMI/AMR*, Not Good for sub‐stations (Q: Why?)

*AMR/AMI AUTOMATIC METER READING/ADVANCED METERING INFRASTRUCTURE

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2. Narrowband (NB):

• Operating at 3 – 500 kHz.

• Data Rate: Up to 500 kbps (usually several kbps)

• Considered for sub‐station communications

3. Ultra Narrowband (UNB):

• Operating at 30 Hz – 3 kHz.

• Data Rate: Up to 100 bps (very low, but good enough!)

• Communication Range: 150 km or more

• Current Applications: AMI, AMR, Demand Response (Direct Load Control)

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Advantages:

PLC can provide an extensive coverage, since the power lines are already installed almost everywhere. This is advantageous especially for substations in rural areas where there is usually no communication infrastructure.

The communication network can be established quickly and cost-effectively.

The utility has full control over communications.

No licensing is required.

It is suitable point to point communications.

PLC channel handles data rates up to 2400 bps using conventional modem.

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Disadvantages:

Carrier signal can be affected by external conditions.

Impedance changes occur dynamically, and these can seriously affect the PLC signal. Open circuit problem is the worst case.

PLC signals are affected by noise resulting from switching transients and lightning.

Attenuation and distortion of signals are immense due to the reasons such as physical topology of the power network and load impedance fluctuation over the power lines. In addition, there is significant signal attenuation at specific frequency bands due to wave reflection at the terminal points. Therefore, the communication over power lines might be lost due to high signal attenuation and distortion.

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Disadvantages:

There are some security concerns for PLC since power cables are not twisted and use no shielding which means power lines produce a fair amount of Electro Magnetic Interference (EMI). Such EMI can be received via radio receivers easily. Therefore, the proper encryption techniques must be used to prevent the interception of critical data by an unauthorized person.

Lack of regulations for broadband PLC: Fundamental regulation issues of PLC should be addressed for substantial progress to be made. The limits of transmitted energy and frequencies employed for PLC should be determined in order to both provide broadband PLC and prevent the interference with already established radio signals such as mobile communications, broadcasting channels and military communications. In this respect IEEE has developed a standard to support broadband communications over power.

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Disadvantages:

Suffers from lower capacity. Spectrum from 50 to 500 kHz inherently limits system expansion.

New technological advances have recently enabled a prototype communication modem which achieves a maximum total capacity of 45 Mbps in PLC. However, since power line is a shared medium, the average data rate per end user will be lower than the total capacity depending on coincident utilization, i.e., the number of users on the network at the same time and the applications they are using.

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1.4 Power System Communications-Communication Media – Radio

Frequency/Microwave CommunicationsRF has been used for more than 50 years for control and operation of power networks. Today power utilities use RF through the HF, VHF, UHF and EHF band for tele-metering, AMR, control and operations.

When compared to conventional wired communication networks, wireless communication technologies have potential benefits in order to remotely control and monitor substations, e.g., savings in cabling costs and rapid installation of the communication infrastructure. On the other hand, they are more susceptible to Electro Magnetic Interference (EMI) and often has limitations in bandwidth capacity and maximum distances among communication devices.

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1.4 Power System Communications-Communication Media - RF/Microwave

CommunicationsFurthermore, since radio waves in wireless communication spread in the air, they can be received by unauthorized people/organizations (eavesdropping) and it might be a threat for communication security.

Electric utilities exploring wireless communication options have two choices;

utilizing an existing communication infrastructure of a public network, e.g., public cellular networks or

installing a private wireless network.

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CommunicationsUtilizing an existing communication infrastructure of a public network might enable a cost-effective solution due to the savings in required initial investment for the communication infrastructure. However, there may be security problems.

On the other hand, private wireless networks enable electric utilities to have more control over their communication network. However, they require a significant installation investment as well as the maintenance cost.

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CommunicationsIn electric system automation, wireless communication technology has already been deployed. Recently, Short Message Service (SMS) functionality of the digital cellular network has been applied for remote control and monitoring of substations. The control channel of the cellular network is also utilized in some alarm-based substation monitoring cases.

However, both of these communication technologies are suited to the applications that send a small amount of data and thus, they can not provide the strict Quality of Service (QoS) requirements that real time substation monitoring applications demand.

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CommunicationsAdvantages

• Utilizing an existing (public) wireless communication network might enable a cost-effective solution.

• Rapid Installation: The installation of wireless communication is faster than that of wired networks.

• Improved reliability and reduction of downtime,

• A physical link is not required between TR and RF

• Provide up to 9600 bps data rates,

• Isolation from power systems switching effects.

• Provide bandwidth more than sufficient to meet the needs of an electric power networks.

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1.4 Power System Communications-Communication Media - Radio

Frequency/Microwave CommunicationsDisadvantages:

• Limited Coverage : Private wireless networks provide a limited coverage. On the other hand, utilizing existing public wireless network, e.g. cellular network, or WiMAX technology can support much more extensive coverage compared to wireless local area networks. However, some geographical areas, e.g., remote rural locations, may still not have any wireless communication services.

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• Capacity: Wireless communication technologies provide typically lower QoS compared to wired communication networks. Due to limitations and interference in radio transmission, a limited bandwidth capacity is supported and high bit error rates (BER =10-2 to 10-6) are observed in communication. In addition, since wireless communication is in a shared medium, the application average data rate per end user is lower than the total bandwidth capacity, e.g., maximum data rate of IEEE 802.11b is 11 Mbps while the average application data rate is approximately 6 Mbps.

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• Security: Wireless communication poses serious security challenges since the communication signals can be easily captured by nearby devices. Therefore, efficient authentication and encryption techniques should be applied in order to provide secure communication.

• Frequency allocation and license required.

• Equipment channel capacity is limited to one voice grade channel per licensed transmitter.

• Public concern for radiation from transmitter.

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1.4 Power System Communications-Communication Media - Fiber Optic Cable

Fiber-optic communication systems, which were first introduced in the 1960s, offer significant advantages over traditional copper-based wired communication systems.

They are one of the technically attractive communication infrastructures, providing extremely high data rates.

In addition, its Electro Magnetic Interference (EMI) and Radio Frequency Interference (RFI) immunity characteristics make it an ideal communication medium for high voltage operating environment in substations.

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Furthermore, fiber optic communication systems support long distance data communication with less number of repeaters compared to traditional wired networks. This leads to reduced infrastructure costs for long distance communication that substation monitoring and control applications demand. For example, the typical T-1 or coaxial communication system requires repeaters about every 2 km whereas optical fiber communication systems require repeaters about every 100-1000 km.

Although optical fiber networks have several technical advantages compared to other wired networks, the cost of the optical fiber itself is still expensive to install for electric utilities. However, the enormous bandwidth capacity of optical fiber makes it possible for substations to share the bandwidth capacity with other end users which significantly helps to recover the cost of the installation.

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In this respect, optical fiber communication systems might be cost-effective in the high speed communication network backbone since optical fibers are already widely deployed in communication network backbones and the cost is spread over a large number of users.

As a result, fiber optic networks can offer high performance and highly reliable communication when strict QoS substations communication requirements are taken into account.

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Fiber optic systems that are used for communications are made of: Transmitter, receiver, fiber optic conductor and repeaters.

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Presented By The Fiber Optic Association

©2004, The Fiber Optic Association, Inc.

Fiber Optic Cable

• Protects the fibers

wherever they are

installed

• May have 1 to over

1000 fibers

Presented By The Fiber Optic Association

©2004, The Fiber Optic Association, Inc.

Fiber Has More Capacity

This single fiber

can carry more

communications

than the giant

copper cable!


Advantages:

It has extremely high bandwidth capacity and can provide high performance communication for automation applications. Current FO transmission systems provide transmission rates up to 10 Gbps using single wavelength transmission and 40 Gbps to 1600 Gbps using wavelength division multiplexing (WDM). In addition, very low bit error rates (BER=10-15) in fiber optic communication are observed. Due to high bandwidth capacity and low BER characteristics, optical fiber is used as the physical layer of Gigabit and 10 Gigabit ethernet networks.

They don’t radiate significant energy and do not pick up interference from external sources. Thus, compared to electrical transmission, optical fibers are more secure from tapping and also immune to EMI/RFI interference and crosstalk.

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Advantages:

unaffected by lightning and electrical storms, immune to ground potential rises.

small physical size and flexibility,

no licensing required,

has long life expectancy in underground and underwater installations,

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Disadvantages:

repeaters may require very 15/30 kms, newly design fiber may only require a repeater once every 150 kms.

special connector required to align fibers,

TR and RC are required to convert electrical signals into light and back again.

Installation costs might be expensive in order to remotely control and monitor substations. However, fiber optic networks might be a cost-effective communication infrastructure for high speed communication network backbones, since optical fibers are already widely deployed in the communication network backbones and the cost is spread over a large number of users.

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1.4 Power System Communications-Communication Media - Satellite Communication

SystemsThe whole world from the busiest urban centers to the most remote islands, can be interconnected by satellite communications networks that are capable of providing economical and reliable transmission of communications signals, including voice, data and video.

The frequency used in satellite links are 4/6GHz, 12/14 GHz, and 20/30 GHz.

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1.4 Power System Communications-Communication Media - Satellite Communications

SystemsAdvantages:

Global Coverage: Satellite communication supports a wide geographical coverage (including remote, rural, urban and inaccessible areas) independent of the actual land distance between any pair of communicating entities. In case no communication infrastructure exists, especially for remote substations, satellite communication provides a cost-effective solution.

Rapid installation: Satellite communication offers clear advantages with respect to the installation of wired networks. A remote substation can join a satellite communication network by only acquiring the necessary technical equipment without the need for cabling to get high-speed service. Cabling is not a cost-effective nor a simple job when the substation is located in a remote place.

Large bandwidth more than the needs of an electrical power utility,

Short of a satellite failure.77


SystemsDisadvantages:

Delay in communication: The transport protocols developed for terrestrial communication links such as TCP are not suitable for satellite communication, since necessary data rate adjustments of TCP can take a long time in high delay networks such as satellite networks. On the other hand, it is possible to reduce the round-trip delay by using satellites in lower orbits.

Satellite channel characteristics: Different from cabled and terrestrial network communications, satellite channels characteristics vary depending on the weather conditions and the effect of fading, which can heavily degrade the performance of the whole satellite communication system.

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SystemsDisadvantages:

Placing a satellite in an orbit (35 000 kms above the earth) is costly. But this is not required for an electric power utility to enter into satellite communications.

Although satellite communication can be a cost effective solution for remote substations if any other communication infrastructure is not available, the cost for operating satellites (the infrastructure cost and monthly usage cost) for all substation communication networks is still higher than that of other possible communication options. High initial investment for satellite transceivers is one of the limitations of satellite communication.

Inherent channel delay which could not tolerated for some high speed applications, such as high speed protection.

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1.4 Power System Communications -Communication Media

As a result:

A variety of communications media is available in power system applications. Each communication technology/media has its own advantages and disadvantages that must be evaluated to determine the best communication technology for electric system communications. In order to avoid possible disruptions in electric power systems due to unexpected failures, a highly reliable, scalable, secure, robust and cost-effective communication network between substations and a remote control center is vital. The choice of the communication systems depends on:

Technical requirements of the application, Geographic considerations, Availability of established systems, Economics.

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RESULT

In order to convert the present traditional power system into a Smart Grid, a computer network is needed in parallel with the present electric power infrastructures.

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RESULT

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Ch1 Electric Power Systems

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Transcript of Ch1 Electric Power Systems