information and communication technologies in modern power systems

Otto-von-Guericke Universitt Magdeburg

Research project Masters

Information and communication technology in power system - technology reviewDate of submission:

20 March 2014

Student Name: Wasim M. H. Al-Ghafir

Student ID:

204971

Birth:

12.10.1989, Gaza/Palestine

Supervisors: M.Sc. Bartlomiej Arendarski

Dr.-Ing. Przemyslaw Komarnicki

Examiner: Prof. Dr.-Ing. Zbigniew A. Styczynski

Table of ContentsList of FiguresiList of Tablesii1. INTRODUCTION11.1 Power grid11.1.1 Electrical distribution in power systems12. COMMUNICATION INFRASTRCUTRE22.1 Conceptual reference model22.2 The use of communication technologies 33. COMMUNICATION CONCEPTS43.1 Data flow map43.2 Communication requirements63.3 Challenges of communication technologies74. WIRED ICT84.1 Power Line Communication (PLC)84.1.1 Narrowband PLC84.1.2 Broadband PLC94.1.3 Applications in the grid94.1.4 Standards114.2 Fiber optics Communication114.2.1 Applications in the grid114.2.2 Standards124.3 Digital Subscriber Line(xDSL)124.3.1 Applications in the grid134.3.2 Standards134.4 Conclusion135. WIRELESS ICT145.1 IEEE 802.11 (WLAN or WiFi)145.1.1 Applications in the grid155.1.2 Standards165.2 IEEE 802.16 (WiMAX)165.2.1 Applications in the grid175.2.2 Standards175.3 GSM/ GPRS175.3.1 Applications in the grid185.3.2 Standards185.4 IEEE 802.15.4 (Zigbee)185.4.1 Applications in the grid195.4.2 Standards195.5 Conclusion196. STANDARDS AND PROTOCOLS196.1 SCADA196.2 General standards216.2.1 IEC 61850236.2.2 IEC 61970246.3 Protocols246.3.1 TCP/IP256.3.2 Ethernet267. PRIORITIZATION OF COMMUNICATION DATA FLOW FOR DIFFERENT VOLTAGE LEVELS278. SUMMARY AND CONCLUSIONS329. REFERENCES35List of Figures

Figure 1.1: Grid structure1

Figure 2.2.1: Smart grid architecture3Figure 3.3.1: Substation architecture6Figure 4.1.3: Block diagram of PLC modem9Figure 4.2.1: Fiber optics communication system12Figure 6.1.1: SCADA architecture21Figure 6.2.1: IEC 61850 substation architecture23Figure 6.3.1: Operation of two IP hosts26Figure 7.1: Communication technologies distribution, units,

world markets29Figure 7.2: Different voltage level standards (today and future)31List of TablesTable 3.3.1: Flows of data5Table 5.1: IEEE 802.11 PHY15Table 5.3.1: Specifications of GSM/GPRS18Table 6.2.1: Overview of power grid standards22Table 6.3.1: TCP descriptions25Table 7.1: Penetration of communication technologies in power grid28Table 7.2: communication Technologies specifications in power grid301. Introduction

1.1 Power grid

An electrical grid is an interconnected network of used to deliver the electricity from the generation side to the consumption side as shown in Figure 1.1. The grid consists of generation stations that generate electricity at High Voltage (HV), sometimes it is needed to increase the voltage level to be connected to the grid, for that step up transformers are used then transmission lines deliver the power from one side to another side. The transmission network can transfer power to a long distance, sometimes across countries. The next stage is in the substation where step down transformers are used to step down the power from the transmission level to the distribution level voltage. In the final stage the power is sometimes further stepped-down from the distribution level to the required service level.

The power grid has been aging and some of its components can cause problems in the near future in the grid due to the deterioration of materials. Nowadays the demand for high quality electricity has increased over the past years.

Figure 1.1: Grid structure, [2]

1.1.1 Electrical distribution in power systemsThe distribution systems network is responsible for carrying the electricity from the transmission system and lowering the voltage level from Medium Voltage (MV) to Low Voltage (LV), to the costumer using step-down transformers. The distribution grid consists of transmission lines, transformers inside the substation and wiring, etc.

Todays electric power distribution network is very complex system and does not satisfy the needs of the modern life requirements, due to its problems such as; lack of automated analysis, poor visibility, mechanical switches causing slow response times, lack of situation awareness, etc[3]. Those problems caused blackouts, loss of electricity around the world, so the need of a new infrastructure has emerged, using the new knowledge and new technologies of the 21st century.

2. Communication infrastructure

In the last decades, the developments in computer and communication technologies have affected the power grid in both positive and negative way. The positive side can be summarized as: the increase the efficiency of the grid, more secure and reliable operation of the system. On the other hand, the negative side is summarized as: the grid can be more complex and needs to be monitored for faults which can affect the delivery of electricity to the consumer, and in some technologies the security can be an issue.Information and Communication Technologies (ICT) are the technologies used in manipulation, processing data and transferring it from one side to another using a medium of some sort.

1.2 Conceptual reference model

Different conceptual models and architectures have been proposed to implement the ICT in the grid as shown in Figure 2.2.1.In Figure 2.2.1 the smart grid architecture, where the communication infrastructure connecting all the components of the grid the modern grid does not only consider electricity lines, it also consider the communication lines which can be implemented into the transmission lines (e.g. Power Line Communication) or it can have separate lines. A high reliable and secure two end communication in the modern grid to solve the issues of the old power grid and delivers the modern consumers needs.

Figure 2.2.1: Smart grid architecture, [1]

1.3 The use of communication technologies

These are technologies used to communicate between two devices or more, in power grids, ICT are used for data transmission from the monitored device or element to the operator for diagnosis, monitoring, control and protection of the system, in a more reliable, secure, efficient environmental-friendly, safe and stable way. Also ICTs have made communication between markets possible which helped on the demand and supply process.3. Communication concepts

There are some requirements to be considered to implement ICT into the modern grid. In this section the requirements and the challenges of ICT will be discussed.

1.4 Data flow map

The data being transmitted by the communication technologies are categorized into four classes:

Raw data

Pre-processed data from substation as reports Historical dataThe raw data is collected by substations Supervisory Control And Data Acquisition (SCADA) at the substation, using the substations Intelligent Electronic Devices (IEDS) before sending to its centralized system. The raw data is not directly used in applications other than for archiving. Substation massage contains information about Circuit Breaker (CB) status, power flow measurements, alarms, relay operation reports, synchronized samples, real-time load and connectivity information. These reports generated by different applications and exchanged among various users in the control center..[4]

Table 3.3.1 shows the flow of data specifications (type, path, volume and class) and requirements for different paths in the substation.

If the requirements are met for different paths then the messages would be transmitted and received without errors.Table 3.3.1: Flows of data,[4]

NoDataFrom ToClassEstimated Data VolumeRequirements

1CB statusSubstationAlarm processing210kbReal-Time

2Over current AlarmSubstationAlarm processing210kbReal-Time

3Relay Operation ReportSubstationAlarm processing210kbReal-Time

4Power Flow DataSubstationFault Location2100kbReal-Time

5HistorianDatabaseFault Location4100kb-1MbOffline

6Event filesSubstationFault Location2100kbReal-Time

7System info.SubstationFault Location2100kbReal-Time

8RequestFault LocationDatabase--10kb--

9Synchronized SamplesSubstationCascading Analysis2100kbSynchronization

10Power Flow Data SubstationCascading Analysis2100kbReal-Time

11System Info.SubstationCascading Analysis2100kbReal-Time

12Event FilesSubstationCascading Analysis2100kbReal-Time

Figure 3.3.1 is a diagram of the communication paths. Arrows represent the direction of the data flow, and the numbers on the paths are consistent with the numbering of data in Table 3.3.1.[4]

Figure 3.3.1: Substation architecture, [4]

1.1 Communication requirements

The requirements of the technology used in the power grid, can be different from system to system and from technology to technology, the communication requirements include:

The amount of data to be transferred with this technology and how often and speed of transfer.

If it is needed to transfer the data synchronously or asynchronously

Whether the flow is uni- or bidirectional What level of security and error-control are needed The location of the application (receiver) on the communication infrastructureThe following is a general description of the requirements in various paths:

Substations and IEDs: Data must be in broadcast-subscription mode. Some requirements include the data rate of several Kbps to several Mbps, depending of the characteristics of the IEDs.

Control center and substation: data must be in point-to-point mode. Data rates up to several Mbps.

Among Applications: Data must be in point-to-point mode. Data rates of several Mbps up to Gbps to handle the large data flow.[4]1.2 Challenges of communication technologies

ICTs have many advantages; however there are some disadvantages and challenges which did not exist or was not consider important before or after using ICT in power grid.

ICT opened possibilities to security problems and cyber attacks; it can also increase the cost of the investment on the grid. Some of the challenges in the existing communication infrastructure are mentioned below:

Bandwidth

Most of the communication networks used in the modern power grid are low-bandwidth network technologies. If new data is needed to be collected, extra bandwidth would be needed for the extra large data size, so if the communication device cannot handle that, it would be needed to be replaced which is extra cost for the system.

Latency

Latency is decide by the transfer data and number of switches the data passes through while transferred, in some applications which intended to support the control and operation of the system, latency becomes the most important problem. The most important requirement comes from the cascading event detection, where the data should be transferred within few milliseconds.

Data compression

For the events that are stable without much change in the waveforms and measurement, data compression is used to help timely transfer of information and improve efficiency and reduce latency.

Congestion management

Under the condition of heavy traffic in the communication channel, the key problems in the congestion management are data classification and prioritized communication channel.[4]3. Wired ICT

In the following section, a review on the ICT that involve wires/cables in the transfer of data and their standards and applications will be presented.

1.3 Power Line Communication (PLC)

One of the oldest technologies used in the power grid. It involves introduction of a modulated carrier signal over the existing power line cables for two way communication. PLC is classified into two major types: Narrowband PLC and Broadband PLC.[5]

1.3.1 Narrowband PLCThis type of PLC has an operating frequency of 3-500 KHz. It is more suitable for sensing and communication purposes and low bandwidth applications.[5] Low data rate Narrowband PLC

The low data rate Narrowband PLC is a single carrier based technology, with data rate up to 10Kbps.

High data rate Narrowband PLC

The high data rate Narrowband PLC is a multi-carrier technology with data rate less than 1 Mbps.

1.3.2 Broadband PLC

The operating frequency range in this technology is 2-250 MHz with data rates up to hundreds Mbps, it is more suited for end-user and internet applications due to the high speed.1.3.3 Applications in the grid

Before discussing the possible applications of PLC in the power grid, the PLC modem that is used to connect the device to the power line should be discussed.

Figure 4.1.3 shows the concept of PLC modem and how it is connected to the transmission line.

Figure 4.1.3: Block diagram of PLC modem, [7]

Power Line Communication is one of the leading technologies for grid applications that need low frequency bandwidth communication (Narrowband PLC) such as smart metering, lighting control, solar, plug-in electrical vehicle, and security .[7]For these applications, PLC plays an advantageous role, in terms of bandwidth, power and cost needs. Developing an efficient PLC is not an easy task, consideration of some challenges should be taking into account due to the fact that power lines have inherently noisy channel, and require a robust design to ensure the reliability requirement, also every application is different and developers need to optimize the designs with variety of factors. Some of the key applications of Power Line Communication involve automation of the Medium Voltage (MV) grids and substations. The tasks involves here are location, isolation and fault restoration which need a low data rates for communication.[5]

The automatic/Advance Metering Infrastructure (AMI) is another application which requires relatively low data rates, so the Narrowband PLC is suited for this purpose. The advantage of using low data rate Narrowband PLC is that the low frequency signals pass easily through the MV/LV transformers as compared to the high frequency signals due to the inductive nature of the transformer [5]. This can be solved by the use of couplers but the cost will increase.

Another application is in plug-in electrical vehicle communication, SAE J23931TM specifies the communication protocols for vehicle charging applications.[8] A challenge in this application is temporal and spatial variation of the input impedance, adaptive impedance matching circuit is needed for such a design.

Some of the recent applications in MV distribution grids:

Monitoring: measurements on devices and network elements.

Operational services: remote control, emergency signals, security systems, messaging.

Network-management optimization: minimizing the effects of faults/network maintenance on the system.[9]

1.3.4 Standards

In this section, the standards which define and regulate the data flow in PLC technology will be discussed. Some of the standards are:

Low data rate Narrowband PLC: standards of IEC 14908-3 (Lon Works), IEC 14543-3-5 (KNX, BUS), CEA600.31 (CEBus), IEC 61334-3-1 (DLMS), IEC 61334-5-1.[5]

High data rate Narrowband PLC: standards and recommendation developed by IEEE 1901.2, ITU-T G.henm, PRIME and G3-PLC.[5]

Broadband PLC: The standards developed for this includes IEEE 1901, TIA1113, (HomePlug 1.0), ITU-T G.hn (G.9960/G.9961), HD-PLC [6].

1.4 Fiber optics communication

Fiber optics communication is a method of transmitting data from one place to another by sending pulses of light through an optical fiber[9]. At rates up to 400 Gbit/s, but typical 10 or 40 Gbps[10].The biggest advantage of fiber optics that, it is the most effective solution for transferring the data in a fast way and in a long distance communication with minimum power loss, also the nature of the dielectric in the fiber cables, make it nearly impossible to remotely detect the signal passing within the cable.

1.4.1 Applications in the grid

As mentioned before fiber optics has high data rates, so it can be implemented wherever a high bandwidth needed e.g. in transmissions voltage level, also it can be implemented instead of PLC technology, but it will cause an increase of cost due to the fact that fiber optics cables need to be bought and installed. Figure 4.2.1 shows the use of fiber optics cables in substation communication instead of power lines, as it is known the faster the data Is received to analyze, the faster the response would be, so using fiber optics for protection of devices would be the optimum application.

Figure 4.2.1: Fiber optics communication system.[11] The modern substation automation requires control of many devices within the network such as circuit breaks and switching relays.[11]

1.4.2 Standards

Standards of fiber optics communications will be presented in this section. ITU-T G.651.1 "Characteristics of a 50/125 m multimode graded index optical fiber cable.

ITU-T G.652, "Characteristics of a single-mode optical fiber cable. Also know as standard SMF (Single-Mode Fiber optics) is most common used standard for fiber optics communication.1.5 Digital Subscriber Line (xDSL)

Digital Subscriber Lines (DSLs) are high-speed digital data transmission technology that uses the twisted pairs wires of the voice telephone network.[1]

It can have frequencies higher than 1 MHz in ADSL (Asymmetric Digital Subscriber Line) enabled telephone line. xDSL refers to many types of DSL technologies such as ADSL(upload rate: up to 2 Mbps, download: up to 256 Kbps).etc. The latest technology is SHDSL (Standard for Single-Pair High-speed Digital Subscriber Line) which supports even higher than 4.6 Mbps over longer distances.

The existence of phone lines reduces the installation cost, but sometimes a contract between the consumer and the telephone company is needed to enable that service on the phone line. Another reason or advantage can be the widespread availability as nowadays almost every house has a telephone line, also the high bandwidth data transmissions. These reasons are the most important for making the DSL technology the first choice for electricity suppliers to implement smart meters. However, xDSL faces some challenges in terms of access line regulation, dependence on the customer and installation cost in rural areas.[12]1.5.1 Application in the grid

Compared to fiber optics, DSL technology has a lower installation cost and lower bandwidth.

Smart Metering Infrastructure: Compared to PLC, xDSL would have higher installation cost, because usually, the cables infrastructure will need another link (wired or wireless) to the smart meter which needs permission from the consumer.

Also xDSL is used instead of power line communication in the low frequency applications of PLC, but it depends on the region and the distance between the transmitting and receiving sides.[12]

1.5.2 Standards

Standards of xDSL will be presented in this section. These are a group of standards from different xDSL technologies, ITU G.992.x, where x is from 1 to 5 . Better known as G.dmt for ADSL1.1 Conclusion

To conclude, wired communication technologies, such as PLC, xDSL and fiber optics are costly for wide area deployments but they are used to increase the reliability, communication capacity, and security. So it is a trade off, between cost and reliability, capacity and security. On the other hand, wireless communication technologies can reduce the cost but provide lower bandwidth and security issues, which will be discussed in the following chapter.[1]5. Wireless ICT

5.1 IEEE 802.11 (WLAN or WiFi)

Wireless Local Area Network (WLAN) or Wi-Fi is the most famous among the other wireless standards; it was developed by Wi-Fi alliance under the IEEE 802.11 standards. The physical and Media Access Control (MAC) layers also were developed under the same standards. Most popular among these versions are IEEE 802.11b and 802.11g, the newest is IEEE 802.11n. Unlike the cellular and WiMAX networks, the 802.11 WLANs operate solely on unlicensed spectrum at 2.4 GHz and 5 GHz [13].

IEEE 802.11 standard defines a MAC layer and a physical layer. In the physical layer, the type of modulation, maximum indoor/outdoor range and operating frequency are defined. There are four types of physical layers that are widely in use: 802.11b 2.4 GHz, 802.11g 2.4 GHz, 802.11a 5 GHz and 802.11n (draft) 2.4 and 5 GHz PHY.[13]

The MAC layer provides:

Media access control via carrier sense multiple access/collision avoidance (CSMA/CA).

Prioritization for up to eight priorities.

Confidentiality and integrity via encryption and message digests;

Fragmentation and reassembly.[13]

IEEE 802.11n (draft) modifies the 802.11 standard to add support for packing of multiple upper layer protocol packets into a single IEEE 802.11 frame to improve throughput.[13]

Table 5.1 presents a summary of the different PHY specifications currently in use.

It comes to concern that using different modulation, the data rates changes and the throughput also.

Table 5.1 IEEE 802.11 PHY [Cisco Systems 2009a]

PHY

typeApproval

dateOperating

frequencyModulationTypical

throughputNet bit rateMax

indoorrange

(ft)Max

outdoorrange

(ft)

802.11b19992.4 GHzDSSS5-7 Mbps11

Mbps100300

802.11a19995 GHzOFDM25-14 Mbps54

Mbps50100

802.11g20032.4 GHzOFDM14 Mbps54

Mbps100300

802.11n20092.4/5 GHzOFDM with

MIMO100 Mbps150

Mbps300600

WiFi provides robust performance in a shared spectrum and noisy Radio Frequency (RF) channel environment. It also supports all Internet Protocol (IP) protocols, also wide range of data rates with point to point and point to multipoint communications. Security features for secure and authentic data communication are also implemented, making it strong network solution for grid applications.[5] However, the Interference, reliability and availability of industrial grade WLAN/WIFI equipment, and short coverage and short distances are major drawbacks of WLAN.

5.1.1 Application in the grid

Automatic Metering Infrastructure (AMI): Involve relaying information from the energy meters back to the utility central database. A scenario where there are many meters, this involves Neighborhood Area Network (NAN) which relays the information to the nearest collector station (access points) in their region.[5] Using that, WLAN reduced the operational costs by elimination the need of human readers.

Remote system monitoring and equipment fault diagnostics (remote sensing): In power systems nowadays, safety and reliability have become one of the most critical tasks. System breakdowns caused by component faults, environmental factors, could cause huge losses both in the economical and public concern.[14]Many of the system malfunctions can be avoided if the system is well-monitored and the elements are better coordinated. Wireless sensor is implemented for that case, to monitor elements of the system, such as voltage, current, generator rotational speed etc.

Wireless Supervisory Control And Data Acquisition (SCADA) technology: Many of the wireless SCADA systems operate in a broadcast mode where there is a point to multipoint communication between the devices on a particular channel, meaning that all devices can communicate with each other and any message sent can be received by all others on the channel.[13]5.1.2 Standards

The standards used to regulate the communication in WLAN are: IEEE 802.11a/g/n/b where (a/g/n/b) is the physical layer type.5.2 IEEE 802.16 (WiMAX)

Worldwide Interoperability for Microwave Access (WiMAX) is a wireless communication technology developed using the IEEE 802.16 standards for wireless broadband.[5]

IEEE 802.16 specifies the physical and MAC layers. The physical layer involves the signal modulation, Orthogonal Frequency-Division Multiple Access (OFDMA) with other features including Multi-Input-Multi-Output (MIMO) based on the antenna systems used in Non-line of Sight (NoS) capability.[5] On the other hand, MAC layer incorporates the power saving techniques such as sleep mode, idle mode, etc.

WiMAX is specifically designed for point-to-multipoint communications with data rates up to 70 Mbps and long distance up to 50km; it has two frequency bands, one for line-of-sight (11-66 GHz) and the other for non-line of-sight (2-11 GHz)[5].

WiMAX provides reliable back-end communication link (high data rates and point to multipoint capability), and low overall installation cost and large coverage area.

5.2.1 Application in the grid

Automatic Metering Infrastructure (AMI).

Video surveillance: In this case it is used for security reasons, due to the high data rates; it can be an advantage to use WiMAX to observe some critical elements in the system such as substations. Real-time communication link: used in case of real time protection of relays, and sending/receiving real time signals from the system operators for example.5.2.2 Standards

The standards family of WiMAX is: IEEE 802.16d/e/m where (d/e/m) are the physical layer type which changes the operating range and data rates.5.3 GSM/ GPRS

GSM (Global System for Mobile) is the most popular cellular network deployed all over the world. General Packet Radio Service (GPRS) employs packet based transfer of data over the circuit switched GSM network.[5]

GSM architecture consists of four components (mobile handset, base station subsystem, network switching substation and operation support substation). It is considered among the most secure communication networks used nowadays.

Among the reasons of using such technology are: GSM is mature Wide coverage, it is almost covering the whole world It has less deterioration of signal inside buildings Repeaters can be used to amplify the signalOn the other hand there are some limitations to GSM:

Quality of Service (QoS) is a serious problem in cases where absolute reliability of communication is required such as in substation protection, remote monitoring, etc. The utilities do not have direct control over the communication network; it is the job of the provider company to control that.[5]

It has low data rates as shown in Table 5.3.1 in the next section The amount of traffic on the service can affect the quality of the signal5.3.1 Application in the grid

Table 5.3.1 summarizes the specifications, applications and some of the limitations of GSM. Table 5.3.1 Specifications of GSM/GPRS.[5]

TechnologySpectrumData rateCoverage rangeApplicationsLimitations

GSM900-1800 MHzUp to 270 Kbps1-10 kmAMI, substation automation and protection, transmission line monitoring and protectionLow data rates

GPRS900-1800 MHzUp to 270 Kbps1-10 kmAMI, substation automation and protection, transmission line monitoring and protectionLow data rates

AMI: SIM (Subscriber Message Service) cards are embedded in the meters and the recorded data is relayed to the database via GPRS or SMS.[5]

Substation automation and protection purposes, it can also be used to monitor distributed energy resources as well.[5]

5.3.2 Standards

GSM standard developed by European Telecommunications Standards Institute (ETSI) which defines how the data should be formatted to be transmitted.5.4 IEEE 802.15.4 (Zigbee)

Zigbee is a wireless technology that has low power usage, data rates, complexity and cost that made it suited for low energy applications, such as automatic meter reading, energy monitoring, etc.

Zigbee has 16 channels of 5MHz each in the 2.4 GHz band. Data rates up to 250 Kb/s and range 30-50m. On the other hand, there are some constraints in the practical implementation, such as low processing capability, small memory size, small delay requirements, short range and being subject to interference with other appliances.[5]

5.4.1 Application in the grid

AMI: reading the meters. Monitoring energy consumption.5.4.2 Standards

The standard used to regulate and manage the data flow in Zigbee IEEE 802.15.4

5.5 Conclusion

In this chapter, various wireless communication technologies which are used in power grids were presented, their advantages/disadvantages and their applications in the grid. Wireless technologies have in common is that they reduce the installation cost, but provide constrained bandwidth and security issues which should be considered before using them in the power grid.

6. Standards and protocols

6.1 SCADASupervisory control and data acquisition (SCADA) system for a power distribution application is a PC-based software package.[24] Data is collected from the electrical distribution system which mostly originated at substations. A substation has varying numbers of controllers and operator interface points depending on the size and complexity of the data.[24]SCADA distinguished itself from other control systems by being a large-scale process that can include multiple sites, and large distances.[15]

Common system components:

Remote Terminal Units (RTUs) connect to sensors in the process and convert the sensor signal (analogue) to digital data. RTUs often have some embedded control capabilities to achieve the boolean logic operations.

Programmable Logic Controllers (PLCs) Connected to sensors in the process and convert the signal to digital data. PLC has more sophisticated control capabilities, and one or more programming language, than RTUs.

Telemetry systemIt is used to connect PLCs and RTU with the control center, it is the media used to transfer the data, it can be telephone lines or others networks.

Data acquisition server

It is the software service which uses the industrial protocols to establish a connection between the RTU and PLC to the control centers via the telemetry system. HumanMachine Interface(HMI)

It is the device that presents the processed data to the system operator, through it; the system operator can monitor and interact with the process.

Historian

It is the software responsible to process the data and create the visible graphs on the HMI through boolean events, and other algorithms and processing procedures.

Supervisory (computer) system

Collecting the data on the process and sending the control signals to the process.

Communication infrastructure: The communication technology used to connect the supervisory system to the RTUs.[15]In typical substation, one or more Programmable Controllers (PCs) are located at different control and monitoring points. The links between those PCs and the central PC is generally Ethernet-based that uses intranet.[23]SCADA does not only collect data, it also allow commands to be issued from central control and monitoring points to substations if desired situation allow that, such commands can enable a full remote control of the substation .[24]

Benefits of Implementing SCADA systems for electrical distribution:

Increases reliability

Eliminates the need for manual data collection

Fast detection of error by monitoring the system

Protecting the workers, by fast detection and addressing of the problem Detect future problems; provide better routine maintenance of equipment and spot areas for improvement

Various ways of viewing the data in Historian, which improve efficiency.[24]Figure 6.1.1 shows the main components of SCADA systems, the operator uses HMI to view the data and make the decision about problems.

Figure 6.1.1: SCADA architecture, [16]

6.2 General standards

In the following section, general standards of ICT will be presented as shown in Table 6.2.1, and some of the important standards will be discussed.In the previous chapters of ICT wired or wireless technologies, standards for specific technology were presented. In this section, standards for various ICT will be shown.These standards give the specifications and models of how the data should flow in the system and defines the cyber security for communication technologies. Table 6.2.1 shows the common standards nowadays, the applications of these standards and a short detail on what these standards are, respectively. Table 6.2.1: Overview of power grid standards.[1]

StandardDetailsApplication

IEC 61970/

IEC 61969Provides Common Information Model (CIM): IEC 61970 works in transmission domain and IEC 61969 works in distribution domain Energy Management Systems(EMS)

IEC 61850Flexible, future proofing, open standard, communication between devices in substation automation systems, transmission, and distributionSubstation automation

IEC 60870-6Data exchange between utility control centers, utilities power pools, regional control centersInter-control center communication

IEC 62351 part 1-8Defines cyber security for the communication protocolsInformation security systems

G3-PLCProvides interoperability, cyber security, and robustnessAMI

IEEE P1901High speed Power Line CommunicationsPLC applications: AMI

ITU-T G.9955/G.9956Contain the physical and data link layers specificationsDistribution automation, AMI

ISA100.11aOpen standard for wireless systemsIndustrial automation

ANI C12.19Flexible metering model for common data structures and industry vocabulary for meter data communicationsAMI

ANI C12.22Data network communications are supported and C12.19 Tables are transportedAMI

M-BUSEuropean standard and providing the requirements for remotely reading all kinds of utility metersAMI

SAE J2293Standard for the electrical energy transfer from electric utility to Electric Vehicles(EV)Electric Vehicle supply equipment

SAE J2836Supporting use cases for plug-in Electric Vehicles communicationElectric Vehicle

SAE J2847Supports communication messages between PEVs and grid componentsElectric Vehicle

6.2.1 IEC 61850A standard from the International Electro-technical Commission (IEC) that defines the communication between devices in transmission, distribution and substation automation systems.[1]

It defines the general and specific functional requirements for communication in substations. These requirements are used as forcing functions to help in the identification of the services and data models, application protocol, and the underlying transport, network, data link, and physical layers that will meet the overall requirements.[17]IEC 61850 is flexible, open standard, compatible with Common Information Model (CIM) used in monitoring, protection and control applications. IEC 61850 does not only specify the protocol elements (how the bytes are transmitted), it also provides a suitable model showing how to organize the data in power system devices in such a way that is consistent in all the devices in the manner of types and brands. This help in elimination of the tedious non-power system setting efforts.[23]Figure 6.2.1 shows an example of substations IEC 61850 architecture with the use of Ethernet.Figure 6.2.1: IEC 61850 substation architecture, [23]Ten parts of this standard are now International Standards. This standard addresses many of the digital worlds issues, especially, standardization of data names, creation of a comprehensive set of services, implementation over standard protocols and hardware, and definition of a process bus. Ongoing researches are discussing the utilization of IEC 61850 as substations control center communication protocol. Soon IEC 61850 will become the choice for network solutions in the substations and beyond.[23]

6.2.2 IEC 61970

IEC 61970 and IEC 61968 two standards, that provide what is called a Common Information Model (CIM), which is important for exchanging the data between networks and devices in the grid. IEC 61970 works in the transmission level and it deals with the application program interfaces for Energy Management Systems (EMS). It provides guidelines that facilitate.[18]:

The integration of application developed by different suppliers.

The exchange of information to systems external to the control center environment.

The provision of interfaces for data exchange across new systems.IEC 61970-301 represents the main part of this standard series and includes most of the objects required to model power networks. Also the IEC 61970 contains the Component Interface Specifications (CIS) which define how to combine the platform independent data models and the generic interfaces to be used with communication standards as well as the Generic Interface Definitions (GID) focusing on the status of exchanged data and its use compliant to CIM semantics. One of the main tasks of the CIM is to provide a platform independent data model. Mappings to specic technologies order, like Resource Description Framework (RDF), Extensible Markup Language (XML), and Web Ontology Language (OWL) are specified to make these models applicable.[25] 6.3 Protocols

Interoperability of ICT has improved by use of a functionally layered protocol in accordance with the internation ogranization for standardization (ISO) and other protocols such as TCP/IP, Ethernet.In this section, a review on the important protocols used to regulate the data flow in the communication technologies will be discussed.6.3.1 TCP/IP

The Transmission Control Protocol (TCP) is one of the bases protocols of the Internet Protocol suite (IP), and it is usual that the entire suite is called TCP/IP.[21] TCP/IP specifies how data should be formatted, addressed, transmitted, routed and received at the receiver side.[22]TCP/IP is organized into four abstraction layers which are used to organize related protocols according to the network. The layers from the lowest to the highest are:

Link layer: containing communication technologies for a single network segment (link) Internet layer: connecting independent networks, so it establishes internetworking Transport layer: handling process-to-process communication Application layer: interfaces to the user and provides support services.[22]Table 6.3.1 summarizes the descriptions of TCP. In respect of transmission speed, retransmission ability, and data interface to application.Table 6.3.1: TCP descriptions,[22]Description TCP

Transmission speed High

Retransmission Delivery of all data is managed, and the lost data is retransmitted automatically

Data interface to application Stream-basted, data is sent with no particular structure.

The layers near the top (i.e application layer) are logically closer to the user application, while bottom layers are closer to the physical transmission of the data.[21], the following Figure 6.3.1 shows the operation between two IP hosts and the layers of the protocol.

Figure6.3.1: Operation of two IP hosts, [22]

6.3.2 EthernetEthernet is one of the widely accepted standards nowadays. The main idea that two peers communicate by a cable not necessary in a direct cable bewteen them, peers communicate with a switch and the switch forward the message to the destination.

The Ethernet standards consist of several wiring and variables of the Operation System Interfaces (OSI) physical layer in use with Ethernet.

Industrial Ethernet is included in IEC 61850 and it has the following specifics:

100 mbps bandwidth.

Non-blocking switching technology.

Priority tagging for important messages.

Time synchronization.

Using Ethernet-based strategy in substation network has many advantages such as high capacity, flexibility to support more than one application at the same time even if the applications are different.

Figure 6.2.1 shows the substation architecture using Ethernet strategy. Virtual LAN allows the Ethernet switch to deliver datasets to only those switch ports/IEDs that have subscribed to the data.[23]7. Prioritization of communication data flow for different voltage levelsAfter making a review on the technologies used in modern power grid, the question comes to mind is which ICT solutions are used in different voltage levels (i.e. generation, distribution, transmission, and consumption levels) and reasons for one technology to be dominant in that voltage level. In this chapter a review on technologies used in different voltage levels and percentage use of technologies around the world will be discussed. Table 7.1 summarize the communication technologies used and solution that can be developed, also it reveals the applications and current status of these technologies for different voltage levels.

In generation: GSM/GPRS has penetration for the communication there. Other communication technologies find it hard to penetrate that level of voltage. Due to robust nature of GSM based solutions. Also WiFi and WiMAX based communication solution, have good potential to be developed for this domain.

In transmission and distribution: PLC based communication solutions have more penetration for information sharing. Those solutions are quite mature and could be consider among the oldest solutions. After PLC, GSM/GPRS is the second most penetrative technology in this voltage level and it poses a competition to the PLC based solutions especially in the substation applications (automation, protection, monitoring, etc.). Also Zigbee based solutions are being developed which will give it a strong competition among the other technologies in those applications. Fiber optics used where high speed communication needed to monitor and protect transmission lines.Table 7.1: Penetration of communication technologies in power grid.[5]ICTGenerationTransmissionDistributionConsumption

Conventional generationDistributed renewable energy based generationTransmission line monitoring & protectionInsulator monitoringFACTs monitoring & controlSubstation automation & protectionDistribution line monitoring & protectionEquipment monitoring & protectionHome automation & controlIndustrial automation & controlAutomatic Metering ReadingPHEVs

PLC??

Fiber optics????

Zigbee???

WLAN ???

WiMAX ???????

GSM & GPRS

: In use, some mature solutions available.: On-going research, some solution available but under testing.?: Not currently in use, solution can be developed.In consumption: GSM/GPRS has the most penetration in this area, due to the high amount of research done on using this technology. PLC is the other mostly common used technology for Automatic Metering Infrastructure (AMI). Also Zigbee and WiFi are the other competitors in this domain, but currently, the amount of researches being done on Zigbee is much more than on WiFi.Figure 7.1 shows the percentage of each ICT used in power grids. It is noticed that the Narrowband PLC technology is the dominant; also IEEE 802.15.4(Zigbee) has a good situation now due to its advantages, and low power applications as mentioned before.

Figure 7.1: Communication Technologies distribution, units, world markets,[19]

Table 7.2 shows the specifications of ICT such as operating range (spectrum), data rates, coverage range, applications and limitation in power grids.

It is noticed that in sense of data rates the fiber optics is the highest technology, but due to the cost, it is not very used where the cost is an issue but it has mature solutions in transmission lines monitoring and protections. PLC and WiMAX are the dominants in sense of data rates, but their limitations should be considered while making the network. Zigbee is used for AMI which is low power application and does not need much data rates, also GSM/GPRS used in AMI but it has lower data rates than Zigbee but it is more widespread than GSM/GPRS.Table 7.2: Communication technologies specifications in power grid.[5],[1]TechnologySpectrumData rateCoverage rangeApplicationsLimitations

GSM /GPRS900-1800 MHz Up to 270 Kbps 1-10 km AMI, demand response, Low data rates

WiMAX 2.5 GHz, 3.5 GHz,

5.8 GHz Up to 70 Mbps 10-50 Km(LOS)

1-5 Km (NLOS) AMI, demand response Not widespread

PLC 1-30 MHz 2-3 Mbps 1-3 Km AMI, fraud detection Harsh, noisy channel/enviro-nment

Zigbee 2.4 GHz, 868 -915 MHz 300 Kbps 30-50 m AMI, HAN Low data rate, Short range

Fiber Optics 500-1000 MHz Up to 400 Gbps Up to 240 Km Sensors, AMI Costly, require regular maintenance

Figure 7.2 shows the various protocols for different voltage levels. In the same voltage level there are various technologies which communicate with the system operator using different protocols, respectively. Communication between different voltage levels uses different protocol than the technologies in these voltage levels which will generate more complexity in the system.Figure 7.2: Different voltage level standards (today and future)Due to the increase of complexity of the grid, researches are made to unify the standards and protocols in all voltage levels which will improve the operation of the system with the respect of monitoring, protection, and control.Unification of standards and protocols can help system operators at a voltage level to detect any fault or monitor the system at a different voltage level, due to the fact that the technologies have the same standards in all voltage levels, and simply connecting the sensors 8. Summary and conclusions

A review on used Communication Technologies and their applications in the power grid and some concepts related to it such as standards and protocols was presented in this research report.

In the first three chapters, an introduction about the power grid, the advantages and reasons of implementing communication technologies in power grids communication, communication infrastructure, requirements and challenges of the technologies used nowadays in power grids around the world was discussed.

In chapter four, a review on wired Information and Communication Technologies (ICT) was presented i.e., technologies such as: Power Line Communication (PLC), Fiber optics, Digital Subscriber Line (xDSL). The most famous one is Narrowband-PLC which is used for low frequency applications and fiber optics used where a very high data rates needed, e.g., in real-time communication for substation protection or in transmission lines protection and monitoring. DSL technology also is used for low frequency application, but sometimes the cost is higher than PLC system, e.g., in AMI another link (wired or wireless) should be established for the smart meter to be connected to the data collecting station, which needs permission from the consumer. In conclusion the wired communication technologies are costly compared to the wireless technologies but offer a higher capacity of data transfer solution with a more reliable system.In the fifth chapter, a review on wireless ICT, their advantages, applications and limitations was presented. The dominant of the wireless technologies for the low power applications is Zigbee, also WLAN and WiMAX are used in urban areas or where the physical connection is not possible or costly. GSM/GPRS is used for low data rates applications such as AMI and substation automation and protection purposes. In conclusion, the wireless ICTs are mainly cheaper than wired ICT but they offer limited bandwidth and security issues which did not exist before using them.In the sixth chapter, a summary on the standards and protocols used in managing the data flow in the ICT of the power grid was presented. SCADA is one of the important control and data acquisition systems especially in distribution grids. It increases the system reliability, eliminates the need for manual data collection, and detects future problems etc. Also there are some other standards which were developed for ICT networks. These standards give the specifications and models of how the data should flow in the system and defines the cyber security for communication technologies.

The important standards such as IEC 61850 and IEC 61970 were shortly discussed. IEC 61850 defines the general and specific requirements for communication in substations, also it provides a suitable model showing how organizing the data in power system devices in a consistent manner. IEC 62970 provides a Common Information Model (CIM) which is important for exchanging the data between networks. It helps the integration of application developed by different suppliers in the power system, also the exchange of information to external systems.In the seventh chapter, various ICT solutions for different voltage levels were discussed and pointing out the dominant of these technologies in different voltage levels. In generation, GSM/GPRS is the dominant ICT due to the robust nature of that technology. In transmission and distribution, PLC is dominant and GSM/GPRS is competing to be dominant. Zigbee based solutions are being developed and it could be a competitor in the future. In consumption, GSM/GRPS has the most penetration in this level. Also the percentage of different ICT use was shown in Figure 7.1, it is noticed that Narrowband PLC is dominant now and in the future around the world also Zigbee has a good percentage due to the huge amount of researches to use it in power grids.In conclusion, for a more reliable and secure system is required; the use of hybrid network of various ICT would be a suitable solution more than the use of a single ICT network. Taking one technologys advantages and trying to suppress the limitations of that technology using another technology. The future research would deliver a more efficient solution, also a new concept has emerged smart grid (a smart grid is a modernized electrical grid that uses ICT to gather and process information to improve the efficiency, reliability, and sustainability of the production one of its tasks is to unify the standards and protocols in all voltage levels among many other tasks.In the near future, the solutions of existing technologies will be developed so the limitations of those technologies would be suppressed in a hybrid network or in different manner. If fiber optics solutions become cheaper, due to decrease in manufacturing cost, it would be a more suitable solution than PLC and it will take over PLC applications. The fast development in communication technologies will help the power grid to be more reliable and secure against cyber attacks such as data mining.9. References

[1] Smart Grid Technologies: Communication Technologies and Standards, Vehbi C. Gngr, D. Sahin, T. Kocak, S. Ergt,C. Buccella, C. Cecati and G. Hancke, IEEE.

[2] United States Department of Energy SVG User: J JMesserly Avalible: http://en.wikipedia.org/wiki/Electric_power_distribution.

[3] U.S. Department of Energy, 2011.[Online]. Available: www.oe.energy.gov

[4] Communication Requirements and integration options for smart grid deployment, Pow. Sys. Eng. Research Center, PSERC publication 12-03.

[5] Evolution of Communication Technologies for smart grid applications, by A. Usman, S. Shami.

[6] Power line communications and the smart grid. In: First IEEE international conference on smart grid communications (SmartGridComm). by Galli S, Scaglione A, Wang Z. IEEE; 2010. p. 3038.

[7] http://www.ti.com/solution/power_line_communication_modem.[8] Shaver D. Narrowband PLC solutions for AMI achieve long distance communications and exibility with immediate market impact. In: IEEE international conference on consumer electronics (ICCE). IEEE; 2011. p. 601602.19.

[9] Application of Narrowband Power-Line Communication in Medium-Voltage

Smart Distribution Grids, by T. A. Papadopoulos, C. Kaloudas, A. Chrysochos. IEEE 2013.

[10] http://en.wikipedia.org/wiki/Fiber-optic_communication.[11] Solution for smart grid automation, by firecomms.[12] Communication technologies and networks for Smart Grid and Smart Metering by CDG 450 Connectivity Special Interest Group (450 SIG) September 2013.

[13] A Survey of Wireless Communications for the Electric Power System by BA. Akyol, H. Kirkham, SL. Clements, MD Hadley Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830

[14] Application of Wireless Sensor Networks in Smart Grid ~Opportunities, Challenges & Technologies Available (A Survey) ,by P. Ghune, R. N. Ghune, P. Pandey & P. Mishra..[15] http://en.wikipedia.org/wiki/SCADA.html

[16] http://relaymagazine.org/the-importance-of-technology-integration-for-public-power-systems/

[17] IEC 61850 Communication Networks and Systems In Substations, by M. Adamiak , D. Baigent,GE Digital Energy and R. Mackiewicz,SISCO.

[18] http://www.iec.ch/smartgrid/standards/

[19] http://newenergynews.blogspot.de/2010/10/where-and-how-and-when-smart-grid-is.html

[20] Information and communications for smart grid by G. Ramalho, J.de Carvalho Filho, P. Marcio, P. Ribeir

[21] Vinton G. Cerf, Robert E. Kahn, (May 1974). "A Protocol for Packet Network Intercommunication". IEEE Transactions on Communications 22 (5): 637648.[22] Requirements for Internet Hosts Communication Layers, R. Braden (ed.), October 1989.[23] Technical Overview and Benefits of the IEC 61850 Standard for Substation Automation by R. Mackiewicz SISCO, Inc. and S. Heights, MI .[24] SCADA Systems Automate Electrical Distribution by Indusoft. Available : www.indusoft.com/Portals/0/PDF/White-Papers/Whitepaper_SCADA%20Systems

%20Automate%20Electrical%20Distribution.pdf[25] ICT and Energy Supply: IEC 6190/61968 Common Information Model by M. Specht and S. Rohjans .Available: www. link.springer.com/content/pdf/10.1007%2F978-3-642-34916-4_6.pdf