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Phasor Measurement Unit in Wide Aera Control

A Phasor Measurement Unit is a device which measures both sinusoidal and non sinusoidal waveforms on the electrical network grid using a common time source for synchronization. The above Time synchronization allows synchronized real-time measurements of multiple remote measurement points on the network grid and the measurement is called as Sycnchrophasor.[1]

Figure 1- Block diagram PMUs

The first digital PMU version was developed at Virginia Tech. later Macrodyne designed and built commercial unit. Currently there are more than 40 North American utilities that have PMU installed for analysis of power system problems .[2]

The main funding for the early development came from US Department of Energy, US Electric Power Research Institute, and the US National Science Foundation.[3]

The need for synchronized sampling first appeared in the design of protection systems: data samples were used in different substations far apart. This work resulted in the invention, at Virginia Tech, of the symmetrical component distance relay. [4]

After this groundwork, the first idea of a PMU was introduced in 1988. The work had then its first industrial application at Macrodyne Co.[4]

The important stages in the development of PMU are:

 Invention of Symmetrical Component Distance Relay (SCDR)

 Synchronization of Sampling Clocks

Development of the prototype PMU

 Commercial PMU.

 Field Installations.

 Applications Research.

Synchrophasor application [5]

Classification of synchrophasor application  

Situational awareness

Reliability coordinators

 1-Situational awareness

 2-State estimation

 3-Email notification

 4-Frequency  stability/islanding

Analysis / A ssessment Planners .

1- Baselining .

2-Post-event analysis . 3-Model calibration and validation .

4- New applications test & evaluation

Monitoring / alarming Operators .

1-Real-time monitoring 2-Real-time visualization .

3- Real-time alerts and alarms .

4- Event detection, disturbance location.

Advanced applications Researchers .

1-Emergency control .

2-Wide-area control system .

3- Special protection scheme

4- Remedial action scheme.

 Table 1- History of PMUs[6]

PMU  standard development

1980 First introduce in Virginia Tech

1988 First PMU prototype Invented at Virginia Tech

1992 First commercial PMU

1995 First Synchrophasor  Standard :IEEE1344

2001 Updated IEEE1344

2003 Big boost US blackout

2005 Standard updated :

- IEEE C37.118.1- Measurment specifications

- IEEE C37.118.2-Communications specifications

2011 IEEE C37.118.1'

2012 Synchrophasor Conformity Assessment Steering Committee (SCASC)

2014 IEEE C37.118.1a'  Contributed to:

 ' TSS certification program .

' PDC standard development .

' Draft for mapping C37.118.2 data to 61850.

 Phasor Data Concentrator (PDC)

A Phasor Data Concentrator (PDC) is a PMU data collecting device that synchronizes the measurements taken at every time instant independent of when the data was received . Similar to the PMU, the PDC time needs to be synchronized. PMUs phasor information in form of data stream is transmitted either via dedicated lines between specified locations, or over a switched link that is established for the purpose of the communication to PDCs. The phasor information is also sent to additional PDCs connected to other power utilities. PDC can also receive data from other PDCs.[7]

WIDE AREA MONITORING SYSTEM (WAMS)

A measurement system that incorporates PMUs deployed over large portions of the power system is known as Wide Area Monitoring System (WAMS). The effective utilization of these technologies is very useful for improving power system reliability and power quality.

 The basic components of WAMS are as follows:

1) PMUs.

 2) PDCs .

3) Super PDC.

 4) Communication networks.

 The PMU is an intelligent measuring device to address many power quality problems around the world. PMUs are becoming an integral part in many power system applications from load flow analysis and state estimation to analyzing blackout causes. It is used to measure the voltage and current waveform that is synchronized with a clocking signal obtained continuously from the Global Positioning System (GPS) as per the synchrophasor standards.[7]

Figure 2 WAMS Architecture

Phasor measurment unit in the world :

B. France

 The development of a coordinated scheme was carried out based on centralized comparison of the voltage angles of the system obtained from PMUs.

 C. Scandinavia

There is a great potential for PMU applications in Scandinavia. Smart control based on Phasor measurement can be used as an alternative to adding new transmission lines by increasing power transmission capacity.

D. China

The China State Grid will have about more than 250 PMUs installed. Researchers in China are putting more emphasis in improving systems security and reliability using PMU.

E. Other Countries

 It has been reported that have installed and integrated PMU for research to develop working prototypes for wide area monitoring and control: Japan, Switzerland, 4 units; Cortia, 2 units; Greece, 2 units; Mexico, more than 4 units and South Africa, 2 units.

 F. Existing Phasor Measurement Units in India

The PMU pilot project in Northern Region, India consists of PMUs along with GPS installed at Selected 4 substations of the NR Grid. The system provides phase angle difference, along with phase voltage magnitudes, power flow, frequency and rate of change of frequency. VI. CONCLUSION GPS based phasor technology provides high speed (sub second) coherent data that are not available with traditional SCADA measurements in order to monitor power system dynamics. With the growing interest in phasor technology (PMUs) throughout the world, it is clear that these systems will be implemented in most major Electrical networks.}

Comparision between SCADA and GPS Based Phasor Technology.

Phasor Measurment

Existing synchrophasor installations

INDIA

{The Indian power system is growing at an accelerated pace. The grid is divided into five electrical regions. With large generation addition taking place and a continuous expanding grid, the grid is spreading geographically(Applications of PMU measurements in the Belgian electrical grid)}

Phasor measurment unit PMUs in the world :

1. North America

In the eastern part of the United States, the Eastern Interconnection Phasor Project (EIPP). In 2007, both efforts (EIPP and RTDMS) have been combined in the North American Synchrophasor Initiative (NASPI) that also covers Canada and Mexico. This technology has been used for postdisturbance data analysis and early warning systems, and has improved system models for faster system restoration. More than 200 PMUs have been installed across North America.[8]

With the 2009 funding of 13 synchrophasor projects under the American Reinvestment and Recovery Act, the North American electric industry added over 800 new phasor measurement units and numerous synchrophasor data communications networks into the power grid. Today there are over 1,000 PMUs installed across North America, and many local and regional phasor data concentrators collecting real-time, high-speed, timesynchronized information about grid conditions to enhance grid operations and protect grid reliability.[9]

Figure 2 ' Data Flows from Transmission Owners to Regional Data Hubs and Between RCs.[9]

2. Brazil

 Phasor  measurement applications in Brazil were started in the early 1990s by the Study Committee of the Interconnected Operation Coordination Group (GCOI), prior to the deregulation of the Brazil energy sector.

Since late 2000, the Brazilian independent system operator ONS has launched two WAMS-related projects aiming to implement a large-scale synchronized phasor measurement system (SPMS) for both offline and realtime applications:

- Deployment of a Phasor Recording System: The main goal of this project is to specify and deploy a SPMS to record SIN system dynamics during longduration wide-area disturbances, envisioning the most probable future real-time applications.

- Application of Phasor Measurement Data for RealTime System Operation Decision Making: The main goal of this project is to extend the initial  SPMS for control center real-time applications, such as phasor visualization, modal frequency alarming, and state estimator improvement for supporting system dispatcher real-time decisions.[8]

Fig 3- Brazilian National Interconnected Power System (SIN).[8]

PMU  standard development In Brazilian

1998 ONS was created and started

1999 Operate  NIPS in January Two months later,blackout occurred and revived the interest in PMU application.

2000 ONS prepared a first PMU

2005 Establishing the framework, under which the responsibilities and tasks for ONS and utilities in implementing a synchronized phasor measurement system (SPMS) are clearly defined

2007-2009 ONS  has launched two PMU

Table 2- PMU standard development In Brazilian. [10]

3. Europe

2.1. France - Scheme against loss of synchronism

G. Michel. Wide-area protection and emergency control. Proceedings

of the IEEE, 2005.)

2.2. Switzerland

Swiss grid has developed a power oscillation monitoring (POM) system which is capable of detecting one of the two major oscillation modes in the UCTE power grid [W. Sattinger, R. Baumann, and P. Rothermann. A new dimen-

sion in grid monitoring. Transmission and Distribution, 2007.]. The most visible mode is the east-west mode which causes active power swings in the east-west direction. This mode is detected by comparing the frequency between Switzerland and Greece. The second mode causes the north-south interarea oscillation, which is monitored on the tie-line from Switzerland to Italy. Online measurements areexchanged between some countries for monitoring oscillations: Austria, Croatia Greece, Italy, Slovenia and Switzerland.

As the power transfer load through the Swiss transmission system is equivalent in magnitude to the system load itself, corridor monitoring is a very important task. This is achieved by making synchronized phasor measurements to measure the phase difference across the corridor. So the system loading and the complete topology can be monitored base on these two measurements only.( Applications of PMU measurements in the Belgian electrical grid)

2.3 Croatia(HEP-TSO Schweitzer Engineering Laboratory. Synchrophasor

applications in the croatian power system. Technical report, SEL, 2009.)

3. Scandinavia

4. Russia

5. Brazil

6. China

7. India()

(SYNCHRONIZED MEASUREMENTS AND APPLICATIONS DURING POWER SYSTEM DYNAMICS)

References:

[1] E. S. Percis, 'Wide Area Monitoring , Protection and Control ( Wampac ) Application in Transmission Grid ' a Literature Review,' pp. 1119'1128, 2016.

[2] J. D. La Ree et al., 'Synchronized Phasor Measurement Applications in Power Systems,' vol. 1, no. 1, pp. 20'27, 2010.

[3] A. G. Phadke, 'Synchronized phasor measurements a historical overview -,' pp. 476'479, 2002.

[4] 'phasor measurment unit and wide area montroing.' .

[5] C. Huang et al., 'Data quality issues for synchrophasor applications Part I: a review,' J. Mod. Power Syst. Clean Energy, vol. 4, no. 3, pp. 342'352, 2016.

[6] R. De Vries, 'Phasor Measurement Units ( PMUs ) and Time Synchronization,' no. January, 2013.

[7] S. Kumar, M. K. Soni, and D. K. Jain, 'Monitoring of Wide Area Power System Network with Phasor Data Concentrator (PDC),' Int. J. Inf. Eng. Electron. Bus., vol. 7, no. 5, pp. 20'26, 2015.

[8] A. G. Phadke, 'The wide world of wide-area measurement,' IEEE Power Energy Mag., vol. 6, no. 5, pp. 52'65, 2008.

[9] North American SynchroPhasor Initiative, 'PMUs and synchrophasor data flows in North America,' Smartgrid.Gov, pp. 1'5, 2014.

[10] R. Moraes and H. Volskis, 'Challenges for Large-Scale PMU Application for the Brazilian Interconnected Power System,' Monit. Power Syst., no. April, pp. 1'8, 2008.

Figure 4  WAMS Architecture

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