SYSTEM-WIDE disturbances in power systems are a challenging

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1 270 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010 A Novel Back Up Wide Area Protection Technique for Power Transmission Grids Using Phasor Measurement Unit M. M. Eissa, Senior Member, IEEE, M. Elshahat Masoud, and M. Magdy Mohamed Elanwar Abstract Current differential protection relays are widely applied to the protection of electrical plant due to their simplicity, sensitivity and stability for internal and external faults. The proposed idea has the feature of unit protection relays to protect large power transmission grids based on phasor measurement units. The principle of the protection scheme depends on comparing positive sequence voltage magnitudes at each bus during fault conditions inside a system protection center to detect the nearest bus to the fault. Then the absolute differences of positive sequence current angles are compared for all lines connecting to this bus to detect the faulted line. The new technique depends on synchronized phasor measuring technology with high speed communication system and time transfer GPS system. The simulation of the interconnecting system is applied on 500 kv Egyptian network using Matlab Simulink. The new technique can successfully distinguish between internal and external faults for interconnected lines. The new protection scheme works as unit protection system for long transmission lines. The time of fault detection is estimated by 5 msec for all fault conditions and the relay is evaluated as a back up relay based on the communication speed for data transferring. Index Terms Digital protection, discreet Fourier transform, (GPS) system, synchronized phasor measurement, time synchronization. I. INTRODUCTION SYSTEM-WIDE disturbances in power systems are a challenging problem for the utility industry because of the large scale and the complexity of the power system. When a major power system disturbance occurs the protection and control actions are required to stop the power system degradation, restore the system to a normal state, and minimize the impact of the disturbance [1]. The present control actions are not designed for a fast developing disturbance and may be too slow. Further, dynamic simulation software is applicable only for off-line analysis. The recent enlargement and increased complexity of power system configurations has led to adjacent arrangements of short and long distance power transmission lines, both connected to Manuscript received May 20, First published December 11, 2009; current version published December 23, Paper no. TPWRD M. M. Eissa was with the Faculty of Engineering, Electrical Engineering Department, Helwan University, Cairo 11795, Egypt. He is now with King Abdul- Aziz University, Jeddah 21415, Saudi Arabia ( mmmeissa@yahoo.com). M. E. Masoud and M. M. M. Elanwar are with the Faculty of Engineering, Power Department, Helwan University at Helwan, Cairo 11795, Egypt. Color versions of one or more of the figures in this paper are available online at Digital Object Identifier /TPWRD the same busbar in a substation [2]. This causes difficult situations when relay engineers coordinate reach or operate time among distance relays. To cope with this, current differential protection which utilizes wide-area current data would be effective for wide-area backup protection although such protection needs system-wide timing synchronism for the simultaneous current sampling at all remote terminals and data exchanges among them. In this area, an adaptive Phasor Measurement Unit (PMU) based protection scheme for both transposed and un-transposed parallel transmission lines is given [3]. The development of the scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of eigenvalue/eigenvector theory to decouple the mutual coupling effects between parallel lines, the fault detection and location indexes are derived. A fault detection/location technique with consideration of arcing fault discrimination based on phasor measurement units for extremely high voltage/ultra-high voltage transmission lines is presented in [4]. The proposed arcing fault discriminator can discriminate between arcing and permanent faults within four cycles after fault inception. Some techniques presented fault location algorithm based on phasor measurement units for series compensated lines [5]. A new wide area differential protection (WADP) system is proposed to suit the need of the shipboard application [6]. The close proximity of all the components in a shipboard power system makes communication less of an issue than in a landbased system. With an overall view of the protected system and by use of a differential search algorithm, a minimum fault isolation area is decided. A very few papers are published for applications of wide area on transmission lines protection. Most of the published papers are used for determining the fault location on the transmission lines. The suggested paper provides a new technique for wide area protection using PMU. This paper introduces protection scheme depending on comparing positive sequence voltage magnitudes for specified areas and positive sequence current phase difference angles for each interconnected line between two areas on the network. The paper will cover all fault events. The technique uses the time synchronized phasor measurements. This provides a dynamic view of the power system. The measurements are processed in a system protection central (SPC). This capability is used to set up a wide area control, protection and optimizing the platform by means of new fast communication system and (GPS) /$ IEEE

2 EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT 271 Fig. 1. Three zones of operation for each stand alone relay. Fig. 2. The new protected zones of the proposed relay. II. CONVENTIONAL PROBLEMS The distance relays which are widely applied in the protection today and involve the determination of impedance achieve operating times of the order of a period of the power system frequency. A distance relay is designed to only operate for faults occurring between the relay location and the selected reach point, and remains stable for all faults outside this region or zone [7]. The resistance of the fault arc takes the fault impedance outside the relay s tripping characteristic and, hence, it does not detect this condition. Alternatively, it is only picked up either by zone 2 or zone 3 in which case tripping will be unacceptably delayed [8]. The distance relays are based on stand alone decision, while each relay operates independently according to three different zone of operation, see Fig. 1. The mal-operation or fail-to trip of protection is determined as one of the origins to raise and propagate major power system disturbances [9]. A vast majority of relay mal-operations is unwanted trips and have been shown to propagate major disturbances. Backup protections in fault clearance system have the task to operate only when the primary protection fails to operate or when the primary protection is temporarily out of service. The recent complexity and enlargement of power systems makes it difficult to coordinate operation times and reaches among relays. In the areas of power system automation and substation automation, there are two different trends: centralization and decentralization. More and more dynamic functions are moving from local and regional control centers toward central or national control centers. At the same time we also observe more intelligence and decision power moving closer towards the actual power system substations. Greater functional integration is being enclosed in substation hardware. In view of global security of power systems, the action algorithms of conventional backup protections possibly are not best choices because the operations of individual relays are hardly coordinated each other. Therefore, the principle of the protection design needs innovation to overcome the above problem. Modern protection devices have sufficient computing and communications capabilities to allow the implementation of many novel sophisticated protection principles. Therefore, a novel wide-area backup protection system is reported in this paper. This system is capable of acting as the substitution of conventional distributed backup protections in substation. To ensure the fast responsibility of such a system to the emergent events, the communication requirements are discussed as well. Conclusively, the proposed system is designed by two ways. First, in substation, concentrate some conventional backup protection functions to an intelligent processing system; second, concentrate the coordinated and optimized processing and controlling arithmetic of all backup protection in a region into a regional processing unit. The communication of data among them is carried via optic-fiber networks. The relay decision is based on collected and shared data through communication network. The suggested technique satisfies high degree of reliability and stability while it is based on shared decision rather than stand alone decision. The suggested technique can see all the power system area and can deal with the transmission lines as unit protection, see Fig. 2. The primary purpose of these systems is to improve disturbance monitoring and system event analysis. These measurements have been sited to monitor large generating sites, major transmission paths, and significant control points. Synchronized phasor measurements provide all significant state measurements including voltage magnitude, voltage phase angle, and frequency. III. COMPONENTS OF PHASOR MEASUREMENT UNIT The technology of synchronized phasor measurements is well established. It provides an ideal measurement system with which to protect, monitor and control a power system, in particular during conditions of stress. The essential feature of the technique is to measure positive sequence (negative and zero sequence quantities if needed) voltages and currents of a power system in a real time with precise time synchronization. This allows accurate comparison of measurements over widely separated locations as well as potential real-time measurement based control actions. Very fast recursive discrete Fourier transform (DFT) calculations are normally used in phasor calculations. In the suggested technique, a positive sequence voltage and phase angle of the positive sequence current is used. The DFT technique is a short-time variation of the Fourier analysis. While the Fourier transform is applied to signals in the continuous time domain, the DFT is applied to time-domain signals represented by sequences of numbers. The basic phasor measurement process is that of estimating a positive-sequence, fundamental frequency phasor representation from voltage or current waveforms.

3 272 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010 Fig. 3. Synchronized phasor measurement block diagram. Fig. 3 shows the analog power signal that converted into digital data by the analog to digital converter. For example, if the voltage is needed to be measured, the samples are taken for each cycle of the waveform and then the fundamental frequency component is calculated using (DFT). The figure also shows a simple block diagram explaining the procedure of measured voltage or current analog signal. The sampled data are converted to a complex number which represents the phasor of the sampled waveform. Phasors of the three phases are combined to produce the positive sequence measurement. The figure includes a hardware low-pass filter (Hardware LPF) for antialiasing and an analog-to-digital (A/D) converter for analog-to-digital conversion. The system of supervision permits capturing records of the same event at different points in the power system with a unique time reference, the phasor measurement units at present are located strategically, with the purpose of capturing information on the impact of contingencies at the local or system level. Fig. 4 shows the electric system with the location of the PMUs. The phasor measuring unit is represented by a discrete phase sequence analyzer block which convert 3 phase signals (Vabc or Iabc) to a positive, negative and zero sequence component magnitudes and angle. Each phase signal (Va, Vb and Vc) is converted to real and imaginary component using Discrete Fourier Transform. The positive sequence component is calculated in sequences analyzer by the following equation: where, the overall process to calculate positive, negative or zero sequence component using Matlab simulink. Fig. 4. The PMUs arrangement with phasor data concentration and system protection center. IV. COMMUNICATION ISSUES AND BACK UP RELAYS The application of the wide area in the protection is not straight forward from the communication point of view. In such case the communication issues related to time delay is discussed here. Standard communication systems are adequate for most phasor data transmission. The issue for data communications includes speed, latency and reliability. Communication speed (data rate) depends on the amount of phasor data being sent. A. Communication Options Available Communication links used by WAPS include both wired (telephone lines, fiber-optics, power lines) and wireless (satellites) options. Delays associated with the link act as a crucial indicator to the amount of time-lag that takes place before action is initiated. The delays are an important aspect and should be incorporated into any power system design or analysis, as excess delays could ruin any control procedures adopted to stabilize the power grid. B. Communication Delay Causes Although more and more control systems are being implemented in a distributed fashion with networked communication, the unavoidable time delays in such systems impact the achievable performance. Delays due to the use of PMUs and the communication link involved are due primarily to the following reasons. Transducer Delays: Voltage transducers (VT) and current transducers (CT) are used to measure the RMS voltages and currents respectively, at the instant of sampling. Window Size of the DFT: Window size of the DFT is the number of samples required to compute the phasors using DFT.

4 EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT 273 Processing Time: The processing time required in converting the transducer data into phasor information with the help of DFT. Data Size of the PMU Output: Data size of the PMU message is the size of the information bits contained in the data frame, header frame and the configuration frame. Multiplexing and Transitions: Transitions between the communication link and the data processing equipment leads to delays that are caused at the instances when data is retrieved or emitted by the communication link. Communication Link Involved: The type of communication link and the physical distance involved in transmitting the PMU output to the central processing unit can add to the delay. Data Concentrators: Data concentrators are primarily data collecting centers located at the central processing unit and are responsible for collecting all the PMU data that is transmitted over the communication link. C. Delay Calculations Delay calculations form an important aspect of WAMS; these delays indicate the viability of a particular communication medium, since large communication delays amount to slower controller actions that can correct power grid instabilities and oscillations. Communication delay given in [10], [11] can be expressed as where is the total link delay, is the fixed delay associated with transducers used, DFT processing, data concentration and multiplexing, is the link propagation delay, L is the amount of data transmitted, R is the data rate of the link, and is the associated random delay jitter. Delay calculations can be made on the assumptions that there are phasor measurements, each 4 bytes in length, 10 input status channels, each 2 bytes in length, and the combined delay caused by processing, concentrators, multiplexing and transducers is estimated to be around 75 msec. This is the fixed delay and is independent of the communication medium used. The propagation delay is dependent on the medium and thus is a function of both the medium and the physical distance separating the individual components of WAMS. We have assumed that media like fiber-optic cables, power lines, and telephone lines, on an average, have a propagation delay of around 25 ms. Considering the total length of the PMU packet, the delay caused due to the amount of data transmitted and the data rate can then be estimated to be around 125 ms, considering a telephone line channel with an average capacity of 33.6 kbps. In the case of substations, where isolation circuits are required, the telephone line channel capacity could drop to as low as 9.6 kbps, creating a bottleneck, and thereby increasing the delay to more than 200 ms. Even though power lines can reach speeds of up to 4 Mbps. Standard communication systems are adequate for most phasor data transmission. The issues for data communications include speed, latency, and reliability. Communication speed (data rate) depends on the amount of phasor data being sent and the number of messages. A PMU sending 10 phasors at 30 messages has an actual data rate of about 17 kbps. Reliability in TABLE I THE INTERCONNECTED AREAS this application includes both error rate and component failures. Such protection scheme suggested here needs to a very high media of communication system, the available data transfer can reach speed up to 2 Mpbs [10], [11]. From above the proposed relay is evaluated as a backup relays from the point of view data handling through the communication channels, in spite of the fast detection time estimated by 5 msec for all fault cases. V. THE TECHNIQUE COMPONENTS BASED ON WIDE AREA MEASUREMENT SYSTEM The primary purpose of these systems is to improve disturbance monitoring and system event analysis. These measurements have been sited to monitor large generating sites, major transmission paths, and significant control points. Synchronized phasor measurements provide all significant state measurements including voltage magnitude, voltage phase angle, and frequency. Most of these phasor measurement systems have been implemented as real-time systems. With these systems, phasor measurement units (PMUs) installed at substations send data in real time over dedicated communications channels to a data concentrator at a utility control center. This approach allows the data to be used in System Protection Center (SPC) as well as being recorded for system analysis and monitored via SCADA system as shown in Fig. 4. PMUs measure the bus voltage(s) and all the significant line currents. These measurements are sent to a Phasor Data Concentrator (PDC) at the control center. The PDC correlates the data by time tag to create a system-wide measurement. The PDC exports these measurements as a data stream as soon as they have been received and correlated. System protection center (SPC) receive Data stream and make a wide area protection depending on wide area view. This principal of operation is used in this paper. WAPS schemes are designed to detect abnormal system conditions, take pre-planned corrective actions intended to minimize the risk of wide-area disruptions and isolate the faulted segment from the over all power system. WAPS depend on WAMs to take hieratical action depending on wide area monitor of the over all network. VI. THE STUDIED NETWORK Part of the 500/220 kv Egyptian interconnected electrical network is used for the study; five main buses that represent five different areas with 500 kv are selected to verify the suggested technique. The selected five different areas with buses are given in Table I. Fig. 5 shows the selected five areas from

5 274 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010 Fig. 5. Single line diagram of the studied network. Fig. 6. Positive sequance current angles. TABLE II THE LENGTHS AND ANGLES the overall network. In the single line diagram, each bus represents the selected area in the simulation that can connect the 500 kv network with 220 kv network through three single phase 500/220 kv power transformers. A sampling frequency of 20 khz for a system operating at a frequency of 50 Hz is used in this study. Table II defines each transmission line that connecting two neighboring areas. The lengths of the transmission lines are given in km. is defined as the absolute difference between positive sequence current angles measured at transmission line terminals. Fig. 6 shows the positive sequence current angles measured at transmission line terminals, from its area to the other connected area. VII. THE PROPOSED TECHNIQUE The proposed technique is based mainly on two components to identify the faults on the transmission lines. The first component is the voltage reduction due to fault occurrence. The second component is the power flow direction after fault occurrence. The phase angle is used to determine the direction of fault current with respect to a reference quantity. The ability to differentiate between a fault in one direction or another is obtained by comparing the phase angle of the operating voltage and current. The voltage is usually used as the reference polarizing quantity. The fault current phasor lies within two distinct forward and backward regions with respect to the reference phasor, depending on the power system and fault conditions [12] [14]. The normal power flow in a given direction will result in the phase angle between the voltage and the current varying around its power factor angle. When power flows in the opposite direction, this angle will become. For a fault in the reverse direction, the phase angle of the current with respect to the voltage will be [14]. The main idea of the proposed technique is to identify the faulted area. This can be achieved by comparing the measured values of the positive sequence voltage magnitudes at the main bus for each area. This can result in the minimum voltage value that indicates the nearest area to the fault. In addition to that, the absolute differences of the positive sequence current angles are calculated for all lines connected with the faulted area. These absolute angles are compared to each other. The maximum absolute angle difference value is selected to identify the faulted line. The above two keys of operation can be mathematically described as follows: where is the positive sequence voltage magnitude measured by PMU and located at area 1, 2, 3 m, to n. For a fault occurred on the grid, the output from (1) is the minimum positive sequence voltage magnitude which indicates the nearest area to the fault. Suppose that the nearest area to the (1)

6 EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT 275 Fig. 7. The logic implementation of the technique. Fig. 8. Matlab simulink block daigram. fault is indicated by number m. The next step is to compare the absolute differences of positive sequence current angles for all lines connecting area m with all other neighboring areas and then selecting the max one. This can be explained as where is the absolute difference of positive sequence current angle for a transmission line connecting area m with area n. This can be described by the following equation: The above process can be implemented logically in Fig. 7. The output of the logic action is the faulted line. The following sub-sections will explain the stages of the proposed technique. VIII. OVERALL STAGES OF THE PROPOSED TECHNIQUE The studied configuration system is classified into 5 different areas, the following section explain the main components of the proposed technique. Fig. 8 shows more details about the elements used in the protection technique. A. Data Preparation (Bay Level) Each area contains one PMU which receives analog signals from (CTs) and (VTs) in bay level. Voltage transformers (VTs) on the main bus for each area receive 3 phase voltage (Vabc) to the PMU. Current transformers (CTs) on each line terminal receive 3 phase current (Iabc) to the PMU. PMU converts the analog voltage and current signals to digital samples synchronized in time of measuring, the Discrete Fourier Transform method inside PMU calculates the positive sequence voltage and current phasors. (2) (3) B. Output From PMU The output signal from the PMU is the positive sequence voltage and the positive sequence currents & nm nm respectively, where Positive sequence voltage magnitude for area # n. : Positive sequence voltage angles for area # n. Positive sequence current magnitude for interconnected line between area # n and area # m. Positive sequence current angle for interconnected line between area # n and area # m. For the proposed technique, only positive sequence voltage magnitudes and positive sequence current angles nm are selected. C. Phasor Data Concentrator PDC The PDC is considered as a computer database that contains data from five phasor measurement units (PMUs). Each PMU sends measuring data through fast communication system to PDC which correlates the data by time tag to create a systemwide measurement. D. System Protection Center SPC In WAMs, the PMUs are strategically placed throughout a wide coverage area. The PMUs form part of local devices called system protection terminals (SPT). SPTs are able to run complete or parts of distributed control algorithms and can communicate directly with other SPTs, substation equipment and system protection centers (SPC) which is responsible for protection, monitoring and control of the power grid. E. Data Manipulation in SPC SPC receives data stream from PDC and provides a wide area protection depending on wide area view. In the SPC unit, the measuring values of positive sequence voltage magnitudes are

7 276 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY 2010 Fig. 9. Three phase voltage signals at each area. Fig. 10. Three phase current signals for all lines connected to the faulted area (area 2 ). compared, the minimum voltage magnitude is selected, and the nearest area to the fault is detected. IX. THRESHOLD BOUNDARY The final performance of the technique is identified by satisfying two criteria. The first criterion concerns the comparison of the positive sequence voltage magnitudes at the bus and then selecting the minimum voltage value that indicates the faulted area. The voltage magnitude should go lower than setting value amounted by 0.95 of the operating voltage. The second criterion is used to compare of the absolute difference of the positive sequence current angles and selecting the maximum one. This value should go higher than some positive threshold boundary amounted by 100. A trip output is produced when the above two conditions are met. The final trip logic combines the decisions using the AND gate logic shown in Fig. 7. X. CASE STUDY An extensive series of study is examined on the power system given in Fig. 8. All fault events are studied and a sample of the results is given here. More details about the different cases of faults can be given in [15]. As mentioned above, the studied network is classified into 5 neighboring areas. The 5 areas are connected with each others by six lines. Three phases to ground fault are located on line 1 which connecting area 1 with area 2, see Fig. 8. Fault location is placed away from area 1 and area 2 by 100 and 45 km respectively. The three phase voltage signals at each area are recorded and displayed in Fig. 9. The three phase current signals for all lines connected to the faulted area are recorded and displayed in Fig. 10 as: line 1 connecting area 2 with area 1; line 3 connecting area 2 with area 3; Line 5 connecting area 2 with area 4. Fig. 11. Positive sequence voltage magnitudes. Fig. 11 shows the output from the five PMUs, the graph shows the five positive sequence voltage magnitudes (PSVM) for five different areas during fault. The minimum value is selected which indicates the nearest area to the fault (area 2 ). The next step is used to identify the faulted line. Fig. 12 shows the absolute diffrences of positive sequance current angles (PSCA) for all lines connecting the faulted area (area 2 ) with all other neighboring areas (areas 1, 3, 4 ). The graph shows the maximum absolute difference of positive sequence currrent angle (about 175 ) that refers to line 1. The time taken to reach the threshold voltage is about 4 ms. While the time taken to reach the threshold angle is 3 ms, then the fault can be detected in about 4 ms. A single phase to ground fault is located on transmission line TL3, see Fig. 8, which connecting area 2 (Kurimat) with area 3 (Cairo 500). The distance between fault location on the transmission line and the nearest

8 EISSA et al.: A NOVEL BACK UP WIDE AREA PROTECTION TECHNIQUE FOR POWER TRANSMISSION GRIDS USING PHASOR MEASUREMENT UNIT 277 Fig. 12. Positive sequance current angle absolute differences for all lines connected to the faulted area (area 2 ). Fig. 14. Positive sequence current angles (absolute difference) for all lines connected to area 2. Fig. 15. Positive sequence voltage magnitudes measured from five places on the network. Fig. 13. Positive sequence voltage magnitudes measured from five places on the network. Kurimat bus is 20 km. The 3-phase voltage signals measured from Kurimat bus are recorded. The 3-phase current signals for all transmission lines connected to Kurimat are also recorded. Fig. 13 shows the five PSVM (Positive Sequence Voltage Magnitudes). The minimum value is selected to indicate that the nearest area to the fault is area 2. Fig. 14 shows the absolute differences of PSCA (Positive Sequence Current Angles) for all lines connecting the faulted area 2 with all other neighboring areas 1, 3 and 4. The angles difference of TL3 is the maximum value given by 160. This means that the current is reversed from one terminal only. It is clear that the fault is internal and this transmission line must be isolated. The figures also show the threshold boundary. A double-phase to ground fault is located on transmission line TL1, see Fig. 8. The distance between the fault point on the transmission line and the nearest bus Samalout is 45 km. The 3-phase voltage signals measured from area 1 are recorded. The 3-phase current signals for all transmission lines connected with Samalout are also recorded. Fig. 15 shows the five PSVM for five different areas during the fault. The minimum Fig. 16. Positive sequence current angles (absolute difference) for all lines connected to area 1. value is selected to identify the nearest area to the fault as area 1. Fig. 16 shows the absolute differences of PSCAs for all lines connecting area 1 with all other neighboring areas (area 2 and area 3 ). The angles difference measured at the transmission line terminals (TL1) recorded maximum difference by

9 278 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 25, NO. 1, JANUARY This means that the current is reversed from one terminal only. It is clear that the fault is internal and the transmission line must be isolated. Figs. 15 and 16 show also the threshold boundary with time estimated by 3 msec. XI. CONCLUSION The paper presents a new protection technique for transmission grids using phasor synchronized measuring technique in a wide area system. The protection scheme has successfully identified the faulted line allover the interconnect system. The relay descried in this paper represents a new state-of-art in the field of interconnected grid protection for many reasons. The relay is based on sharing data from all areas. One relay is used instead of many stand alone relays with different complexity coordination. The relay has the feature of unit protection in identifying the faulted zone. One and only one trip decision is issued from the protection center. The relay has a very fast detection time estimated by 5 msec for all fault cases. In the near future and with a very fast communication links the relay can be considered as a main relay on the interconnected grids. REFERENCES [1] Wide Area Protection and Emergency Control, 2002, IEEE Members, Working Group C-6. [2] U. Serizawa, M. Myoujin, K. Kitamura, and N. Sugaya, Wide area current differential backup protection employing broadband communication and time transfer systems, IEEE Trans. Power Del., vol. 13, no. 4, pp , Oct [3] C.-S. Chen, C.-W. Liu, and J.-A. Jiang, A new adaptive PMU based protection scheme for transposed/untransposed parallel transmission lines, IEEE Trans. Power Del., vol. 17, no. 2, pp , Apr [4] Y.-H. Lin, C.-W. Liu, and C.-S. Chen, A new PMU-based fault detection/location technique for transmission lines with consideration of arcing fault discrimination Part I: Theory and algorithms, IEEE Trans. Power Del., vol. 19, no. 4, pp , Oct [5] C.-S. Yu, C.-W. Liu, S.-L. Yu, and J.-A. Jiang, A new PMU-based fault location algorithm for series compensated lines, IEEE Trans. Power Del., vol. 17, no. 1, pp , Jan [6] J. Tang and P. G. McLaren, A wide area differential backup protection scheme for Shipboard application, IEEE Trans. Power Del., vol. 21, no. 3, Jul [7] S. H. Horowitz and A. G. Phake, Power System Relaying. Taunton, Somerset, U.K.: Research Studies Press, [8] M. M. Eissa, New principle for transmission line protection using phase portrait plane, IET Gener. Transm. Distrib., vol. 3, no. 1, pp , [9] D.-Q. Wang, S.-H. Miao, X.-N. Lin, P. Liu, Y.-X. Wu, and D. Yang, Design of a novel wide-area backup protection system, in Proc. IEEE/PES Transm. Distrib. Conf. Exhib.: Asia Pac. Dalian, China, 2005, pp [10] B. Naduvathuparambil, M. C. Valenti, and A. Feliachi, Communication delays in wide area measurement systems Lane Dept. of Comp. Sci. & Elect. Eng., West Virginia University, Morgantown, WV, , [11] R. Klump and R. E. Wilson, Visualizing real-time security threats using hybrid SCADA/PMU measurement displays, in Proc. 38th Hawaii Int. Conf. System Sci., 2005, p. 55c. [12] M. M. Eissa, Development and investigation of a new high-speed directional relay using field data, IEEE Trans. Power Del., vol. 23, no. 3, pp , Jul [13] M. M. Eissa, A new digital feed circuit protection using directional element, IEEE Trans. Power Del., vol. 24, no. 2, pp , Apr [14] M. M. Eissa, Evaluation of a new current directional protection technique using field data, IEEE Trans. Power Del., vol. 20, no. 2, pp , Jul [15], Protection of Interconnected Electrical Networks Using Phasor Synchronized Measuring Technique, Ph.D. dissertation, Helwan University-Faculty of Engineering at Helwan, Cairo, Egypt. M. M. Eissa (M 96 SM 01) was born in Helwan, Cairo, Egypt, on May 17, He received the B.Sc. and M.Sc. degrees in electrical engineering from Helwan University, Cairo, Egypt, in 1986 and 1992, respectively, and the Ph.D. degree from the Research Institute for Measurements and Computing Techniques, Hungarian Academy of Science, Budapest, Hungary, in He is a Professor at Helwan University. In 1999, he was invited to be a Visiting Research Fellow at the University of Calgary, Calgary, AB, Canada. His research interests include digital relaying, application of widearea networking to power systems, power quality and energy management, and wide-area protection. Dr. Eissa received the Egyptian State Encouragement Prize in advanced science in 2002 and the Best Research in advanced engineering science from Helwan University in M. E. Masoud, photograph and biography not available at the time of publication. M. M. M. Elanwar, photograph and biography not available at the time of publication.