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Distance relaying algorithm for phasor measurement unit assisted zone‐3 relays of series compensated wind integrated system

2019; Institution of Engineering and Technology; Volume: 13; Issue: 21 Linguagem: Inglês

10.1049/iet-gtd.2019.0488

1751-8695

Tapan Prakash, Soumya R. Mohanty, V. P. Singh,

Power System Optimization and Stability

IET Generation, Transmission & DistributionVolume 13, Issue 21 p. 4788-4797 Research ArticleFree Access Distance relaying algorithm for phasor measurement unit assisted zone-3 relays of series compensated wind integrated system Tapan Prakash, Corresponding Author Tapan Prakash tapanprakashsinha@gmail.com orcid.org/0000-0002-0772-3733 Department of Electrical Engineering, National Institute of Technology Raipur, Raipur, IndiaSearch for more papers by this authorSoumya R. Mohanty, Soumya R. Mohanty Department of Electrical Engineering, Indian Institute of Technology (BHU), Varanasi, IndiaSearch for more papers by this authorVinay Pratap Singh, Vinay Pratap Singh orcid.org/0000-0002-9279-1086 Department of Electrical Engineering, Malaviya National Institute of Technology Jaipur, Jaipur, IndiaSearch for more papers by this author Tapan Prakash, Corresponding Author Tapan Prakash tapanprakashsinha@gmail.com orcid.org/0000-0002-0772-3733 Department of Electrical Engineering, National Institute of Technology Raipur, Raipur, IndiaSearch for more papers by this authorSoumya R. Mohanty, Soumya R. Mohanty Department of Electrical Engineering, Indian Institute of Technology (BHU), Varanasi, IndiaSearch for more papers by this authorVinay Pratap Singh, Vinay Pratap Singh orcid.org/0000-0002-9279-1086 Department of Electrical Engineering, Malaviya National Institute of Technology Jaipur, Jaipur, IndiaSearch for more papers by this author First published: 23 October 2019 https://doi.org/10.1049/iet-gtd.2019.0488Citations: 4AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract The signals of wind integrated system are contaminated with inter-harmonic components which may result in erroneous calculations of apparent impedance seen by the distance relays. Therefore, it is indispensable to filter these signals before being used by relays. Presently, the measurements obtained from phasor measurement units (PMUs) are effectively used by distance relays for zone-3 protection. However, PMUs use discrete Fourier transform (DFT) algorithm to compute phasors which may produce incorrect results in presence of inter-harmonics. To overcome this issue, a matrix pencil method is proposed as a pre-processing filtering technique for PMU assisted distance relays. The analog input signals to PMUs are filtered by the matrix pencil algorithm to eliminate inter-harmonics present in the signals and the phasors are computed using DFT algorithm. These phasors are utilized by zone-3 distance relays to estimate the impedance trajectories. To test the effectiveness of proposed distance relaying algorithm, IEEE 14-bus system with a series compensated line is integrated with wind energy and is simulated under diverse test cases of different operating conditions. The impacts of fault resistances, type of faults and fault inception angles on the performance of proposed technique are examined and the results are compared with different signal processing techniques. Nomenclature phase angle complex amplitude of signal apmlitude of signal harmonic frequency white noise estimated fundamental phasor of current fundamental phasor of current estimated by MPA design constants L pencil parameter M length of sampled data output power of DFIG mechanical wind turbine power R residues input signals to relay diagonal matrix unitary matrix unitary matrix reduced matrix sub-matrix obtained from sub-matrix obtained from estimated fundamental phasor of voltage input signals used in estimation of fundamental phasor fundamental phasor of voltage estimated by MPA signal data matrix apparent impedance impedance of protected line impedance when multiplied to current yields polarization voltage 1 Introduction Presently, the demand for clean energy has increased manifolds resulting in massive integration of renewable energy systems to the conventional power networks. Wind energy is one of such systems which has gained more attention of power sector in last few decades [1]. In earlier stages, wind energy conversion system used to produce variable output power owing to changing wind speeds. However, development in power electronics interfacing and their application to doubly fed induction generator (DFIG) has minimised voltage and current fluctuations to a great extent [2]. However, the effects of wind integration on several variables of existing power system like voltage, current, frequency, output power etc. cannot be eliminated completely. In fact, the introduction of power electronics interfacing is responsible for injections of inter-harmonic components in the grid [3]. It is utmost required to study the effects of inter-harmonics on wind integrated system. In past, several studies have reported the impacts of wind integration on conventional system [4–6]. Transmission line protection has been a vital research area for years [7]. Performance study of transmission line protection system in the presence of wind power is one of recently growing areas of investigation [2, 8–10]. The dynamic nature of wind systems affects the working of distance relays resulting in its overreaching and/or underreaching [11, 12]. Apart from this, the inter-harmonic and sub-harmonic components injected in the system may affect the performance of distance relays [13, 14]. These components introduce errors in calculation of impedances seen by relays resulting in their maloperation. Therefore, it is required to eliminate these components from the signals in order to achieve appropriate performance of the distance relays. In addition to several impacts of wind integration on the protection schemes of the system, series compensation of a line also affect protection schemes. Reports are available in the literature regarding impacts of series compensation on distance protection and their corresponding mitigations [15–18]. The performance of distance relays in context of zone-3 protection (Z3P) for series compensated lines is one of the more attended areas of research. With the development of wide-area measurement system, real-time synchronised measurements are obtained by phasor measurement units (PMUs). These measurements are used to mitigate the issues for distance relays regarding Z3P of series compensated lines [19–22]. Discrete Fourier transform (DFT) algorithm integrated within PMUs is generally used to compute voltage and current phasors. However, DFT algorithm may fail to compute correct phasors from inter-harmonics dominated signals which are inherently present in wind integrated system. Therefore, it is indispensable to filter the input signals to eliminate inter-harmonics before PMUs compute the respective phasors. In view of the above discussion, the present work is motivated to use matrix pencil algorithm (MPA) [23] as a pre-processing filtering technique to eliminate the presence of inter-harmonics from the signals before being processed by PMUs to compute phasors for distance relaying regarding Z3P of series compensated wind integrated system. Apart from DFT and MPA algorithms, there are other advanced signal processing techniques like extended Kalman filter (EKF), estimation of signal parameters via rotational invariance techniques (ESPRITs), etc. to filter the contaminated signals but the performance of MPA regarding elimination of noise and inter-harmonics from the signals is better than above techniques [24]. In this work, a distance relaying algorithm based on (MPA + DFT) algorithm is proposed for Z3P. This relaying algorithm helps in the accurate calculation of impedance trajectories resulting in an appropriate performance of zone-3 distance relays. To test the effectiveness of the proposed technique, several test cases are carried out on IEEE 14-bus test system integrated with wind energy operating under different conditions. The effects of fault resistances, type of faults and fault inception angles (FIAs) on performance of proposed technique are additionally examined. The major highlights of the work are listed below. A distance protection scheme for Z3P of series compensated wind integrated systems is proposed. MPA is used as pre-processing filtering technique before PMUs to eliminate the presence of inter-harmonics in signals. A distance relaying algorithm based on the integration of MPA and DFT algorithm is proposed. Several test cases are carried out to examine the effective performance of the proposed technique. The impacts of fault resistances, type of faults and FIAs on the operating time of relay based on proposed technique are examined. A comparison of the proposed scheme is carried out with DFT, EKF and ESPRIT algorithms for all studied cases to establish its superior performance. 2 Test system under study 2.1 Modified IEEE 14-bus test system In this work, IEEE 14-bus test system is considered for all simulations. The detailed data of the system are taken from [25]. The system is modified by replacing one synchronous generator located at bus 1 with a wind farm of 300 MW. The detailed model of DFIG is used in the simulation. The modified single line diagram of the test system is illustrated in Fig. 1. Series compensation of 50% is provided at the middle of line 1-5. For this purpose, a fixed capacitor of value 105.79 µF is placed on the line 1-5. The impedance of line 1-5 is . For each study, the relay is assumed to be located at bus 2 while complete line 1-5 falling within Z3P of the concerned relay is the protected line. Fig. 1Open in figure viewerPowerPoint Single line diagram of the modified IEEE 14-bus test system 2.2 Modelling of the wind farm A DFIG-based generating unit is considered in this work. The schematic diagram of DFIG-based wind generation is shown in Fig. 2. Pitch angle control is provided to adjust the aerodynamic torque when wind speed is above the rated value. Crowbar protection is given to the rotor side. A back-to-back converter is provided to connect the rotor side of DFIG to the external grid. A space vector control scheme is adopted for pulse width modulation. Each unit has a rated capacity of 5 MW. A total of 60 units are used to create a wind farm of total 300 MW capacity. Fig. 2Open in figure viewerPowerPoint Schematic diagram of DFIG-based wind generation Pitch angle control generally employs proportional–integral (PI) controller. The working mechanism of the control scheme is depicted in Fig. 3. Two PI controllers are used to adjust the pitch angle. The difference of mechanical wind turbine power p.u. and the reference value 1.1 p.u. is fed as input to one of the controllers while the difference of output power of DFIG p.u. and reference value 1.0 p.u. is fed as input to other controllers. The summation of output of both controllers is used to decide the correct pitch angle for the wind turbine. Fig. 3Open in figure viewerPowerPoint Schematic diagram of pitch angle control of DFIG 3 MPA-based distance relaying algorithm 3.1 Overview of MPA MPA is a well known parametric method which is introduced to estimate parameters of damped sinusoids in the noisy signals [23]. Any signal can be represented as a sinusoidal model and a complex exponential model as shown below. (1) (2)where and are the amplitude and complex amplitude, respectively. is the phase angle, is the harmonic frequency and is the white noise. MPA solves generalised eigenvalue problem to estimate the amplitude and phase angle of the signal. The basic steps of MPA are demonstrated below. (i) Read sampled data and determine its length M. (ii) Define pencil parameter L where L lies in the range . (iii) Obtain a data matrix of size from the sampled data . (iv) Perform singular value decomposition on matrix as below (3)where is an unitary matrix, is a diagonal matrix, is a unitary matrix, and is a conjugate transpose of . (v) Choose a parameter in such a manner that the singular values of beyond are very small tending towards zero. (vi) Obtain a reduced matrix utilising the rows corresponding to significant values. (vii) Form two sub-matrices and from by deleting last and first columns of , respectively. (viii) Obtain a matrix from the two sub-matrices using (4)where symbol signifies pseudo-inverse. (ix) Solve the left-handed eigenvalue problem as shown below (5) (x) Compute the residues by solving following equation. (6) (xi) Compute amplitude, phase angle, frequency and damping ratios. 3.2 Signal processing model (SPM) using MPA and PMU In this section, a SPM is proposed where MPA is used as pre-processing filtering technique before phasor computation by DFT algorithm integrated within PMUs. Therefore, the output phasors are results of signal processed through (MPA + DFT) algorithm. The proposed block diagram of SPM is shown in Fig. 4. Apart from MPA block, other blocks of proposed SPM are same as PMU defined by IEEE standard C.37.118.1 and exhibits principles suggested in [26]. The signals obtained from current and voltage transformers are fed to MPA block of SPM. In proposed SPM, MPA block acts as the replacement of low-pass filter used in PMUs. Apart from filtering noise present in the signals, MPA block provides an added advantage of eliminating inter-harmonic components from the signals. In this model, at first, the signals are filtered using MPA and then the filtered signals are processed with blocks within PMUs to compute the phasors as shown in the figure. In this work, a PMU with a sampling frequency of 10 kHz is considered. An analog-to-digital converter with 14 bits is used to convert the sampled signal into digitised signal. The one pulse per second global positioning system is assumed to synchronise the time to universal time constant (UTC). The sampling time of the signal is taken as UTC for simulation studies in this work. A time-stamp to the measured data is applied at each sampling instant which remains attached to output phasor of PMU. A quadrature oscillator is present in basic architecture of PMU where a correlation of input signals with quadrature waveforms are carried out at nominal frequency . The output of the model is a fundamental phasor having magnitude proportional to the voltage with a phase rotating at the rate of . Consequently, this technique provides accurately computed phasors which are utilised by distance relays in calculation of impedance trajectories. Fig. 5 shows the output signal of proposed SPM. Three-phase instantaneous voltage used as input to SPM is shown in Fig. 5a. Time-stamp obtained at each sampling interval is shown in Fig. 5b. In Figs. 5c and d, the positive sequence voltage magnitude and fundamental frequency of the signal are illustrated, respectively. Fig. 4Open in figure viewerPowerPoint Proposed SPM Fig. 5Open in figure viewerPowerPoint Measurement of signal through SPM (a) Three-phase instantaneous voltage, (b) Time stamp, (c) Positive sequence voltage magnitude, (d) Fundamental frequency 3.3 Proposed distance relaying algorithm A distance relaying algorithm for Z3P of series compensated wind integrated system is proposed using SPM in this work. Distance relay algorithms extract the fundamental frequency component of voltage and current signals. In general, the distance relay model comprises a phase comparator that responds to the displacement of phase angles between input signals [27]. The basic model of distance relay is represented as follows: (7) (8)where and are two input signals responsible for issuance of the trip signal; and are design constants; is the impedance of the protected line; is impedance which when multiplied by current yields polarisation voltage; and are input signals used in estimation of fundamental frequency phasor. After, the computation of phasors and , the distance relay calculates the phase difference . If a fault occurs, i.e. if the fault impedance falls into the region inside the Mho circle, then the phase difference between and is . In the other case, if the impedance falls out of the Mho circle, the phase difference between and is . The flowchart of operating principle of distance relay model is shown in Fig. 6. Fig. 6Open in figure viewerPowerPoint Flowchart of the distance relay model The presence of inter-harmonics in these signals produces an error in estimation of fundamental frequency components. The distance relay model with error in estimation is characterised by (9) (10)where and are the estimated fundamental phasors of voltages and currents and the terms and are errors in estimation due to ith inter-harmonic component in the signal. The basic idea behind SPM-based distance relaying algorithm is to compensate the errors in phasor estimation obtained by conventional techniques. The compensated phasors should be treated as the fundamental phasors in distance relay model. The expressions for error compensation using estimated phasors by MPA are presented below: (11) (12)where and are fundamental phasors of voltages and currents estimated by MPA. For Mho relay characteristics, the term in (12) is equal to zero. 4 Estimation of inter-harmonics in wind integrated system In this section, the estimation of inter-harmonics in wind integrated system using conventional DFT and MPA algorithm is illustrated. The results are obtained for the system operating under normal conditions. The corresponding results are depicted in Figs. 7 and 8. The active power and reactive power injected by wind farm into the grid are shown in Figs. 7a and b, respectively. In Figs. 7c and d, three phase instantaneous voltages and currents are illustrated. Fig. 8a shows the power flow in series compensated line while Fig. 8b shows the power flow in line 1-2. The estimation of inter-harmonics by DFT algorithm and MPA are carried for a phase of current injected by wind farm in the grid. Figs. 8c and d depicts the estimated inter-harmonics by DFT algorithm and MPA, respectively. From the figures, it can be clearly observed that MPA is more capable of eliminating inter-harmonics from the signal in comparison to DFT algorithm. This behaviour of MPA makes it suitable for application as a filtering technique in wind integrated system. Fig. 7Open in figure viewerPowerPoint Wind integrated system under normal operating conditions (a) Active power supplied by the wind farm, (b) Reactive power supplied by wind farm, (c) Three-phase instantaneous voltage, (d) Three-phase instantaneous current Fig. 8Open in figure viewerPowerPoint Wind integrated system under normal operating conditions (a) Power flow in series compensated line, (b) Power flow in line 1-2, (c) Estimated inter-harmonics by DFT, (d) Estimated inter-harmonics by MPA 5 Simulation results and discussion In this work, the role of MPA is explored as a filtering technique applied to the basic blocks of PMU to form a SPM. The proposed SPM is used in distance relaying algorithm to compensate the errors in estimation of fundamental phasors caused due to inter-harmonics. The algorithm results in correct computation of phasors resulting in appropriate operation of zone-3 distance relays meant for Z3P of series compensated wind integrated system. The detailed model of wind farm integrated to IEEE 14-bus test system is simulated in PSCAD/EMTDC environment. MPA is implemented in MATLAB. Different test cases are considered to test the performance of proposed technique. Comparative analysis of proposed scheme with DFT and other advanced signal processing techniques like EKF and ESPRIT is presented for considered cases. A simulation time of 3 s is considered throughout all simulations. The relay is located at bus 2 while the protected line is line 1-5. The zone settings and range of tripping time settings for the relay are listed in Table 1. Table 1. Zone settings and range of tripping time settings for relay Zones Zone-1 Zone-2 Zone-3 , s instantaneous 0.3–0.4 0.8–1 5.1 Fault on line 1-5 before series compensation In this case, a three-phase to ground fault is initiated on the line 1-5 before series compensation at 1.1 s and continued till simulation time of 3 s. Under this scenario, the fault lies in zone-3 of relay located at bus 2. The obtained simulation results are illustrated in Figs. 9 and 10. In Figs. 9a and b, the active and reactive powers supplied by wind farm to the grid are shown, respectively. From the figures, it can be observed that the active power supplied by wind farm to the grid decreases when fault occurs and then after wind farm tries to maintain the rated active power supply while reactive power supplied by wind farm increases in the event of fault which is soon after maintained at rated value. The three-phase instantaneous voltage and the current are depicted in Figs. 9c and d, respectively. The power flow in series compensated line is shown in Fig. 10a while the power flow in line 1-2 is shown in Fig. 10b. From the figures, it is noticeable that the active power flow in series compensated line 1-5 increases drastically in the event of occurrence of fault before compensation whereas active power flow in line 1-2 decreases steeply after fault inception. Fig. 10c shows the variations in phase difference for different methods. From the figure, it can be seen that for the proposed technique, the value of is which is less than while for DFT, the value of is . This signifies that Mho relay correctly identifies the fault with the proposed technique in comparison to conventional DFT algorithm working alone. The Mho relay characteristics with impedance trajectories obtained from DFT, (MPA + DFT), (EKF + DFT) and (ESPRIT + DFT) algorithms are illustrated in Fig. 10d. From this figure, it can be clearly seen that the impedance trajectory obtained via (MPA + DFT) stays well within zone-3 of line while impedance trajectory obtained with DFT algorithm is reaching the boundary of zone-3. In case of impedance trajectory obtained with (EKF + DFT) algorithm, the trajectory enters zone-3 which means it is performing better than DFT algorithm but in comparison to (MPA + DFT) and (ESPRIT + DFT) algorithms, the number of required samples is more which points towards its slower response. ESPRT algorithm is a parametric method which solves generalised eigenvalue solutions like MPA algorithm. Therefore, the performance of (ESPRIT + DFT) algorithm is better than (EKF + DFT) and DFT algorithms but found to be worse than (MPA + DFT) algorithm. The above discussion suggests that the proposed algorithm is efficient in estimating fundamental phasors after eliminating inter-harmonics resulting in correct calculation of apparent impedance seen by the relay. Fig. 9Open in figure viewerPowerPoint Wind integrated system under the occurrence of fault on line 1-5 before series compensation (a) Active power supplied by wind farm, (b) Reactive power supplied by wind farm, (c) Three-phase instantaneous voltage, (d) Three-phase instantaneous current Fig. 10Open in figure viewerPowerPoint Wind integrated system under occurrence of fault on line 1-5 before series compensation (a) Power flow in series compensated line, (b) Power flow in line 1-2, (c) Variations of phase difference , (d) Mho relay characteristics with impedance trajectories 5.2 Fault on line 1-5 after series compensation Under this case, a three-phase to ground fault is initiated on the line 1-5 after series compensation at 1.1 s which is sustained throughout the simulation period of 3 s. The fault lies in zone-3 of relay located at bus 2. In Figs. 11 and 12, the simulation results for the mentioned scenario are illustrated. In Fig. 11a and b, the active and reactive power supplied by wind farm to the grid are shown, respectively. From the figures, it can be seen that the occurrence of fault after series compensation decreases the active power supplied by wind farm to the grid but power supply is maintained at its rated value very soon while the reactive power supplied by wind farm increases after inception of fault and then maintained at its rated value for the rest of simulation period. The three-phase instantaneous voltages and the current are shown in Figs. 11c and d, respectively. The power flows in series compensated line and line 1-2 are shown in Figs. 12a and b, respectively. The figures suggest that when fault occurs after series compensation then active power flow in the compensated line 1-5 is maintained at reduced value after the occurrence of fault whereas the active power flow in line 1-2 is maintained at an increased value after fault inception. Fig. 12c shows the variations in phase difference for different methods. From the figure, it can be seen that for the proposed technique, the value of is which is < while for DFT, the value of is . This signifies that Mho relay correctly identifies the fault with the proposed technique in comparison to conventional DFT algorithm working alone. The Mho relay characteristics with impedance trajectories obtained from DFT, (MPA + DFT), (EKF + DFT) and (ESPRIT + DFT) algorithms is illustrated in Fig. 12d. Similar observations as obtained in previous section can be deduced from Mho relay characteristics in this case also. The impedance trajectories obtained via (MPA + DFT), (ESPRIT + DFT) and (EKF + DFT) algorithms enter zone-3 of line while impedance trajectory obtained with DFT algorithm remains at the boundary of zone-3 which means that DFT algorithm is not efficient in estimating fundamental phasors from the signals contaminated with inter-harmonics. (EKF + DFT) and (ESPRIT + DFT) algorithms show slower response than (MPA + DFT) technique. This fact affirms the superior performance of proposed relaying algorithm over conventional DFT and other algorithms. Fig. 11Open in figure viewerPowerPoint Wind integrated system under the occurrence of fault on line 1-5 after series compensation (a) Active power supplied by wind farm, (b) Reactive power supplied by wind farm, (c) Three-phase instantaneous voltage, (d) Three-phase instantaneous current Fig. 12Open in figure viewerPowerPoint Wind integrated system under the occurrence of fault on line 1-5 after series compensation (a) Power flow in series compensated line, (b) Power flow in line 1-2, (c) Variations of phase difference , (d) Mho relay characteristics with impedance trajectories 5.3 Effect of type of fault The performance of proposed distance relaying algorithm is examined with different types of fault. The purpose of this test case is to determine the effect of type of faults on the operating time of relay based on DFT and proposed algorithms. For all simulations under this case, a fault is initiated on line 1-5 after series compensation at 1.1 s and continued till the end of simulation period of 3 s. The obtained results are listed in Table 2. From the table, it can be clearly observed that in case of each type of faults, the operating times of relay based on DFT and (EKF + DFT) algorithms are beyond the tripping time settings of zone-3. The relay based on (MPA + DFT) and (ESPRIT + DFT) algorithms are operating correctly following the tripping time settings of zone-3 but the response of (ESPRIT + DFT) algorithm is slower than (MPA + DFT) algorithm. Additionally, it can be noted that the operating time of the relays goes on decreasing with the severity of the fault. The above discussion signifies the superior performance of proposed algorithm regarding Z3P of series compensated wind integrated system. Table 2. Effect of type of faults on operating time (s) of relay Method Type of fault AG BC BCG ABC ABCG DFT 1.5089 1.4209 1.4180 1.3870 1.1924 EKF + DFT 1.4282 1.4002 1.3620 1.2729 1.1812 ESPRIT + DFT 1.0120 0.9586 0.9324 0.9102 0.8923 MPA + DFT 0.9123 0.9088 0.9023 0.8992 0.8782 5.4 Effect of fault resistance The effect of increasing fault resistance on the performance of the distance relaying algorithm is examined in this case. For simulation, a three-phase fault is initiated on line 1-5 after series compensation at 1.1 s and continued till the simulation period of 3 s. The fault resistances are increased from 10 to 100 . The obtained results are tabulated in Table 3. From the table, it can be clearly seen that the operating times of relay based on DFT and (EKF + DFT) algorithms are greater than the specified tripping time settings of zone-3 for all fault resistances. On the other hand, the operating times of the relay based on (MPA + DFT) and (ESPRIT + DFT) algorithms remain within specified range. However, the response of (ESPRIT + DFT) algorithm is slower in comparison to proposed algorithm. Further, it can be noticed that the increase in fault resistance results in decrease in operating time of relay. From the above discussion, it can be concluded that the proposed algorithm is efficiently performing regarding Z3P of series compensated wind integrated system. Table 3. Effect of fault resistance on operating time (s) of relay Method Fault resistance 10 30 50 70 100 DFT 1.3106 1.3027 1.2986 1.2630 1.2245 EKF + DFT 1.3024 1.2982 1.2735 1.2521 1.2226 ESPRIT + DFT 0.9865 0.9432 0.9154 0.8936 0.8645 MPA + DFT 0.8821 0.8624 0.8592 0.8225 0.8128 5.5 Effect of FIA The effect of different FIAs on the performance of the distance relaying algorithm is examined in this case. For simulation, a three-phase fault is initiated on line 1-5 after series compensation at 1.1 s and stays till the end of simulation period of 3 s. FIAs are varied from to . The obtained results are listed in Table 4. From the table, it can be clearly seen that the operating times of relay based on DFT and (EKF + DFT) algorithms are more than the specified tripping time settings of zone-3 of the protected line. While the operating times of the relay based on (MPA + DFT) and (ESPRIT) algorithms are well within the specified limits. However, the response time of (MPA + DFT) algorithm is faster in comparison with (ESPRIT + DFT) algorithm. In addition to above discussion, it can be observed that the operating times of relay increase with the increase in FIAs. From the above analysis, the efficient performance of proposed algorithm is validated for Z3P of series compensated wind integrated system. Table 4. Effect of FIA on operating time (s) of relay Method FIA, deg. 0 30 60 90 120 DFT 1.1215 1.1440 1.1862 1.2322 1.2947 EKF + DFT 1.1136 1.1398 1.1820 1.2286 1.2534 ESPRIT + DFT 0.9082 0.9268 0.9657 0.9892 1.1040 MPA + DFT 0.8761 0.8834 0.8912 0.9158 0.9329 6 Conclusion In this work, a matrix pencil method is proposed as a pre-processing filtering technique for PMU-assisted distance relays for Z3P of a series compensated wind integrated system. The signals in a wind integrated system are contaminated with inter-harmonics which are required to be filtered out before being used for any relaying purpose. The proposed distance relaying algorithm achieves the mentioned objective by filtering the input signals to PMUs by MPA to eliminate inter-harmonics at first and second, by computing phasors from DFT algorithm integrated within PMUs. These computed phasors are utilised by zone-3 distance relays to calculate the apparent impedances. To test the effectiveness of proposed distance relaying algorithm, IEEE 14-bus system integrated with wind energy and 50% series compensation to one of the transmission line under different test cases of normal and contingent operating conditions is simulated. Additionally, the effects of fault resistances, type of faults and FIAs are examined in the proposed algorithm. Apart from DFT algorithm, the proposed scheme is found to be effectively performing in comparison to other advanced signal processing techniques like EKF and ESPRIT. 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