Wide-area Backup Protection Scheme Research Articles

Wide-Area backup protection against asymmetrical faults in the presence of renewable energy sources

Conventional protection schemes have essentially been developed for power systems dominated by synchronous generators. High penetration of power-electronic interfaced renewable energy sources (PEIRESs) can adversely impact the reliability of protection systems, thereby increasing the risk of widespread disturbances. This paper proposes a robust wide-area backup protection (WABP) scheme against asymmetrical faults for transmission systems with high penetration of renewables. The scheme exploits the full potential of available synchrophasors without placing any rigid constraints on PMU locations. To this end, the faulted line and a few appropriately selected PEIRESs are replaced by equivalent current sources using the Substitution Theorem. The remaining PEIRESs are substituted by their equivalent impedances accounting for their response to a fault, considering the control strategies and overcurrent limits of these PEIRESs. This results in a linear system of equations whose solution readily indicates the faulted line on account of the weighted sum of squared residuals (WSSR) concept. To add to the security of the proposed scheme, the fault distance on the pinpointed line is also calculated and checked to ensure it lies within the acceptable range. A total of more than 80,000 simulations conducted on the IEEE 39-bus test system verify that the proposed scheme performs properly irrespective of the numbers/locations of PEIRESs and their control strategies.

A Missing Data Tolerant Wide-Area Back-Up Protection Scheme for Transmission Network

The proposed scheme develops a missing data tolerant wide area back-up protection scheme for power transmission network with fewer PMUs. The scheme assumes division of power system into different coherent groups. The fault detection index (FDI) is used to detect a fault in the system network using active power transfer and angular difference between voltages of connected areas or summation of negative and zero sequence current components in each area. The faulted area is then identified by change in area-current (CAC) using current contribution towards each area and finally, the faulted line is identified for the respective faulted area using distance to fault (DF) index. The scheme is extensively tested on a New-England 39-bus system for several fault and stressed scenarios considering all PMU data available and PMU data loss at some of the buses. For this, the PMUs are deployed at less than half number of system buses. The maximum response time of the proposed scheme is approximately 260 ms which is well within the third zone operation time of distance relays for back-up protection. The test results including the comparative assessment with existing schemes indicate that the proposed scheme can be a potential candidate for enhancing the performance of the wide-area back-up protection in the transmission network.

A Differential Voltage-Based Wide-Area Backup Protection Scheme for Transmission Network

This article proposes a differential voltage-based scheme to identify the faulted line in the transmission system. Initially, the placement of phasor measurement unit (PMU) is carried out. Based on the PMU placement, three subnetwork types are evaluated. Further, a differential voltage-based algorithm is applied to each subnetwork in a system. The tripping decisions for each dependent subnetwork are carried out in steps by providing separate timer settings for them. The load encroachment and fault conditions for a particular case is distinguished by applying modified distance relaying and sequence component-based algorithms to the proposed differential voltage-based scheme. Extensive tests are carried out for several fault and stressed conditions on a New England 39-bus system on MATLAB/Simulink platform. The proposed scheme is also validated for different test cases on a modified WSCC 9-bus system on real-time digital simulator platform for assessing its ability to perform in real time.

Integrated Wide-Area Backup Protection Algorithm During Stressed Power System Condition in Presence of Wind Farm

Stressed power system conditions such as power swing, voltage instability and load encroachment may influence the secure operation of conventional backup protection at their third zone (zone 3). In this paper, a new integrated backup protection algorithm for distance relay is proposed based on wide-area measurements to distinguish the fault-stress conditions in the presence of offshore wind farm (WF). Presence of WF creates problem for distance relay due to varying wind speed and wide fluctuations in voltage and current signal during fault condition. In this work, two criteria are proposed to analyze and to identify the events. The first criterion compares the positive-sequence bus voltages in order to identify the faulty bus. According to second criterion, the absolute positive-sequence impedance angle difference between the lines connected to that faulty bus is computed to identify the faulty line. Numerous test cases with the WSCC 3-machine, 9-bus and IEEE 39 bus power system models have been simulated using EMTDC/PSCAD software. Results for different fault cases, power swing, load encroachment and voltage instability, and various non-fault cases like capacitor switching, demonstrate the efficacy of the wide-area backup protection scheme. Comparative assessment reports with the existing methods are also presented.

Wide area backup protection scheme for distance relays considering the uncertainty of network protection

Although local protection methods can perform well at speed, in a real network where network uncertainties are unavoidable, these methods may result in inaccurate performance. Therefore, the use of other methods, such as wide area protection, can lead to more accurate results because of using comprehensive information via telecommunication links. In this paper, a wide area protection algorithm is presented to cover the mal-operation of relays due to the network uncertainties. In this method, an objective function is defined based on the performance status of various zones of distance relays, the values of which will be different for each line. Depending on the position of each relay on the transmission line, weighting factors for objective function are determined based on the optimization algorithm and taking into account the possible uncertainties of the power grid. The proposed method has been implemented on IEEE 9-bus system and has proved high detection precision and performance accuracy.

Wide-Area Measurement-Based Adaptive Backup Protection for Shunt Compensation Environment

In this paper, the localization issue associated with distance relay protecting a transmission line with static synchronous compensator (STATCOM) is discussed. Generally, distance relay is mal-operated due to the dynamic behaviour of STATCOM during its inductive and capacitive modes of operation. Because, STATCOM operation creates the problem of correct measurement of fault distance and is responsible of under-reach and over-reach of distance relay. Furthermore, high fault resistance is also the reason of under-reach along with STATCOM operation. To overcome aforementioned challenges, an adaptive wide-area backup protection scheme (WABPS) is addressed which compares the calculated impedance and referenced impedance. Calculated impedance is the difference between impedance measured by relay and impedance contributed by fault resistance. Referenced impedance is the sum of fault impedance and impedance contributed by STATCOM. If calculated impedance is less than referenced impedance, then the relay will generate a trip signal. Proposed WABPS is inherent directional and provides information about fault detection, fault distance, and fault resistance during dynamic operation of STATCOM. The performance of the proposed WABPS is evaluated using technology of synchronize phasor measurement and communication channel. A 230 kV, 50 Hz system with a 24-pulse STATCOM is simulated and validated using PSCAD/EMTDC software package.

Optimal PMU allocation for high-sensitivity wide-area backup protection scheme of transmission lines

In spite of the outstanding benefits provided via phasor measurement units (PMUs) to smart grids in the field of wide area protection, they increase the cost of the infrastructure. Based on PMU location and system topology, subsets of buses and lines are formed representing backup protection zones (BPZs). This paper introduces a proposed criterion to overcome the shortage in formulating the BPZs. Also, this paper presents a proposed framework to define the optimal PMU locations regarding wide area BPZs. The framework is expressed as a multi-objective function, which aims to enhance the system observability, increase the number of transmission lines belonging to BPZs and increase the BPZ threshold sensitivity. The genetic algorithm technique (GA) is used to obtain the optimal locations of PMUs for different cases. The effectiveness of the proposed framework is evaluated by investigating the 14-bus IEEE standard system for different cases of fault location, type and resistance. Furthermore, the 39-bus system is considered for some cases as a larger system. The results show the possibility of enhancing the sensitivity of the BPZs of the system regarding optimal PMU locations.

A modified wide-area backup protection scheme for shunt-compensated transmission lines

In this paper, a new modified methodology has been proposed to protect shunt-compensated transmission lines as properly as uncompensated lines. The proposed scheme initially selects the nearest buses to the fault location based on data provided by the phasor measurement units (PMUs). Three buses with the minimum magnitude of the positive-sequence voltages or maximum magnitude of negative (or zero)-sequence voltages are selected as the nearest buses to the fault location. All connected lines to these buses are designated as suspected. Afterward, the suspected line with the maximum absolute difference of positive (or negative)-sequence current angle is concluded as the faulted line. The effectiveness of the proposed technique has been evaluated under various fault scenarios in WSCC 9-bus and IEEE 39-bus test systems in MATLAB/SIMULINK platform. The outputs clearly reveal that the recommended scheme finds the faulted line precisely under different fault types, fault locations, fault resistances, and shunt-compensator types within 3 ms. The modified scheme can also detect high-resistance asymmetrical faults accurately exploiting negative-sequence current angles instead of the positive ones.

Wide-Area Backup Protection Against Asymmetrical Faults Using Available Phasor Measurements

This paper proposes a robust and computationally efficient wide-area backup protection (WABP) scheme against asymmetrical faults on transmission systems using available synchronized/unsynchronized phasor measurements. Based on the substitution theorem, the proposed scheme replaces the faulted line with two suitable current sources. This results in a linear system of equations for WABP, with no need of full system observability by measurement devices. The identification of the faulted line is attributed to the sum of squared residuals ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SoSR</i> ) of the developed system of equations. To preserve accuracy, the scheme limits the calculations to the assessment of the negative-sequence circuit of the gird. Relevant practical aspects that have not been properly addressed in the literature, namely the non-simultaneous opening of circuit breakers (CBs) and their single-pole tripping for single-phase to ground faults are investigated. The linearity of the formulations derived removes concerns over convergence speed and potential time-synchronization challenges. The proposed scheme is able to identify the faulted line and retain this capability for hundreds of milliseconds following the fault inception. More than 20 000 simulations conducted on the IEEE 39-bus test system verify the effectiveness of the proposed WABP scheme.

Decentralised wide‐area back‐up protection scheme based on the concept of centre of reactive power

Here, a new decentralised approach-based wide-area back-up protection (WABP) scheme is proposed for faulted line identification (FLI). The scheme is divided into two sub-routines, i.e. possible faulted region (PFR) identification and FLI. Initially, the power system under study is divided into different coherent regions. The concept of centre of reactive power (CORP) is used to accomplish the task of PFR. Once the faulted region is identified, FLI is done by continuously monitoring the direction of reactive power flow (DORPF) of each line within the PFR. The proposed scheme is extensively tested on IEEE-39 bus test system for different types of faults. The performance of the scheme under stressed system conditions is also investigated. The obtained results show that the suggested algorithm is able to maintain the balance between dependability and security aspects of the protection logic.

Enhancing Performance of Wide-Area Back-Up Protection Scheme Using PMU Assisted Dynamic State Estimator

Wide-area measurements consisting of phasor measurement information, are lately used for monitoring and protection purposes. However, due to certain constraints related to usage of phasor measurement units (PMU) at all the buses, optimal placement of PMUs are needed for wide area applications. Further, limitations of supervisory control and data acquisition measurements and erroneous PMU measurements due to noise and communication link failure at some instant leads to the requirement of dynamic state estimation (DSE) using PMU information. The proposed scheme deals with wide area back-up protection scheme utilizing cubature Kalman filtering-based DSE in conjunction with fewer PMU measurements for obtaining full observability. A voltage-based index is derived using the DSE information to identify the faulty line. The scheme is tested for several faulted as well as stressed conditions such as line outage, generator outage, load encroachment and voltage stressed conditions including measurement error and missing data at some of the PMU buses. Extensive test on New England 39-bus system indicate that the proposed wide-area back-up protection scheme can reliably take appropriate action for back-up zone.

PMU Placement With Channel Limitation for Faulty Line Detection in Transmission Systems

This paper presents a new phasor measurement unit (PMU) placement methodology to provide the required data for wide-area backup protection scheme. The presented placement method is primarily a binary linear optimization problem whose constraints are defined to detect faults on transmission lines based on the difference between voltage values of a bus obtained from two different paths, while the full observability of the system is also guaranteed. To consider the limitation on the number of PMU channels, a new bi-level approach is also proposed in this paper, in which the upper level is aimed to find the best solution among different submatrices, while the lower level finds the best PMU placement solution for each submatrix. Therefore, the contribution of this paper is to propose a methodology to optimally locate minimum number of PMUs in a power system in a way that while full observability of the system and its wide-area backup protection are assured, the types of each PMU—in terms of its number of channels as well as the lines whose currents should be measured by the PMU to satisfy the constraints—are determined. The performance of the proposed methodology is evaluated on standard test power systems.

Wide-area backup protection and protection performance analysis scheme using PMU data

This paper presents a wide-area backup protection scheme that incorporates protection performance analysis based solely on voltage from Phasor Measurement Units (PMUs). The system reports and summarizes information relating to fault detection, and identification of the faulted circuit(s) protection/circuit breaker operation (i.e. whether it is correct or not), in a short period of time. It can also be applied as an effective and relatively simple, fast, wide-area backup protection to improve the resilience of power systems. Case studies are presented, where the proposed wide-area backup protection scheme is validated using the IEEE 14-bus network. It is demonstrated that the proposed scheme is capable of correctly detecting faults (including high-resistance faults) in less than 100 ms from fault inception and can report on whether the protection/circuit breakers have operated as expected within a further 100 ms, thereby coordinating with existing protection systems with a view to enhancing the system reliability and security by appending existing protection systems with system-wide information. Applicability of the developed system to large-scale power systems is also demonstrated. Discussion relating to how this method can be cost effective through exploitation of existing PMU data, which may already be used for other purposes, is included.

Wide-Area Backup Protection Scheme for Transmission Lines Considering Cross-Country and Evolving Faults

Wide-area fault detection and location for cross-country and evolving faults have not been discussed before in the open literature. This paper presents an innovative wide-area backup protection scheme for untransposed transmission lines considering cross-country and evolving faults. Synchronized voltages and currents measurements in the phase domain are used for fault detection and location. The proposed scheme can distinguish transmission line faults from other external faults or different operating conditions. The faulty line is correctly identified, and the locations of all fault types including cross-country and evolving faults are estimated precisely. The proposed scheme is investigated under different fault locations, fault resistances, fault types, and fault inception angles. In addition, the influence of transmission line parameter errors and synchronization errors on the proposed scheme is investigated. Extensive simulation studies are applied to New England 39-bus test system, and the simulation results prove that the proposed scheme yields better performance for all simulated cases.

A New Decentralized Approach to Wide-Area Back-Up Protection of Transmission Lines

This paper presents a decentralized-approach-based wide-area back-up protection scheme to identify the faulted line in a power transmission network. The proposed scheme divides the whole power system under study into different protection zones (PZs) corresponding to generator bus(es). Furthermore, a “gain in momentum” (GIM) index at each generator bus is used to minimize the search set. This information helps in reducing the search space to the PZ corresponding to the generator bus with highest GIM following a fault. This area is termed as a vulnerable protection zone (VPZ). Once the VPZ is identified, positive-sequence voltage magnitudes of each bus within the VPZ are monitored to locate the bus closest to the fault (BCF). Finally, reactive power-flow information of each line connected to the BCF is used to identify the faulted line. The performance of the proposed scheme is extensively validated on the Western System Coordinating Council-9 bus system, the IEEE-39 bus New England system, and 246-bus North India Grid using the Power System Simulation for Engineering. The test results indicate that the proposed scheme is highly effective for the WABP of transmission lines.

A New Wide-Area Backup Protection Scheme for Series-Compensated Transmission System

This paper presents a new wide-area backup protection scheme based on the phase angle of positive-sequence integrated impedance (PAPSII). The proposed scheme uses phasor measurement units (PMUs) that comply with standard C37.118.1-2011 for retrieving the phasor information. The PMUs provide the positive-sequence phasor information of the voltage and current signals at each and every bus of a system to a phasor data concentrator (PDC). The positive-sequence integrated impedance of each line of the system is extracted, and the PAPSII of each line is continuously monitored at the PDC. The values of the PAPSII help in identifying the faulted line of the power transmission system. The proposed scheme is extensively tested for different types of fault scenarios on a three-machine nine-bus power transmission network on a real-time digital simulator platform. Critical issues such as voltage inversion, current inversion, load encroachment, and the power swing are addressed in the proposed scheme. The test results indicate that the proposed scheme can overcome the limitations of existing backup protection schemes and can provide a reliable protection measure.

An adaptive supervised wide-area backup protection scheme for transmission lines protection

Maloperation of conventional relays is becoming prevalent due to ever increase in complexity of conventional power grids. They are dominant during power system contingencies like power swing, load encroachment, voltage instability, unbalanced loading, etc. In these situations, adaptive supervised wide-area backup protection (ASWABP) plays a major role in enhancing the power system reliability. A balance between security and dependability of protection is essential to maintain the reliability. This paper proposes multi-phasor measurement units (MPMU) based ASWABP scheme that can function effectively during faults besides power system contingencies. MPMU is an extended version of Phasor Measurement Unit (PMU). It is an intelligent electronic device which estimates the synchronized predominant harmonic phasors (100Hz and 150Hz) along with the fundamental phasors (50Hz) of three phase voltages and currents with high precision. The proposed ASWABP scheme can detect the fault, identify the parent bus, determine the faulty branch and classify the faults using MPMU measurements at System Protection Center (SPC). Based on these MPMU measurements (received at phasor data concentrator (PDC) at SPC) the appropriate relays will be supervised to enhance the overall reliability of the power grid. Numerous case studies are conducted on WSCC-9 bus and IEEE-14 bus systems to illustrate the security and dependability attributes of proposed ASWABP scheme in MATLAB/Simulink environment. Also, comparative studies are performed with the existing conventional distance protection (Mho relays) for corroborating the superiority of the proposed scheme regarding security and dependability. Comparative studies have shown that the proposed scheme can be used as adaptive supervised wide-area backup protection of conventional distance protection.

PHASOR MEASUREMENT UNIT BASED WIDE AREA BACKUP PROTECTION SCHEME FOR POWER TRANSMISSION LINES

Protective relays, pivotal devices that can quickly identify and isolate fault area in power systems, is of great importance for ensuring power system security and reliability. This paper proposes a wide area backup protection scheme for identifying the faulted zone in power transmission lines. This scheme uses the data of wide area measurement systems (WAMS) with constrained number of phasor measurements which are synchronized by nature. First, the number of PMUs required for the scheme is optimized and then, the transmission network is divided into backup protection zones (BPZs) based on the PMU placement and network topology. Whenever the fault arises in a transmission network, the sum of zero and/or positive sequence currents entering the faulted BPZ highly increases, and hence, the faulted BPZ can be determined. This scheme determines the faulted zone quickly and precisely and thereby, reducing the effect of the various faults on the power grid. The proposed method is tested and simulated using a standard WSCC 9-bus system using MATLAB/Simulink.

An spatiotemporal information system based wide-area protection fault identification scheme

The paper presents a synchronized phasor measurement based fast and accurate comprehensive wide area back-up protection scheme for transmission lines. The proposed scheme uses Koopman Mode Analysis (KMA) technique on fault current data obtained from Phasor Measurement Units (PMUs) for fault identification in back-up protection. The principal advantage of Koopman operator is that it is based on spatiotemporal information system (STIS). In real world applications, often time and space exists together and hence, dealing with spatial aspect without considering temporal aspect is of limited use. The wide area back-up protection scheme is developed using STIS for fault identification and classification including wide variations in operating conditions of the power network. The New England 39 bus system is used as the test system which is developed on Dig-Silent power factory commercial software (PF4C) platform for evaluating the performance of proposed technique. Further, the efficacy of the proposed scheme is also tested for stressed conditions such as symmetrical fault during power swing and load encroachment and found to work effectively.

An Advanced Fault Locating Technique with WAMS based Backup Protection Scheme for Power System with Simultaneous Faults

Protection of power systems is important for stable and uninterrupted operation of power network. Maloperation of traditional back up protection schemes (e.g-Zone3 maloperation) causes many catastrophic phenomenon like cascaded tripping in power systems. So, some defensive mechanism are needed for taking care of such failures in power systems and to increase their security and reliability. Due to hugeness and complexity of Modern power systems, they are controlled, monitored and protected by Wide Area Measurement systems (WAMS). WAMS increases the efficiency and reliability of power networks and prevent the chance of blackouts and cascading failures in tandem. A synchronized phasor measurement-based wide-area backup protection scheme is presented in the paper where the magnitude of sequence voltages of buses at a system protection centre are used to identify the faulted area, bus closest to the fault and faulted line. The proposed method is tested for several faults including simultaneous faults in power systems with interconnections also. This technique is found to be Reliable, accurate and fast with contemporary synchronized measurement based technology. It is expected that numerous disastrous blackouts, cascaded tripping of power networks can be avoided and reliability and security of the power systems can be improved by the scheme. The study of new and improved back up protection scheme is done on a WSCC-3 machine-9 bus system. The data is simulated through EMTDC/PSCAD and MATLAB /SIMULINK software.