Proposed Protection Algorithm Research Articles

New Algorithm for Protection of Double Circuit Transmission Lines Using Modal Currents

This paper presents a new protection algorithm for double circuit transmission lines using the sum of ratios of modal currents. Relay-operating characteristics is proposed using the complex ratio of modal currents. The proposed algorithm estimates modal domain line parameters and identifies the faulty phases for single pole-tripping applications even during inter-circuit faults. The scheme is sensitive to high resistance internal faults and also detects internal faults with outfeed. The proposed scheme is immune to mutual coupling and is found robust to uncertainties in parameter estimation due to measurement inaccuracies. The scheme is tested for its effectiveness to deal with current transformer saturation and synchronisation error. The scheme protects series compensated double circuit transmission lines even in the presence of current inversion. Exhaustive case studies in electromagnetic transient program (EMTP)/alternate transient program are performed on 400 kV, 300 km, double circuit transmission lines and the proposed protection algorithm is implemented in MATLAB. The results confirm the superiority of the proposed scheme.

Online Detection of Power Swing Using Approximate Stability Boundaries

This paper presents a power swing detection algorithm in multi-machine power systems, which uses wide-area synchrophasor measurements and is based on Zubov's stability boundaries. Zubov's boundary method, an approximation of the famous Lyapunov function, is very common for numerical analyses of power system stability. This work extends the concept of Zubov's approximation boundaries to online protection applications. First, the proposed protection algorithm constructs a series of Zubov's stability boundaries on power angle-frequency (δ-ω) plane for generators based on real-time measurements from phasor measurement units/merging units. Then, it tracks the trajectory of each generator in the δ-ω plane after the disturbance to differentiate out-of-step (OOS) conditions from stable swings. The proposed approach is suitable for online applications, which is a significant improvement over the existing methods for swing detection since it does not require offline studies and network reduction. Effectiveness of the proposed method is shown using a single-machine infinite bus and New-England 10-machine 39-bus systems. The proposed method is also implemented in a hardware-in-the-loop setup with a customized IEC 61850-based OOS relay, and performance is compared with a commercially available relay.

An intelligent protection scheme to deal with extreme fault currents in smart power systems

In modern power systems, the generation capacity is increasing significantly for responding to high electric energy demands. This generation expansion directly affects the level of short circuit in transmission systems and increases the fault current magnitude, which may pass the breaking capacity of circuit breakers. To deal with extreme fault currents in power systems, an intelligent protection scheme is proposed in this paper, which removes the necessity of installing expensive fault current limiters. This protection scheme uses communication capabilities defined in IEC 61850 to design smart cascading switching actions to isolate the faulty part of the system. In fact, it is a supervisory protection algorithm in addition to the conventional distance protection, which is the main protection of HV transmission systems. This protection is activated if the fault current is higher than breaking capacity of circuit breakers; otherwise, the conventional distance protection is responsible to clear the fault. Numerical results obtained from implementing the proposed protection algorithm in a 400 kV system demonstrate the effectiveness of this method in terms of fault clearing time, stability margin improvement and power system economy.

\xb5PMU-based smart adaptive protection scheme for microgrids

The concepts of microgrids (MGs) and smart grid represent the recent targeted revolution towards fully smart electrical network integrated with high penetration of renewable energy sources (RESs). The protection system of MGs becomes a challenge due to variable characteristics of its currents, bidirectional power flow and output power fluctuations of RES, causing selectivity and sensitivity issues for conventional protective devices (PDs) with fixed setting. In this paper, a smart protection scheme (SPS) is proposed using micro-phasor measurement units (µPMUs) to obtain the continuous rapid synchronized phasor measurement data. And it is communicated with a microgrid central controller (MGCC) through highly reliable communication architecture to carry out online smart adaptive protection scheme. Fault index coefficients and abnormality coefficients are calculated for each feeder to detect the fault location and the abnormality case. Detailed modeling of an MG including 10-bus connected distribution system with integrated distributed generation (DG) is simulated using ETAP software. The proposed protection algorithm is modeled and evaluated using MATLAB software. The proposed fault detector and abnormality detector can enable quick and accurate fault identification and isolation.

High impedance fault protection scheme for smart grids based on WPT and ELM considering evolving and cross-country faults

In this research a novel communication based high impedance fault (HIF) protection scheme is proposed on the basis of wavelet packet transform (WPT) and extreme learning machine (ELM). The scheme is applied to the protection of transmission and distribution lines considering evolving and cross-country faults. Fault detection and clearing are the most important tasks of all protection systems, however, simultaneous and complex faults are the cases that most of the conventional protection systems are incapable of making appropriate decisions. The bottlenecks of the conventional protection systems are more highlighted when the faults are HIF. In this study, WPT, which is one of the useful methods in signal processing, is utilized to extract high frequency coefficients of three phase currents of both ends of transmission line. Furthermore, ELM which is an artificial neural network based classifier, is employed to detect the faulted phases. Consequently, the proposed protection algorithm will be compared with the distance protection as a conventional protection system and also with a recently proposed HIF protection algorithm to verify its robustness, security and dependability. The proposed method is not sensitive to the location, inception angle and impedance of the faults, power swing, power system topology and noise.

Fault detection and location algorithm for DG‐integrated distribution systems

The overcurrent protection on the traditional distribution system uses local measurements and settings as a basis for decision-making. However, connection of multiple distributed generators with different short-circuit characteristics makes the local measurements unpredictable, leading to possible loss of protection coordination. In order to solve this problem, this study proposes an algorithm that achieves its protection function through load flow and sensitivity calculations based on voltage measurements. The algorithm is built on a modelling approach that splits the distribution network into a series of overlapping protection zones. The overlapping feature is realised logically through peer-to-peer communications between intelligent agents located in adjacent zones. A sensitivity-based electrical signature was identified that is generated when a fault occurs within a zone. Simulation results show that the proposed protection algorithm is able to identify the zone in which the fault has occurred and the specific faulted node or line section in that zone. The fault current contributions, or no contributions, of the distributed generators (DGs) do not impact the operation of this algorithm.

Centralised busbar differential and wavelet‐based line protection system for multi‐terminal direct current grids, with practical IEC‐61869‐compliant measurements

This study presents a method for discriminative detection of direct current (DC) faults on voltage source converter-powered multi-terminal high-voltage direct current transmission systems using two fundamental guiding principles, namely instantaneous current-differential and travelling waves. The proposed algorithm utilises local voltage and current measurements from all transmission lines connected to a DC busbar, and current measurement from the DC side of the converter. The scheme operates at a sampling frequency of 96 kHz, which conforms with IEC 61869-9. No long distance communication is involved while measurements and signal exchange within DC substations are enabled by the utilisation of IEC 61850. Performance is assessed firstly through detailed transient simulation, using verified models of modular multi-level converters, hybrid DC circuit breakers and inductive DC-line terminations. Furthermore, practical performance and feasibility of the scheme are evaluated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed protection algorithm can effectively, and within a very short period of time (i.e. <;1 ms), discriminate between busbar and line faults (internal faults), while remaining stable during external faults. Additionally, it has been demonstrated that IEC 61869-9 is suitable for enabling fast DC protection schemes incorporating travelling waves.

Backup protection scheme for transmission line compensated with UPFC during high impedance faults and dynamic situations

This study presents a backup protection scheme for transmission line compensated with unified power flow controller (UPFC) using power differential protection algorithm. In this scheme, power differential feature is evaluated from the apparent power flow in each phase at the local and remote bus to discriminate between the fault and normal situation. The proposed protection algorithm can be integrated with the conventional distance protection to supervise its operation during stressed conditions. Extensive fault simulation studies have been performed for different types of fault with several conditions and critical dynamic situations/issues such as load encroachment, power swing and high impedance fault (HIF). A 500 kV three machines four bus transmission system with UPFC has been used to validate the performance of the proposed scheme using MATLAB software. The test results depict that the proposed scheme is robust against HIF, power swing and load encroachment. It is not affected by the variation in pre-fault power flow angle and synchronisation delay. The proposed scheme has also been tested for current transformer (CT) and coupling capacitor voltage transformer (CCVT) transient error, which brings out the superiority of the scheme.

Single-Ended Differential Protection in MTDC Networks Using Optical Sensors

This paper presents a method for rapid detection of faults on voltage source converter multiterminal HVdc transmission networks using multipoint optical current sensing. The proposed method uses differential protection as a guiding principle, and is implemented using current measurements obtained from the optical current sensors distributed along the transmission line. Performance is assessed through detailed transient simulation using MATLAB/Simulink models, integrating inductive dc-line terminations, detailed dc circuit-breaker models, and a network of fiber-optic current sensors. Moreover, the feasibility and required performance of optical-based measurements is validated through laboratory testing. Simulation results demonstrate that the proposed protection algorithm can effectively, and within very short period of time, discriminate between faults on the protected line (internal faults), and those occurring on adjacent lines or busbars (external faults). Hardware tests prove that the scheme can be achieved with the existing, available sensing technology.

The Minimum Interference p-Cycle Algorithm for Protection of Space Division Multiplexing Elastic Optical Networks

In optical networks, failures can imply in great loss of data due to high transmission rates, leading to the need of employment of protection mechanisms. This paper introduces a novel algorithm to provide Failure-independent path protecting p-cycle with minimum interference for path protection in elastic optical networks using space division multiplexing. The proposed protection algorithm reduces rejections of future requests and makes no assumption about specific patterns of arrival of requests. The algorithm is compared to the FIPPMC algorithm and to an algorithm based [1]. Results indicate that 100% protection for single failures can be provided by the proposed algorithm.

Analysis of Single Frequency GPS Receiver Under Delay and Combining Spoofing Algorithm

Global position system (GPS) has become a satellite based critical international navigation and timing system. Navigation has a significant effect in our daily life. Hence, such a commonly used system is an interesting goal for criminal utilizing. Trusting GPS navigation, need spacious knowledge to inadvertent and intentional interferences. The position deviation in GPS, which is subject to spoofing, is analyzed in this paper. Serious research into spoofing has been carried out in recent years. One of the basic requirements and major challenges in designing anti-spoofing methods and evaluating a successful GPS spoofing countermeasure is collection of actual spoofing data used to verify the proposed protection algorithm. Since actual spoofing data is acquired through an expensive spoofer-receiver device, preparing genuine spoofing data without expensive spoofing devices, including extra software or hardware, can be helpful in the development of anti-spoofing studies. In this paper, after providing a refined assessment of existing approaches, a new practical and low-cost technique is proposed that helps to generate a set of spoofing data only with the employment of software receiver and a set of real GPS measurements. In this way, a new kind of spoofing data is resulted by utilizing delay and mixing procedure. This data will be generated in victim receiver antenna, if a spoofer-receiver device is used in practice. After explanation of the spoofing algorithm, its influence on the GPS receiver is studied in details, and then validation of proposed method is proved by appropriate tests.

Protection of standard-delta phase shifting transformer using terminal currents and voltages

This paper presents a new standard-delta phase shifting transformer (PST) protection technique based on the normal operating voltage–current (v–i) relationships of the PST equivalent circuit. These voltage–current relations are used to define the v–i differential equations, which are further used to detect and discriminate the internal and external faults. Using the v–i differential relationships, the proposed protection relay computes small or zero (ideally) differential quantity during normal and external fault conditions. However, in the event of an internal fault, the v–i relationships become invalid and the proposed differential relay therefore computes significantly large differential quantity. A comparative performance analysis of the proposed protection technique and the former methods, that make use of the current differential principle, suggest that the proposed technique offers a more secure protection solution of the standard-delta PST. It successfully detects and discriminates the internal/external faults, while remaining stable during a magnetizing inrush current and the saturation of the series winding, and offers a high degree of tolerance against external faults with current transformer saturation. A real representation of a standard-delta PST has been modeled in PSCAD/EMTDC to simulate various normal and faulted conditions to test and validate the performance of the proposed protection technique. Implementation of the proposed protection algorithm requires currents, voltages and tracking of the tap-changer position.

A Practical Protection Coordination Strategy Applied to Secondary and Facility Microgrids

In a conventional distribution system, protection algorithms are designed to operate on a unidirectional high fault-current level. In a microgrid, a fault current from distributed generation (DG) may bring about a relay malfunction because of the bidirectional and relatively small fault current. Therefore, the conventional protection scheme is not applicable to microgrids and a new protection method must be developed. In this paper, two protection coordination algorithms which can be applied for facility and secondary microgrids are proposed, respectively. The proposed protection algorithms eliminate faults not by the EMS signal but by directional relays. Moreover, this makes the algorithms flexible regardless of the types and numbers of DG. The proposed protection algorithms were simulated at the KEPCO RI Microgrid Demonstration Site.

A complete motor protection algorithm based on PCA and ann: A real time study

Protection of an induction motor (IM) against possible faults, such as a stator winding fault, due to thermal deterioration, rotor bar and bearing failures, is very important in environments in which it is used intensively, as in industry as an actuator. In this work, a real time digital protection algorithm based on principal component analysis (PCA) and neural network method is presented for induction motors. The proposed protection algorithm covers internal winding faults (also known as stator faults), broken rotor bar faults, and bearing faults. Many laboratory experiments have been performed on a specially designed induction motor to evaluate the performance of the suggested protection algorithm. The hybrid protection algorithm described in this paper uses is based on a three phase rms supply. These currents are first preprocessed by PCA to extract distinctive features called residuals. The calculated residuals are applied to a feed-forward back-propagation neural network as input vectors for decision making. Outputs of the network are signals denoting winding fault, rotor bar fault, bearing fault, and normal operation. The proposed algorithm is implemented by using Matlab^{TM} and C++ with a NI-DAQ data acquisition board.

A Traveling-Wave-Based Protection Technique Using Wavelet/PCA Analysis

This paper proposes a powerful high-speed traveling-wave-based technique for the protection of power transmission lines. The proposed technique uses principal component analysis to identify the dominant pattern of the signals preprocessed by wavelet transform. The proposed protection algorithm presents a discriminating method based on the polarity, magnitude, and time interval between the detected traveling waves at the relay location. A supplemental algorithm consisting of a high-set overcurrent relay as well as an impedance-based relay is also proposed. This is done to overcome the well-known shortcomings of traveling-wave-based protection techniques for the detection of very close-in faults and single-phase-to-ground faults occurring at small voltage magnitudes. The proposed technique is evaluated for the protection of a two-terminal transmission line. Extensive simulation studies using PSCAD/EMTDC software indicate that the proposed approach is reliable for rapid and correct identification of various fault cases. It identifies most of the internal faults very rapidly in less than 2 ms. In addition, the proposed technique presents high noise immunity.

Development and Implementation of a Novel Fault Diagnostic and Protection Technique for IPM Motor Drives

This paper presents the practical implementation of a novel fault diagnostic and protection scheme for the interior permanent-magnet (IPM) synchronous motors using wavelet packet transform (WPT) and artificial neural network. In the proposed technique, the line currents of different faulted and normal conditions of the IPM motor are preprocessed by the WPT. The second level WPT coefficients of line currents are used as inputs of a three-layer feedforward neural network. The proposed protection technique is successfully simulated and experimentally tested on the line-fed and inverter-fed IPM motors. The Texas Instrument 32-bit floating-point digital signal processor TMS320C31 is used for the real-time implementation of the proposed protection algorithm. The offline and online test results of both line-fed and inverter-fed IPM motors are given. These test results showed satisfactory performances of the proposed diagnostic and protection technique in terms of speed, accuracy, and reliability.

TRAVELLING WAVE-BASED FAULT LOCATION SCHEME FOR MULTI-END AGED UNDERGROUND CABLE SYSTEM

This paper presents a novel wavelet-based fault location scheme for aged cable systems when synchronized digital fault recorded data are available at the two terminals of each cable. The availability of digital fault recorders at a reasonable cost allows the use of many of these devices at major substations. Thus, many cable lines have data available at both ends. The proposed scheme estimates the fault location in multi-end aged cable system using the theory of wavelet singularity detection as a powerful signal processing tool, the arrival of the first and second voltage travelling waves at both sides of the power cables can be identified reliably. The proposed scheme has the ability to eliminate the effect of the change in the propagation velocity of the travelling waves. This will help solving the problem of cable changing parameters especially the changing of the relative permittivity of the cable over its age that causes a large error in all fault location techniques, which use the value of propagation velocity in calculations. The method is valid even with very close faults to busbars. Characteristics of the proposed protection algorithm are analysed by extensive simulation studies using ATP/EMTP. The obtained results indicate an accepted degree of accuracy for the proposed fault locator scheme.

Impedance estimation including ground fault resistance error correction for distance protection

A distance protection scheme, which uses phasors of symmetrical components not only for supporting features but also for the core function of the distance calculation, is described in this paper. The sequence current and voltage phasors are numerically efficiently extracted from the phase quantities by two Clarke and three discrete Fourier transformations. A fault resistance during ground faults can depreciate the reliability of standard-distance protection algorithms. The described algorithm includes a method to compensate errors in the inductive reactance measurement caused by the ground fault resistance. This enhances the reliability of the distance protection scheme for faults around the remote-transmission line end. Simulation results demonstrate the performance of the proposed protection algorithm.