Distance Relay Operation Research Articles

Accelerated Zone II Operation of Distance Relay Using Impedance Change Directions

Legacy distance protection introduces an intentional delay before the trip command for zone 2 internal faults. Instantaneous fault clearance in such faults can be achieved if distance relays are equipped with reliable communication. However, communication channel is not available or enabled in some lines. Besides some channels are prone to faults occurred on the line degrading their reliability. To overcome such drawbacks in instantaneous fault clearance, a local algorithm is proposed that uses the relay local signals to accelerate the trip for zone 2 internal faults. The change seen in the relay impedance resulted by remote circuit breaker operation (RCBO) is the decision criterion in this method. The related impedance change equations are analytically derived and formulated. It is shown that the proposed method outperforms the similar approaches and improves their shortcomings in light-and no-load conditions and zero resistance faults. While most of the methods in the literature are not sensitive enough to detect single-phase RCBO, which is common during single-phase transient faults, significant improvement is attained by the proposed method in this regard. Performance of the proposed method is investigated under various fault and system conditions. Simulation results disclose high reliability of the proposed algorithm during all these conditions.

An adaptive approach for three zone operation of digital distance relay with Static Var Compensator using PMU

Modern energy transmission systems suffer from great voltage dropping due to enormous loads. Therefore appropriate schemes should be devised to regulate the voltage. FACTS devices such as Static Var Compensator are often used for this purpose. However, SVC at mid-point of transmission line may leads to deteriorate of distance relay operation, resulting in inaccurate estimation of faults locations i.e. over-reach or under reach for different cases. This paper proposed a new algorithm that utilizes synchronized phasors measurement (SPM) to enhance the operation of distance protection zone in many aspects. The proposed method is tested for 230 kV system simulated in EMTDC/PSCAD with Bergeron model of transmission line. The results prevailed for adaptive approach scheme are more accurate, victor and robust in equivalence with usable transmission line distance protection with SVC.

Distance Relaying with Power Swing Detection based on Voltage and Reactive Power Sensitivity

Abstract Sudden changes in loading or configuration of an electrical network causes power swing which may result in an unwanted tripping of the distance relay. Hence, it becomes utmost necessary to rapidly and reliably discriminate between actual fault and power swing conditions in order to prevent instability in power network due to mal operation of distance relay. This paper proposes a novel method for the discrimination between fault and power swing based on rate of change of voltage and reactive power measured at relay location. The effectiveness of the proposed algorithm is evaluated by simulating series of power swing conditions in PSCAD/EMTDC® software for different disturbances such as change in mechanical power input to synchronous generator, tripping of parallel line due to fault and sudden application of heavy load. It is revealed that the distance relay gives successful tripping in case of different fault conditions and remains inoperative for power swing with the implementation of the proposed algorithm. Moreover, the proposed scheme has ability to distinguish the symmetrical and asymmetrical fault occurrence during power swing condition.

Ground distance relay compensation in the presence of delta‐hexagonal phase shifting transformer

In this study, the effects of the delta-hexagonal phase shifting transformers (PSTs) on the operation of distance relays and their trip boundaries are investigated under different fault resistances and locations. Existence of fault resistance in phase-to-ground faults creates an unreliable operation of distance relays. Trip boundaries are used to determine the fault resistance effects on the impedance calculated by the relay. Moreover, PSTs are used to control the power flow in transmission lines. Finally, a feasible method for eliminating the PSTs detrimental effects on the operation of the distance relays is presented. This method, which uses the voltage difference between the PST terminals, is getting prevalent in modifying the operation of the distance relays even under the high resistance faults. Phasor measurement units (PMUs) are used to calculate this voltage as PMU signals and a remote signal system is used to transmit them to the system protection centre. All the simulations are conducted with Electro-Magnetic Transient Program.

An adaptive distance protection scheme in the presence of phase shifting transformer

Distance relays detect transmission line faults and their locations by measuring the voltage and the current signals. Also, phase shifting transformers (PSTs) are used to control the power flow in electrical power systems. PSTs protect transmission lines from thermal overloading, improve the stability of transmission system and control the power flow between different networks. Unfortunately, existence of PST in a transmission line vitiates the operation of protection relays by altering the voltage and current signals. In this paper, the effects of the delta–hexagonal PST on the operation of distance relays are investigated by both analytical and computational methods under different fault types and locations. Results of investigations reveal that the PST causes the distance relays to under-reach. Finally, a feasible method for eliminating the PST detrimental effects on the operation of the distance relays is presented. This method uses the voltage difference between the PST terminals to modify the operation of the distance relays. The phasor measurement units (PMUs) are used to calculate this voltage and remote signal systems are used to transfer it to the system protection center (SPC). All the simulations are conducted with electro-magnetic transient program (EMTPWorks).

Adaptive Distance Protection to Prevent False Relay Tripping during Power Swing

The existing distance relay is accommodated with starting function to detect short-circuits in power system. However, this function proves vulnerable to distance relay operation as it could falsely send a tripping signal during power swing. Hence, it is important to introduce an adaptive concept to the distance protection to prevent such false tripping. This paper presents a simple and effective adaptive protection algorithm for power swing prevention based on Under Impedance Fault Detector (UIFD) characteristics, in which capable to identify the power swing condition and adjusting the relay setting accordingly to avoid system mal-operation.

Effect of STATCOM – ES on Distance Relay Operation in a Series Compensated System

Abstract Flexible AC transmission systems or FACTS help in a big way to realize a smart grid, which can be used by utilities to reconfigure power flows in real time, maximizing throughput and minimizing losses. It will also facilitate incorporating wind, solar, and other intrinsically intermittent sources of energy into the grid. A static synchronous compensator equipped with energy storage (STATCOM - ES) can provide two degrees of freedom to inject both real and reactive current into the bus. This paper aims at developing the DQ model of a series compensated system which also incorporates a static synchronous compensator with energy storage and analyzing its effect on the operation of distance relay. The emulated conductance and susceptance by STATCOM - ES under various operating conditions is determined and its’ effect on impedance at the generator terminals is investigated. Effect of real and reactive power exchange by STATCOM – ES on the measured impedance and operation of distance relay is analyzed.

Simulation of Distance Relay Operation on Fault Condition in MATLAB Software/Simulink

Simulation of Distance Relay Operation on Fault Condition in MATLAB Software/Simulink

A New Algorithm to Stabilize Distance Relay Operation During Voltage-Degraded Conditions

This paper deals with the possible operation of distance relays during impending voltage instability and presents a new method to prevent its maloperation in power system voltage-degraded conditions. The proposed method successfully discriminates between fault occurrence and system incidents during stressed voltage conditions, even for the most severe cases such as sudden equipment outages and high impedance faults. The proposed scheme successfully blocks maloperation of relay zone 3 where the degraded condition is detected. It is based on the rates of change of voltage and current magnitudes. These values are different during fault occurrences in comparison with the corresponding values during stressed conditions system incidents. Simulation results verify the effectiveness of the proposed method.

Intelligent Power Swing Detection Scheme to Prevent False Relay Tripping Using S-Transform

Abstract Distance relay design is equipped with out-of-step tripping scheme to ensure correct distance relay operation during power swing. The out-of-step condition is a consequence result from unstable power swing. It requires proper detection of power swing to initiate a tripping signal followed by separation of unstable part from the entire power system. The distinguishing process of unstable swing from stable swing poses a challenging task. This paper presents an intelligent approach to detect power swing based on S-Transform signal processing tool. The proposed scheme is based on the use of S-Transform feature of active power at the distance relay measurement point. It is demonstrated that the proposed scheme is able to detect and discriminate the unstable swing from stable swing occurring in the system. To ascertain validity of the proposed scheme, simulations were carried out with the IEEE 39 bus system and its performance has been compared with the wavelet transform–based power swing detection scheme.

Adaptive distance relay algorithm for double circuit line with series compensation

With the onset of fault, nonlinear operation of Metal Oxide Varistor (MOV) in series compensated line introduces error in distance estimation. Distance relay reach accuracy depends on several factors. Mutual coupling effect in double circuit line is highly nonlinear and depends on circuit configuration, fault resistance and remote source infeed. This may lead to inadvertent operation of distance relay for faults outside the operating zone. Variations in system condition, effect of shunt capacitance effect and fault resistance influence distance relay healthy operation. Adaptive setting in digital platform is a greater advantage to estimate the change-in system condition and modify the relay characteristics using the recent information. This paper presents an adaptive algorithm for protection of double circuit series compensated line using local end information. The adaptive algorithm is derived for single-line-to-ground fault condition. A 400kV two source system is considered and simulated using EMTDC/PSCAD.

Synchrophasor-Assisted Zone 3 Operation

Zone 3 operation of distance relay serves as a remote backup in case of primary failure. Conditions, such as power swing, load encroachment, and voltage and transient instability, cause incorrect zone 3 operation. The detection of faults during such stressed conditions poses a further problem. This paper proposes a synchrophasor data-based technique for correct zone 3 operations by discriminating the fault from different stressed situations. This discrimination is accomplished using impedances calculated from voltage and current signals from synchrophasors placed at strategic locations. The proposed method is tested in the IEEE 39-bus New England system and found to be accurate.

Prevention of Cascaded Events of Distance Relay Zone Three Using Logic Controls

This paper presents a new method to prevent cascaded events caused by zone 3 elements of distance relays due to transmission line overload by using logic controls. A proposed adaptive distance relay algorithm provides a new concept to distinguish between actual faults and flow transfers and secures time to perform remedial controls by a defense system during cascaded events. Maloperation of distance relay is a very critical situation, leading to more operation of other distance relays and finally partial or total blackout. Logic controls are used to insure the operating decision through observing the system parameters and compare it with a setting already being input to the system. When distance relay is activated and the logic controls find that the system is healthy (unfaulted) and that the activation resulted from transmission line overload not real fault, the operation signal will be blocked to protect the system from maloperation.

Power swing and voltage collapse identification schemes for correct distance relay operation in power system

The new techniques were presented for preventing undesirable distance relay maloperation during voltage collapse and power swings in transmission grids. Initially, the work focused on the development of a fast detection of voltage collapse and a three-phase fault at transmission lines by using under impedance fault detector (UIFD) and support vector machine (SVM). Likewise, an intelligent approach was developed to discriminate a fault, stable swing and unstable swing, for correct distance relay operation by using the S-transform and the probabilistic neural network (PNN). To illustrate the effectiveness of the proposed techniques, simulations were carried out on the IEEE 39-bus test system using the PSS/E and MATLAB software.

An interactive software of distance relaying for analysis of electrical events and educational use

This article presents an interactive software application to analyze and validate the operation of distance relays and its application for educational use. The design stages and theoretical fundamentals of distance relays are described and the proposed application has been structured to evaluate various design alternatives that include signal processing and different tripping characteristics. The software allows for the evaluation and analysis of distance relay operation with real time or simulated events in several commercial and academic electrical programs. Several examples are presented to illustrate the capabilities of this graphical software tool.

Digital distance protection of transmission lines in the presence of SSSC

In this paper the impact of Static Synchronous Series Compensator (SSSC) on the impedance calculated by distance relay is investigated. Analytical results are presented and verified by detailed simulations. Six different phase to phase and phase to ground measuring units of the distance relay are simulated to resemble the behavior of the relay. It is shown in this paper that zero sequence of the injected voltage by 48 pulse SSSC converter has the most impact on the apparent impedance seen by the phase to ground fault measuring unit and cause under reaching of distance relay. It can be concluded from the results that SSSC located in the middle of the transmission line cause to divide trip characteristics of distance relay into two separate parts. It is also shown that the over-reaching operation of distance relay might happen in some cases in the presence of SSSC. All the detailed simulations are carried out in MATLAB/Simulink environment.

A Classification Approach Using Support Vector Machines to Prevent Distance Relay Maloperation Under Power Swing and Voltage Instability

Distance relays, in the power transmission systems, are susceptible to the maloperation under certain system events, such as power swings and voltage instability, which drive the apparent impedance trajectories into the protection zones of the relay. Fast and reliable detection of the symmetrical faults, occurring during power swings, poses another challenge to operation of the distance relays. This paper introduces a new classification and protection scheme based on support vector machines (SVMs) for offering supervisory control to the operation of the conventional distance relays. The proposed scheme segregates the power system events into faults, power swings, and voltage instability. This paper also proposes a new index, called the relay ranking index, for identifying the relays most vulnerable to the maloperation due to power swings and voltage instability. The proposed SVM classifiers can work in unison with the conventional distance relay unit. The performance of the proposed scheme has been tested on a nine-bus WSCC system and 39-bus New England system.

Intelligent detection of unstable power swing for correct distance relay operation using S-transform and neural networks

The conventional power swing schemes used in distance relay operation are not fast enough to detect and distinguish a fault, stable swing and unstable swing and this may lead to unintended tripping of protection devices. Therefore, there is a need for fast detection of unstable swings so as to improve the reliability of distance relay operation. This paper presents an intelligent approach for detecting unstable swings during distance relay operation using the S-transform signal processing technique and artificial neural networks. To illustrate the effectiveness of the proposed approach, simulations were carried out on the IEEE 39 bus test system using the PSS/E software. Test results showed that the proposed approach using S-transform, multi layer perceptron network and probabilistic neural network can accurately detect and classify fault, stable swing, unstable swing, fault clearance and post fault events for correct distance relay operation.

Secure Remote Backup Protection of Transmission Lines Using Synchrophasors

We consider the problem of detecting a fault on a transmission line from the residual vector of a synchrophasor state estimator (SynSE). For a transmission line under fault, we identify six operating modes depending upon location of the phasor measurement units (PMUs). We show that in five operating modes, the fault is seen in the residual vector while in one mode, the fault will not reflect in the residual vector. The analysis leads us to propose a remote backup protection scheme for supervised zone-3 operation of distance relays. In case of inadequate PMU penetration in the system, the implementation of SynSE can even be restricted to a small subsystem of critical lines.

Fast Distance Relay Scheme for Detecting Symmetrical Fault During Power Swing

The power swing caused by various disturbances will affect distance relay behavior and may result in relay misoperation. This paper provides a fast detection scheme for symmetrical fault during power swing for distance relay, which is based on extracting the high-frequency component energy of forward and backward traveling waves induced by faults. The multiresolution analysis based on wavelet transform has the ability to decompose the analyzed signals into different frequency bands. The selection of mother wavelet and the number of levels of wavelet transform are carefully studied. The fault can be identified by feature extracting from the d1 component of Daubechies-8 (Db8) wavelet transform. The proposed approach is verified by using the IEEE reference model implemented by using the Alternate Transients Program and the test results have been presented in this paper. This proposed method can be used for distance relay operation blocking or monitoring.