Power transmission systems of today are operating closer to their limits due to economic and environmental constrains. As a consequence, many systems around the world experience voltage collapse leading to partial or complete blackouts. Load shedding is a cost effective solution for preventing system collapse. In this paper, a new load shedding scheme based on the algorithm of time to voltage collapse is presented. The developed scheme uses not only local voltage and current measurements but also measurements from nearby buses to determine optimum time and location for load shedding. The developed scheme was tested using the IEEE 30-Bus test system for variety of operating conditions.

Modern power transmission system operate closer to their maximum capacity due to economic limitation and environmental regulations. As a consequence, power systems around the world experience voltage collapse incidence leading to partial or complete blackouts. In this paper a new wide area protection scheme to prevent from voltage collapse based on subset of current and voltage measurements is developed. The developed algorithm takes into consideration not only the current state of the system but also future load increase. The technique improves the performance of the commonly used local-based protection schemes. The developed method was tested on the IEEE 30-Bus test system for different operational scenarios. The results obtained from simulation studies indicated that the algorithm is able to estimate system parameters and also calculate time to voltage collapse.

This study describes a support vector machine (SVM)-based technique for identifying loss-of-excitation (LOE) condition in synchronous generators from other disturbances such as external faults and power-swing conditions. In this new approach, only one zone of LOE is required and the time coordination is reduced significantly. The proposed method is compared with traditional two-zone impedance method. Several operating conditions within the generator capability are used to verify the generality of the SVM-based classifier. The proposed classifier identifies an LOE condition in all cases before the impedance enters the larger mho impedance zone. Faults and power-swing conditions are identified correctly, thereby preventing incorrect operation of the LOE impedance zone.

This paper evaluates the performance of a new least squares approach that improves the accuracy and speed of convergence of the voltage phasors estimated during CCVT transient conditions. A justification of the validity of the linear mathematical model for the CCVT used is provided together with a short study about the risk of transient ferroresonance. Also, a discussion is presented about operating times of numerical distance relays and the importance of the new phasor estimation considered. The methodology followed to achieve a realistic evaluation in a variety of scenarios is presented. The results show the improvements achievable in most conditions, but also highlight an example scenario where the new method has limitations.

The overexcitation limit of synchronous generator plays an important role in the voltage stability of power systems. Achieving maximum use of the overexcitation capability requires adequate coordination between generator control and protection. This paper provides an example of coordination between overexcitation limiter (OEL), field overcurrent protection and automatic voltage regulator (AVR) for a synchronous generator. The coordination achieved is then verified by a model simulation using an electromagnetic transient program for practical scenarios of interest. Suggested modifications to the ST1A type exciter model are presented to represent the complete functionality of the OEL function.

A new procedure for out-of-step protection by mapping the equal area criterion conditions to the time domain is proposed in this paper. The classification between stable and out-of-step swings is done using the accelerating and decelerating energies, which represents the area under the power-time curve. The proposed methodology is simple and overcomes some of the difficulties associated with the previous techniques. The proposed approach is based only on the local electrical quantities available at the relay location, and does not depend on the network configuration and parameters. The proposed algorithm has been tested on a single-machine infinite bus and a three-machine infinite bus system using software simulations. A digital prototype of the relay has also been implemented on the hardware and its performance has been assessed in a closed-loop mode using a real-time digital simulator. The simulation results and the hardware testing results confirm the validity of the approach presented.

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literatures that were published previously and are contained in various volumes of the IEEE transactions.

This article introduces a new algorithm to detect the out-of-step condition in a power system based on energy equilibrium criterion in the time domain. The proposed energy equilibrium criterion is developed using the concept of equal area criterion in the power-angle domain, and it eliminates the numerical computations required to find the critical clearing time to detect the out-of-step condition. The proposed algorithm detects the out-of-step condition based on the real-time transient energy information available from the local substations. The effectiveness of the proposed algorithm is tested on a single-machine infinite-bus system, a two-machine infinite-bus system, and a three-machine infinite-bus system. The performance of the proposed algorithm is compared with an existing concentric rectangle scheme. The simulation results show that the proposed algorithm can be applied to larger systems and is faster compared to the concentric rectangle scheme.

It is becoming increasingly clear that electric power systems are undergoing rapid changes due to deregulation, the penetration of new technologies, and the adoption of efficient computation, communications, and control mechanisms. The primary goal of this paper is to recognize the importance of education and the training of future protection engineers and, second, to suggest course content needed to meet this challenge.

A new least squares technique to reduce the impact of the transient response of coupling capacitor voltage transformers (CCVTs) on the performance of distance relays is described. Several factors that affect the frequency and time responses of CCVTs are considered. The effect of the transient response on the phasor-estimates is illustrated. An improved least squares technique, which uses the knowledge of the frequency of the CCVT transients while estimating the phasors, is presented. A case, taken from a set of studies, is included to demonstrate the performance of the proposed approach. The robustness of the method is verified by a CCVT parameter sensitivity study.

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions:

This paper addresses some of the issues associated with the conventional relay designs and presents an improved distance relaying pre-processing algorithm. Instantaneous current and voltage values obtained directly from the power system have been used to obtain the processed inputs. The presented algorithm has been combined with a neural network approach to eliminate the process of phasor estimation, which is usually used in most numerical relaying algorithms. The neural network has been trained to recognize the phase difference between the processed inputs, and therefore eliminates the need of calculating phasors. The processed inputs given to the neural network have a direct relationship with the outputs expected from a relay, which helps to use a data window lesser than one full cycle to accurately detect faults, making the algorithm faster than traditional designs. The neural network based relay has been trained using pure sinusoidal values and tested on a 17-bus power system simulated in PSCADtrade. The results show that the relay is able to detect faults in lesser time as compared to conventional relay algorithms while maintaining the integrity of relay boundaries.

This paper introduces a new method to detect out-of-step condition in power system based on an energy equilibrium criterion in the time domain directly. The proposed criterion is obtained using the concepts of equal area criterion in power angle domain but eliminates the need for numerical computations required in the earlier algorithm. The proposed algorithm uses power-time curve for computing the system transient energy to detect the stability of the system. The effectiveness of the proposed algorithm is tested on a single machine infinite bus and a three machine infinite bus system. The simulation results show that the proposed algorithm is general, accurate and applicable to complex power systems.

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions.

Voltage instability is closely related to the maximum load-ability of a transmission network. The energy flows on the transmission system depend on the network topology, generation and loads, and on the availability of sources that can generate reactive power. One of the methods used for this purpose is the voltage instability predictor (VIP). This relay measures voltages at a substation bus and currents in the circuit connected to the bus. From these measurements, it estimates the Thevenin's equivalent of the network feeding the substation and the impedance of the load being supplied from the substation. This paper describes an extension to the VIP technique in which measurements from adjoining system buses and anticipated change of load are taken into consideration as well

This paper describes the impact of the transient response of coupling capacitor voltage transformers (CCVTs) on the performance of distance relays. Several factors that affect the frequency and time responses of CCVTs are considered. The effect of the transient response on phasor estimation is illustrated. A new least squares phasor estimation technique, which uses the knowledge of the frequency of the CCVT transients, is presented. A sample case, taken from a set of studies, is included to demonstrate the performance of the proposed approach

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions.

Power system blackouts are a very rare phenomenon in a well-planned interconnected power system. Nevertheless it is very important to have plans and systems in place to handle any eventuality even if it is remote. This report brings out various issues related to protection during a system restoration process. Power system protection is critical to a safe, efficient, and reliable power system. Protection engineers take every possible care to ensure that protection systems are designed considering all predictable eventualities and these constraints have grown over time. However, during system restoration, after a major blackout, it is possible for the protection elements to be presented with situations, which they can mistake for an unhealthy power system and the protection elements may operate. The prime concern during a power system blackout is to bring the system back to normalcy as fast as possible. At times, if proper care is not taken, the protection system can hinder and delay the restoration of the power system. This report discusses various such conditions that can occur during the blackstart of a power system and also suggests solutions to manage them without compromising the objectives of protection system i.e., to ensure a safe, efficient, and reliable power system.

The most commonly used systems for protecting transmission and subtransmission lines belong to the family of distance relays. Over the past eighty years, successful designs based on electromechanical, solid-state and digital electronics technologies have been produced and marketed. These relays implement various characteristics, such as impedance, offset-impedance, admittance, reactance and blinders. The artificial neural network based designs of distance relays proposed so far work well for ideal fault conditions but are not able to maintain the integrity of the boundaries of the relay characteristics of generic designs. This paper reviews ANN models that have been proposed in the past for protecting components of power systems and presents a methodology that fully exploits the potential of ANNs in designing generic distance relays that retain the integrity of the boundaries of their characteristics

This paper presents a method for calculating zone-2 setting of distance relays without causing coordination problems. The proposed method is based on the impedance seen by distance relays when faults are simulated on the reach of zone-1 of primary relays for the maximum and minimum generation outputs of the power system. It is shown that the proposed method increases the reach of zone-2 relays without causing coordination problems. The proposed method is modified for use in an adaptive protection system. It is shown that further improvements can be achieved when settings are calculated using the proposed method and the prevailing system conditions. Measures to alleviate the impact of communication failure are discussed. The proposed method and its adaptive version were applied to an existing power system and some results are reported in the paper.