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Synchronized phasor measurements are becoming an important element of wide area measurement systems used in advanced power system monitoring, protection, and control applications. The recently issued revised standard C37.118 for synchrophasors has facilitated interoperability of phasor measurement units (PMUs) from different manufacturers. This standard defines performance for compliance when the input signals are in steady state. The performance of PMUs under transient conditions is not considered by the standard at this time, although clearly PMUs will be subjected to inputs under transient conditions. This paper is an attempt to provide the authors' views on how one may approach the question of standardizing PMU response under transient conditions. Index Terms--Electrical transients, electromechanical transients, global positioning system (GPS), phasor, phasor measurement unit (PMU), power system, real-rime measurements, synchronized measurements, synchrophasor.

Breaker failure (BF) protection provides backup for circuit breakers (CBs) and associated control wiring. Traditionally, CBs are not duplicated, but monitored by BF relays when ordered to trip. Upon a failure of a breaker to interrupt the current, the BF relay opens adjacent breakers to isolate the problem. The total trip time under a BF condition is often tightly fit into the critical fault clearance time as determined by system stability. With narrow stability limits in today's power systems, coordination margins for the operation of BF functions are becoming scarce. This imposes a requirement for the fast reset time of BF protection. In its first part, this paper presents a novel algorithm for numerical current-based BF function with a fast 0.5-cycle reset time even under severe subsidence current. In the second part, the paper addressed the problem of fast and secure recognition of binary inputs for both BF initiation and BF detection based on the auxiliary breaker contacts. This novel algorithm works with analog representation of binary signals and provides security under induced transients, battery ground faults, and other interfering events. Index Terms--Battery ground faults, breaker failure (BF) initiate, breaker failure (BF) protection, contact bouncing, contact oxidation, debouncing, subsidence current, switching transients.

Owing to several advantages over traditional phase shifters, applications of hexagonal phase-shifting transformers (PSTs) keep expanding. These transformers are built with unique connections of their windings, neither delta nor wye. Modeling and protection methods are not yet fully established for hexagonal phase shifters. This work is divided in two parts. In Part I, a digital model of a hexagonal PST has been developed and validated. This part presents protection techniques for hexagonal PSTs. Several novel protection schemes have been developed based on ampere-turn balance equations of a hexagonal PST. These schemes include linear and nonlinear current-based protection methods, a power-based technique, and a phase comparison method. Protection schemes that require position of the tap changer for maximum sensitivity as well as a method to work without this extra information are presented. The developed techniques have been validated with digital and physical made-to-scale transformer models, and implemented on a general-purpose microprocessor-based relay platform. This material is of value to protection engineers facing the problem of protecting hexagonal PSTs. Index Terms--Differential power protection, differential protection, hexagonal winding connection, phase comparison protection, phase shifting transformer (PST), short-circuit protection.

Owing to several advantages over traditional phase shifters, applications of hexagonal phase-shifting transformers (PSTs) keep expanding. These transformers are built with unique connections of their windings, neither delta nor wye. Short-circuit modeling and analysis methods are not yet fully established for hexagonal phase shifters. This work is divided into two parts. In this part, a digital model of a hexagonal PST is developed and validated. This original material is of assistance when performing short-circuit system studies, relay setting calculations, as well as when modeling internal faults and developing protection techniques for the transformer itself. This paper explains construction of hexagonal PSTs, deriving their sequence impedances under varying taps and compares the model with manufacturer test data and a physical made-to-scale model developed specifically for this study. The transient model introduced in this paper can easily be integrated into the commonly used Alternate Transients Program and real-time digital simulator modeling environments. Part H of this work presents original protection methods for hexagonal PSTs. Index Terms--Hexagonal winding connection, phase-shifting transformer (PST), short-circuit studies, transient simulation.

The classical two-parameter Fourier algorithm for computing synchrophasors is appropriate when the underlying voltage and current waveforms are sinusoids with constant amplitude and phase angle and with a frequency equal to the assumed value. Synchrophasor measurements, however, are applied in power systems to track dynamic conditions where, by definition, currents and voltages, though resembling sine-waves, exhibit changes in their magnitudes and vectorial positions. This paper presents a novel algorithm for estimating synchrophasors under such dynamic conditions. In contrast to the classical Fourier algorithm, our model is a complex Taylor expansion, yielding several parameters in the model to be estimated. Four-and six-parameter models are presented corresponding to first and second order Taylor expansions. This paper derives a compensation method for canceling the error in the classical Fourier algorithm that arises under dynamic conditions, shows comparative simulation and test results and describes an efficient implementation. Application of the error cancellation method to other phasor algorithms and extending the technique to higher order Taylor expansions, are discussed. Implementation of synchrophasor measurements on protection and control intelligent electronic devices (IEDs) is discussed, and solutions are presented that allow for secure integration. Index Terms--Estimation, phasor measurement, power system frequency, power system measurements, power system oscillations, synchrophasor, Taylor-Fourier transform.

Motor bus transfer involves the process of transferring a bus that has several critical motors to an alternate source of power when the main power source feeding them is interrupted. Bus transfer is a time-critical application in which the transfer process depends on various parameters such as the type of motor, load on the motor at the time of transfer, the inertia of the motor, and the combined open-circuit time constant of the various motors present in the bus at the time of transfer. A new high-speed bus-transfer scheme is presented in this paper, which determines the type of bus transfer possible based on the first one cycle of voltage information available from the motor bus after it is interrupted. A new algorithm is proposed to predict the open-circuit time constant of the combined motors within one cycle of interruption of the motor bus. Based on the predicted open-circuit time constant and the alternate source circuit breaker-closing time, the algorithm determines if a high-speed bus transfer is possible for that bus. If a high-speed bus transfer is not possible, the scheme determines effectively the next possible type of bus transfer, which is an in-phase transfer or residual voltage transfer based on user settings. The performance of the scheme for a typical thermal power plant, a cogeneration plant, and a nuclear power plant auxiliary is shown in this paper. Index Terms--Automatic bus transfer, fast bus transfer, intelligent electronic devices (IEDs), residual voltage transfer.

This paper presents a new generator relay design, stator differential function in particular, coping with extreme cases of current transformer ICT) saturation: both ac saturation under large currents and/or residual flux; and dc saturation under low currents but large and long-lasting dc components. The algorithm is a subcycle algorithm with fastest times reaching half a cycle including overall response of the relay hardware. Analysis of the response of a traditional differential function under CT saturation is included to provide setting guidelines for legacy relays. Index Terms--Current transformers (CTs), directional comparison, generator protection, saturation, saturation detection, spurious differential current, stator differential protection.

This paper presents a digital relay scheme for the primary protection of power transformers. A multi-criteria algorithm is developed based on fuzzy sets for the decision making part of the scheme. The cost of wrong decision-making and the amount of information inflow are used along with several standard criteria to improve the reliability of the protection. It is shown that the proposed scheme, if properly tuned, can enhance the sensitivity and selectivity of the digital relay and mitigate problems associated with conventional relay schemes. Key words: Digital Transformer Protection, Decision Making, Fuzzy Sets.

This paper presents a new first zone algorithm for distance protection of series compensated lines. The algorithm detects faults with the reach of 75-85% of the line length by measuring two distinctive impedances, using three adequate regions on the impedance plane and applying appropriate logic functions. The algorithm estimates instantaneous values of the voltage drop across the series capacitors on-line, and compensates for this signal when calculating the impedance valid for faults behind the series capacitors. The other impedance (without compensation) is calculated for faults in front of the series capacitors. An explicit selecting procedure for the two impedances is not required since the presented relaying method asserts directly the fault within or outside the first zone. The algorithm is presented in detail and extensively tested using the EMTP model of a 400 kV 300 km transmission line. The enclosed results demonstrate high speed, dependability and security of the new algorithm. Index Terms--Distance protection, first zone element, numerical relaying, series compensated line.

This paper defines underlying performance quality measures for designing, optimizing, setting and evaluating the protective relaying algorithms and equipment. The paper starts with evaluation of digital measuring algorithms, and gradually introduces the performance indices for the operating principles, relays and protection systems. Multi-objective formal ranking methods based on fuzzy set theory are used to combine diverse measures into composite performance indices enabling evaluating and optimizing various functions of protective equipment. Index Terms--Fuzzy sets and logic, multi-objective evaluation, protective relaying, testing.

This paper presents a new method for accurate linking of diverse simulation techniques. The method employs a Functional Modeling (FM) approach and facilitates linking of different simulation techniques as well as combining separate simulation engines. In addition, the presented method enables system decomposition with freely selected cuts as well as natural and efficient parallel computations. Discussion of advantages and various applications is also included. Index Terms--Decomposition, digital simulation, functional modeling, numerical methods.