Bogdan Kasztenny

Development and Implementation of a Synchrophasor Estimator Capable of Measurements Under Dynamic Conditions

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.

A new accurate fault locating algorithm for series compensated lines

Summary form only given as follows. This paper presents a new, accurate and robust fault locating algorithm for series compensated lines. The algorithm is developed as a one-end fundamental frequency based technique and offsets both the series compensation effect and the reactance effect resulting from the remote end in-feed. The method uses phase coordinates (abc) instead of symmetrical components [012]. The basic algorithm is presented for a line compensated by one three-phase bank of series capacitors. The presented fault locating method has been extensively tested using the EMTP model of a 400 kV 300 km transmission line. The enclosed results demonstrate very high accuracy and robustness of the algorithm.

First zone algorithm for protection of series compensated lines

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 online, 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.

Dynamic compensation of capacitive voltage transformers

This paper presents the digital algorithm for on-line dynamic compensation of the secondary voltage of a capacitive voltage transformer (CVT). The adopted CVT model together with the assumed simplifications is given first. Next, the compensating algorithm based on digital inversion of the CVT transfer function is derived. Frequency domain analysis and quantitative evaluation of the compensation follow. The ATP-EMTP simulations are included that show the improvement of the measurement of protective criteria quantities as a result of dynamic compensation of a CVT.

Fuzzy logic controller for on-load transformer tap changer

This paper presents a new fuzzy logic controller (FLC) for on-load tap change control for distribution transformers. The model of a transformer with its tap changing mechanism is given first. Next, the FLC is presented in detail. The proposed algorithm is optimized from the numerical point of view and proved to be implementable on contemporary programmable logic controllers (PLCs). Simulation results are included that compare the proposed control algorithm with the classical inverse-time controller and prove the efficiency of the new solution.

Digital relays improve protection of large transformers

High demands are imposed on power transformer protective relays. Requirements include dependability (no missing operations), security (no false trippings), and speed of operation (short fault clearing time). The operating conditions of power transformers do not make the relaying task easy. Protection of large power transformers is one of the most challenging problems in the power system relaying area. Advanced digital signal processing techniques and artificial intelligence (Al) approaches to power system protection provide the means to enhance the classical protection principles and facilitate faster, more secure, and dependable protection for power transformers. Also, it is anticipated that, in the near future, more measurements will be available to transformer relays, owing to both substation integration and novel sensors installed on power transformers. All of this will change the practice for power transformer protection. This article briefly reviews the state of the art, but is primarily devoted to discussion of new approaches and future directions in digital relaying for power transformers.

Adaptive measuring algorithm suppressing a decaying DC component for digital protective relays

Abstract This paper presents a new adaptive phasor estimation algorithm for digital protective relaying. The algorithm is completely immune to an exponentially decaying dc component regardless of its initial magnitude and time constant. The algorithm is primarily intended for current signals and improves both magnitude and impedance measurements. The new technique is based on the recursive full-period Fourier filter with a separate adaptive function allowing for thorough rejection of the dc signal component. The comparative analysis of the algorithm, both analytical and by simulation, is included. The presented algorithm outperforms known measuring techniques including the digital mimic filtering broadly used in todays relays.

A method for linking different modeling techniques for accurate and efficient simulation

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.

Two new measuring algorithms for generator and transformer relaying

This paper presents new digital measuring algorithms for generator and transformer protection. Two methods are proposed to make the estimation of amplitudes of the fundamental frequency component and the higher harmonics immune to frequency deviations. The first method is based on the software re-sampling of the physical data window and on the simultaneous iterative estimation of the frequency. The second algorithm employs the amplitude estimator having unique frequency response in the entire frequency spectrum and enables direct compensation for the frequency deviations. Also a new Volts/Hertz inverse-time algorithm is proposed which does not call for the direct measure of frequency. It relies on the second method and uses the amplitude estimator having the gain close to the inverse of the frequency; therefore, it acts as a direct amplitude-to-frequency estimator. The proposed algorithms were analyzed analytically and tested using EMTP simulations.

Modeling and Protection of Hexagonal Phase-Shifting Transformers—Part II: 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. 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.