Timothy J. Browne

Latency Viewed as a Stochastic Process and its Impact on Wide Area Power System Control Signals

A method of calculating the communication delay (latency) for measurements and control signals in a power system is shown. The basis of the calculation is a dedicated communication channel for control signals. The time delay calculation is examined using a dynamic equivalent of the Western Electricity Coordinating Council transmission system. The impact on control system response is discussed. The application given is a wide area control system for interarea mode damping. Results demonstrate that control signal latency can degrade the performance of controls in a wide area control system.

A Comparative Assessment of Two Techniques for Modal Identification From Power System Measurements

Power system oscillatory behavior can be analyzed in terms of modes, expressed as exponentially modulated sinusoids, exhibited in signals measured on the system. These signals are driven by the behavior of a large, nonlinear, time-variant system. In this paper, two modal identification methods are examined comparatively: Prony analysis and a method based on the Hilbert transform. Considerable structural differences exist between the two methods. Prony analysis yields modes which are directly expressed as exponentially modulated sinusoids, whereas the Hilbert method provides a more general solution. Synthetic and measured signals are used in the comparison. Some general conclusions are drawn from the analysis of several signals, including two sets of measured field data.

Nonstationary Approaches to Trend Identification and Denoising of Measured Power System Oscillations

This paper discusses the application of nonstationary time-frequency analysis techniques to identify nonlinear trends and filtering frequency components of the dynamics of large, interconnected power systems. Two different analytical approaches to examine nonstationary features are investigated. The first method is based on selective empirical mode decomposition (EMD) of the measured data. The second is based on wavelet shrinkage analysis. Experience with the application of these techniques to quantify and extract nonlinear trends and time-varying behavior is discussed and a physical interpretation of the proposed algorithms is provided. The practical application of these techniques is tested on time-synchronized phasor measurements collected by phasor measurement units (PMUs). Numerical simulations computed using time-energy nonstationary methods are critically compared with conventional approaches.

Power Quality as an Educational Opportunity

This letter describes electric power quality as an important component of electric power engineering education. Because power quality engineering relies on signal processing concepts as well as applied power engineering, students in both undergraduate and graduate educational programs find the topics cross-disciplinary, practical, and motivational.

Monitoring intelligent distribution power systems — A power quality plan

Power system monitoring capabilities and requirements are evolving rapidly. The traditional monitoring framework in Australian distribution networks involves biannual readings of maximum demand at each distribution substation. As utilities respond to developments in metering and communications technology, automated collection and retrieval of quasi-real-time system data between substations and central repositories is now feasible. This gives network managers a significantly increased understanding of distribution network dynamic activity such as daily and seasonal load profiles. This leads to the increased ability of utilities to exploit metering data for power quality analysis purposes. This paper examines the scope for, and challenges associated with, integration of power quality monitoring with advanced metering. Emphasis is directed towards technical and regulatory conditions applying to Australian distribution utilities. Particular consideration is given to the different characteristics of the various types of sites where monitoring is required.

Conditions for the assessment of the harmonic compliance of an installation

Methods of allocating harmonic emission limits to customer installations have evolved considerably, as evidenced by the development of harmonic guides such as IEEE-519 and IEC/TR 61000-3-6. However, there is only limited consensus on appropriate techniques validating compliance of installations with those limits. Existing techniques are reviewed and related problems are examined. Conditions which acceptable tests of compliance should meet are proposed.

Harmonic allocation using IEC/TR 61000-3-6 at the distribution/transmission interface

IEC Technical Report 61000-3-6 gives principles to be applied to ensure acceptable harmonic levels in power systems. Detailed analysis methods have been developed to apply these principles to both distribution and transmission systems. At the transmission/distribution interface, it is found that transmission harmonic allocations can be as little as one third of the allocation which would be given to an equivalent distribution load. Possible adverse consequences are discussed and several modifications to avoid this mismatch are given. The recommended modification is a hybrid approach combining aspects of both the distribution and transmission allocation methods.

Innovative and emerging concepts in power system instrumentation

Abstract Sensory information is used in power systems for protection, control, operator monitoring and decisions, and record keeping. Because of the importance of instrumentation, the development and use of innovative sensors is of concomitant importance. This article summarizes a few concepts in the area of innovative power system instrumentation. The instrumentation techniques are categorized by energy types: electric, magnetic, atomic, chemical, kinetic, luminous, and thermal. Since sensors detect energy in one form or another, categorization of sensors by energy type is a convenient way to describe sensors. Innovative instrumentation categories are identified for power engineering applications. Because this article is an assessment of innovative sensory technologies, some projected advantages and disadvantages are cited.

The Assessment of the Measurement of the Poynting Vector for Power System Instrumentation

The concept of using the Poynting vector to measure power system quantities is examined critically. The properties of this vector are described and a potential value in the area of instrumentation of losses is discussed. The main difficulties are highlighted. Potential application areas lie in the instrumentation of high voltage insulator losses and transmission class reactor losses.

Allocated harmonic quantities as the basis for source detection

A considerable body of literature examines assessment, from measurements, of whether it is the network or a customer installation which makes the greater contribution to harmonic distortion at a point of common coupling. However, the customer contribution to harmonic distortion at a point of common coupling depends heavily upon the definition chosen for that contribution. For example, expressing contributions as currents instead of voltages or vice versa may lead to large changes in results. Further, it can be shown that the harmonic voltage at the point of common coupling cannot be expressed independently of the network conditions, meaning that the customer contribution under existing definitions is a function not just of the customer parameters but of the network parameters as well. In the harmonic framework described by the technical report IEC/TR 61000-3-6, adopted as a standard in some jurisdictions, each customer installation is entitled to a harmonic allocation; that is, the right to inject a certain quantity of harmonic distortion into the network. IEC/TR 61000-3-6 suggests procedures for determining the allocated emission levels based on the harmonic voltage planning level at each bus. The problem of harmonic source detection can be recast as a search for customer installations exceeding allocated injection levels. With this approach, the challenge ceases to be comparison of the contributions made by the network and customer sides to observed harmonic distortion. Instead, it is shown that the problem becomes a process of reconciliation of the allocated quantity with field measurements.