Kenneth E. Martin

WACS-Wide-Area Stability and Voltage Control System: R&D and Online Demonstration

As background, we describe frequently used feedforward wide-area discontinuous power system stability controls. Then we describe online demonstration of a new response-based (feedback) Wide-Area stability and voltage Control System (WACS). The control system uses powerful discontinuous actions for power system stabilization. The control system comprises phasor measurements at many substations, fiber-optic communications, real-time deterministic computers, and transfer trip output signals to circuit breakers at many other substations and power plants. Finally, we describe future development of WACS. WACS is developed as a flexible platform to prevent blackouts and facilitate electrical commerce.

Use of the WECC WAMS in Wide-Area Probing Tests for Validation of System Performance and Modeling

During 2005 and 2006, the western electricity coordinating council (WECC) performed three major tests of western system dynamics. These tests used a wide-area measurement system (WAMS) based primarily on phasor measurement units (PMUs) to determine response to events including the insertion of the 1400-MW Chief Joseph braking resistor, probing signals, and ambient events. Test security was reinforced through real-time analysis of wide-area effects, and high-quality data provided dynamic profiles for interarea modes across the entire western interconnection. The tests established that low-level optimized pseudo-random plusmn20 -MW probing with the pacific DC intertie (PDCI) roughly doubles the apparent noise that is natural to the power system, providing sharp dynamic information with negligible interference to system operations. Such probing is an effective alternative to use of the 1400-MW Chief Joseph dynamic brake, and it is under consideration as a standard means for assessing dynamic security.

Current Status and Experience of WAMS Implementation in North America

The 15 years of successful implementation of wide-area measurement systems (WAMS) in the WECC power grid have shown significant value of WAMS data in system dynamic modeling and validation, FACTS control validation and pilot implementations of wide area protection schemes. The August 14 2003 blackout in the eastern interconnection of the North America revealed the urgent need for wide-area information acquisition for better power grid operations. The Eastern interconnection phasor project (EIPP) was launched in 2003 to deploy a WAMS system in the eastern interconnection. Development of IEEE C37.118, a standard for phasor data acquisition and transmission, will aid in deployment of phasor measurement systems for WAMS applications. Technologies of phasor measurement units (PMUs) with high precision time synchronization and phasor data concentrators (PDCs) for phasor data aggregation and event recording are key to the success of WAMS implementation. This paper reviews the WAMS development in the North America and presents current and potential WAMS applications including dynamic modeling and validation and wide-area control. Past experience shows a promising future of WAMS in improving power system planning, operation and control. However, there remain challenges to make phasor measurement consistent and to meet both slow and fast data application needs

Visualizing Real-Time Security Threats Using Hybrid SCADA / PMU Measurement Displays

This paper explores ways to highlight threats to power system security by displaying data from phasor measurement units (PMUs) and SCADA data sources simultaneously. SCADA measurements provide a picture of the steady-state health of the system, whereas PMUs capture the faster variations that may indicate small-signal stability problems. The software system described in this system gathers SCADA and PMU data and displays them on a geographic map of the system. The system uses contour plots to show the variation of a measurement with location, even when adjacent measurement points are widely spread. The system superimposes trend plots on this display to show the past variation of a quantity over a user-specified time window. The goal of the system is to help operators gauge the present security of the grid.

Performance evaluation of phasor measurement systems

After two decades of phasor network deployment, phasor measurements are now available at many major substations and power plants. The North American SynchroPhasor Initiative (NASPI), supported by the US Department of Energy and the North American Electric Reliability Corporation (NERC), provides a forum to facilitate cultivating the efforts in phasor technology in North America and globally. Phasor applications have been explored and some are in todays utility practice. The IEEE C37.118 Standard is a milestone in standardizing phasor measurements and defining performance requirements. To comply with the IEEE C37.118 and to better understand the impact of phasor quality on applications, the NASPI Performance and Standards Task Team (PSTT) has prepared two comprehensive documents which leverage prior industry work (esp. in WECC) and international experience. The first document describes PMU testing based on both IEEE C37.118 requirements and required dynamic performance tests. The second document describes characterization of PMUs and instrumentation channels based on practical information. This paper summarizes the accomplished PSTT work and presents the methods for phasor measurement evaluation to assure consistent PMU system performance.

Synchrophasor Standards Development - IEEE C37.118 & IEC 61850

The concept of a phasor synchronized with the power system was introduced in the 1980s and standardized for the first time with the standard IEEE 1344. That measurement concept was further developed in the current synchrophasor standard, IEEE C37.118 that was completed in 2005. It is currently undergoing revision to fully define the measurement in all conditions including dynamic changes in the power system. The standard has been split into measurement and data exchange to harmonize it with the IEC 61850 standard. This paper summarizes the synchrophasor concept, reviews the governing standards, and surveys the ongoing standards development.

Evaluation of PMU Dynamic Performance in Both Lab Environments and under Field Operating Conditions

Capturing system dynamics is one important feature of phasor measurements. To ensure PMU accurately reflect system dynamic behavior, one must evaluate the dynamic performance of a PMU. PMU dynamic performance evaluation includes three aspects: PMU modeling studies, laboratory testing and field evaluation. This paper briefly reviews the general PMU model structure, and then continues on PMU dynamic performance evaluation from actual field measurements. Reasons for field evaluation include: (1) inappropriate field settings of a PMU would generate unexpected phasor measurements; and (2) many conditions can not be easily produced in a lab environment. PMU field evaluation includes aspects like time synchronization, timing inconsistency due to filtering, frequency calculation issues, parasitic oscillations/processing artifacts, etc. Actual WECC measurement examples will be presented. Dynamic PMU testing in a lab environment is explored with a special focus on PMU filtering characteristics. How the phasor quality would impact derived system dynamic characteristics is addressed in the later part of this paper.

PMU Testing and Installation Considerations at the Bonneville Power Administration

BPA has a real-time phasor measurement system with more than 22 PMUs installed in substations feeding data to a control center. To assure the quality and accuracy of the measurement, BPA has developed an extensive test plan for PMUs. From simple beginnings of basic tests, these procedures have continually evolved with both the variety of PMU equipment and applications for which the data was used. Current test methods under development are aimed for more comprehensive characterization of PMU measurement and test process simplification. Basic test procedures assure steady state accuracy of magnitude, phase, and frequency measurement. Dynamic testing includes step changes to magnitude, phase and frequency as well as signals modulated on the power (60 Hz) waveform. These tests characterize speed of response, reproduction of measured values, and rejection of interference. All these effects have an analogy in the actual power system, so the results can be reasonably applied. Developing methods simplify the generation of test signals and analysis of results. A goal is to test for all measurement aspects that may create a problem and correct these before deployment. In addition, determining characteristics that can be used to adjust all measurements to the same basis will enable the performance of precision analysis regardless of the make or model of PMUs that are making the measurements.

Laboratory Performance Evaluation Report of SEL 421 Phasor Measurement Unit

PNNL and BPA have been in close collaboration on laboratory performance evaluation of phasor measurement units for over ten years. A series of evaluation tests are designed to confirm accuracy and determine measurement performance under a variety of conditions that may be encountered in actual use. Ultimately the testing conducted should provide parameters that can be used to adjust all measurements to a standardized basis. These tests are performed with a standard relay test set using recorded files of precisely generated test signals. The test set provides test signals at a level and in a format suitable for input to a PMU that accurately reproduces the signals in both signal amplitude and timing. Test set outputs are checked to confirm the accuracy of the output signal. The recorded signals include both current and voltage waveforms and a digital timing track used to relate the PMU measured value with the test signal. Test signals include steady-state waveforms to test amplitude, phase, and frequency accuracy, modulated signals to determine measurement and rejection bands, and step tests to determine timing and response accuracy. Additional tests are included as necessary to fully describe the PMU operation. Testing is done with a BPA phasor data concentrator (PDC) which provides communication support and monitors data input for dropouts and data errors.

Estimation of Eastern Denmark's electromechanical modes from ambient phasor measurement data

In this paper we report on the preliminary results of a collaborative investigation effort between researchers in North America and Europe aiming to baseline the electromechanical modes and mode shapes of the Nordic system from synchronized phasor measurement data. We provide an overview on the Danish power grid and its interconnections, and describe the features of an experimental phasor measurement unit designed by DTU which is used to provide the measurements used in this investigation. Parametric and non-parametric block processing techniques are applied to 48 hours of ambient data recorded at the Radsted and Hovegård substations in Eastern Denmark. The estimated modes are in agreement with those shown in eigenanalysis studies, and other measurement-based investigations. More importantly, the emergence of a new 0.8 Hz mode in Sjælland is reported.