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.
Third zone revisited Horowitz, S.H.; Phadke, A.G.
IEEE transactions on power delivery,
2006-Jan., 2006, 2006-01-00, 20060101, Volume:
21, Issue:
1
Journal Article
Peer reviewed
Zone 3 of a step-distance protection scheme has been identified as one of the contributing causes of cascading failures in power systems. The National Electric Reliability Council (NERC) has issued ...rules, and the IEEE Power System Relaying Committee (PSRC) has discussed recommendations to reduce the undesirable operation of this component of the protection chain. It is the purpose of this paper to reexamine the application of zone 3, to describe situations where it can be properly utilized, where it can be removed without reducing the reliability of the system protection and, if used, how it can be modified or set. A table is presented for a variety of station designs and protection schemes including two common local backup relay systems and the associated application of a remote third zone. Finally, the concept of critical locations is introduced which can assist the relay engineer in determining if potential zone 3 undesirable operations are a serious threat to the system and help determine if the expense and difficulty of removing zone 3 or modifying the relay or its associated station is justified.
This paper presents techniques for identifying placement sites for phasor measurement units (PMUs) in a power system based on incomplete observability. The novel concept of depth of unobservability ...is introduced and its impact on the number of PMU placements is explained. Initially, we make use of spanning trees of the power system graph and a tree search technique to find the optimal location of PMUs. We then extend the modeling to recognize limitations in the availability of communication facilities around the network and pose the constrained placement problem within the framework of Simulated Annealing (SA). The SA formulation was further extended to solve the pragmatic phased installation of PMUs. The performance of these methods is tested on two electric utility systems and IEEE test systems. Results show that these techniques provide utilities with systematic approaches for incrementally placing PMUs thereby cushioning their cost impact.
Synchronized phasor measurements have become a mature technology with several international manufacturers offering commercial phasor measurement units (PMUs) which meet the prevailing industry ...standard for synchrophasors. With the occurrence of major blackouts in many power systems around the world, the value of data provided by PMUs has been recognized, and installation of PMUs on power transmission networks of most major power systems has become an important current activity. This paper provides a brief introduction to the PMU and wide-area measurement system (WAMS) technology and discusses the uses of these measurements for improved monitoring, protection, and control of power networks.
Wide area measurements have been widely used in the energy management systems (EMS) of power systems for monitoring, operation, and control. In recent years, the advent of synchronized phasor ...measurements has added another dimension to the field of wide-area measurements. At the same time, the field of protection systems has been dominated by computer based relays, which make it relatively easy to communicate with relays and thus include them in many innovative protection systems. Special Protection Systems (SPS) or Remedial Action Schemes (RAS) are one example of integration of communication and protection systems. In recent years-due to operational demands imposed on transmission networks by deregulation it has become clearer that wide-area measurements and their integration in protection and control systems is a necessity. This paper documents the state-of-the-art in modern sensor, communication, and protection technologies which show great potential for innovations in protection and control systems for the future.
Considering the dynamic characteristics of phase-locked loop (PLL), the effect of interaction between doubly fed induction generator (DFIG) and power grid on system low-frequency oscillation is ...revealed from the perspective of dissipation energy. First, the dynamic energy model of DFIG with PLL is derived, and the component that varies nonperiodically is extracted and defined as the dissipation energy. Second, the dissipation energy is decomposed into the free dissipation energy and DFIG-grid coupled dissipation energy. On this basis, the free dissipation intensity and coupled dissipation intensity are defined, which, respectively, characterize the immanent damping of DFIG and the DFIG-grid interaction degree. Thus, the contribution degree of DFIG to electromechanical oscillation is quantified for evaluation, and the mechanism of interaction between DFIG and power grid is further revealed. Finally, hardware-in-the-loop simulation tests with real-time digital simulator of the IEEE 10-machine 39-bus system verify that when the oscillation frequency of PLL is close to electromechanical oscillation frequency, strong coupling and resonance exist between DFIG and grid, and negative dissipation effect on the oscillation of DFIG will result. Thus, DFIG, as an oscillator, continuously injects dynamic energy to the grid, causing the system to oscillate to instability.
IEEE Standard 1344-1995 1 on measurement of synchronized phasors of power system currents and voltages has been revised and published as IEEE Standard C37.118-2005 2. This paper has been prepared by ...the IEEE Working Group who developed the revised version. The purpose of the paper is to acquaint the power engineering community of the availability and content of this new standard, highlight some of the key differences between the old and new versions, and introduce several applications of this powerful technology.
In LCC-HVDC system, existing DC line protection methods have poor immunity to the fault resistance in internal fault cases, and easily mal-operate in external fault cases. In view of this problem, a ...new pilot directional protection scheme for HVDC lines based on grounding resistance is proposed. First, the impedance characteristic equations of the converter considering different commutation failure scenes are established. Then, by combining the impedance characteristics of different components, the fault transient network of LCC-HVDC system is built. On this basis, the frequency band where the fault component network is inductive is derived, and the equation of grounding resistance is constructed using the voltages and currents on two line ends in the inductive network in different frequency bands. And then, a protection criterion is formed according to the consistency between the grounding resistance and the actual fault resistance. Finally, simulation tests on the RT-LAB platform verify that, the proposed method can correctly identify different types of internal and external faults, unaffected by the variations in the operating status of the converter and the operation mode of AC system. It is simple, reliable and strongly immune to the fault resistance. Besides, it does not require the interaction of synchronous information, thus it is easy to implement.
In view of the complex correlation between Doubly Fed Induction Generator (DFIG) internal components and control links which makes it difficult to locate the oscillating source in the equipment ...level, a DFIG equipment-level oscillating source locating method based on dynamic energy flow is proposed. Firstly, the energy correlation topology network of DFIG internal components and control links is constructed. On this basis, the analytical expressions of dynamic energy flows of DFIG internal components and control links are derived. And then, through Partial Directional Coherence (PDC) analysis, the values of causality between dynamic energy flows of DFIG internal components and control links are calculated, and the diagram of DFIG internal oscillation transmission causality is depicted. Thus according to the distribution pattern of causality values in the causality diagram, the oscillation transmission route is identified and the oscillating source is located. Finally, simulation tests in Real Time Digital Simulator (RTDS) of IEEE 10-machine 39-bus system verify that, the proposed method can quantitatively describe the intensity of interaction between dynamic energy flows of DFIG internal components and accurately identify the oscillation transmission route and the oscillating source in the equipment level. The proposed method can accurately track the original control link/physical component that causes the system to oscillate. Therefore, this paper will facilitate research on DFIG parameter tuning and oscillation suppression measures for low-frequency oscillation in power system.
