Verification of an advanced power system restoration support system using an operator training simulator

This paper describes an advanced restoration support system for regional load dispatching and local supervisory control centers. A model-based diagnostic task shell is applied to diagnose network faults, and an inference algorithm not dependent on a specific power system has been developed exclusively for restoration plan determination. With this system, adjustments for network fault diagnosis, necessitated by power system facility expansion or alteration, can be made simply by adding or changing models. Restoration knowledge can be partially revised in the case of restoration policy change. Connected on-line to an operator training simulator, this system's restoration support performance has been verified through daily restoration training. In this process, several problems of the system were detected and corrected. Consequently, it has become possible for the system to support restoration almost as well as a trainee, thereby confirming that connecting this system to an operator training simulator is an effective method for both verifying and improving restoration support system performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper describes basic principles and purpose for applying wide area protection schemes, also known as remedial action schemes (RAS) or system protection schemes (SPS). In the areas of power system automation and substation automation, there are two different trends: centralization and decentralization. More and more dynamic functions are moving from local and regional control centers towards central or national control centers. At the same time we also observe more "intelligence" and "decision-power" moving closer towards the actual power system substations. Greater functional integration is being enclosed in substation hardware. This raises discussions concerning reliability (security and dependability). The main targets for this paper are to: (1) sort out the terminology used in this area; (2) describe different application areas and related requirements; (3) illustrate different design principles - "top-down", "bottom-up", hierarchy, flat, etc., for different applications; (4) identify similarities and differences between classic equipment protection and system protection -concerning philosophy as well as concerning product and system design; and (5) show the value of wide area protection; (6) illustrate the great breakthrough for wide area protection, since the introduction of synchronized phasor measurements, based on PMUs (phasor measurement units).

This paper presents an intelligent support system for local power system control centers that has been tested in a practical local control centers. A special modular structure is applied to enhance the processing time and to spare memory. This reconstructed modular knowledge base would be eventually indispensable to enhance the performance of an intelligent system; furthermore, based on this structure, a distributive structured large intelligent system that consists of many enhanced substation automation systems would be easily realized with some supervisory meta-inference system.

Incorporation of reactive capability curves and area interchanges in multi-area optimal power flow for operator training simulator

The operator training simulator (OTS) of Northeast China Power System is the first OTS in China, developed by Tsinghua University and installed in the Electric Power Dispatching and Communication Bureau of Northeast China. This paper describes the research works on the dynamic stability program in OTS of Northeast China Power System (DSPOTSNC),which covers: the hardware configuration; mathematical model and calculation method; and parallel transient stability method using five transputers. The relationship between dynamic stability program and other programs in the OTS, the difference between DSPOTSNC and ordinary dynamical program are also discussed in the paper.

Güç sistemleri, elektrik enerjisinin kesintisiz bir şekilde tüketiciye ulaştırılmasını sağlayan ve birbiriyle koordineli çalıştırılan ekipmanların toplamı şeklinde ifade edilen kompleks yapılardır. Ancak bazı durumlarda güç sisteminde tam ya da kısmi olarak sistem çökmesi meydana gelebilmektedir. Bu sistem çökmesi bazen hemen giderilebilirken bazen de giderilmesi uzun sürmektedir. Uzun süren kesintiler sonrasında toplumsal yaşam, gündelik faaliyetler ve üretim faaliyetleri sekteye uğramakta; bu durum maddi olarak büyük bir kayba yol açmaktadır. Güç sisteminin tamamında meydana gelen bir sistem çökmesi sonrasında özenilerek hazırlanmış olan güç sistem restorasyonu planları hemen uygulanmaya başlanmalıdır. Güç sisteminin restorasyonunda kritik bir rol oynayan yeniden toparlanma özellikli güç üretim ünitelerinin konumu ve kapasitesi, sistem çökmesi sonrasında uygulanacak olan restorasyon stratejisine karar vermede büyük bir öneme sahiptir. Yapılan bu çalışmada güç sisteminin tam çökmesi sonrasında yeniden toparlanma özellikli güç üretim santrallerinin sistem restorasyonunda önemini anlamak için gerçek veriler kullanılarak simülasyon çalışması yapılmıştır. Yapılan çalışmada sistem çökmesi ve sistem restorasyonunun uygulama safhalarında güç üretim birimlerinin davranışları incelenmiştir. Güç sistem restorasyon planları hazırlanırken dikkat edilmesi gereken hususlar ile ilgili bilgi verilmiştir.

The existing operator training simulators (OTSs) simulate the slow dynamics of power systems in real time but this limits the capability of simulating accurate dynamic behaviour after a disturbance. A feasibility study for the modelling of real time transient stability behaviour in the OTS is described. The goal was to analyse not only the CPU timing for the OTS simulation cycle with real time transient stability analysis but to also investigate the resulting improvements in the quality of the OTS. The results confirm that the transient stability can be simulated in real time for systems of realistic size on readily available workstations. More importantly, the results show significant differences in the dynamic behaviour when transient stability is simulated, strongly suggesting that the present OTSs do not provide enough accuracy for training under certain conditions.

Independent system operators (ISOs) are responsible for the secure and economic operation of the power systems. Accordingly, ISOs should solve an optimal power flow to minimize the operating cost of a system while meeting the system's security constraints. However, transmission congestion could drastically limit more economical generating units from being dispatched in the power system operation. In this paper, a decentralized transmission switching is introduced in the operation of multi-area power systems to manage the congestion both on regional transmission lines and tie lines while considering credible contingencies. Our proposed methodology relies on a decentralized optimization methodology. Thus, regional control centers in areas would be able to locally manage the congestion within their regional networks as well as tie lines connecting them to their neighboring areas. Several testing systems are studied in this paper to test the effectiveness of the proposed method.

In this paper, a novel distributed dynamic state estimation (DSE) method for real-time monitoring of power systems is implemented. In modern large-scale power grids, the number of deployed meters and the frequency of collecting data have remarkably increased. Such a growth in the spatiotemporal size of collected data overwhelms the existing monitoring system with a centralized star structure. Streaming of data from all meters of the network to the central control center also increases communication latency. To overcome these challenges, the power system is partitioned into subsystems with local estimators, and the DSE process is distributed among local estimators. The distributed DSE is hosted at regional control centers and utilizes distributed extended Kalman filtering based on internodal transformation theory to estimate the dynamic states of power systems. The local estimators only require data within their own subsystem, and information is exchanged only between neighboring subsystems. The proposed distributed DSE is implemented on a 68-bus test system, and its accuracy is demonstrated.

Electrified aircraft propulsion concepts show potential in using propulsion airframe integration to decrease fuel burn and emissions. Even though electrification offers component efficiency values greater than 90 percent, at high power levels this results in the generation of significant amounts low grade waste heat. A major challenge of electrified aircraft propulsion is managing that heat while minimizing any penalties associated with a thermal management system. This paper explores the potential benefit of power distribution and thermal management innovations at the aircraft system level demonstrated on a turboelectric single-aisle concept. The first innovation is high-efficiency components that eliminate over half of the waste heat. The second takes advantage of the outer mold line of the aircraft to reject heat directly to the environment passively, instead of adding active cooling loops that negatively impact the weight, power, and drag of the aircraft. In order to fully grasp the impact of the advanced power system, we develop methods of modeling the power and thermal management systems to be integrated in the full aircraft conceptual model. In our first model, which acts as a baseline for our study, the aircraft is designed with a state of the art DC power system and active cooling loops. Our second model includes an advanced power system with active cooling, which results in a fuel burn reduction of 2.5 percent. Finally, in our third model, we assess the benefit of an outer mold line cooling scheme with the advanced power system. The outer mold line cooling scheme with an advanced power system yields an additional 0.8 percent reduction in fuel burn, for an overall fuel burn reduction potential of 3.3 percent in addition to aerodynamic benefits from propulsion airframe integration enabled by electrified aircraft propulsion.

The second part of the scientific article reveals the administrative and legal principles of Local Free Legal Aid Centers, clarifies the system of public institutions that ensure their functioning. It is noted that Local Centers are formed by the Ministry of Justice, they are non-profit organizations, have the status of a juridical person, and they are territorial branches of the Coordination Center. They provide free secondary legal aid to certain categories of the population. The activities of local centers are conditionally divided into the following areas of work: organization of work with lawyers, provision of free primary and secondary legal aid, internal management, legal education work, interaction with other subjects in the field of preventing and combating domestic violence. Today there are Coordination Center, 23 regional centers, 84 local centers with 428 bureaus. Free legal aid is provided by 6760 lawyers, who are competitively selected, and about 1500 full-time lawyers of the free legal aid system. Subsidiary bodies that ensure work of the free legal aid system are the Steering Board of the regional and relevant local centers for the provision of free secondary legal aid, the interregional resource and communication platform, the Supervisory Board. The Steering Board is a permanent advisory body at the regional level. It consists of the director of the regional center and the directors of the relevant local centers. The Chairman of the Steering Board is the Director of the Regional Center, who approves the personal stuff of the Board. The network of the interregional resource and communication platforms (legal clubs "Pravokator") operates at the Coordination Center in the cities of Dnipro, Kyiv, Lviv, Odessa, Kharkiv. The main purpose is the professional development of specialists of the free legal aid system. The Supervisory Board was established to ensure the effective implementation of state policy in the field of free legal aid, for independence and transparency in the management of the Free Legal Aid System. The main tasks of the Supervisory Board are: supervision of the system, promoting the activities of the Coordination Center and its territorial branches in the implementation of long-term tasks, ensuring the independence of system management, increasing public confidence to the system of free legal aid.

Guest Editorial

Power system performance is affected by dynamic characteristics of hydraulic governor-turbines during and following any disturbance, such as occurrence of a fault, loss of a transmission line or a rapid change of load. Accurate modelling of hydraulic governor-turbines is essential to characterise and diagnose the system response during an emergency. In this article, both detailed and simplified hydraulic systems governed by proportional-integral-derivative and proportional-integral controllers are modelled. This article examines their transient responses to disturbances through simulation in Matlab/Simulink. The article also investigates the dynamic performance of an isolated hydraulic system through evaluating stability margins, eigenvalues, root loci and frequency deviation time responses of the system. The results obtained provide an insight into the stability of the power system governed by different governor settings. References P. Kundur. Power System Stability and Control. McGraw-Hill, 1994. D. H. Thorne and E. F. Hill. Field testing and simulation of hydraulic turbine governor performance. IEEE Transactions on Power Apparatus and Systems, PAS-93(4):1183--1191, July 1974. doi:10.1109/TPAS.1974.294066. J. M. Undrill and J. L. Woodward. Nonlinear hydro governing model and improved calculation for determining temporary droop. IEEE Transactions on Power Apparatus and Systems, PAS-86(4):443--453, April 1967. doi:10.1109/TPAS.1967.291853. Richard C. Dorf and Robert H. Bishop. Modern Control Systems. Pearson Educational, Inc, 2005. L. N. Hannett, J. W. Feltes, and B. Fardanesh. Field tests to validate hydro turbine-governor model structure and parameters. IEEE Transactions on Power Systems, 9(4):1744--1751, November 1994. doi:10.1109/59.331426. IEEE. IEEE guide for the application of turbine governing systems for hydroelectric generating units. IEEE Std 1207-2004, pages 1--121, 2004. IEEE. Hydraulic turbine and turbine control models for system dynamic studies. IEEE Transactions on Power Systems, 7(1):167--179, Feb 1992. doi:10.1109/59.141700.

Restoring a large-scale power system has always been a complicated and important issue. A lot of research work has been done on different aspects of the whole power system restoration procedure. However, more time will be required to complete the power system restoration process in an actual situation if accurate and real-time system data cannot be obtained. With the development of the wide area monitoring system (WAMS), power system operators are capable of accessing to more accurate data in the restoration stage after a major outage. The ultimate goal of the system restoration is to restore as much load as possible while in the shortest period of time after a blackout, and the restorable load can be estimated by employing WAMS. Moreover, discrete restorable loads are employed considering the limited number of circuit-breaker operations and the practical topology of distribution systems. In this work, a restorable load estimation method is proposed employing WAMS data after the network frame has been reenergized, and WAMS is also employed to monitor the system parameters in case the newly recovered system becomes unstable again. The proposed method has been validated with the New England 39-Bus system and an actual power system in Guangzhou, China.

R296-time wide area stability control of electric power system also increases the scale complexity and data transmission capacity of power communication network while realizing the interconnection of large interconnected power grids. The time delay caused by the randomness of signal transmission brings great difficulties to the analysis and control of the dynamic performance of the power system. In this paper, the problem of time delay and error code in communication network is analyzed, and the interaction between communication system and power system is analyzed by using the mathematical model of delay and error. Combined with the example of a provincial network and a particular power system, the effect of communication delay on the cascading failure of power and communication system is analyzed by OPNET simulation.