Experiences on using a workstation cluster to implement a real-time digital transient network analyzer

The authors report results confirming the practicability of a real-time digital simulator for the bulk power transmission network using a commercially available component called a transputer. The use of the method of characteristics to model transmission lines combined with the architecture of the transputer allows a parallel processor connection topology identical to that of the network, where one or more transputers are assigned per bus. There is no theoretical limit on the size of the network. Present technology allows an integration step size in real time of about 150 mu s for a full three-phase model. >

A few years ago, the study and simulation of fast power system phenomena in real-time, was the private ground of analog simulators. But the limitation in modeling, the complexity and the costly maintenance of these simulators was a brake upon their development and made their profitability uncertain. The testing of power system equipment such as controls, relays or power electronic devices needed a new type of simulator, much more versatile and cost-efficient than their predecessors: the real-time digital transient network analysers (DTNA). Until a few months ago, the design of DTNAs was based on dedicated technologies. Today, the ever increasing calculation power has now reached a level that allows real-time simulations of fast phenomena to be carried on standard computers. The authors present in this paper a new and fully digital TNA that relies on a standard computer.

Steady-state overvoltages can occur on EHV transmission systems during various system operating conditions. The voltage waveforms are characterized by a periodic waveform which may be distorted by harmonics if iron saturation of equipment on the lines occurs. This paper discusses the results of digital and transient network analyzer (Anacom) studies which analyzed system parameters with respect to their effect on harmonics in steady-state overvoltages. Special emphasis was focused on the factors influencing harmonic distortion of the steady-state voltages.

Ice disasters, such as ice storms, can cause serious damage to power systems. To understand ice disasters’ influences on power systems, this paper introduces a resilience evaluation frame for transmission and distribution systems during ice disasters. First, we built a vulnerability model for transmission and distribution systems under ice disaster weather. Then, we established an optimal load power shedding model for transmission and distribution systems. After this, according to the vulnerability model and the optimal power load power shedding model, we generated the fault scenario set of a system in the influence of an ice disaster. According to the curve of system resilience, we propose two resilience evaluation indices of transmission and distribution systems under ice disaster weather. Finally, we verified the efficacy and rationalization of the established resilience evaluation framework with an example in which a transmission and distribution system is coupled with a six-bus transmission system and two distribution systems. This study highlights the necessity of resilience assessment of transmission and distribution systems during ice disasters.

Tectonic movement along faults is often reflected by characteristic geomorphological features such as linear valleys, ridgelines and slope‐breaks, steep slopes of uniform aspect, regional anisotropy and tilt of terrain. Analysis of digital elevation models, by means of numerical geomorphology, provides a means of recognizing fractures and characterizing the tectonics of an area in a quantitative way. The objective of this study is to investigate the use of numerical geomorphometric methods for tectonic geomorphology through a case study. The methodology is based on general geomorphometry. In this study, the basic geometric attributes (elevation, slope, aspect and curvatures) are complemented with the automatic extraction of ridge and valley lines and surface specific points. Evans' univariate and bivariate methodology of general geomorphometry is extended with texture (spatial) analysis methods, such as trend, autocorrelation, spectral, and network analysis. Terrain modelling is implemented with the integrated use of: (1) numerical differential geometry; (2) digital drainage network analysis; (3) digital image processing; and (4) statistical and geostatistical analysis. Application of digital drainage network analysis is emphasized. A simple shear model with principal displacement zone with an NE–SW orientation can account for most of the the morphotectonic features found in the basin by geological and digital tectonic geomorphology analyses. Copyright © 2003 John Wiley & Sons, Ltd.

In the process of power supply to final consumers, an important amount of energy is lost in the transmission and distribution systems due to technological and non-technological losses. Technical losses represent an economic loss with environmental effects at national level, and its optimization should be performed from an overall national's perspective, regardless of the institutional organization of the sector and ownership of operating electricity utilities. The volume of energy losses in the power transmission and distribution systems is important, as it is generally up to 3 - 13%. The volume of power losses in Romanian power transmission and distribution systems is important, the level being of about double to the average in Europe. The current paper presents the research results of the authors regarding the real time monitoring and analysis systems for power losses, in electrical transmission and distribution systems.Within the research project, it was developed a dedicated system, successfully tested within a 5 years partnership with CNTEE “Transelectrica” - SA, on a transformer of 250/250/80MVA 400/121/20 kV from 400/110 kV Pelicanu Substation and respectively on the 400 kV overhead power line (118 km) Bucuresti Sud - Pelicanu.The tests results showed the importance of evaluation by real-time measurements, compared to the results of evaluations by calculations, of active power losses at power transformers and overhead power lines, respectively. Values several times higher were found for the values of active power losses measured online, in real time, than those determined by calculations.Online measurements have shown that there may be cases when large industrial consumers produce current and voltage harmonics well above the maximum allowable limits specified in the standards. The harmonics are transmitted practically undamped by the windings of the power transformers and on the transmission power lines (in the case of tests, even more than 100 km away from the place of their production).The online measurement of active power losses on the 400 kV overhead power line, 119 km, showed that corona losses are insignificant especially during periods of atmospheric humidity below 85%, and that active losses on power lines are practically resistive losses. The resistive losses on the measured high voltage overhead power lines are much higher than the calculated ones. The difference is determined by the fact that the calculation of active power losses on power lines includes the value of ohmic resistances of conductors evaluated based on line conductor resistivity or possibly based on ohmic resistance measured at a certain moment, and not the real value of the ohmic resistance of the line in real time (which changes over time due to the change in the state of the multitude of joints of the OHL conductor sections).

Analyzing the interactions between transmission and distribution (T&D) systems is becoming imperative with the increased penetrations of distributed energy resources (DERs) on electric power distribution networks. An assessment of the impacts of DERs connected to distribution system on the transmission system operations is required especially for the conditions leading to increased level of system unbalance. In this paper, a coupled T&D analysis framework is developed through co-simulation approach. The framework separately solves the decoupled T&D models. The T&D interactions are captured by exchanging the power flow solutions at the point of common coupling (PCC). The proposed co-simulation framework adopts an iterative coupling approach that results in a co-simulation model close to the stand-alone T&D system model. The proposed framework is tested using IEEE-9 bus transmission system model and EPRI’s Ckt-24 test distribution feeder model. A case study in which the IEEE-9 bus model interfaced with three ckt24 models is also presented to demonstrate the scalability of the approach. The conditions of convergence by exchanging the boundary variables at the PCC are examined in detail using several case studies with varying levels of load unbalance.

The software and digital is the development trend of vector network analysis. Combined with the idea of software radio, this paper presented a design scheme of vector network analyzer and discussed the key technologies and implementation. Firstly this paper studied the principle and composition of vector network analyzer, the overall design of the system hardware was given. Secondly, we discussed the related theories of the design and key technology. The research contents include: The technology of real-time wideband spectrum analysis, Real time dynamic range expanding technology, Wideband digital downconversion Technology, and Variable rate signal processing. The system structure and working process of the key system function had detailedly designed. Through the numerical simulation and experimental verification, we proved the correctness and feasibility of the design scheme.

A competitive decentralized framework for Volt-VAr optimization of transmission and distribution systems with high penetration of distributed energy resources

This chapter has introduced the important concept of insulation coordination of high voltage systems. The reader should be aware that increasing environmental and aesthetic concerns regarding the utilisation of overhead electrical power transmission lines have resulted in critical evaluation of underground alternatives and, in particular, at opportunities to further reduce the cost ratio between overhead and underground distribution and transmission systems. A joint CIGRE Working Group has been established to evaluate the influence of transient over-voltages on AC cable insulation design. Briefly, if one considers the inherent costs associated with cable systems (cable and accessories) then, by reducing the required withstand capability with improved protection devices and network design philosophy, one could develop a more economic underground system.

Railway interlocking systems can be implemented as distributed systems, where each part of a station is handled by a separate logical unit. The logical units of such systems form a network and communicate by interchanging messages. Such distributed architectures are well known in large industrial control systems. There are several design practices and also algorithmic task partitioning methods that are applicable in distributed control systems. Some of such methods can also be adapted in designing of railway interlocking systems as well. In the case of such systems, the communication time between components must be kept low. Namely each separate controller in a given route must be able to exchange their internal state within a limited time in order to permit the train movement authorization. This limitation could cause high traffic load, if every logical unit would be interconnected with each other. Therefore, the main goal of the minimization is to reduce the number of connections between logical units. This can achieved by distributing and assigning the topological railway objects to certain logical units.

A medium power Current Source Converter (CSC) based Active Power Filter (APF) system is designed and implemented to suppress the amplification of low order harmonics at the Medium Voltage (MV) interface bus between the distribution and transmission systems, owing to the presence of large shunt capacitor banks installed only for reactive power compensation. For this purpose, four CSC based APF units designed at 1.0 kV are operated in parallel, and connected to the 31.5 kV MV bus via a specially designed coupling transformer. In each APF module, a specially designed LC-type input filter eliminates the switching ripples, and active damping method embedded into the control software suppresses harmonic frequencies around the natural frequency of the input filter. The resulting system can operate at relatively high frequencies in the range from 2.0 to 3.0 kHz, depending upon which selected harmonics among 5th, 7th, 11th, and 13th are to be eliminated. Furthermore, in order to reduce the installed capacity of CSCs, Selective Harmonic Amplification Method (SHAM) is applied to the APF system described in the paper. MV APF system has been built as a mobile system for temporary connection to a problematic MV interface bus, until a permanent solution is found for that location in the distribution system.

In real time communication network capability measuring are crucial tasks because every resource of network is frequently change their state. In the mobile ad hoc network, link capacity utilization computation is very challenging task due to network topology frequently change, that totally depends on their network structure. So that in the ad hoc scenario all the network capacity utilization measure at end of simulation, where include the entire sub graph that will perform communication in any time. In the preceding some author calculates energy utilization, network congestion status and enhances the routing strategies. Through those work here we take every parameter that depends on the communication and find out the utilization, such parameters are network bandwidth, mobile node processing power, buffer, energy and signal strength utilization with respect to communication path between source to receiver. In this paper some of network parameter are initialize constant manner such as node initial energy, channel, buffer size, processing power that prefix and rest of parameter i.e. bandwidth, signal strength dynamically define at the time of communication. After that while communication start than all the parameter utilize that calculate with respect to complete path from source to destination. The utilize parameter apply into the fuzzy classification and calculate class level of particular complete path in `low', `medium', `high' level that helps to identify the network capability utilization. The result section shows identification of network path resource utilization in terms of bandwidth, energy, signal strength, buffer and processing power and impacts of these parameter based on packet delivery fraction, routing load, throughput, no. of data sends, receives and energy consumption etc.

Real-time simulation of distribution system is challenging due to its' complex structure consisting of DGs. In this literature, a real-time simulator for distribution system with DG integration based on the field programmable gate array (FPGA) is realized for hardware emulation. The overall framework and asynchronous multi-rate interface method between DG with high nonlinearity and distribution system is proposed. The models of main components in distribution system are designed in FPGA. The hardware parallelism and highly pipeline design is utilized to guarantee real-time simulation, which has strong generality and flexibility. The simulator uses a floating point arithmetic calculation to achieve high accuracy. To validate the new simulator, a photovoltaic-battery hybrid generation system and a typical distribution system integrated with PV generation system are emulated in the hardware. The time-step of DG system and distribution system reach 1.096μs/1.696μs and 2μs/2μs respectively. The captured waveforms show excellent accuracy in comparison to the offline simulation in PSCAD/EMTDC. The time-step is less than RTDS which indicate a higher precision. The resource consumption of FPGA also show advantage compared with RTDS.

ePHASORsim tool offers real-time dynamic simulations for transmission and distribution power systems. Applications such as contingency studies, testing control devices, operator training, and SCADA system tests are examples for employing this tool. This paper describes the hardware and software architecture of the ePHASORsim and its development. The accuracy of the tool has been evaluated in comparison to other commercial, but non-real-time, simulation packages for both transmission and distribution systems. Its real-time performance has been tested with a time-step of 10ms on a real-time simulator for large-scale power systems in the order of 20000 buses, 5000 generators, and over 9000 control devices.