Designing for Disaster

A static VAr compensator (SVC) was installed at the Eddy County substation near Artesia, New Mexico. It was put into commercial operation in April 1992. Before the commissioning period, a phase of extensive testing and analysis of the digital closed loop control was undertaken. This work was done using the actual control hardware and software in conjunction with an analog TNA and with digital simulation models of control and power systems. Results of this work were checked with the power system during field commissioning of the SVC. This paper gives an overview of the closed loop control design. It presents some results from the TNA tests, digital simulation and commissioning field tests of the SVC operation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In Japan, to realize low-carbon society, Advanced Low Carbon Technology Research and Development (ALCA) Project has been promoted to develop low-carbon technologies. The hydrogen cooled super-conducting generator (SCG) is one of them. SCGs have advantages such as low synchronous reactance and expansion of leading power factor operation, which expands the stability limit of power grid. Therefore, hydrogen cooled SCGs can be effective not only to low carbonization but also to stabilize high renewable energy (RE) penetration power grid. This study intend to model SCG with quick response excitation on electromagnetic transient (EMT) analysis software named eXpandable Transient Analysis Program (XTAP) and analyze grid stability, behavior of machines at power system fault situation, etc. accurately in order to reveal advantages of installing SCGs with quick response excitation.

A multiscale power system modeling methodology for the integrative simulation of electromagnetic and electromechanical transients is introduced, implemented and validated. It makes use of frequency-adaptive simulation of transients (FAST) in which the shift frequency appears as a new parameter in addition to the time step size. For fast electromagnetic transients, tracking of instantaneous waveforms as in the Electromagnetic Transients Program (EMTP) is performed. When slower electromechanical transients involving power oscillations prevail, the Fourier spectra of the waveforms are shifted by typically either 50 or 60 Hz to eliminate the ac carrier and enable envelope following as in phasor-based simulation. An algorithm for the automatic setting of both shift frequency and time step size is proposed. Multiscale models of transformers, synchronous machinery, and transmission lines based on FAST are developed. The line model is distinguished in that it bridges both lumped and distributed parameters to efficiently emulate scale-bridging phenomena from steady state to traveling waves. The overall methodology is thoroughly validated: first against a staged field test involving transients of line energization and recovery on the network of the Bonneville power administration (BPA); then through comparison with an EMTP-type simulator in modeling diverse transients on a four-machine two-area power system.

A comprehensive state-space model of two-stage grid-connected PV systems in transient network analysis

A cryogenic power cable is expected to be capable of carrying bulk power as a main transmission line in a future metropolitan electric power system. It is important to establish a strategy of how to sustain power supply when such a highly densified power supply route trips from the network due to contingency. It is proposed here that the bulk power transmitted by the cryogenic cable could be distributed into the parallel conventional transmission lines by suitable circuit breaker operations in the system. In this process, power‐flow routes are forced to be changed with a remarkable modification in the system configuration. In this paper, the power swings associated with the large power‐flow change following contingent faults are analyzed by means of a transient network analyzer. It is found that the proposed system modification could be realized without any harmful power swing if the parameters in generators as well as in control devices have conventional magnitudes. It is shown also by simulations that the margin to occurrence in an unstable power swing is left sufficient even if the parameters deviate somewhat from the present magnitudes.

Smart Grid integrates communication and computation technologies into power systems. Research on interdisciplinary topics between power system and communication systems requires models for both systems. There are several power system models available representing standard power systems and real power systems. However, lacking of their corresponding communication infrastructure information leads the difficulty of communication system modeling. In this paper, a communication infrastructure model compatible to Nordic 32 power system model has been developed and presented. In this model, Wide Area Monitoring System (WAMS) is incorporated with Supervisor Control and Data Acquisition system. The parameters of this model are based on the data from a Nordic electric power utility. Validation of the model is performed through comparison of results from simulation and a previous empirical data study performed on the same utility network. In additional, this model is simulated by using different Quality of Service (QoS) mechanism. The obtained results show that congestion management mechanisms introduce slight additional delay to the highest priority traffic. But traffics with lower priority can be benefit from congestion management mechanisms. The proposed model can be widely used for other research on Nordic 32 power system.

Guest Editorial: Situational awareness of integrated energy systems

Nowadays, there is quite high demand for electromagnetic transient (EMT) analysis programs and real-time simulators for power systems. In addition to the conventional demand such as overvoltage, over-current and oscillation simulations, the new demand that includes simulations of power-electronics circuits and power quality is increasing. With this background, development groups of EMT programs and real-time simulators have made progress in terms of computational performance and user experience. In Japan, Central Research Institute of Electric Power Industry has newly developed an EMT analysis program called XTAP (eXpandable Transient Analysis Program). This article overviews these international and domestic development trends of EMT analysis programs and real-time simulators.

The results of Transient Network Analyzer (TNA) studies evaluating the feasibility of low-side switching long transformer terminated lines is reported. It is shown that overvoltages following line dropping and fault clearing can severely stress surge arresters and circuit brtakers exceeding capabilities specified in ANSI standards. These overvoltages are often not carefully considered in design studies, since the available literature on low-side switching of EHV transmission lines primarily deals with energizing the line and transformer.1,2,3,4

Most investigations of power system transient behaviors are performed using computer simulation packages like the Electromagnetic Transients Program (EMTP). Scale modeling using Transient Network Analyzers (TNA) is still done, but decreasingly so as computer simulation models for system components are gradually improved. Engineers and researchers who perform transient simulations typically spend only a small amount of their total project time actually running the simulations. The bulk of their time is spent constructing the overall system model. Obtaining parameters for component models. Benchmarking the components models to confirm proper behaviors, and Benchmarking the overall system model to verify overall behavior. Only after the component models and the overall system model have been verified can one confidently proceed to run meaningful simulations. Even then, if there are some transient event records to compare against, more model benchmarking and adjustment may be required. Here, the authors present recommendations on how to obtain the parameters needed to model overhead transmission lines and transformers, the two most prevalent components of a power system.

Precise load curtailment (PLC) is a verified technology to use demand side resources in pilot project in Jiangsu province, China. A simulation method of PLC is proposed in this paper and this module is united with a power system simulation module. Both of these two modules use the same power system model with a hierarchical database. In PLC simulation module, the power of two DC lines is the action condition variable for load curtailing. When load curtailment is triggered by DC blocking event which simulated in power system simulation module, the PLC simulation module will calculate the amount of loads that will be curtailed and the power of these loads will be modified in power system model. Then the power system simulation module will calculate the power flow and system frequency. The simulation framework and the load curtailment strategy are illustrated, as well as the PLC simulation modeling methods. At last, the simulation cases with different curtailment strategies are also discussed in this paper.

Amorphous alloy is increasingly widely used in the iron core of power transformer due to its excellent low loss performance. However, its potential harm to the power system is not fully studied during the electromagnetic transients of the transformer. This study develops a simulation model to analyze the effect of transformer iron core materials on ferroresonance. The model is based on the transformer π equivalent circuit. The flux linkage–current (ψ–i) Jiles–Atherton reactor is developed in an Electromagnetic Transients Program-Alternative Transients Program and is used to represent the magnetizing branches of the transformer model. Two ferroresonance cases are studied to compare the performance of grain-oriented Si-steel and amorphous alloy cores. The ferroresonance overvoltage and overcurrent are discussed under different system parameters. Results show that amorphous alloy transformer generates higher voltage and current than those of grain-oriented Si-steel transformer and significantly harms the power system safety.

The wavelet transform is introduced as a method for analyzing electromagnetic transients associated with power system faults and switching. This method, like the Fourier transform, provides information related to the frequency composition of a waveform, but it is more appropriate than the familiar Fourier methods for the nonperiodic, wide-band signals associated with electromagnetic transients. It appears that the frequency domain data produced by the wavelet transform may be useful for analyzing the sources of transients through manual or automated feature detection schemes. The basic principles of wavelet analysis are set forth, and examples showing the application of the wavelet transform to actual power system transients are presented.

An electronic arc model has been developed which simplifies the study of harmonic phenomena in are furnace power systems on a transient network analyzer (TNA). The model helps insure the proper magnitude and phase relationship of the harmonies at each loading condition. The simulation procedures and arc model characteristics are described. Also, some examples of typical study results are given.

Overall critical evaluation of the dynamics of EHV dc-power transmission requires that a variety of system conditions and effects of many parameters be studied. Problems can be strictly electrical or electromechanical. In general, those that fall in the former category are of short time duration, while those in the latter may be either of intermediate duration, on the order of 1 second, or of long duration, from 2 to 40 seconds. The approach used, whether it be 1) a physical model such as a transient network analyzer; 2) an analog computer, sometimes called an electronic differential analyzer, or 3) a digital computer, will depend upon the specific problem at hand. The capabilities and limitations of the analog computer in providing solutions to electromechanical problems are outlined in this paper, and the results reported give insight into the dynamic performance characteristics of a dc link under constant current or power control, with or without a parallel ac line.