• Energy Research
• Closed Access close
• US close
• CA close
• GB close
• Electric Power Research Institute close

Load modeling plays an important role in transmission planning studies to anticipate the response of a power system following fault. The composite load model is the latest and the state-of-the-art load model available for transmission planning studies. Many utilities in the US are already using the composite load model or transitioning to use the composite load model for their transmission planning studies. However, the usage of any aggregated load model can in some cases lead to unanticipated and suspect simulation results during certain grid conditions. This paper briefly introduces the composite load model and presents two scenarios where an informed sensitivity study can help transmission planners gain deeper insights into otherwise ambiguous results obtained while using the composite load model during simulations.

This paper gives a introduction of a SMES unit using 2G HTS wires. A complete SMES system including both superconducting coils and control circuit has been designed to operate at 77 K. Three single-phase H-bridge converters have been used in the control circuit. A loop control signal is sent out by using 32 fixed point Digital Signal Processor (DSP). The complete circuit has been both modelled in simulation and built experimentally. The results validate that this SMES successfully compensates a voltage sag in a power system.

Audible noise of can-type filter capacitors in high- voltage direct current converter stations originates from the vibration of capacitor cases, so it is meaningful to investigate the vibration characteristics. However, no experiment under practical excitations or thorough theoretical analysis was presented for the vibration characteristics. This study theoretically and experimentally investigated the vibration characteristics of can-type filter capacitors with stacked elements parallel to bottom. The vibration amplitude was found to be proportional to voltage squared. If the frequency spectrum of excitation voltage included several harmonics (more than three), vibration amplitude on some specific frequencies was related with the phases of these voltage components. Each capacitor surface had a concavo-convex vibration shape and the vibration of the bottom surface and the side surfaces were in opposite phases. The vibration amplitude of the bottom surface was the largest. Moreover, frequency characteristics of capacitor vibration were studied. The frequency response of the bottom surface was bigger than that of narrow and broad side surfaces for lower frequencies, while was smaller for higher frequencies. It was inferred that bottom surface vibration was mainly caused by elastic forces from direct contact and side surfaces vibration mainly came from damping forces from dielectric liquids.

Tuning a complex multi-loop PID based control system requires considerable experience. In today's power industry the number of available qualified tuners is dwindling and there is a great need for better tuning tools to maintain and improve the performance of complex multivariable processes. Multi-loop PID tuning is the procedure for the online tuning of a cluster of PID controllers operating in a closed loop with a multivariable process. This paper presents the first application of the simultaneous tuning technique to the multi-input-multi-output (MIMO) PID based nonlinear controller in the power plant control context, with the closed-loop system consisting of a MIMO nonlinear boiler/turbine model and a nonlinear cluster of six PID-type controllers. Although simplified, the dynamics and cross-coupling of the process and the PID cluster are similar to those used in a real power plant. The particular technique selected, iterative feedback tuning (IFT), utilizes the linearized version of the PID cluster for signal conditioning, but the data collection and tuning is carried out on the full nonlinear closed-loop system. Based on the figure of merit for the control system performance, the IFT is shown to deliver performance favorably comparable to that attained through the empirical tuning carried out by an experienced control engineer.

The defects of the present fault chain model of power grid cascading failures have been summarized and a defined method for forecasting cascading failures is presented based on a fault chain model and Fuzzy C-Means. First, in order to reduce the workload and overcome the limitation of present means, this method selects a number of lines with the high value of predictive index to be the next outage lines during fault chain forecasting. Then, this paper analyzes the correlations among lines. Finally, taking IEEE 39-bus system as example, the rationality of the method proposed is verified based on comparison with other means.

The first part of this two-paper series discusses the motivation of implementing a primary frequency response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the response reliably. PFR is the immediate, autonomous response of generation and demand to system frequency deviations. It is the critical response required to avoid triggering under- and over- frequency relays or instability that could lead to machine damage, load-shedding, and in the extreme case, blackouts. Currently, in many restructured power systems throughout the world, ancillary services markets have been developed to incent technologies to provide the services to support power system reliability. However, few ancillary services markets include a market explicitly incentivizing the provision of PFR. Historically, PFR was an inherent feature available in conventional generating technologies, and in most systems, more was available than needed. Yet, recent trends in declining frequency response, the introduction of emerging technologies, and market behavior may soon require innovative market designs to incent resources to provide this valuable service.

Partial discharges (PD) detection for power equipments mainly includes the pulse current method, transient earth voltage (TEV) method, ultrasonic detection method, ultra-high-frequency (UHF) method, and optical detection method. Among them, those PD detection methods realized based on optical fiber sensing technologies has the advantages of safety, insulation and anti-electromagnetic interference. So they are suitable to be designed as embedded or intrusive sensors installed into the power equipments of PD on-line monitoring or live detection with prospects for development. In this paper, the measurement methods of PD ultrasonic signals based on optical fiber sensing technologies, principle parameters and advantages and disadvantages are summarized. At last, the optical fiber sensing technology using extrinsic Fabry-Perot Interferometers (EFPI) is pointed out that it has good application prospect due to its high sensitivity and stability.

Abstract The difficulties of ultrasonic examination of dissimilar-metal welds in BWR and PWR plants are discussed. Improved examination techniques were developed and are described. The complex structure of dissimilar-metal welds and the use of highly attenuating austenitic weld metals and castings make conventional shear-wave examination ineffective. An ultrasonic test procedure using refracted longitudinal-wave transducers was developed for examining the dissimilar-metal welds in the nozzle-to-safe-end joints in BWR recirculation piping. The techniques were developed in the laboratory with mock-ups containing notches and intentional cracks. Four field trials of the procedures using manual and automated methods were conducted to verify the laboratory results. Signal-processing techniques were investigated, and a spatial signal-averaging method was found to be effective in improving signal-to-noise ratios. For welds less than about 38 mm (1·5 in) thick, transducer frequencies of 2 MHz could be used and were capable of reliably detecting cracks with depths about 20% of the wall thickness or greater. Thicker welds required the use of large-element 1 MHz transducers. The best flaw detection performance was obtained with large angles of refraction (60° or greater).

An effect experiment of a 10 kV oil-immersed transformer injected by the nanosecond pulse is conduced in this paper. To carry out the experiment, an equivalent 10 kV transmission line (TL) platform is constructed where the characteristic impedance of TL is designed as practical value. By injecting the nanosecond pulse with increasing amplitude, the injected current and response current as well as the injected voltage are measured simultaneously. Based on the measured data, the effect of transformer is analyzed.