Open source cable models for EMI simulations

This paper describes the progress of work towards an Open Source software toolset suitable for developing Spice based multi-conductor cable models. The issues related to creating a transmission line model for implementation in Spice which include the frequency dependent properties of real cables are presented and the viability of spice cable models is demonstrated through application to a three conductor crosstalk model. Development of the techniques to include models of shielded cables and incident field excitation has been demonstrated

Fast fault location scheme for distribution systems based on fault transients

This paper presents a combined double-end and single-end fault locator for distribution systems. The technique lies under the impedance based category and uses the fault generated high frequency components to locate the faults. The combination of double-end and single-end allows the method to discriminate between faults on the main feeder and those on laterals. Also, the method only requires a short data window as it depends on the high frequency components. The evaluation of the method considers different system and fault parameters e.g. loading taps, loading unbalance, fault type and fault resistance. To validate the proposed technique, the IEEE 34 nodes system is used to simulate different test cases

Real time parameter estimation for power quality control and intelligent protection of grid-connected power electronic converters

This paper presents a method to identify power system impedance in real-time using signals obtained from grid- connected power electronic converters. The proposed impedance estimation has potential applications in renewable/distributed energy systems, STATCOM, and solid state substations. The method uses wavelets to analyze transients associated with small disturbances imposed by power converters and determine the net impedance back to the source. A data capture period of 5ms is applied to an accurate impedance estimation which provides the possibility of ultra fast fault detection (i.e. within a half cycle). The paper describes how the proposed method would enhance the distributed generation operation during faults

Impedance sensitive STATCOM control for systems supported by renewable generation

Reactive power control is known to be an effective means of controlling voltage; however, for optimal performance, the system reactance must be known. Power systems with high re-newable energy penetration have been known to have voltage stability issues. To further complicate this issue, distributed renewable sources are likely to have an effect on the local sys-tem impedance. As a result, connection and disconnection of such sources is likely to result in significant changes in system impedance. In this paper, impedance estimation is used to dy-namically tune the controllers of a STATCOM so that consis-tent dynamic performance may be obtained. The method has been verified through simulation and through laboratory-based experimentatio

Development and testing of an experimental power system fault demonstrator

In this paper a laboratory demonstrator for the study of power system faults is described. The facility has been developed in order to experimentally investigate a number of fault location and power system protection technologies developed by the authors and their colleagues at higher power levels and with more representative system parameters than has previ¬ously been possible. In addition to describing the facility itself, this paper also describes the validation of a previously studied method using the new demonstrato

Influence of an inverter based DG on a double-ended fault location scheme

This paper describes the influence of Distributed Generation (DG) on a double ended fault location based on measuring the high frequency fault transients. The additional non-fundamental frequency current components from DG will influence the accuracy of an impedance based fault location technique based on non-fundamental frequencies. A double-ended impedance based fault location technique that utilizes the high frequency content (up to 5 kHz) is studied. The study showed that double-ended method is still able to locate a fault with a maximum error of 4% compared to the case without DG which showed a percentage error up to 2%

A double end fault location technique for distribution systems based on fault-generated transients

This paper presents a fault location technique for distribution systems. It is a two end impedance based technique that uses the fault generated transients to estimate the fault distance over a broad range of frequencies. Then, curve fitting is applied to find the final estimated fault distance. Firstly, the paper introduces the method for the system represented as a lumped RL model. Then, generalized to consider the distribution line capacitance. The technique accounts for presence of loading taps, heterogeneous feeder sections, single phase, two phase and three phase loads and unbalance in distribution system. Single line to ground, line to line, and three phase faults are considered at different fault resistance values up to 100 Ω. Also, the effect of fault inception angle and resolution of analogue to digital converter is investigated. IEEE 34 nodes system is used to evaluate the proposed method

High frequency impedance based fault location in distribution system with DGs

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals

An islanding detection method for multi-DG systems based on high-frequency impedance estimation

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system

A phase-space approach for propagating field–field correlation functions

We show that radiation from complex and inherently random but correlated wave sources can be modelled efficiently by using an approach based on the Wigner distribution function. Our method exploits the connection between correlation functions and the Wigner function and admits in its simplest approximation a direct representation in terms of the evolution of ray densities in phase space. We show that next leading order corrections to the ray-tracing approximation lead to Airy-function type phase space propagators. By exploiting the exact Wigner function propagator, inherently wave-like effects such as evanescent decay or radiation from more heterogeneous sources as well as diffraction and reflection can be included and analysed. We discuss in particular the role of evanescent waves in the near-field of non-paraxial sources and give explicit expressions for the growth rate of the correlation length as a function of the distance from the source. The approximations are validated using full-wave simulations of model sources. In particular, results for the reflection of partially coherent sources from flat mirrors are given where the influence of Airy function corrections can be demonstrated. We focus here on electromagnetic sources at microwave frequencies and modelling efforts in the context of electromagnetic compatibility