For smart grid development, one of the key expectations is that the data should be accessible to and readily interpreted by different applications.Presently, protection settings are represented using proprietary parameters and stored in various file formats.This makes it very difficult for computer applications to manipulate such data directly.This paper introduces a process that translates the proprietary protection setting data into IEC 61850 standardised format and saves the data as System Configuration description Language (SCL) files.A code generation process that allows rapid implementation of the translation process is proposed.Among various applications, the paper demonstrates how such a translation process and generated SCL files can facilitate the development of an intelligent system for protection setting error detection and validation.
This paper presents an assessment of the performance of distance protection for transmission lines in the presence of Quadrature Booster Transformers (QBs). The use of QBs in the UK transmission grid is increasing to maximise the utility of existing infrastructure as well as enabling rapid network modifications as dictated by operational requirements. An analysis is performed with the aid of a real time digital simulator (RTDS) to quantify the extent of error which may lead to the mal-operation of distance protection on transmission lines with QBs installed and operating under different scenarios. Using QBs in the future for more active constraint management may cause further complications that stretch existing protection schemes' capability. These issues are also considered. Furthermore the scope for an adaptive relaying solution is defined with focus on a wider scale coordination of protection for networks with QBs installed.
The impact on the distribution grid when Electric Vehicles are connected is an im-portant technical question in the development of new smart grids. This paper looks in detail at the predictive capability of a model, calculating harmonic voltage and current levels, in the situation where an electric vehicle is being charged by an in-ductive charging plate which acts as a substantial source of harmonic distortion. The method described in this paper models distortion at the LV side of the distribution grid by reconstructing the HV harmonic distortion levels seen at a typical LV sub-station. Additional LV connected harmonic-rich current sources can then be added, allowing a quantitative analysis of the impact of such sources on the distribution grid in terms of measurable harmonics magnitude and phase angle with respect to the fundamental.
Offshore wind plant will play an increasingly important role in future decades if ever‐stringent requirements of energy security and low carbon emissions are to be met. Although some analyses of the DFIG impact on system stability have previously been reported, none are based on a large network representing a real system, or the large network is simply not publicly available. This paper describes one such suitable equivalent dynamic model for stability studies based on the UK transmission system. The methodology for appropriate control system design and adjustment of the parameters under different dispatch conditions is presented. Two important aspects contributing to future system stability are studied in detail, namely maximum value of the rate of change of frequency and transient stability. Following National Grid future energy scenarios, a number of detailed case studies are presented to quantify the impact of key influencing factors including the size of the largest generating unit for n −1 contingency, amount of primary system response, and frequency dependency of load. The study concludes that none of the individual factors can provide a complete solution and that careful cost benefit analysis is needed to determine the proper mix of services and reinforcements needed in the future.
Abstract This paper presents a comprehensive evaluation of the HVDC system's impact on distance protection via systematic and realistic experimental tests, along with theoretical analysis of the root causes of the identified compromised protection performance. A methodology for quantifying the impact of Synchronous Compensation (SC) in supporting the distance protection operation is also established. In this work, the performance of two widely used physical distance protection relays have been evaluated using a realistic Hardware'In'the'Loop (HIL) testing environment, where a total of 480 cases have been tested under a wide range of system scenarios. Representative cases with compromised protection performance are selected, where issues of under/over'reach, faulted phase selection and impedance measurement are identified and analysed. Furthermore, a method for quantifying the required SC level to address the under/over'reach issues resulting from HVDC systems is presented. The method establishes the relationship between the angle difference of the two'end fault current infeeds of the protected line and the SC level. Based on this relationship, the required SC capacity to constrain the angle difference within a targeted limit can be estimated, which offers a useful tool for system operators to appropriately size the SC's capacity with additional valuable insights from the distance protection perspective.
When faults occur in the microgrids, high frequency transients will be superimposed on the system currents and voltages. The magnitude of those transients will attenuate as it encounters the discontinuity points in the network such as busbars, or any other impedance discontinuity points. This phenomenon can also be quantified by wavelet energy, which provides a useful tool to detect faults and locate the faulted feeder in the microgrid. In this paper, a novel protection scheme based on the transient wavelet energy of the superimposed current extracted by the Maximal Overlap Discrete Wavelet Transform (MODWT) algorithm is developed to detect faults and locate the faulted feeder in microgrids. Compared with existing protection schemes, the proposed protection scheme has the advantage of being largely immune to the changes in system fault level, fault types and positions, microgrid operating status and the control strategies deployed on the inverters, while presenting much lower requirement on the sampling frequency (10 kHz) compared with travelling wave-based methods. Unlike the conventional differential protection, the proposed scheme does not require synchronized measurement or high bandwidth communication channels, and thus, it can be considered as an economical and promising solution for microgrids.
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