This paper presents an expert system that is able to classify different types of power system events to the underlying causes (i.e., events) and offer useful information in terms of power quality. The expert system uses the voltage waveforms and distinguishes the different types of voltage dips (fault-induced, transformer saturation, induction motor starting), as well as interruptions (nonfault, fault induced). A method for event-based classification is used, where a segmentation algorithm is first applied to divide waveforms into several possible events. The expert system is tested using real measurements and the results show that the system enables fast and accurate analysis of data from power quality monitors.

Expert System for Classification and Analysis of Power System Events

Classification of power quality events – A review

The role of built environment energy efficiency in a sustainable UK energy economy

The unified power quality conditioner (UPQC) is known as an effective compensation device to improve PQ for sensitive end-users. This paper investigates the operation and control of a single-phase three-leg UPQC (TL-UPQC), where a novel space vector modulation method is proposed for naturally solving the coupling problem introduced by the common switching leg. The modulation method is similar to the well-known space vector modulation widely used with three-phase voltage source converters, which thus brings extra flexibility to the TL-UPQC system. Two optimized modulation modes with either reduced switching loss or harmonic distortion are derived, evaluated, and discussed, in order to demonstrate the flexibility brought by the space vector modulated TL-UPQC. Simulations and experimental results are presented to verify the feasibility and effectiveness of the proposed space vector modulation approach as well as two mentioned modulation modes.

Control Strategy for Single-Phase Transformerless Three-Leg Unified Power Quality Conditioner Based on Space Vector Modulation

Power quality monitors in the occasion of a disturbance can either save the actual voltage waveform that contains the event or the corresponding RMS. The latter option reduces significantly the memory that is needed for saving the event. This paper shows that even with this type of monitoring, analysis of the measurements can be in depth. The paper proposes a method for automatic classification of power system events using RMS voltage measurements. The system is tested with measurements from a distribution network and the results show that classification is possible for the considered types of events. Finally, the limitations of this type of monitoring are shown.

Automatic classification of power system events using RMS voltage measurements

Scottish Power supplies electricity to a customer base of three million in the south of Scotland and Manweb. A high proportion of the manufacturing and process industries in Scotland are involved in semiconductor production, requiring a consistent and high quality power supply. The quality of supply is therefore important to both customers and Scottish Power in terms of attracting and keeping new industry and business. This paper discusses why power quality is such an important issue and then discusses Scottish Power's company strategy to improve power quality. The strategy is chiefly based on the classification of voltage dips as a quality of supply indicator. The voltage dips are detected by digital fault recorders (DFRs) installed across the Scottish Power distribution system. This strategy enables Scottish Power to provide industrial and commercial customers with tangible system performance reporting and feedback. This method of network assessment also promotes practical dialogue between Scottish Power and the customer during the specification of new customer loads to ensure that the subsequent load characteristics do not degrade the performance of the load or the network. Two case studies are examined.

Power quality issues-a distribution company perspective

Future cities are likely to be characterized by a greater level of renewable energy systems deployment. Maximum impact will be achieved when such systems are used to offset local energy demands in contrast to the grid connection of large schemes. This paper elaborates a method whereby passive renewable technologies are deployed locally to reduce energy requirements while active renewable technologies are deployed to meet a significant portion of the residual demand. A modelling system for the identification of suitable schemes is then described and its application to a real case reported.

On the integration of renewable energy systems within the built environment

The paper presents a new simulation based method for harmonic distortion level evaluation at the point of common coupling in power system distribution networks. The proposed method aims to calculate the anticipated levels of voltage and current distortion by performing comparative simulation studies based on the information on the existing power quality profiles and the planned future network configuration including inverter connected embedded generation. Time domain simulation is used in order to calculate current and voltage waveforms which then can be analysed with FFT algorithm. The paper gives a detailed explanation of the method followed by the case study performed on a fragment of an actual LV distribution network. In order to provide a holistic assessment of harmonic distortion weekly profiles are analysed in 10 minute intervals which is consistent with the approach proposed in the European standard EN 50160.

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I. Hunter

Papers

Power quality issues-a distribution company perspective

On the integration of renewable energy systems within the built environment

Assessment of harmonic distortion levels in LV networks with increasing penetration levels of inverter connected embedded generation

Power quality and the impact of building-integrated renewables