Pertti Järventausta

Using fuzzy sets to model the uncertainty in the fault location process of distribution networks

In the computerized fault diagnosis of distribution networks the heuristic knowledge of the control center operators can be combined with the information obtained from the network database and SCADA system. However, the nature of the heuristic knowledge is inexact and uncertain. Also the information obtained from the remote control system contains uncertainty and may be incorrect, conflicting or inadequate. This paper proposes a method based on fuzzy set theory to deal with the uncertainty involved in the process of locating faults in distribution networks. The method is implemented in a prototype version of the distribution network operation support system. >

Customer Classification and Load Profiling Method for Distribution Systems

In Finland, customer class load profiles are used extensively in distribution network calculation. State estimation systems, for example, use the load profiles to estimate the state of the network. Load profiles are also needed to predict future loads in distribution network planning. In general, customer class load profiles are obtained through sampling in load research projects. Currently, in Finland, customer classification is based on the uncertain customer information found in the customer information system. Customer information, such as customer type, heating solution, and tariff, is used to connect the customers with corresponding customer class load profiles. Now that the automatic meter-reading systems are becoming more common, customer classification and load profiling could be done according to actual consumption data. This paper proposes the use of the ISODATA algorithm for customer classification. The proposed customer classification and load profiling method also includes temperature dependency correction and outlier filtering. The method is demonstrated in this paper by studying a set of 660 hourly metered customers.

Smart grid power system control in distributed generation environment

This paper discusses the general aspects of smart grids and focuses on some distribution level smart grid features, such as interconnection of distributed generation and active distribution management, using automated meter reading (AMR) systems in network management and power quality monitoring, application of power electronics in electricity distribution, plug-in vehicles as part of smart grids, and frequency based load control as examples of interactive customer gateway.

Coordinated Voltage Control in Distribution Networks Including Several Distributed Energy Resources

Connecting distributed generation (DG) to weak distribution networks can often cause voltage rise problems. Traditionally, these voltage rise problems have been mitigated by passive methods such as reinforcing the network. This can, however, lead to high connection costs of DG. The connection costs can in many cases be lowered if active voltage control methods are used instead of the passive approach. In this paper, two coordinated voltage control algorithms suitable for usage in distribution networks including several distributed energy resources are proposed and studied. The first algorithm uses control rules to determine its control actions and the second algorithm utilizes optimization. The operation of the implemented algorithms is, at first, studied using time domain simulations. Thereafter, the network effects and costs of both algorithms are compared using statistical distribution network planning and also practical implementation issues are discussed.

A case study of a voltage rise problem due to a large amount of distributed generation on a weak distribution network

The paper is a case study about the integration of a relatively large amount of distributed generation into a weak distribution network. The main focus is on a comparison of methods to increase the integration capacity of distributed generation and on technical requirements from the distribution network companys point of view. The methods studied do not require major investments in the network. The paper considers voltage issues and the load transfer capability of a distribution network including wind power mills. The studies are based on real-life distribution network and load curve data.

Statistical Charging Load Modeling of PHEVs in Electricity Distribution Networks Using National Travel Survey Data

In this paper, statistical charging load modeling of plug-in hybrid electric vehicles (PHEVs) in electricity distribution networks is studied. Usefulness of National Travel Survey data in the modeling is investigated, and a novel modeling methodology is proposed where detailed car use habits are taken into account and statistical distributions of charging energies can be produced. Using the modeling methodology some example calculation results of a Finnish case study are presented with further analysis and sensitivity studies. The example calculations are made mostly from viewpoint of the Finnish distribution networks and their modeling traditions but the method can be applied internationally when relevant travel survey data is available. Example calculations are analyzed in order to assess reasonability and practical usability of the models. The models produced by the methodology can easily be used in network calculation tools commonly used by distribution network operators.

Enhanced Load Profiling for Residential Network Customers

Anticipating load characteristics on low voltage circuits is an area of increased concern for Distribution Network Operators with uncertainty stemming primarily from the validity of domestic load profiles. Identifying customer behavior makeup on a LV feeder ascertains the thermal and voltage constraints imposed on the network infrastructure; modeling this highly dynamic behavior requires a means of accommodating noise incurred through variations in lifestyle and meteorological conditions. Increased penetration of distributed generation may further worsen this situation with the risk of reversed power flows on a network with no transformer automation. Smart Meter roll-out is opening up the previously obscured view of domestic electricity use by providing high resolution advance data; while in most cases this is provided historically, rather than real-time, it permits a level of detail that could not have previously been achieved. Generating a data driven profile of domestic energy use would add to the accuracy of the monitoring and configuration activities undertaken by DNOs at LV level and higher which would afford greater realism than static load profiles that are in existing use. In this paper, a linear Gaussian load profile is developed that allows stratification to a finer level of detail while preserving a deterministic representation.

Use case analysis of real-time low voltage network management

Real-time low voltage network management is becoming possible thanks to massive smart meter rollouts, integration of them to distribution network management systems and utilization of distributed energy resources in distribution network management. Nowadays low voltage network management is emerging by integrating automatic meter infrastructure to centralized systems like SCADA/DMS. European project INTEGRIS is proposing a distributed approach based on hybrid and meshed communication. The paper is focused on low voltage network management use cases developed within the context of INTEGRIS and their ICT requirements to test the level of performance provided by the ICT architecture developed in the mentioned project.

RTDS verification of a coordinated voltage control implementation for distribution networks with distributed generation

In weak distribution networks the amount of distributed generation (DG) is usually limited by the voltage rise effect. The voltage rise can be mitigated using passive methods such as increasing the conductor size which can, however, be quite expensive. Also active voltage control methods can be used to reduce the maximum voltage in the network. In many cases active voltage control can increase the capacity of connectable DG substantially which can lead to significantly lower connection costs. In this paper, operation of an active voltage control algorithm is viewed. The algorithm controls the substation voltage and DG reactive power and determines its control actions based on the state of the whole network. The algorithm is implemented as a Matlab program and communication between Matlab and SCADA is realized using OPC Data Access. Correct operation of the algorithm is verified using Real Time Digital Simulator (RTDS). The same algorithm could also be implemented as a part of the distribution management system (DMS).

Methods for earth fault identification and distance estimation in a compensated medium voltage distribution network

This paper introduces methods for the indication and location of earth faults in a compensated medium voltage distribution network. Algorithms for determining the total phase-to-earth admittance and unbalance of the medium voltage distribution system and each of its MV feeders are presented. Information on earth fault distance can be obtained by rearranging the faulted feeder, normally operated radially, into a closed ring over some healthy feeder. The fault distance along both feeders can be determined by using two different values of the zero sequence voltage and corresponding zero sequence currents of the feeders. Two other methods based on reactive and active components of zero sequence currents can also be used. All the methods presented usually require a compensation of earth fault current. Both fault location and determination of these previously mentioned parameters have been tested in the real compensated MV distribution system.