Pekka Verho

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. >

Studies to Utilize Loading Guides and ANN for Oil-Immersed Distribution Transformer Condition Monitoring

There are plenty of proper monitoring methods to evaluate the condition and possible incipient failures of a power transformer. For distribution transformer monitoring, the methods are usually too expensive and/or time consuming to use. However, cost-efficient methods for distribution transformer monitoring are needed and one possibility for this is to utilize loading and temperature information measured from the network. The monitoring methods presented in the paper are based on the existing IEC and IEEE standards and neural-network analysis. The methods are used to calculate the top-oil and hot-spot temperature as well as the loss of life of a transformer. The calculated results are verified with measured top-oil temperature values. The possibilities to utilize studied methods in a larger scale for distribution transformer monitoring are also discussed in this paper

AI-based methods in practical fault location of medium voltage distribution feeders

The fault location expert system is an application of a distribution management system, which is a part of the integrated control center environment composed of different computer systems and distribution automation. The expert system applies AI-based methods (e.g., object-oriented modeling, blackboard technique, fuzzy reasoning, decision tree) in incorporating data on external systems in order to support the control center operator in network operation. At present the expert system is in everyday use in several distribution utilities.

Applying reliability analysis in evaluation of life‐cycle costs of alternative network solutions

Electric utilities are enforced to control trustworthily total lifetime costs caused by their network components without jeopardizing the reliability and security of the network. New distribution planning methods and procedures are needed in order to meet the expectations and performance targets of regulators, company owners and customers in the re-regulated environment. One of the most challenging tasks for electrical utilities is the consideration of reliability as a part of long term planning of the network. In order to respond to these requirements, an advanced IT-solution has been created, which provides reliability analysis as a part of the network planning process. The software implementation and the developed models for reliability analysis are presented briefly in the paper. The focus of the proposed paper deals with studies in which alternative network solutions are evaluated using the developed application. For each alternative the total lifetime costs are calculated, including reliability costs. The optimal plan depends on the selection of reliability optimization criteria: the reliability costs may consist only of direct utility costs, but they can also include customer interruption costs and even the costs of voltage dips. The paper presents and evaluates results of example studies and discusses the correlation between the utility strategy and optimal network structure

Interference of touch dimmer lamps due to PLC and other high frequency signals

The interference of touch dimmer lamps due to PLC signals has found to be a common interference problem in Finland after the installation of smart meters that use PLC. One reason for this is the lack of equipment immunity standards for voltage frequencies below 150 kHz. This paper will study controlled discontinuous high frequency signal burst effect to two touch dimmer lamps in the laboratory environment. Both lamps were disturbed due to these signals. Based on the results it is possible that interference problems can occur even if the distance between lamp and the PLC device is close to 100 m. Paper will also show the measurement results on how one plug-in type filter improve interference situation. Results show that the amplitude of the signal burst will decrease at lamp side but filter also affects signal levels at mains side.

Experiences on narrowband powerline communication of automated meter reading systems in Finland

According to Finnish legislation, at least 80 % of the energy meters have to be remotely readable and provide hourly based energy data by the end of 2013. In April 2011 Tampere University of Technology (TUT) in co-operation with Finnish Energy Industry conducted a questionnaire to Finnish distribution network operators (DNOs) to map the installation status of the remotely readable meters, the communication technologies used in the meters and the interference problems experienced so far, related to, especially, PLC (power line communication) systems. The questionnaire dealt with both the interference caused by customer apparatus to PLC and vice versa. On-site measurements to study common customer apparatus disturbing the PLC were also conducted in 2012 in the networks of a few DNOs. Most common disturbance sources were frequency converters and switch mode power supplies. The measurements indicate that in addition to the lack of emission standards below 150 kHz the aging of customer equipment may be a relevant cause of interference problems.

Advanced reliability analysis for distribution network

One of the most challenging tasks for network utilities is to reduce costs and improve reliability at the same time. In order to manage the task successfully advanced IT-solutions are needed providing reliability analysis as part of the planning process. This paper presents advanced reliability analysis for distribution network. A sophisticated failure rate model has been developed based on failure statistics of the network and engineer judgement. Practical fault management process and statistics has been analyzed in order to model the customer outage times in different fault situations. Outage cost model for different customer groups are used in order to reach financial results by the analysis. The practical implementation and some demonstration studies are presented in the end of the paper.

Applying reliability analysis in evaluation of life-cycle costs of alternative network solutions

Electric utilities are enforced to control trustworthily total lifetime costs caused by their network components without jeopardizing the reliability and security of the network. New distribution planning methods and procedures are needed in order to meet the expectations and performance targets of regulators, company owners and customers in the re-regulated environment. One of the most challenging tasks for electrical utilities is the consideration of reliability as a part of long term planning of the network. In order to respond to these requirements, an advanced IT-solution has been created, which provides reliability analysis as a part of the network planning process. The software implementation and the developed models for reliability analysis are presented briefly in the paper. The focus of the proposed paper deals with studies in which alternative network solutions are evaluated using the developed application. For each alternative the total lifetime costs are calculated, including reliability costs. The optimal plan depends on the selection of reliability optimization criteria: the reliability costs may consist only of direct utility costs, but they can also include customer interruption costs and even the costs of voltage dips. The paper presents and evaluates results of example studies and discusses the correlation between the utility strategy and optimal network structure

Method to increase sampling frequency by merging multiple measurements

The use of transient-based methods in IEDs (Intelligent Electronic Devices) in distribution substations has been very rare. The additional unit cost of an IED due to a higher sampling frequency has been considered too high in comparison with the benefits it can provide. This document describes a method to artificially increase the sampling frequency of the IEDs current and voltage measurements by using lower sampling frequency measurements from multiple IEDs. This method makes it possible to utilize transient-based algorithms in a substation without the need to have devices with high sampling frequency. Also power quality functions benefit from this increase of the sampling frequency.

Intelligent configuration management of distribution network

This paper deals with the computerized configuration management of a distribution network. A distribution management system (DMS) has been developed and integrated to other information systems. The DMS provides various functions for configuration management: topology supervision, restoration, maintenance outage planning and reconfiguration. The field crew management and outage cost modeling subfunctions are utilized in the intelligent configuration management functions of the DMS.