The electrical distribution network is in front of stage of several changes, the communication network joint to the Information Technologies (IT) is taking a relevant importance where the Power Quality has been defined as one of the fundamental vectors of the electrical utilities.
The Power Quality is the concept which tries to standardize in the electrical networks its standard of the quality. This concept is divided in three important spotlights: the availability, the wave quality and the commercial quality. This thesis is based in the first of these three pillars.
The availability is a key point in order to keep a high-reliability level in the electrical network. In fact, it is possible to indicate that it is the most important in front of the others because without it never it will be possible to have a properly ready network.
This chapter exposes the motivation for which the fault location problem is present in electrical distribution networks. Following the object and the tasks which are needed to reach this achievement are presented. Finally, the organization of the document and the content of each chapter are indicated. This PhD thesis has been developed during the period 2014-2018 in Escola Tècnica Superior d’Enginyeria Industrial de Barcelona (ETSEIB) from Universitat Politècnica de Catalunya (UPC), although some researchers has been developed and published in a previous period in several congresses and journals since 2011 by the author.
1.1 Motivation
Nowadays in the current electrical distribution networks the availability has been implemented correctly until now. In recent years the penetration of Distribution Energy Resources (DER) has had a big impact in electrical distribution network. This fact can difficult considerably the fault detection in these networks because the current can flow in both direction and it will depend on the current topology in every moment. However, these new actors will provide more efficiency to the network in front of the traditional generation.
It is important does not forget the other pillars of the Power Quality: wave quality and commercial quality. Both points are very important in order to have a good quality in the network, therefore it is necessary to analyse the impact of DERs also in these features of the networks, overall in wave quality.
In front of this scenario is very important to introduce new kind of automation which aims to help to locate a fault and after that to establish a quick restoration. Systems such as Fault Location Isolation and Service Restoration (FLISR) can contribute considerably in order to enhance the availability of the system.
As mentioned before the IT has evolved considerably in recent years although the Internet of Things (IoT) has taken a big relevance in the industry and other sectors of the society but today is the moment of the electrical network. The number of sensors in electrical distribution networks were not high and the information of the process was hide until recent year. It is important to highlight that in last years the Distribution System Operator (DSO) has increased the sensors in the network in order to have more information and to enhance the commercial quality. This is the moment to introduce new algorithms and new procedures in order to enhance the availability of the network. In fact, the Transmission System Operator (TSO) has also enhanced their networks due to the introduction of new DERs.
1.2 Goals
This thesis studies the implications that the automation can provide to the current and future electrical distribution network. Therefore, the first goal of this document is to establish the state of the art of the automatic fault location in distribution networks and in a second term to define the bases to develop an algorithm about fault location to enhance the Power Quality of the electrical distribution networks. The first of these goals includes a previous study about the current situation of fault location in distribution network. The study was started in the subject Power Electric Systems, in ETSEIB, where a report was required to fulfil with all the conditions of this subject. This initial report established several points to analyse the problems related with automatic fault location in the network. This document was the first step to establish the knowledge and the bases to develop the PhD thesis. Therefore, in this document it is possible to find the first knowledge about automatic fault location, although this document has evolved along the period of PhD because there has been a continuously evolution in this area.
On the other hand, the second goal tries to define the main important points to develop an algorithm focused in two important features: location and restoration in electrical network distribution. In fact, a network electric operator has a huge issue when there is a fault in a network, for this reason one of the goals of this document is to pose algorithms which can combine the two properties: Location and Restore.
1.2.1 Goal: State of the art
The State of the art about automatic fault location is focused in the elaboration of a document with a lot of references which develop the topic. As it has been defined in the introduction, the document is composed by four important points: network quality, faults, fault location and restoration.
These four points are the four steps to define correctly the state of the art because it is the four questions to ask after a fault in the network. The first of these questions is to know the quality system of the network to know the possibilities to isolate the fault, after this point it is necessary to know the kind of the fault to start the process to develop the isolation process. Later to know the location is a fundamental point to
start the isolation process opening the circuit breakers and switch-disconnectors in the distribution network. Once time the fault is isolated the next step is to restore the network in order to recover the users without supply.
The state of the art of this topic has a huge dimension due to there are different ways to detect a fault in the network. For this reason, one of the goals of this initial document is to reach a definition about the different ways to detect all the defects.
This goal is completed with other topics such as IEC 61850 and IoT standards which can contribute significantly in the new stages for automation in the electrical distribution networks. It is important to highlight that this kind of standards can help significantly in the evolution of the procedures to reconfigure the network.
1.2.2 Goal: fault locator algorithm
This document shows different papers about simple algorithms focused in fault location combining the restoration. These algorithms have been the first stone to develop the fault locator algorithm proposed in this document.
The proposed algorithm seeks to make a first stage to locate a fault in the network through different parameters and in a second stage to propose a process restoration of the network in order to isolate the fault and recover the supply for the users of the network.
The main goal of the fault Locator algorithm is to reach a sustainable level of fault detection in order to enhance the quality in electrical network. In fact, the improvement of quality is focused in several concepts as the document will be presented in next chapters although one of them is the availability of the energy supply. Therefore, after a fault there are two important problems: the fault and the availability of the energy for the users, knowing the fault is possible to establish a possible solution to recover the supply in the customers to maintain or improve the quality indices of the network.
1.3 Contents
In order to develop this state of the art, several points have been studied. The first one has been the network quality where three parts can be found: the availability quality, the wave quality and the commercial quality. As the most related part with the goal of this document is the availability quality, it is possible to find the description of quality indices to evaluate the network. Besides in this part, the network architectures are analysed.
It is important to develop this point to understand the different situations which are in electrical network under a fault.
In another part there is an analysis about detection faults in electrical network distribution. This is a key point inside of this PhD thesis due one of the goal of this is to contribute in the development of this area. In this part it will be analyse the concept of fault locator and the different devices and network control systems to detect a fault in order to conclude finally in some algorithms to detect them.
Following, different control technologies are showed to manage an electrical distribution network. In this part there will be an introduction of the Smart Grid concept and the current status of the Feeder Automation concept. In this chapter the IoT standards and IEC 61850 are explained such as key tools for the automatization of the network.
Finally, the distribution network restoration is showed with different centralized and decentralized restoration procedures which contribute to complement the Feeder Automation concept for the electrical network distribution.
As additional points, there are the mentioned references in this document from different publications and the appendix about the publications, participations in committees and congress presentations of the author related with the topic.