The Why of Adaptive Protections in Modern Electrical Networks

Abstract

Electrical networks are evolving and taking on more challenges as the inclusion of renewable energy and distributed generation units increase, specially at distribution levels. Big trends of generating electricity with alternative and renewable resources has promoted the formation of distribution networks subsystems or micro grids, capable of supplying their own electric demand and to export energy to the interconnected system, if necessary. However, the effects of these generation units into the network and into the microgrid as well are many, as harmonic distortion, voltage flickers and especially in electrical protections.This paper provides an overview about implementation of renewable energy and distributed generation worldwide, as well as an introduction to microgrids concept and its main impacts and challenges into the electric systems. Finally, the main impacts of microgrid on protection equipments are presented at a distribution level, being adaptive protections one of the solutions to the dynamic changes of the electric system.

Identification and Analysis of Technical Impacts in the Electric Power System Due to the Integration of Microgrids

“…Since the concept of MGs is referred to by many authors, and there is no standard definition for MGs, it is important to first explore more general concepts such as the smart grid (SG) before an MG concept is built. It is then possible to consider the SG as an updated system of transmission lines, substations, transformers, smart meters, and other elements that, by means of digital and information technology, allow bidirectional communication between the user and the EPS so that energy can be delivered and received efficiently with reliability and security [8,9].…”

“…However, in a system in which the MG is connected to the system, in the presence of a fault, the DG component of the MG will be in charge, along with the distribution grid itself, of contributing to the fault. If the traditional reclosers operate when the fault occurs, they would only be able to clear the situation on the network side, leaving the MG as the only contributor to the fault [27,29,33]; therefore, the fault goes from a transient state to a permanent one [30,31], and when the connection of both systems is restored, problems will be generated due to the union of the two unsynchronized systems [9].…”

“…However, the fault current is an important configuration parameter of the protection equipment because it allows the selection of the operating ranges of the relays. Then, if the fault current decreases or changes significantly, the operation of the protection equipment can be severely limited and affected, and this represents partial or total blindness of the relay [9,29,30,33].…”

“…Erroneous Operation This phenomenon occurs when a fault appears and the MG together with the system contribute to the short circuit, causing the fault current level to change, so the protection equipment is not able to identify and recognize that it is a faulty situation, and this impacts the sensitivity of the protection equipment [9,29,30].…”

Adaptive Multi-Agent-Zonal Protection Scheme for AC Microgrids

“…One of the current challenges in microgrid (MG) installation is the development of reliable protection and control schemes that guarantee the correct operation of these micropower systems [1]. The protection schemes used in traditional systems, i.e., with radial power flows, are designed to work with high levels of fault currents [2] and operate in such a way that when a fault occurs, they can isolate the affected areas to maintain continuous service in the rest of the network and reduce the probability of equipment damage. However, power system operation is dynamically altered by the incorporation of an MG, and traditional protection schemes suffer operational failures [3].…”