Power-system protection

About: Power-system protection is a research topic. Over the lifetime, 6353 publications have been published within this topic receiving 117961 citations.

Agent-based protection scheme for distribution networks with distributed generators

Abstract: This paper describes a novel protection scheme for a distribution network with distributed generators. The network is divided into several segments to facilitate fault isolation. Relay agents protecting the system are installed at points of interconnection between different network segments. These relay agents communicate with the neighboring agents through an asynchronous communication network. A wavelet transform coefficients based technique is proposed to identify the direction of a fault with respect to a node in the network by measuring the transient currents in the branches connected to the node. Relay agents, which use this technique to determine the fault directions with respect to their locations, then collaboratively determine the faulted zone. Simulation studies using PSCAD/EMTDC reveals that this scheme is capable of identifying and locating faults with very high accuracy even for high impedence faults.

System protection schemes in power networks: existing installations and ideas for future development

Abstract: A common type of SPS (system protection scheme) that operates using local criteria is an under-frequency load shedding scheme. This is normally considered final intervention and is often only used when the power network has been divided into islands. Examples of other local SPS are out-of-step detection and undervoltage detection. The paper initially describes how SPS in Canada, France and Romania are used to defend system integrity during unforeseen or extreme contingencies. The examples should be considered as a source of information and also as a challenge to report on experiences with SPS. The paper then discusses possible ideas for future SPS based on available technology and known power system requirements.

Challenges to overcurrent protection devices under line-line faults in solar photovoltaic arrays

Abstract: Solar photovoltaic (PV) arrays behave distinctively from conventional power sources so that they need special consideration in fault analysis and protection. The faults inside PV arrays usually cause overcurrent that may damage PV components. This paper focuses on the challenges to overcurrent protection devices (OCPDs) in a PV array under two types of unique fault scenarios. One is a line-line fault that occurs under low irradiance conditions. In this circumstance, the fault current may not be large enough to trip the OCPDs in the PV array, even when high irradiance occurs later in the day. The other fault scenario is that when PV blocking diodes are used in the PV array, the reverse current may be greatly limited. However, OCPDs might not detect the reverse current properly. In both fault scenarios, the fault may not be cleared successfully by conventional OCPDs. Therefore, faults may remain undetected, which could lead to reduced system efficiency, reduced system reliability, and even unexpected safety hazards.

Comprehensive protection strategy for an islanded microgrid using intelligent relays

Abstract: In this paper, a comprehensive protection strategy is proposed for insuring dependable and secure operation of an islanded microgrid system. This is implemented using microprocessor based relays to prevent unnecessary loss of critical loads and distributed generators (DGs). Several improvements are proposed to clear the way for plug-and-play of distributed generators (DGs) and loads. Furthermore, recommendations are presented to tackle the elusive high impedance fault problem, commonly encountered in distribution systems. In addition, the insufficient power generation due to DG-drop off under temporary fault conditions is also investigated. An optimal directional overcurrent bus protection is also presented. Several case studies and analyses are carried out to demonstrate the proposed protection strategy. Results from simulation using MATLAB/Simulink are also shown.

Frequency and transient behavior of grounding systems. I. Physical and methodological aspects

Abstract: In the paper, the author presents a soil electrical model, based on extensive measurements, from very low frequency to 1 MHz, and in a physical criterion to validate measurement results. A methodology and a computational procedure to determine the frequency and the transient behavior of grounding systems, and the effects of such behavior on safety of people and equipment are also presented. This procedure considers, in correct way, soil electrical characteristics and the treatment of electromagnetic behavior of grounding systems, including propagation and attenuation in dissipative media, as it is the case of soil.