This paper proposes a two-layer in-depth secured management architecture for the optimal operation of energy internet in hybrid microgrids considering wind turbines, photovoltaics, fuel cell unit, and microturbines. In the physical layer of the proposed architecture, the operation of the grid is formulated as a single objective problem that is solved using teacher learning-based optimization (TLBO). Regarding the cyber layer of the proposed architecture, a two-level intrusion detection system (IDS) is proposed to detect various cyber-attacks (i.e. Sybil attacks, spoofing attacks, false data injection attacks) on wireless-based advanced metering infrastructures. The sequential probability ratio testing (SPRT) approach is utilized in both levels of the proposed IDS to detect cyber-attacks based on a sequence of anomalies rather than only one piece of evidence. The feasibility and performance of the proposed architecture are examined on IEEE 33-bus test system and the results are provided for both islanded and grid-connected operation modes.

In this paper, a new method for locating single-phase earth faults on non-effectively earthed medium voltage distribution networks is proposed. The method requires only current measurements and is based on the analysis of the negative sequence components of the currents measured at secondary substations along medium voltage (MV) distribution feeders. The theory behind the proposed method is discussed in depth. The proposed method is examined by simulations, which are carried out for different types of networks. The results validate the effectiveness of the method in locating single-phase earth faults. In addition, some aspects of practical implementation are discussed. A brief comparative analysis is conducted between the behaviors of negative and zero sequence currents along a faulty feeder. The results reveal a considerably higher stability level of the negative sequence current over that of the zero sequence current.

In this paper, two new methods for locating single-phase to ground faults in isolated neutral distribution networks are proposed. The methods are based on the analysis of symmetrical sequence currents. They are solely based on currents, not requiring voltage measurement. The first method employs only the zero sequence current and the second one utilizes the negative sequence current in combination with the zero sequence current. It is revealed why using only zero sequence current with a simple threshold is insufficient and may lead to false results. Using the proposed methods, earth faults with high resistances can be located in isolated neutral distribution networks with overhead lines or cables.

An intermittent or restriking earth fault is a special type of earth fault that is common mostly in compensated cable networks. A great deal of effort has gone into protection against this type of fault. However, locating this fault has not received much attention. Therefore, there is a need to have a reliable method for locating this fault to repair the damaged cable. In this paper, the principles of a new method developed for locating transient intermittent earth faults on distribution networks are presented. The proposed method employs negative and zero sequence currents, and no voltage measurement is required, which means the proposed method has the potential to reduce cost when implemented in practice. It is intended mainly for typical intermittent earth faults in cable distribution networks where the typical fault resistance is in the range of a few ohms. Real data obtained from practical field tests is used to explain the phenomenon. A series of disturbance recordings obtained from field tests validate the proposed method.

Fault location in power networks is important as accurate information about the faulted line section expedites system restoration following a fault occurrence. A number of fault location methods have been proposed. Methods based on injecting a signal into the network and tracking it along the feeder appear to have received limited attention. In this study, fault location methods based on network signalling are examined. Two different types of approaches are presented. The first one is based on injection on a very low‐frequency band, whereas the second one is based on utilising modern modulation technologies on low‐frequency band, under 500 kHz, implemented on software‐defined radios. The simulation results indicate the capability of the proposed methods in determining the location of a single phase‐to‐earth fault in medium‐voltage distribution networks.

One of the distinctive features of smart grids is feeder automation. Fault location is an important part of this feature and has become an essential function for distribution system operators. Reliable fault location expedites the restoration of power following an outage caused by a permanent fault. The most common type of faults in distribution networks is the single phase to ground fault. To locate earth faults in non-effectively earthed medium-voltage distribution networks, a number of methods have been put forward among which methods that are based on fault passage indication appear to be promising. This paper discusses the technical apparatus required for implementing two FPI-based methods in practice.