Search

The operational performance of conventional overcurrent protection relay coordination connected to a distribution network is adversely affected by the penetration of distributed generators (DG) at different buses in the network. To address this problem, this paper proposes a novel adaptive protection coordination scheme using a radial basis function neural network (RBFNN), which automatically adjusts the overcurrent relay settings, i.e., time setting multiplier (TSM) and plug setting multiplier (PSM) based on the penetration of DGs. Short circuit currents and voltages measured at different buses are acquired using the remote terminal units (RTU) connected to different buses within the terminal network. Communication between the various remotes and local end station RTUs is through hybrid communication systems of fiber optic and power line communication system modules. The new adaptive overcurrent protection scheme is applied to the IEEE 33-bus distribution network with and without DGs, for single and multi-DG penetration using both the ETAP and MATLAB software. The simulation results show the proposed scheme significantly improves the protection coordination. [ABSTRACT FROM AUTHOR]

The deterministic directional overcurrent relay (DOCR) coordination approaches find limitation in providing fast and reliable protection to today's distribution networks due to growing integration of distributed generations (DGs). In this paper, an adaptive DOCR protection coordination scheme is proposed using an efficient optimization algorithm called the dragonfly algorithm (DA). The main inspiration of the proposed DA optimization technique originates from static and dynamic swarming behaviours of dragonflies. In this approach, the dominant changes in the network topologies are identified by monitoring the status of the circuit breakers connected at the terminals of the DGs and other main power components. When any dominant changes in the network topologies or operating modes are identified, the fault current for that particular condition is calculated and the new optimal DOCRs settings for the prevailing condition are obtained from the substation central computer in online mode. The comparative results with the existing approaches justify the superiority of the proposed scheme in achieving the minimum overall relay operating time and maintaining the coordination between the primary and backup relay pairs. In the proposed adaptive protection scheme, the average percentage reduction in the overall operating times of DOCRs in the 6-bus and the IEEE 14-bus test systems with different levels DG penetration is found to be 49.7% and 15%, respectively, compared to the existing approaches. [ABSTRACT FROM AUTHOR]

Online adaptive protection scheme provides an appropriate protection to microgrids for various fault conditions irrespective of bidirectional power flow and changing network topology in a grid-connected or islanded mode of operation. The success of this scheme can, however, be undermined as a result of the operational uncertainties caused by the failure in various components in protection system: namely, communication links and circuit breakers. This paper proposes a framework for assessing the impact of such uncertainties on the reliability of centralized adaptive microgrid protection schemes. It first derives appropriate Markov chain models to describe the dynamic uncertainties associated with lines, communication links, and circuit breakers. The Markov models are then used in a Monte Carlo algorithm to evaluate the reliability indices for an adaptive protection scheme. The proposed framework is tested on a sample microgrid in Simulink-Matlab and Java Agent DEvelopment platform, assuming that the respective communication middleware is carried out by multi-agent and communication simulator. It has been shown that the selection of communication technology in an adaptive protection scheme requires special attention to its failure rate and data transmission bit error as well as data transfer speed. In fact, communication technologies with high failure rate and bit error show poor reliability indices that can cause unwanted delays in fault clearance, particularly when GOOSE time sequence latency is considered in the analysis. Besides, an increase in the fault duration can increase the electromagnetic and thermal stresses inflicted on circuit breakers, further undermining the reliability of the protection system. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive protection system applied to distribution electric power systems (EPS) which include distributed generation and active network management (ANM) is proposed. Obtained results provide also coordination and selectivity for all analyzed scenarios, as the possibility to use proposed adaptive protection methodology to indicate the deactivated directional function. Traditional adjustments do not provide an accurate coordination system. Modern techniques of control and operation in EPS have been extremely important to the development of solutions to old EPS problems, like loss of coordination and selectivity in protection systems after topological or operational modifications. Methodologies able to keep all protection devices coordinated after network modifications, provoked by ANM system, are actual and relevant. The benefits of the coupled actuation of these techniques made more evident when small generators have been connected to the power grid, a fact that improves a high level difficult to determine power protection parameters based on overcurrent relays. The obtained results indicate for reductions of up to 45% of the improper operations of protection system when compared to the traditional protection systems. [ABSTRACT FROM AUTHOR]

Electric power distribution systems have been submitted to major changes related to the integration of communication infrastructure and new technologies such as distributed generators, electric vehicles, energy storage systems, smart meters with two-way communication, and digital protection equipment. However, in most cases, the functionalities available in the digital equipment are not fully exploited and the same protection rules applied to electromechanical relays are practiced. In this context, this work proposes a new adaptive protection methodology using the functionalities present or potentially present in modern protection equipment. A mixed integer linear programming model for the calculation of phase protection settings and a multi-objective mixed integer linear programming model for the calculation of neutral protection settings. Additionally, the use of operating zones, based on the Thévenin equivalent impedance, is proposed to trigger the automatic adaptation of the overcurrent protection equipment adjustments. Tests employing the proposed methodology in a real distribution system show that coordination and selectivity are guaranteed in the minimal operation time for different operation conditions. The results attest to the usefulness and efficiency of the proposed methodology in automating and guaranteeing the correct performance of the protection system. [ABSTRACT FROM AUTHOR]