ETF Journal of Electrical Engineering

10

Authors: Vladan Radulović, Vladan Durković

Advanced electric equipment widely used nowadays both in residential as well as in industrial low-voltage power systems have weak surge withstand capability. The electromagnetic sensitivity of these devices requires an appropriate protection against voltage and current surges. Analysis of protection performances of surge protective devices arranged in one-stage and two-stage protection system will be given in the paper for case of resistive load. Analysis will be performed using MATLAB for different values of resistive load’s active powers widely used in low voltage power installations. Performed analysis should to point on possibilities and limitation for proper overvoltage protection.

13

Authors: Slavica Tomović, Igor Radusinović

In this paper, we propose a new SDN (Software Defined Networking) controller design that jointly addresses the problems of optimal traffic engineering (TE), quality of service (QoS) provisioning and failure recovery in ISP (Internet Service Provider) networks. The control logic of the controller is divided into the offline and online component. The online component handles dynamic arrivals of users’ requests in accordance with Service Level Agreements (SLAs). The offline component is responsible for periodic optimization of traffic distribution in the network. The goal of such architecture is to increase acceptance ratio for QoS requests and minimize degradation of background (best-effort) traffic in a scalable manner. Our simulation study has shown that the proposed solution outperforms the competitive one, which is commonly used in MPLS-based ISP networks, even when TE optimization is repeated after relatively long time intervals. This alleviates concerns regarding the scalability of the SDN control plane in large-scale ISP networks.