In this paper, a method for improving the performance of the network protection system in the presence of DGs by use of intelligent devices is proposed. The method, which is implemented on a hierarchical multi-agent structure, can improve the coordination problems between overcurrent relays by using a telecommunications platform based on the IEC-61850 standard information model. By this way, the protection scheme is implemented on three levels on the relays. Each level has tasks that are implemented on a layered multi-agent structure, depending on the layout of the network under certain conditions. At the first protection level performed by relay agents, the relay protection characteristic curve is used along with the functions defined on the intelligent devices. At the second level, a database is used to record the events and the pattern of behavior chosen according to them in order to prevent the flow of information on the network and to speed up the performance of the protection system. Functional patterns recorded in the database allow agents to obtain appropriate settings without sending information to the central unit if similar conditions occur. At the third protection level, in the absence of a similar pattern, the new relay settings are calculated according to the network conditions and transmitted to the network monitoring unit. Finally, in order to verify and validate the proposed method, the proposed scheme is simulated on an experimental network in the ETAP software.

The wireless sensor network (WSN) signifies to a gathering of spatially spread and committed sensors for observing and logging the physical states of the environment and for organizing the information gathered at the central Base station. Many security threats may affect the functioning of these networks. Security of the data in the system depends on the cryptographic procedure and the methods where encryption and decryption keys are developed among the sensors. Symmetric key foundation is one of the best applicable ideal models for safe exchanges in WSNs. The main goal is to improve and evaluate certain issues, such as node attack, to provide better key strength, connectivity, security for node interaction, and throughput. Uniform Balanced Incomplete Block Design (UBIBD) is used to generate the keys allocated by the base station to the cluster head. The cluster head distributes keys to its members using Symmetric Balanced Incomplete Block Design (SBIBD), and the keys are refreshed on a regular basis to avoid out-of-date entries. In wireless sensor networks, compromised nodes can be used to inject false reports. The concept of interacting between sensor nodes using keys and establishing a secure connection aids in ensuring the network's security.

Internal Turn-Turn faults (TTF) are the most common failures in power transformers, which could seriously reduce their life expectancy. Although common protection schemes such as current-based differential protection are able to detect some of the internal faults, some other minor ones (such as TTFs and short circuit near the neutral point) cannot be detected by such schemes. Likewise, these relays may have false trip due to energizing inrush currents, transformer over excitation, and occurrence of CT saturation at one side. In this paper, a novel Linkage Flux Based (LFB) scheme is proposed to detect TTF in power transformers, which uses some Search Coils (SC) located on the transformer legs to sense the related linkage flux. Any difference in induced voltage in the corresponding SCs (located on any leg) suggests passing unsymmetrical linkage fluxes through them (unlike the normal conditions), which stands for the occurrence of a fault inside the transformer. The proposed technique not only can be used to protect power transformers, but also can be employed to find the fault location during repair activities, as well.

In today's power systems, grid parameters are usually monitored by controlling agents to ensure the quality of produced electrical energy. Uninterrupted service to the network customers and continuous power supply may be disrupted through various disturbances. On this basis, the network requires a completely reliable, fast, and precise protection system. The protection of distribution networks is controlled by overcurrent equipment, which is complicated with increasing penetration of distributed generation resources due to change in the direction of current. This paper investigates how these resources affect the coordinated performance of the network protection system and proposes a new solution with the aim of restoration and fixing the miscoordination problem. The proposed method could be implemented on traditional overcurrent protection equipment while being able to meet the challenge of protection coordination with the lowest cost. The simulation results verify the effectiveness of the proposed algorithm.

Due to the increase of users the efficient usage of spectrum plays an important role in digital terrestrial television networks. In digital video broadcasting, local and global content are transmitted by single frequency network and multifrequency network respectively. Multifrequency network support transmission of global content and it consumes large spectrum. Similarly local content are well supported by single frequency network. In order to provide better spectral efficiency both local and global contents are transmitted in single constellation using hierarchical modulation. hierarchical modulated OFDM system provides good spectral efficiency and robustness to the fading environment. In this paper a hierarchical modulated OFDM system for local service insertion is analyzed and its performance under various channels is been discussed. Convolutional encoder is used in this paper.

A new regionalization algorithm is presented to improve wide-area backup protection (WABP) of the power system. This method divides the power system into several protection zones based on the proposed optimal measurement device (MD) placement and electrical distances. The modified binary particle swarm optimization is used to achieve the optimal MD placement in the first step. Next, the power system is divided into small protection zones (SPZ) using the topology matrix of the power system and MD locations. Finally, the SPZs are combined to accomplish the main protection zones and protection centers according to electrical distances, degree of buses, and communication link constraints. The introduced regionalization formulation can help provide a rapid and secure WABP for power systems. This method was applied to several IEEE standard test systems, and the simulation results demonstrated the effectiveness of the proposed scheme.

The rapid growth of grid-connected embedded distributed generations (DGs) is changing the operational characteristics of distribution networks (DNs). In order to implement DNs with DGs, some challenges should be faced, especially concerning protection issues, that may make conventional protection schemes ineffective. MAS techniques can enable the power grid to becomes smarter, reliable, selfhealing, and robust. Its decentralized nature and operational robustness make the MAS application a leading technology. Despite the fast, reliable and multi-purpose operation of MAS-based protection schemes, the inherent delay or failure of communication system must not affect the vital role of fault clearing, i. e., the ever-increasing DGs in DNs as well as network size increase has resulted in a heavy communication burden yielding to delay or even failure in communication. In this paper, an Intelligent protection algorithm is presented that protect the grid, when the connection between agents is lost, by using point-to-point communication between relay agents in the first layer of the MAS. Reduction of the agents used and no need to connect to the higher layers of the MAS are the benefits of this method. For simulation, 16 bus Test DN is used, that The results confirm the applicability of the proposed model for grid protection coordination.

The presence of the inverter distributed generations in the power systems can bring about incoord-ination in the protection system performance while enjoying various advantages. In this paper, a suit-able solution, independent of relay settings, is presented in order to solve the protection problems of inverter island microgrids with circular arrangement. The presence of distributed inverter generation sources causes a change in the direction and amplitude of the fault current at the microgrid level. This problem is more visible in microgrids with circular arrangement. Therefore, conventional protection schemes that consider a single path and a high fault current level compared to load current may be problematic. An important factor for the proper design of a protective system for microgrids is the contribution of the injecting fault current of the inverter sources. In this paper, a protection strategy based on the inverter control of sources is presented and ordinary overcurrent relays with the same characteristic curve are used. When a short circuit fault occurs in the microgrid, an adaptive current limiting strategy is applied using the virtual impedance loop. In this case, the share of fault current of each source is controlled according to the position of the fault, and sources closer to the fault produce a larger fault current. Therefore, the current passing through the protective equipment is closer to the fault than other equipment in the micro grid. And without the need for making connection between protective equipment, the protective coordination is guaranteed.