Transition rule is the probabilistic and stochastic mechanism that ant agents use to evaluate the pheromone intensity in order to decide which is the most attractive point to visit next. Bear in mind that this rule can also include another factor of desirability which is the vision of the edges. For example the vision of Traveling Salesman Problem (TSP) is a symmetrical matrix that contains the inverse of the distance between each edge (city), where the main diagonal are zeros because there is zero distance for reaching the same city. A similar element would be the operation time of relays in coordination problem, but due to the reason that the relays can have many primary and backup operation times, this make the construction of the vision matrix impossible. Thus pheromone intensity will be the only factor used in the transition rule in this thesis. The advantage of having the vision matrix (as in TSP) is that the algorithm always converge in the same result while the disadvantage of not having the vision matrix is that the algorithm give different optimization result in every run. An analogy would be "An All Seen Ant" vs. "A Blind Ant".
Abstract—Recently, nature inspired algorithms (NIA) have been implemented to various fields of optimization problems. In this paper, the implementation of NIA is reported to solve the overcurrent relay coordination problem. The purpose is to find the optimal value of the Time Multiplier Setting (TMS) and Plug Setting (PS) in order to minimize the primary relays’ operating time at the near end fault. The optimization is performed using the Improved Grey Wolf Optimization (IGWO) algorithm. Some modifications to the original GWO have been made to improve the candidate’s exploration ability. Comprehensive simulation studies have been performed to demonstrate the reliability and efficiency of the proposed modification technique compared to the conventional GWO and some well-known algorithms. The generated results have confirmed the proposed IGWO is able to optimize the objective function of the overcurrent relay coordination problem.
v By increasing the negative value of D t mb , the cost of the OF increases. This means that the small negative D t mb 's may be accepted as a result of the optimization because these values do not increase the OF value very much. According to the above discussion, Razavi et al. , the three weighting coefficients (β, α1, α2) must be set by try and error. Therefore, the proposed OF of Razavi et al.  cannot guarantee obtaining the best coordination and the smallest operating time of the relays. To resolve this problem, a new technique should be employed in which the terms of the OF are not stated separately. Therefore, the new technique does not need weighting coefficients. In this paper, we will introduce a novel OF, in section 4, that resolve the mentioned problems of OF of Razavi et al. .
Based on the requirements of sensitivity, reliability, selectivity and speed, relay parameter are set or selected for protective relayscoordination. For the protection of transmission and distribution system the directional overcurrent relay are popularly considered as good technical and economic choice . The overcurrent unit consists of two parameters: (i) Plug Setting (PS) and (ii) Time Dial Setting (TDS). The application of computer in power system relay coordination helps to remove the load of huge mathematical calculation for protection engineers . Conventional classical protection philosophy and several parameter optimization techniques have been proposed for coordinating directional overcurrent relay. For coordination of overcurrent relay, proper setting of relay is important. At first the remote end relays are set, and then corresponding backup relays are set from coordination protection point view. In this way all possible paths are taken into account for optimal setting of relay parameters . The optimizationalgorithm helps to solve the coordination problem by minimizing the operating time of all main relays. The subjected constraint of the problem are as follows-(i)backup relay(operates only when the primary relays fails to respond the fault near to it),(ii)Time Dial Setting(TDS),(iii)Plug Setting(PS) and (iv)minimum operating time of relay. The operating time of the overcurrentrelays holds a non-linear relationship with TDS and PS.
negative impact, DGs add to fault current levels increase and multiple current flow paths during fault [1-6]. These conditions decrease the capability and reliability of the existing design of radial distribution system protection system. Since the introduction of microgrid concept, many attempts have been made to ensure a secure and reliable operation of the microgrid system. One important aspect that has drawn much interest from the researchers is the protection of the microgrid system. Ever since, many researchers have proposed and tested various type of protection schemes that could assist in the implementation of microgrid system. Some of the methods are based symmetrical current components, voltage measurements, current signals and impedance of the system [7-11]. Others use different protection devices such as microprocessor-based relays, differential relays, directional relays and etc [12-15]. These approaches have increased the chances of successful implementation and operation of microgrid system. In the mean time, much concern has been dedicated to the coordination of the protective devices that are used to protect the network since the characteristics of the microgrid is significantly different from the traditional radial distribution network. Particle swarm optimization and genetic algorithm are two widely used algorithms for optimal coordination of DOC relays in the microgrid system [16-18]. Though many algorithms have been proposed and tested, there is still plenty of room to study and evaluate new strategies to cater the new challenges which emerges from dynamic changes in microgrid topology and characteristics. Therefore, it is the intention and motivation of this work to study and propose a coordination strategy for successful microgrid protection and operation.
the operating time of the main overcurrentrelays that is provided by GAs is smaller than that provided by PBIL. From the results, it can be seen that there are larger variations in the fitness value for PBIL algorithm when the number of generation is less than 100 as compared to GAs algorithm. This means diversity is better for PBIL than for GAs for generations less than 100. However, at the end, PBIL settles at a higher fitness value of 48.02 seconds compared to GA, which settles at the fitness value of 19.84 seconds. This means after 100 generations PBIL loses diversity and converges prematurely. Therefore, TMS parameters for overcurrentrelays determined by PBIL results in longer operating time for the main and backup relays. The results of the final fitness values attained by the algorithms are compared in Table 1. From this Table, it can be seen that the relay coordination using GAs gives a total operating time of 19.83 sec. for the main relay, whereas, PBIL gives a total of operating time of 48.02 sec. The same is true for the backup relays, where GAs provide a better result. From these results, it can be concluded that GAs gives a better performance than PBIL.
Abstract This paper addresses the problem of overcurrentrelays (OCRs) coordination in the presence of DGs. OCRs are optimally set to work in a coordinated manner to isolate faults with minimal impacts on customers. The penetration of DGs into the power system changes the fault current levels seen by the OCRs. This can deteriorate the coordinated operation of OCRs. Operation time difference between backup and main relays can be below the standard limit or even the backup OCR can incorrectly work before the main OCR. Though resetting of OCRs is tedious especially in large systems, it cannot alone restore the original coordinated operation in the presence of DGs. The paper investigates the optimal utilization of fault current limiters (FCLs) to maintain the directional OCRs coordinated operation without any need to OCRs resetting irrespective of DGs status. It is required to maintain the OCRs coordination at minimum cost of prospective FCLs. Hence, the FCLs location and sizing problem is formulated as a constrained multi-objective optimization problem. Multi-objective particle swarm optimization is adopted for solving the optimization problem to determine the optimal locations and sizes of FCLs. The proposed algorithm is applied to meshed and radial power systems at different DGs arrangements using different types of FCLs. Moreover, the OCRs coordination problem is studied when the system includes both directional and non-directional OCRs. Comparative analysis of results is provided.
Abstract: The aim of the relay coordination is that protection systems detect and isolate the faulted part as fast and selective as possible. On the other hand, in order to reduce the fault clearing time, distance protection relays are usually equipped with pilot protection schemes. Such schemes can be considered in the Distance and Directional Over-Current Relays (D&DOCRs) coordination to achieve faster protection systems, while the selectivity is maintained. Therefore, in this paper, a new formulation is presented for the relay coordination problem considering pilot protection. In the proposed formulation, the selectivity constraints for the primary distance and backup overcurrentrelays are defined based on the fault at the end of the transmission lines, rather than those at the end of the first zone of the primary distance relay. To solve this nonlinear optimization problem, a combination of Genetic Algorithm (GA) and Linear Programming (LP) is used as a Hybrid Genetic Algorithm (HGA). The proposed approach is tested on an 8-bus, the IEEE 14-bus and the IEEE 39-bus test systems. Simulation results indicate that considering the pilot protection in the D&DOCRS coordination, not only obtains feasible and effective solutions for the relay settings, but also reduces the overall operating time of the protection system. Keywords: Directional Overcurrent Relay, Distance Relay, Pilot Protection, Relay Coordination.
This paper presents an optimal coordination of inverse definite minimum time (IDMT) directional overcurrentrelays (DOCR) in the presence of Wind Energy Farms (WEF). Firstly, the impact of WEF on the relayscoordination is focused, after that we search for the new relays setting to ensure an optimal coordination of the relays. The coordination problem is formu- lated as a constrained nonlinear mono-objective optimization problem. The objective function of this optimization problem is the minimization of the operation time of the associated relays. In terms of decision variables; two types of optimizations are considered in this paper, namely: real parameter optimization where, the time dial setting (TDS), and the pickup current set- ting (I P ) are considered as the real decision variables of the optimization problem and the mixed integer optimization, where the IEC curve characteristic of each relay is added to the previ- ous variables as an integer decision variable. The character- istics of the relays are always chosen arbitrary or by trial and error method. To solve this constrained non linear optimization problem, the particle swarm optimization method is used. The proposed method is validated on IEEE 8-bus power transmis- sion test systems considering various scenarios.
Abstract:- The transmission line fault results in a much larger postfault current than the prefault load current. So overcurrent relaying is widely used for transmission lines. The speed of relaying and selectivity can be sacrificed, to some extent, in LV or MV lines. The other line relays like distance protection relays are too expensive. The percentage cost of the protection, which can be justified is around 10% to 15% of the cost of the equipment or section to be protected. Hence directional overcurrentrelays are commonly used as an economic alternative for the protection of interconnected sub transmission systems, distribution systems, or as a secondary protection of transmission systems. Nowadays, “Numerical Overcurrentrelays” are widely used. So we have considered numerical relay in our case-study. The most important task when installing numerical overcurrent relay on the system is selecting their suitable settings such that their basic protection function is met under sensitivity, selectivity, reliability and speed. The settings should be designed for minimum relay time of operation. That is, the settings should be such that the overall time of operation is minimized while maintaining the selectivity and reliability. Thus, the numerical relay problem is an optimization problem, where the solution is the optimal settings of each relay. Various methods have been proposed to formulate and find the optimal solution for the numerical overcurrent relay problem. In, this paper the proposed techniques are discussed. In this paper the data taken for research is of the real field of The power system at TATA Motors Ltd, Pimpri. The problem is formulated as linear programming problem as a basic case study. The problem is solved using linprog function of the optimization toolbox of the MATLAB software.
Abstract. The integration of system compensation such as Series Compensator (SC) into the transmis- sion line makes the coordination of directional overcur- rent in a practical power system important and com- plex. This article presents an efficient variant of Par- ticle Swarm Optimization (PSO) algorithm based on Time-Varying Acceleration Coefficients (PSO-TVAC) for optimal coordination of directional overcurrent re- lays (DOCRs) considering the integration of series compensation. Simulation results are compared to other methods to confirm the efficiency of the proposed variant PSO in solving the optimal coordination of di- rectional overcurrent relay in the presence of series compensation.
The results obtained from the proposed MPSO Algorithm displayed in Table 7 shows an improvement in the overall tripping timing of the relays. The optimal tripping time of all the primary relays of the 6 Bus microgrid comprising of 14 DOCRs was 3.7903s while that obtained for the existing Katempe-Life Camp feeder for just 2 relays was 3.68s. Using the optimized Relay settings to run fault studies on Line 7 and Single Busbar 2 gave various tripping times for both Clockwise Looping and Anticlockwise Looping Relay coordination as shown in Figures 3 to Figures 12. Table 8 and 9 shows the Relay settings before and after optimization respectively.
Over current relays are usually employed as backup protection. In distribution feeders, they play a more important role and there it may be the only protection provided [1,2]. The problem of coordinating protective relays consists of selecting their suitable settings such that their fundamental protective function is met under the requirements of sensitivity, selectivity, reliability, and speed [3,4]. If backup protections are not well coordinated, mal-operation can occur and, therefore, OC relay coordination is a major concern of power system protection . Each protection relay in the power system needs to be coordinated with the relays protecting the adjacent equipment. The overall protection coordination is thus very complicated. The OC relay coordination problem in distribution system can be defined as constrained optimization problem. The objective is to minimize the operating time of relay for fault at any point. A protective relay should trip for a fault in its zone and should not, for a fault outside its zone, except to backup a failed relay or circuit breaker traditionally; a trial and error procedure is employed for setting relays in multi loop networks. In the past few years, several mathematical techniques have been reported. warakanath and Nowitz  suggested a systematic approach for determining the relative sequence setting of the relays in a multiloop network. They used a linear graph theory approach which provided a directional loop matrix. A minimal set of break points spanning all loops of the system graph were obtained from this matrix.Damborg et al.  extended the graph theoretic concepts and proposed a systematic algorithm for determining a relative sequence matrix corresponding to a set of sequential pairs which reduced the number of iterations. Jenkins et al.  proposed a functional dependency concept for topological analysis of the protection scheme. They expressed the constraints on the relay settings through a set of functional dependencies. A arametric optimization approach was reported by Urdeanneta et al.  that optimized the time multiplier settings (TMS) using the Simplex method. Optimal values of the pick-up currents for selected TMS were then determined by using a generalized reduced gradient technique. The objective of this paper is to present some of the optimization concepts and their use in the project.
In a system where there is a source at more than one of the line terminals, fault and load current can flow in either direction. Relays protecting the lines are, therefore, subject to fault currents flowing in both the directions. If non directional OC relays were used in such system, they would have to be coordinated with, not only the relays at the remote end of the line, but also with relays behind them. Since directional relays operate only when the fault current flows in the specified tripping direction, they avoid coordination with the relays behind them. Directional overcurrentrelays are commonly used as an economical means for protecting power distribution systems. The selection of appropriate settings of these relays under various systems conditions plays an important role in timely removal of the faulty section of power systems. Two methods have been proposed for the coordination of these relays. Ordinary coordination algorithms named Maximum path method considered -[6 ]. However, the solutions found by this method are not optimal in any strict sense. In other words, relay time multiplier settings (TMS) are relatively high shown in this paper.
These are the relays whose time of operation depend entirely on the factors inherent in the manufacturing process without any time delay deliberately introduced. The operating time of such relays can be of the order of milliseconds. It will operate at the same time irrespective of the magnitude of the current, as long as the current is higher than the pick up value. It is used for restricted earthfault and circulation current protection.
the search space. However, due to its complexity, the available computing power available in the game cycle may not be enough for running the A*. Moreover, the environments are dynamic, meaning that changes in the positions of the obstacles may occur. In such dynamic environments high time demanding algorithms, such the A*, may not be a suitable option. Since such algorithms may require many seconds to end, changes in the environment may occur while the algorithms are still running. As a result, the problem solved by the algorithm is no longer the same and consequently the solution found may no longer apply. Also, using the A* in multi-agent games may not be possible, especially in very constrained resources platforms such as tablets and cellphones.
Abstract. In presence of the Distributed Generation (DG) brought new chal- lenges to the protection engineers since novel coordination scheme is no longer appropriate with the penetration of the DG. The extreme case is violation to the primary and backup relay selectivity constraint. This violation will have resulted to the degradation of the relay performance. Therefore, this paper proposes the best location of the DG penetration to decrease the effect of the DG presentation to the relay performance using the grey wolf optimization (GWO) algorithm. The impacts of the DG prior to the location of the insertion are implemented to the radial 7 bus test system. As a consequence, the best location of the DG penetra- tion is then identified.
aerial vehicles (UAV), coordination, robotics, and multi-agent systems. Since there is an overlap between these subjects in the literature, they are not all considered individually in the discussion to follow. This area gives only a brief glimpse of distributed systems literature, as the primary focus of this work is formal methods. For a more comprehensive background of the work inspiring Comhord´u, the reader is referred to [Bouroche, 2007]. Unmanned aerial vehicles (UAV) constitute an emerging discipline in distributed systems. Much of the research in this field focuses on a specialised scenario in which the vehicles operate, usually towards the com- pletion of some task or the testing of some algorithm. In most cases, the focus is on the cooperation of multiple UAVs constituting what is known as a swarm. The need for coordination between multiple UAVs is expressed in [How et al., 2004]: “Future UAV teams will have to autonomously demonstrate cooperative behaviors in dy- namic and uncertain environments”. In [Vries and Subbarao, 2011] a steering technique for swarms of UAVs is proposed and tested using a simulator, with an emphasis on obstacle avoidance. A search and rescue team of UAVs and unmanned ground vehicles (UGV) is given in [Weaver et al., 2013]. In [Wei et al., 2013], a UAV team is proposed for the purpose of “enemy territory reconnaissance, remote area surveillance and haz- ardous environment monitoring.” A similar application of UAV teams is given in [Alvissalim et al., 2012], in which UAVs swarm and self-deploy to restore a telecommunication link that has gone down due to some disaster. Some work is focused more on the dynamics of the vehicles themselves, such as reducing the size of the quadrotors to improve agility [Kushleyev et al., 2013] or using air currents to boost altitude and extend flight duration [Cobano et al., 2013].
In this communication model, guarantees about real-time communication can be provided to both message senders and entities interested in the type of messages it sends. Senders are guaranteed to be able to communicate with a given latency in the actual coverage, and to be notiﬁed within a given time delay if this coverage changes. Senders can therefore adapt their behaviour depending on the value of the actual coverage. On the other hand, entities present within the actual coverage at the delivery time of a message of a type in which they have expressed interest, are guaranteed to receive it. We deﬁne an entity as present within the actual coverage once its is able to receive messages after arriving in the communication coverage. This will take an implementation-dependent time, present, which might be necessary to include the entity in the real-time route for example. We will see in the next section that these guarantees are easily exploitable to ensure system- wide constraints while allowing progress of entities.
Figure 5.12 shows the fault arc model. This model includes fault breaker, ideal switch and UCM controlled resistor element. Fault breaker is used to simulate fault conditions. Different types of faults can be simulated by this fault breaker. For observing primary and secondary arc phenomenon, single-line to ground faults are to be simulated. Ideal switch represents arc extinction and re-strike phenomenon and UCM control resistor element represents primary and secondary arc phenomenon. The block ”Switch Sim” lets the switch to remain in close position until primary arc extinguishes and during the secondary arc period the switch acts according to value computed by ”SecArc” block. The block ”Arc Controller” updates the resistance of the ”Arc resistance” UCM element at every time step. The inputs to this block are primary arc resistance, secondary arc resistance and breaker trip command. This block outputs primary arc resistance to UCM element until trip command issued to line breakers and outputs secondary arc resistance to UCM Controlled Resistor” from the moment the line breakers were tripped.