## 1 Introduction  
Nowadays, there is an increasing demand for high-quality and reliable electrical energy, and consequently, protection systems play a significant role in the improvement of system reliability [1, 2]. One challenge for integrating different energy resources, such as distributed generation (DG), is designing a proper protection scheme [3]. Adding DG to the distribution network changes the electrical parameters of the power system and affects the relay protection, causing several types of problems in the protection coordination. The presence of DG can cause many challenges, such as protection blind spots, decreased fault levels and false tripping of feeders in the existing protection of distribution networks [4, 5]. As reinforcement, false tripping of healthy feeders may be resolved by using a directional overcurrent (OC) relay for the circuit breaker [6]. This research concentrates on the blinding problem of OC relays in the distribution network. The most feasible solution for protecting blind areas is to implement new relay operation characteristics with lower tripping limits. In many cases, this is possible and is thus a simple and efficient way to avoid blinding-related problems. However, some issues may arise when lowering tripping limits:  
* Operation during a fault on an adjacent feeder
* Extreme load/generation combinations
* Starting currents of DG units and other rotating devices  
The relay protection blinding in distribution networks is described in [7; 8; 9]. In [10; 11], the authors present some simulation results to demonstrate scenarios in which the problem may occur. The protection blinding areas may cause delayed operation of OC relays, and in the worst situation, they may lead to the non-tripping of the relay [12; 13]. The fault current seen by an OC relay decreases due to the DG contribution when the DG is located between the fault point and the OC relay. In [14; 15; 16], it is estimated that about 80% to 90% of faults on overhead distribution systems are temporary. Therefore, it is common practice to automatically relclose the breaker after tripping, while it remains open for a short time of typically 1 to 5 s. In some cases, utilities may relclose up to three times. Reclosers are a type of important protective devices in electric power systems that detect overcurrent and break the fault current. Most of temporary faults in overhead distribution systems last only from few cycles to a few seconds. Thus, with their \"trip and relclose\" capability, relcosers can eliminate prolonged outages on distribution systems effectively [17]. In a conventional radial feeder, relcosers are only expected to detect the unidirectional flow of current. Typically, a recloser upstream from the fault location detects the fault current, trips, and goes into a predefined relosing sequence in order to restore service if the fault is of a temporary nature [18; 19]. Optimal placement of protection devices and distributed generators in radial feeders is important to ensure power system reliability [20]. Reclosers have two basic functions in distribution systems: reliability and overcurrent protection [4]. Even though the recloser curve is slightly faster than the feeder OC relay curve, when worst-case faults are considered, it is still possible that the feeder relay to issue a trip command before the recloser does [15]. Therefore, relcosers can improve the reliability of distribution networks. Previously, interruptions shorter than a few minutes were not considered as a source of concerns to most of the customers [21; 22]. Most of the protective schemes used for radial distribution systems involve the coordination of fuses, relcosers and overcurrent relays [23; 24]. Optimal settings of a recloser involve some parameters with random nature such as fault location, fault type, fault resistance and fault nature (temporary or permanent) [22].