O. V. Gnana Swathika

Prims-Aided Dijkstra Algorithm for Adaptive Protection in Microgrids

Decentralization of electric power is possible with the penetration of distributed generators (DGs) in the microgrid (MG) network. Reconfiguration of MG poses a key challenge in identifying suitable protection schemes for varying the topology of the network. In this paper, a central protection center (CPC) is incorporated whose function is to monitor the MG continuously, identify fault occurrence, and locate the exact faulted branch. The proposed Prim-aided Dijkstra algorithm executed continuously in the CPC is responsible for identifying the current topology of the network and aids in identifying the shortest route from the faulted point to the nearest operating source. The CPC is also responsible for adaptively varying the settings of the relays existing in the shortest path identified based on their selectivity levels. This heuristic algorithm is validated on IEEE 21-bus and 40-bus MG test systems for all possible topologies and faults. The proposed algorithm is capable of clearing the fault by disconnecting minimum portion of the network and ensuring continuity of supply to a majority of loads.

Adaptive and Intelligent Controller for Protection in Radial Distribution System

In this paper, a Field Programmable Gate Array (FPGA) based intelligent controller for overcurrent (OC) protection of a radial distribution system is realized. This controller monitors the radial distribution network continuously and when a fault is detected in the network, the FPGA based adaptive and intelligent controller performs the OC relay coordination and trips the appropriate circuit breakers of the system. The FPGA based digital prototype relay for overcurrent protection is realized with Atlys Digilent Spartan-6 FPGA kit. The performance of the FPGA based overcurrent protection technique for a 4-bus radial distribution system is compared with that of the conventional dual simplex algorithm. The proposed FPGA based overcurrent protection algorithm is also tested for an IEEE 33-bus radial distribution network.

Prims Aided Floyd Warshall Algorithm for Shortest Path Identification in Microgrid

Reconfiguration of microgrid results in dynamic variation in topology of the network. Due to this, the conventional protection scheme is no longer applicable in microgrid. Hence the microgrid network demands an adaptive protection scheme, which is a key challenge to protection engineers. It is critical for the protection engineers to know the current topology of the microgrid before a suitable relay coordination technique is deployed on it. This paper proposes a Prims aided Floyd Warshall algorithm, where the Prims algorithm identifies the current topology of the network at any instant of time. In the event of fault occurrence, the output of Prims algorithm is a list of active nodes: utility grid, loads, Distributed Generators (DG) and critical circuit breakers in the network. This list aids the Floyd Warshall algorithm in identifying the shortest path from the node closer to the fault to the utility grid (in grid connected mode) or point of common coupling (in islanded mode). The algorithm ensures minimum portion of network disconnection for fault isolation. The proposed algorithm is tested and validated on an IEEE 21-bus microgrid network in islanded mode and an IEEE 69-bus distribution network with DG included at certain nodes in grid connected mode.

Communication Assisted Overcurrent Protection of Microgrid

An intelligent micro grid controller system with over current protection capability in both the grid-connected and the islanded modes of operation is proposed. To achieve the above strategy a model of small portion of distribution network as if it were a micro grid will be developed and considered. The processor based relays that provide over current protection functions in addition to performing control, measurement, and communication functions will be suitably employed.

Multiple DG Synchronization and De-synchronization in a Microgrid Using PLC

Microgrid is an aggregate of generating units and loads at the distribution level. It operates in two modes: Grid connected mode and Islanded mode. Power continuity is very essential for critical loads in microgrid and maybe achieved vide 100 % standby diesel generator sets in a microgrid network. This paper considers a real time 24/7 Information Technology (IT) campus where even a very short power break will lead to huge commercial loss. Hence it is very important to bring the standby power during the utility power failure. This is achieved through multiple diesel generator sets synchronized in a single panel through a proper sequential logic vide programmable logic controller (PLC). In the event of fault occurrence, based on the receipt of signals from the respective relays, the PLC identifies the fault and issues appropriate tripping commands to the microgrid to safely isolate the fault. The significance of neutral isolating contactor (NIC) and neutral grounding resistor (NGR) in microgrid protection is also analyzed.

Optimum Coordination of Overcurrent Relays in Distribution Systems Using Big-M and Dual Simplex Methods

This paper presents Big-M method and Dual Simplex method for optimum time coordination of over current relays in a distribution network. These methods are used to find the optimized values of time multiplier settings (TMS) of relays using linear programming problem (LPP). Objective function contains artificial variables in Big-M method. Dual simplex gives the optimum solution without introducing any artificial variables. Over current (OC) relay plays a major role in power distribution system. It protects electrical power systems against excessive current which are caused by faults like short circuits, ground faults, etc. The fault is cleared within a least possible time. Big-M and Dual simplex technique are presented in this paper for optimum time coordination of OC relays in a radial fed distribution system.

Optimum Coordination of Overcurrent Relays Using Dual Simplex and Genetic Algorithms

Protection system includes a series of devices whose main purpose is to protect people and primary electric power equipment from the effects of faults. Fault currents cause damage to equipment and are also hazardous to personnel. Thus, there should be a primary and a backup system with proper time grading between systems, i.e. Tripping time should be maximum for the point farthest from the fault location. Over current (OC) relays are used as backup protection against these faults. The coordination time interval must be maintained among relays during faults. Various algorithms are used to optimize the time of operation of these OC relays. This paper implements Dual Simplex and Genetic Algorithms (GA) on a radial network and identifies the time multiplier setting (TMS) of the relay. This facilitates in achieving suitable OC relay coordination of the network.

Optimization of Overcurrent Relays in Microgrid Using Interior Point Method and Active Set Method

Microgrid is an aggregate of generating units and loads at the distribution level. It operates in two modes: grid connected mode and Islanded mode. Fault clearance in a microgrid is a key challenge for protection engineers. This paper aims to identify the optimized values of time of operation of overcurrent relays in a microgrid network. This paper solves the optimization problem using two methods—Interior Point method and Active Set method. Also three types of relays are used to determine which relay works best in similar constraint environment. These methods aid in providing suitable relay coordination in microgrid and clear the faulty portion of network quickly from the healthy portion of network.

Modified Cuckoo Search Algorithm for Fittest Relay Identification in Microgrid

Microgrid is a group of interconnected generating units and loads at the distribution level which operates in two modes—Grid connected mode and Islanded mode. Fault clearance in a microgrid is a key challenge for protection engineers. This paper aims to identify the best fit relay suitable for a microgrid using modified cuckoo search algorithm based on key parameters like current rating, Time Multiplier Setting (TMS), Plug Setting Multiplier (PSM) and time of operation (top). This algorithm aids in providing suitable relay coordination in microgrid and clears the faulty portion of network effectively from the healthy portion of network.

Optimal Coordination of Overcurrent Relays Using Simulated Annealing and Brute Force Algorithms

With the advancement of technology, the electrical world has grown colossally through invention and optimization, hence adopting to the changing environment. With the arrival of power grids, smart grids, micro-grids, etc., there has always been a baggage of responsibility on the protection engineers to come up with a novel, operative, and optimized way to clean faults in the distribution on transmission lines, which focuses on maintaining a maximum tripping time for the point located at the farthest position from the actual location of the fault. Radial networks are susceptible to overcurrent fault conditions. So, for the protection against the faults, the overcurrent relays are used. For a power-protection engineer, it is imperative to maintain and optimize the coordination time interval (CTI) between relays in the course of overcurrent relay coordination. For the clearance of the fault, optimization algorithms are often fetched. In this paper, brute force algorithm and simulated annealing algorithm are implemented on a radial network to optimize the time dial setting (TDS) of relays. Thus, helping to maintain coordination among OC relays in the network.