Overcurrent Research Articles

Protection Relay Setting based on Overcurrent Phenomena in Commercial Building

Nowadays, every single distribution system needs to install an appropriate relay to keep the system safe. The operational and commonly recommended relay for distribution systems is the overcurrent (OC) relay. Throughout the distribution system, the protective relay is one of the methods that can detect and protect the location according to its observation from any fault from abnormal activity. Note that time coordination between the protective equipment relay needs to be a minimum of time interruption to prevent faults occurs. The ideal setting for all coordination protection relays is necessary to protect the device against electrical failure and interference. This paper analyzes the real results data collected for the selected commercial building of an OC relay implemented in a distribution board for high voltage and low voltage downward at a commercial building. All the parameters need to be clarified first before testing has been made and measurement is carried out using the MICROTEST 860 set. Based on the analysis, it proves that according to the IEC Standard of 0.10-time multiplier Setting (TMS) is practical to be used to obtain the operation time in seconds for the current curve set. Other than that, the results show that the normal inverse curve from manual calculation results is more accurate compared to the service setting (SS) made based on the incoming setting in a real commercial building. The case study for OC relay setting is related between current injection and time-tripping, which complies with the IEC 60255-3 standard using its formula. This method was applied to determine the characteristics of the curve. Hence, this research successfully determined the proper methods for the OC relay setting for the power distribution system. Besides, the feasibility and efficiency of OC relay data transmission are tested and checked successfully to implement the measurement method in the relay coordination study.

Dv/dt Sensing-Based Short-Circuit Protection for Medium-Voltage SiC mosfets

This letter presents a novel short-circuit protection (SCP) for medium-voltage (MV) SiC MOSFETs, that utilizes the turn-on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> of SiC MOSFET within a predetermined interval to monitor SC faults. Unlike conventional methods that detect the fault current/voltage magnitude, proposed turn-on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> detection and protection timing sequence enable a very fast fault response time as well as enhance the noise immunity to fast switching of MV SiC MOSFETs. Furthermore, the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> sensing based SCP can be integrated with DESAT circuit to provide over-current (OC) protection (OCP) under the fault-under-load (FUL) condition. The proposed integrated implementation can respond to SC faults without the blanking-time limitation and eliminates the need for the extra high-voltage sensing capacitor to lower cost. Experimental results on 3.3-kV SiC MOSFETs are provided to validate the effectiveness of proposed SCP method.

Protective Relaying Coordination in Power Systems Comprising Renewable Sources: Challenges and Future Insights

This article provides a comprehensive review of optimal relay coordination (ORC) in distribution networks (DNs) that include distributed generators (DGs). The integration of DGs into DNs has become a real challenge for power system protection, as the power flow changes from unidirectional to bidirectional, which complicates the relay settings. The introduction of DGs in DNs requires changes and modifications in the protective schemes to maintain proper operation, reliability, stability, and security of the system. This paper focuses on the impacts of DGs penetration into DNs, including the effects on protective scheme coordination. Various expressions for characterizing the overcurrent (OC) coordination problem, as well as related solution attempts, are discussed. Several optimization strategies and techniques are suggested by scientists to deal with coordination optimization problems aiming to achieve less computation time and better accuracy. All these efforts ultimately aim to define optimal relay settings to achieve ORC by generating the optimal setting of cascading relative OC relays. This comprehensive review provides a broad overview of the contributions of scholars in recent publications in this field, with more than 210 articles reviewed and analyzed. It is a valuable resource for other researchers in the same field who aim to tackle ORC problems in their future endeavors.

Differential Protection Scheme for A Micro Grid with Inverter-Type Sources Based On Positive Sequence Fault Currents

The microgrid (MG) is a coordinated collection of different distributed generation (DG) typesthatsupply local demandthrough a distribution network. MG may operate in two different modes: grid-connected (GC), and islanded (IS)modes.The fault current valuevaries significantly between the GC and IS mode for a MG with inverter-based distributed generators(IBDGs). The fault currents are minimal in the IS mode owing to the power electronics equipment have a limited current carrying capacity. Therefore, the coordination of traditional overcurrent (OC) protection is difficult for these two operation modes. Therefore, a comprehensive MG protection scheme should be established to safeguard MG against all kinds of faults. The main protection strategy proposed in this paperis a positive sequence differential current protection scheme. The envisioned concept can overcome the protective device coordination problems, and all fault types can be detected during both operation modes of MG for radial andloop configurations. The validation of the proposed design is performed using PSCAD/EMTDC software. The results indicate that the maximum fault clearing time for the main protection in GC mode and IS modeisof 31.5 ms and 34 ms respectively. Compared with other schemes, the proposed scheme has a faster clearing time and is less expensive.

Monolithic Integration of Gate Driver and Protection Modules With P-GaN Gate Power HEMTs

The high-speed superiority of GaN power devices with silicon-based peripheral circuits is not yet fully leveraged, mainly due to the parasitic inductance of interconnections. In this article, we demonstrate a GaN-based gate driver with an overcurrent (OC) protection circuit and an undervoltage lockout (UVLO) circuit on a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN gate power HEMT platform. The gate driver features a rail-to-rail output voltage, suppressed gate ringing, and tunable driving speed, all of which are highly desired in high-efficiency and high-speed GaN power systems. To offer timely but reliable protections, the OC protection and UVLO circuit are designed with reference to the switching speed and the threshold voltage of GaN power devices. The OC protection is implemented with a separated sensing branch and blanking time controller, and the response time to an OC event is reduced to 10 ns after the blanking time. The UVLO circuit has a fixed hysteresis of 0.5 V, and its threshold voltage is especially tailored for the GaN integrated circuits.

Advanced Coordination Method for Overcurrent Protection Relays Using New Hybrid and Dynamic Tripping Characteristics for Microgrid

Nowadays, the Overcurrent (OC) and Earth Fault (EF) relays coordination problem is one of the most complex and challenging concerns of power protection and network operators due to the high and volatile generation capacity of renewable energy sources in the grid. In this article, a new and dynamic optimal coordination scheme based on a novel hybrid tripping characteristic has been designed and developed for Over Current Relays (OCRs). Considering the impact of renewable energy sources such as the photovoltaic (PV) system on fault characteristic, this work presents and verifies a novel dynamic and hybrid tripping to achieve minimum tripping time and improve the OCR and EF relays coordination performance in terms of security, sensitivity, and selectivity. The proposed dynamic and hybrid scheme will help the OCRs to cover the EF events, and it has been tested under different fault scenarios compared to the literature. The IEEE-9 and IEEE-33 bus systems are implemented in the ETAP package to validate the effectiveness of the proposed hybrid characteristics against traditionally well-established IEC characteristics. Furthermore, the performance of the proposed advance and dynamic protection approach which doesn’t require a communication infrastructure is investigated for a power network with PV plants under different grid operation modes and topology to provide more robustness protection system. The results, as presented using Industrial software (ETAP), showed that the novel dynamic and hybrid tripping scheme improved the speed of the total time tripping different fault scenarios and location by more than 50% and covers all EF events compared to traditional OCR schemes from the literature. The proposed novel dynamic approach has superior performance in detecting high-impedance faults and significantly reducing the tripping time on the IEEE 33 bus network by 47%.

OC/OL Protection of Droop-Controlled and Directly Voltage-Controlled Microgrids Using TMF/ANN-Based Fault Detection and Discrimination

In this article, we propose a generalized overcurrent (OC) and overload (OL) protection scheme for the droop-controlled and directly voltage-controlled (DVC) inverter-interfaced distributed energy resources (IIDERs) to be used for the protection studies of the alternating-current (ac)-islanded (autonomous) microgrids, and provide a management strategy during and after short circuit (SC) and consequent OLs. The fault is detected, and its type is discriminated by a new method that takes the advantages of both artificial neural networks (ANNs) and transient monitoring function (TMF). By using the proposed strategy, the output current magnitudes of the distributed energy resource (DER) units are limited, and after fault clearance, the microgrid is restored to its normal operating conditions. The proposed OC/OL protection scheme limits the output power of the DERs. In this regard, a generalized fault model is presented, which considers the effect of the control system of the IIDERs. This model exploits a current-limiting strategy (CLS) that can be implemented in different reference frames to enhance the microgrid fault ride-through (FRT) capability. Finally, to demonstrate effectiveness, accuracy, authenticity, and feasibility of the proposed OC/OL protection scheme along with the TMF/ANN-based fault detection method and their desirable performance, offline digital time-domain simulations are done in MATLAB/Simulink environment, and the results are experimentally verified by using the OPAL-RT real-time digital simulator (RTDS).

Integration of wind turbines in distribution systems and development of an adaptive overcurrent relay coordination scheme with considerations for wind speed forecast uncertainty

The integration of renewable energy (RE)-based distributed generation (DG) with electric power distribution systems (DSs) in association with smart grid technology has numerous benefits, however, due to their intermittent nature, the utilisation of RE-based DG may pose threats to the proper operation of conventional overcurrent (OC) protection schemes. The resulting threats, malfunctions, and non-selective actions could occur by relays within the DS, and the development of efficient protection schemes is necessary. The objective of this study is to propose and simulate an adaptive OC protection scheme in DSs in the presence of doubly-fed induction generator (DFIG) wind turbines based on wind speed forecast data with considerations for wind speed forecast uncertainty and a low-voltage ride-through requirement for wind turbines. In each time interval and possible operating mode, the output power of DFIG-based wind turbines and relay setting parameters are determined offline. The results show that the proposed protection scheme prevents malfunctions and non-selective operations of relays, and also provides faster fault isolations, as compared to the conventional OC protection scheme.

Evaluating maximum permissible feeder current in capacitive compensated harmonic polluted networks introducing Apparent RMS Current Ratio Index (ACRI)

Overcurrent (OC) protective relays use different methods to calculate the RMS value of the current signal, based on the CT data. One common technique uses the peak-to-peak value, which is called the Apparent RMS Value in this paper. But using this value, when there are noticeable harmonics in feeders current, may lead to OC relay malfunction. The ratio of maximum possible Apparent RMS value to True RMS value is introduced as the Apparent RMS Current Ratio Index (ACRI). Then maximum permissible current in a feeder is determined so that no relay malfunction is guaranteed. This malfunction occurs more often in capacitor banks feeders in MV/LV substations with big nonlinear loads such as big induction furnaces, especially in resonance situation. Results are investigated on a typical 63 kV/20 kV substation including a big nonlinear load compensated by four back-to-back capacitor banks.

New Method for OC Relay Coordination

Protection relays design and manufacture have arrived to a new level of advancement; hence, numerical relays have appeared recently. They combine all the functions of monitoring, control, and protection in one device. Also these relays have the ability to communicate with each other to share statuses and orders using GOOSE (generic object‐oriented substation events) messages based on communication protocols such as IEC61850. In this paper, a proposed method for overcurrent (OC) relay coordination has been introduced based on numerical relay features of several setting groups and communication capability. This work supposes that the coordination between feeder, bus section, and incomer protection relays, in a substation of single busbar configuration with bus sectionalizer (i.e., bus section), depends on the status of the bus section circuit breaker (CB) as a criterion for determining active relay setting group, to achieve a faster tripping action. ETAP has been used as a simulation software environment. And the simulation results show the advantages of the proposed method in reducing the time needed by the relay to clear the electrical fault. Siemens SIPROTEC series have been used as an example of numerical relays, specifically 7SJ64 as OC relay, which exists in the ETAP library.

Novel Overcurrent Methodology for Flyback Converters: Improving Overcurrent in Industrial Productions

A novel Overcurrent (OC) protection methodology applied for flyback converters is proposed. This technique provides the advantage of immunity to input-voltage variation and inductance deviation from production-line manufacturing, making accurate OC available. Experimental results guarantee highly significant improvement based on OC variation of less than 0.733% under universal-line voltage conditions. Moreover, additional components are unnecessary in a real board, so no burden is placed on circuit design. The advantages of the target features have been analyzed in detail through conscientious simulations, and the feasibilities were verified on prototypical circuits.

Accurate coordination method based on the dynamic model of overcurrent relay for industrial power networks taking contribution of induction motors into account

Induction motors are widely used in the industry. These motors contribute to short-circuit currents (SCCs) by generating transient currents. The transient component in the SCC causes a change in the operating times of the overcurrent (OC) relays and miscoordination between the main and the backup relays. Therefore, the conventional relay coordination methods that use fixed SCCs for a specific fault location are not suitable for industrial power networks. In addition, the contribution of induction motors may cause a false trip in non-directional OC relays at healthy feeder. Here, a method based on the dynamic model of the OC relay is proposed to take the effect of transient component of SCC into account in relays coordination. A new set of constraints is added to the conventional coordination constraints in order to solve the false trip issue. In this case, an optimisation algorithm is needed to coordinate non-directional OC relays. The proposed method is implemented in a power network of cement factory and the results indicate the effectiveness of the proposed method. Here the genetic optimisation algorithm has been used and the simulation has been achieved using DIgSILENT and MATLAB software.

Incorporating Bus-Bar Switching Actions into AC OPF to Avoid Over-Current Status

This paper presents a new AC optimal power flow (AC OPF) model for sub-transmission networks. This model, which consists of sub-transmission and distribution bus-bar switching actions, can avoid undesirable over-current (OC) status and subsequent actions of OC relays. The proposed AC OPF optimizes the bus-bar switching actions along with optimizing sub-transmission control actions. Also, to consider the impact of OC relays’ actions in the proposed AC OPF, the cost of load shedding caused by these relay actions is included in the objective function and is minimized along with the sub-transmission operation cost. The bus-bar switching actions are modeled using binary decision variables. Therefore, the proposed AC OPF model is formulated as a Mixed Integer Non-linear Programming (MINLP) optimization problem. The effectiveness of the proposed model is illustrated on a real-world sub-transmission network of Iran’s power system.

Optimal Coordination of Overcurrent Relay Using Crow Search Algorithm

ABSTRACTThis paper proposed a novel optimization technique derived from the crow search algorithm (CSA) for overcurrent (OC) relay coordination in mesh distribution networks. CSA is a meta-heuristic optimizer algorithm, influenced by the cleverness approach of crows. This algorithm can be treated easily by changing only two parameters like, flock size and iteration. In the present work an objective function (OF) is build up to work out the problems of relay coordination developed from time dial (TDS) setting and also the competence of the proposed technique is verified for four different power system networks and compared with existing techniques. Result and performances are the evidence that the suggested scheme is efficient, precise and simple.

FPGA Based Design and HIL Verification of a Soft-Core Directional-OCR

In the conventional distribution network mostly overcurrent (OCR) relays are in use, however, in case of microgrid the direction of power changes with operating conditions, the need of directional feature of the relay has become a must. Therefore, in this article, the design and hardware prototype of a soft-core directional-OCR (DOCR) on Field Programable Gate Array (FPGA) using a modular design approach is presented. A digital phase detection module has been developed for the estimation of the direction of current flowing through the power system network. A parallel architecture for phase and tripping time computation is used in the proposed design that makes the developed relay faster by reducing the computation time of the algorithm. The Integer arithmetic Verilog hardware description language platform is used to optimize the computational burden and hardware resources. Also, in the developed relay, inverse characteristics viz. extreme inverse and very inverse characteristics of OCR are emulated. The design is implemented on the Virtex ML-505 FPGA development board. The performance of the DOCR is tested by creating the faults at different locations with different values of time dial settings and plug-point-multiplier. Hardware-in-loop verification of the relay is carried out with the real-time-digital simulator and FPGA. The results are compared with the standard DOCR of the RTDS to successfully verify the operation of the designed relay under different fault conditions.

Investigating Phase Over-Current (OC) Protection in Medium-Voltage networks

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. There is always a need to protect expensive power equipment. Protective relaying is a very important part of any electric power system that comes into play during trouble, fault or abnormal condition. The purpose is to isolate unhealthy part of electrical power system while the rest continue their normal operation. The entire electric power system from source to load centers is exposed and subject to natural hazards. The effects of these hazards are capable of interrupting normal operations of the system. Since these hazards cannot be prevented, precautions are taken to minimize or eliminate their effect on the system. The relay is a basic component of any protection scheme. The information (or signals) received from the power system actuates the relay, when necessary, to perform one or more switching actions. The signals are proportional to the magnitudes and phase angles of power system voltages and currents. When the relay receives these signals, it decides to close (or open) one or more sets of normally open (or closed) contacts, and consequently, the trip coil of a circuit breaker will be energized to open the power circuit. This paper investigates over-current relay protection scheme applied to medium-voltage electrical network. Methods of current and time grading have been applied in the coordination of the overcurrent relays in a radial network. Different time/current characteristics of relays such as the normal inverse (NI), very inverse (VI), and extreme inverse (EI) have been examined in order to obtain optimum discrimination.

Investigating Phase Over-Current (OC) Protection in Medium-Voltage networks

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. There is always a need to protect expensive power equipment. Protective relaying is a very important part of any electric power system that comes into play during trouble, fault or abnormal condition. The purpose is to isolate unhealthy part of electrical power system while the rest continue their normal operation. The entire electric power system from source to load centers is exposed and subject to natural hazards. The effects of these hazards are capable of interrupting normal operations of the system. Since these hazards cannot be prevented, precautions are taken to minimize or eliminate their effect on the system. The relay is a basic component of any protection scheme. The information (or signals) received from the power system actuates the relay, when necessary, to perform one or more switching actions. The signals are proportional to the magnitudes and phase angles of power system voltages and currents. When the relay receives these signals, it decides to close (or open) one or more sets of normally open (or closed) contacts, and consequently, the trip coil of a circuit breaker will be energized to open the power circuit. This paper investigates over-current relay protection scheme applied to medium-voltage electrical network. Methods of current and time grading have been applied in the coordination of the overcurrent relays in a radial network. Different time/current characteristics of relays such as the normal inverse (NI), very inverse (VI), and extreme inverse (EI) have been examined in order to obtain optimum discrimination.

Optimum Coordination of Overcurrent Relays using Genetic Algorithm and Particle Swarm Optimization

Electrical Systems are seldom subjected to excessive currents caused due to short circuits and ground faults. Therefore, it is mandatory to protect people and primary electric power equipment from damage or disaster using suitable Protective systems. When the current exceeds the threshold level, Overcurrent (OC) Relay is operated. It is important for a protection engineer to maintain coordination time interval (CTI) among relays during overcurrent relay coordination. For quick clearance of faults, various optimization algorithms are applied to relay parameters. In this paper, Genetic algorithm and particle swarm optimization technique are used to deduce the Time Multiplier Setting (TMS) values of relays implemented on a radial network. This aids in achieving suitable OC coordination of relays.

Improved protection system for phase faults on marine vessels based on ratio between negative sequence and positive sequence of the fault current

This paper presents a new method to protect the radial feeders on marine vessels. The proposed protection method is effective against Phase-Phase (PP) faults and is based on evaluation of the ratio between the negative-sequence and positive-sequence of the fault currents. It is shown that the magnitude of the introduced ratio increases significantly during the PP fault, hence indicating the fault presence in an electric network. In this paper, the theoretical background of the new method of protection is firstly discussed, based on which the new protection algorithm is described afterwards. The proposed algorithm is implemented in a programmable digital relay embedded in a Hardware-in-the-Loop (HIL) test setup that emulates a typical maritime feeder using a Real Time Digital Simulator (RTDS). The HIL setup allows testing of the new protection method under a wide range of faults and network conditions and the experimental results demonstrate its effectiveness in all scenarios conducted. The proposed protection method offers a solution to the protection challenges associated with variability of the short-circuit currents in radial feeders, advancing in this way the traditional mean of protection in maritime feeders, represented by OverCurrent (OC) relays.

FLISR Approach for Smart Distribution Networks Using E-Terra Software—A Case Study

A smart grid concept has been defined in recent years, which emphasizes the importance on smart protection and measurement devices, reliable data communication and high security, optimal energy management system, and fault detection, location, isolation and service restoration (FLISR) of distribution networks (DNs). The main objectives of the FLISR approach are to achieve fast fault processing time, reduce the minimum number of interrupted customers, and improve the power supply reliability of the distribution. The conventional FLISR approach is to use signals of fault indicators (FIs) with distribution network states. The discrete installation of FIs to switches or reclosers may slow the processing time of fault detection and location, so it is necessary to develop a more efficient FLISR approach for smart distribution networks using functions of feeder terminal units (FTUs). In this paper, pick-up and tripping signals of overcurrent (OC) relays in combination with distribution grid states (e.g., switching status of devices, loss of voltage…) sent from feeder terminal units (FTUs) are used to detect and locate different fault types. Fault isolation and service restoration of black-out areas are then performed by solving an objective function with two main constraints, including (i) restoring the possible maximum number of out-of-service loads; and (ii) limiting the minimum number of switching operation. Thirteen performance factors (PF) are used for the post-fault service restoration process, consisting of: (i) Power Flow Violations (PFV), (ii) Bus Voltage Violations (BVV), (iii) Total Operation Cost (TOC), (iv) Lost Power (LP), (v) Outage Customer (OC), (vi) Number of Switching Steps (NSS), (vii) Power Losses (LOSS); (viii) Customer Minutes Interruption (CMI), (ix) Load Minutes Interruption (LMI), (x) MAIFI, (xi) SAIFI, (xii) SAIDI, and (xiii) Protection Validation (PRV). E-Terra platform of a distribution management system (DMS) is used to implement the proposed FLISR approach. Simulation and experiment results from a real 22 kV distribution network are also analysed to validate this FLISR approach. As a result, the novel FLISR approach has the ability to identify effectively the over-reaching of OC relays, indicate a mis-coordination risk of adjacent protection devices on the same feeder, and get the total processing time of fault detection, location and isolation as well as ranking all possible service restoration plans in distribution network at less than two minutes.