Voltage Protection Research Articles

Implementation of protection circuit for over voltage and under voltage protection

This paper identifies the development of an under voltage and over voltage protection in order to avoid damage in load side. Most of the industries and as well as home appliances are very expensive also more sensitive. This may get damaged due to the instabilities in ac mains supply. It can also lead to losses in the electrical circuit. These losses lead to low power factors and wastage of so much power. The fluctuations can cause great impact to the power quality and many precious and expensive equipment may be damaged. It is therefore advisable to have a tripping mechanism to protect the load. The voltage below the rated value are usually caused under unexpected raise in load due to faults in the system, during short circuit conditions and also rapid increase in source impedance due to lose connection in the circuit. The voltage above the rated values are caused by a sudden decrease in load in a circuit having a poor or damaged voltage regulator. The over voltage may also be caused by a damage in the circuit or loose connections in neutral wire. In this paper, the solution to under voltage and over voltage conditions has been carried out. The proposed circuit will be able to work within the voltage ratings of 195–215 V. Anything below that will be considered as under voltage and anything above that will be considered as over voltage. Thus, we can protect the equipment from damage. By doing this, the proposed circuit is able to protect the electrical appliance. The promising results obtained are presented and discussed here.

Fault Location in Solar Farms

Power delivery interruption and catastrophic failures are some of the potential consequences of undetected faults in photovoltaic (PV) arrays. A voltage protection scheme with the minimum number of sensors which is capable of detecting, classifying, and locating line-to-line (intrastring and cross string), line-to-ground, and open-circuit faults in a utility-scale PV array is proposed in this article. The proposed protection scheme consists of three steps. In the first stage, by a simple and efficient algorithm occurrence of any disturbance in the system is detected using some voltage sensors. At this stage, faulty strings in the PV array are also identified. In the second step, using a new least squares-based method, fault and shading conditions are discriminated from each other. Finally, in the third step, the faults inside the faulty string are located using a new method based on multiclass artificial neural networks. Fault location methods that have been developed so far require a large number of sensors or additional equipment for the exact location of faulty modules inside the fault string, but in the proposed method, only one sensor is used per string for fault localization. The proposed scheme for detection and location of faults is evaluated by simulating a typical system in different conditions.

A real-time DWT and traveling waves-based multi-functional scheme for transmission line protection reinforcement

This paper presents a multifunctional scheme to reinforce the protection of Extra High Voltage (EHV)/Ultra High Voltage (UHV) transmission lines. The proposed scheme employs d–q transformed traveling waves and the time of incidence of first traveling waves at both ends of the line for fault detection and location respectively. Furthermore, the faults are classified using energy values of approximation coefficients and the phasors are estimated from the approximation coefficients. The traveling waves are nothing but detail coefficients. The detail and approximation coefficients are obtained using discrete wavelet transform multi-resolution analysis (DWT-MRA) of the 3-ɸ current signals. The proposed algorithm detects and locates a fault within a quarter cycle. The proposed scheme has been implemented on a two-bus and the WSCC-9 bus systems in EMTDC/PSCAD software to verify the efficacy and reliability. Also, it has been realized on a laboratory model of an EHV transmission line of length 200 km using NI cDAQ-9178 chassis, NI-9227 current sensor card, and LabVIEW software. The simulation and hardware results evince the protection reinforcing property of the proposed multifunctional scheme.

Design of control and frequency conversion speed regulation system for mine fan

In order to improve the accuracy and stability of the control system of mine fan, the control and frequency conversion speed regulation system of mine fan was developed based on PLC. Based on the analysis on control technology for mine fan, puts forward the inverter, soft start double mode control strategy, combined with the design of PLC control system hardware circuit and software program, the realization of mine fan starting and soft start, reasonable speed regulating, stop running process control, at the same time have the parameters such as voltage, current detection and fault protection function.

Design and Analysis of Series Loaded Resonant Converter fed by Standalone/PV Source

The deficiency of power is an enormous issue due to higher growth demands among the utility customers which led the focus on renewable energy sources for electricity generation. Solar energy has gained high popularity due to highly abundant, clean, economical and sustainable when compared to other alternative energy sources. The DC-DC converter topologies are used in solar photovoltaic (PV) applications for power conversion due to less cost, highly reliable, highly efficient, and robust operation. These converters incorporate a wide variety of voltage variations and protection against overvoltage. In the recent times, solar power converters using various soft switching techniques due to high switching frequencies which reduce the size, cost, weight and loss of the converter. The series resonant power converters are one such soft switching converter which is widely employed due to their high - efficiency with the benefit of low switching losses. The paper confers on the analysis of Series Loaded Resonant Converter with low loss switching by applying solar PV as an input source. The converter behaviour is observed in various operating modes concerning the resonant frequency. The design parameters of the proposed converter are validated in MATLAB/SIMULINK environment.

Adaptive reclosing strategy for single outgoing line of converter-interfaced wind park using distance relaying algorithm

The 110 kV single outgoing line powered by wind generation usually adopts tripolar tripping and three-phase auto-recloser. The electrical quantities of the single line attenuate quickly after fault tripping, which makes it difficult to identify fault properties during the dead time. Also, due to the high voltage or frequency protection, the converter-interfaced wind generation is prone to be blocked after tripolar tripping. The machine-side circuit breaker is then reclosed temporarily. A fast adaptive auto-reclosing scheme is proposed for three-phase tripping scenarios by injecting sinusoidal currents from interface converter to the faulty line. By re-activating pulse width modulation (PWM) for a very short time, the interface converter works as STATCOM to regulate the output voltage and then an active current injection is realized. Improved distance relaying algorithm is deduced in this injection scenario to locate the fault and achieve fault property identification. After the confirmation of arc extinction, the triggering control of interface converter will be re-activated and the circuit breaker will be reclosed to restore power transmission. The proposed fast three-phase reclosing scheme is validated in PSCAD/EMTDC and the simulation results show the accuracy of fault identification and short reclosing time.

Considering DGs Voltage Protection in Optimal Coordination of Directional Overcurrent Relays to Minimize the Energy Not Supplied

So far, the overall operation time of relays has been used as the objective function in all directional overcurrent relays (DOCRs) optimal coordination problems. However, it cannot guarantee that in an optimal coordination of DOCRs at presence of distributed generations (DGs), the reliability indices will reach the minimum value. The reason is the existence of DGs voltage protection at their connection point to the network. This protection plays a key role in determining participation of DGs in improving network reliability during fault conditions. However, in the previous studies in which the overall operation time of relays is considered as the objective function, the voltage protection of DGs is not taken into account. In this article, coordination between DOCRs and their interactions with the DGs voltage protection is considered in calculation of the energy not supplied (ENS). Also, instead of the overall operation time of the DOCRs, the ENS value is considered as the optimization objective function. A probabilistic hourly seasonal model has been used to model the renewable DGs and the network loads. Various scenarios have been simulated to demonstrate the efficiency of the proposed method over a standard 33-bus radial distribution network.

A Review of the Tools and Methods for Distribution Networks’ Hosting Capacity Calculation

Integration of distributed energy resources (DERs) has numerous advantages as well as some disadvantages. To safely integrate DERs into a given distribution network and to maximize their benefits, it is important to thoroughly analyze the impact of DERs on that particular network. The maximum amount of DERs that a given distribution network can accommodate without causing technical problems or without requiring infrastructure modifications is defined as the hosting capacity (HC). In this work, a review of the recent literature regarding the HC is presented. The major limiting factors of HC are found to be voltage deviation, phase unbalance, thermal overload, power losses, power quality, installation location and protection devices’ miscoordination. The studies are found to employ one of four different methods for HC calculation: (i) deterministic, (ii) stochastic, (iii) optimization-based and (iv) streamlined. Commercially available tools for HC calculation are also presented. The review concludes that the choice of tools and methods for HC calculation depends on the data available and the type of study that is to be performed.

Integration of High Voltage AC/DC Grids into Modern Power Systems

The Special Issue on “Integration of High Voltage AC/DC Grids into Modern Power Systems” is published. A total of five qualified papers are published in this Special Issue. The topics of the papers are control, protection, operation, planning, and scheduling of high voltage AC/DC grids. Twenty-five researchers have participated in this Special Issue. We hope that this Special Issue is helpful for high voltage applications.

Transformer Fuses—Mind the Gap

Fuses are commonly used to provide medium voltage (MV) protection to distribution transformers. Unfortunately, there are certain deficiencies introduced when primary-side fuses are used. In paper mill power systems, given the unique organization of the paper mill loads around individual feeders to facilitate load shedding, it may be advantageous to provide transformer differential relay protection from the primary of the transformer to the load side of the main secondary breaker instead of primary fuse protection. This protection can then trip either a primary-side grounding switch (with fuses) or a primary-side feeder circuit breaker using a fiber or a WiMAX (Worldwide Interoperability for Microwave Access) connection. Protection against overload is provided by a secondary main circuit breaker and by design.

Design of new quick control power protection system of EAST

Aiming at the problems that may arise in the work of the AC-DC-AC converter of the new fast-control power system of the Experimental Advanced Superconducting Tokamak (EAST), a control and protection method for each link is proposed. Based on in-depth research on the protection mechanism of fast control power in the field of nuclear fusion, and combination with the needs of nuclear fusion devices, a surge current suppression circuit, a voltage protection circuit, an overcurrent protection circuit, an overt-emperature protection circuit, an energy leakage protection circuit, and a crowbar were designed. Compared with the traditional protection method, the scheme has a wide protection range, strong reliability and high security. The experimental results show that the power protection system can ensure safe and reliable exit of the power supply in the event of a sudden failure, and effectively protect the superconducting magnets and power components of the superconducting Tokamak experimental device from damage, verifying the correctness and effectiveness of the designed scheme.

Evaluation of Rail Potential and Stray Current With Dynamic Traction Networks in Multitrain Subway Systems

In multitrain subway systems, excessive rail potential and stray current (RP-SC) appear in the reflux system during the dynamic operations of an over voltage protection device (OVPD) and a drainage device (DD), which has not been clarified until now and has seriously affected the safe operation of the systems. To accurately evaluate RP-SC with dynamic traction networks, the equivalent method of the reflux system with mixed parameters is proposed, based on which a new simulation model that considers the dynamic characteristics of OVPD and DD is established. The control characteristics of OVPD and DD are analyzed in the established simulation model with multiple trains operating in the dynamic traction network. Dynamic RP-SC are simulated in different cases and are validated in the field tests at Guangzhou Metro Line 2. Results show that the RP-SC with dynamic traction networks can be effectively evaluated by the proposed model. RP-SC are greatly influenced by the dynamic operations of OVPD and DD, and excessive RP-SC can be mitigated by adjusting the grounding resistances of the closed OVPD.

The design programming simulation as a reference for the adjustment of the relay GFR on the protection of the airway medium voltage 20 KV

Short circuit fault phase to ground and phase to phase is one of the problems that may arise in the operation of the power transformer in a Substation. The interference caused by the presence of a short circuit caused a lot of losses, losses on the transmission system of electricity and losses on the part of consumers of electric energy. One way to overcome this disorder is with safety protection relay OCR and GFR that works with the Power Breaker (Circuit Breaker). This research will create a Programming-Based Object (PBO) using the GUI of MATLAB, where programs are designed is one answer to cope with the calculation of the adjustment GFR (Ground Fault Relay) attached on the network, the validation of the programming that is done using armed forces data from the company, which for reasons of privacy mentioned as XYZ. Great protection Setting of the interference 1 phase ground occurs along the feeder can be concluded that the working time of GFR on the side of the outgoing and incoming have a difference of 0.4 seconds, thus the design of programming windows in this study can be used as a reference as setting tms on GFR which is mounted on an equipment of protection of electric power because it has been in accordance with the applicable standards.

The Characteristics of the pin-Structure with a Discrete Metallic Surface i-Region

Introduction. Currently, an interest in improving pin-structures continues to be the focus of attention of developers of electronic devices. Devices that use controlled pin-structures include: non-volatile memory, static voltage protection device, pin-diodes with adjustable characteristics, etc. However, insufficient attention is paid to the issue of controlling the characteristics of pin-structures by using discrete metallization on the surface of i-region.Aim. Investigation of the influence of discrete metallization of the surface of i-region on static and dynamic characteristics of pin-structure, defect compensation, and efficiency control of the pin-photodetector.Materials and methods. The pin-structure under study consisted of p + -boron-doped region; n + -phosphorusdoped region; i-phosphorus-doped region; semi-insulating substrate; metallization of the substrate; polysilicon control gate; and a silicon oxide dielectric layer. Two-dimensional numerical analysis of the potential distribution, of the concentration of free charge carriers and currents was performed in the Synopsys Sentaurus TCAD environment.Results. Two-dimensional analysis of discretely metallized pin-structures was performed. The stresses applied to the gates of i-region that compensated the influence of defects formed by electron irradiation were determined. Four pin-photodetector structures were modeled, in which the control gates were performed in the form of metal–dielectric–semiconductor structure. The possibility of increasing the sensitivity of the pinphotodetector by applying the corresponding potentials to the gates was demonstrated.Conclusion. An effect of discrete metallization of i-region of the pin-structure was investigated. A method for correcting of the characteristics of the irradiated pin-diode to the initial characteristics was proposed. It makes possible to use such diodes in electronics with high requirements for operating in areas with high radiation. The design of a high-sensitivity photodetector with control gates on the surface of i-region and with the structure of low alloy i-region split into two regions (p- and n–type conductivity) was proposed.

Studies on stator single-line-to-ground faults protection for a Powerformer considering the winding electromotive force distribution

The Powerformer is very different from a traditional generator in terms of the stator winding material, the winding process and the grid-connection schemes. Therefore, the electrical parameters of the stator winding and the distribution characteristics of the electrical fault component are considerably different from those of a conventional generator. If the traditional protection scheme of a generator is simply applied to a Powerformer, the reliability and sensitivity of the protection will be lowered. Therefore, this paper carefully analyzes the tooth width of a Powerformer, the flux density distribution of the tooth, and the distribution of the electromotive force (emf) between the segments of the winding. A distributed parameter model of a Powerformer is established by considering the emf distribution of the Powerformer windings. Accordingly, the zero-sequence fundamental voltage distribution caused by the emf distribution is analyzed. Then, a stator single-line-to-ground (SLG) relay protection scheme is proposed for the Powerformer. The scheme considers the influence of the emf distribution on the fault characteristics and improves the suitability of traditional zero-sequence fundamental voltage protection for the Powerformer. The simulation results show that the scheme has good sensitivity and reliability.

Effects of Distributed Generation on Electrical Power Network and Protection

The energy consumption increases day by day. To meet this need, we need to increase the generation of energy. Due to this growing demand, non-renewable energy sources come into play. One of these solutions is to connect dg to the electrical network. These distribution networks are usually connected to a low voltage network. The trend of the unidirectional force flow has gradually changed. The power supply connected to the electrical network is a bidirectional current flow system. The additional energy is returned to the network. The reliability has been improved. The introduction of the DG into the conventional power supply system poses several challenges, such as: higher short circuit levels, higher load losses, lower energy quality, voltage transients, voltage stability problems, coordination problems of the voltage regulation and protection, and the protection of the system may not work properly, and due to the bidirectional power flows of the DGs, there is a lower contribution of residual current from the DGs connected to the inverters. This article examines the effects of the penetration of DG into DN and suggests possible solutions to reduce these effects. In addition, traditional protection strategies are reviewed with respect to the Dg connected to the energy system.

A Family of Ultrahigh Efficiency Fractional dc–dc Topologies for High Power Energy Storage Device

The application of a nonisolated bidirectional fractional dc–dc topology is proposed for high power energy storage device in this article. The proposed topology has the benefits of ultrahigh efficiency, simple structure, and low cost because it processes only a fractional of the total power. With the existence of an extra-low voltage (LV) power source, the converter voltage stress is only the difference between the dc bus and high voltage (HV) power source, therefore, low-cost LV transistors can be used in HV high power applications. Since a majority of the power is transferred directly between the energy storage device and dc bus, ultrahigh system efficiency can be achieved. Converter operating principle and design considerations such as battery capacity calculation methodologies and over voltage protection (OVP) are presented. A GaN transistor-based prototype is fabricated. Experimental results of a 1.2-kW battery energy storage prototype are presented to validate the analysis. The system efficiency is higher than 99% when a wide input–output voltage range is achieved. The fractional converter is convincing in achieving high efficiency and high conversion power with reduced cost for energy storage devices.

Rooftop Photovoltaic-Battery Systems to Mitigate Overvoltage and Under Voltage in a Residential Low Voltage Distribution System

High penetration of rooftop photovoltaic systems in a residential low voltage distribution system has to be controlled in order to maintain stable voltage condition. Energy storage systems, such as batteries, can be used to absorb excess energy of photovoltaic systems and to shave peak load during on-peak time. This paper proposes guiding principles for the incorporation of energy storage systems into a residential low voltage distribution system with high penetration of rooftop photovoltaic systems. Real residential distribution system circuits and all parameters from the Geographic Information System database of the Provincial Electricity Authority in Thailand were used for simulation analysis to study the application of energy storage systems for regulating voltage in a range of the nominal voltage by 10 %. Solar radiation data from the PVGIS were used. The voltage results were simulated by using the DIgSILENT Power Factory program. Based on the simulation, it was found that the overvoltage and under voltage protection and energy loss reduction could be achieved by (i) installing small battery systems in households and (ii) installing battery stations within the vicinity of the transformer or the weakest point of the circuit.

A Single-Phase Line-Interactive UPS System for Transformer-Coupled Loading Conditions

A line-interactive uninterruptible power supply (UPS) system is one of the important installations implemented by industrial users to provide continuous power to sensitive industrial applications. Such loads often come with isolation transformers for voltage matching and protection purposes. Hence, a line-interactive UPS system experiences a serious problem of transient current when it operates under transformer-coupled loading conditions. The occurrence of this transient current can either impair the apparatus itself or turn on the overcurrent safety devices. In any situation, the interruption of electrical power for sensitive industrial loads is unavoidable. So as to keep the uninterrupted power and to eliminate transient current for industrial applications operating under transformer-coupled loading conditions, we propose a single-phase line-interactive UPS system based on a customary current-regulated inverter. The inverter of the proposed UPS system employs an improved current-regulating scheme implemented in a stationary frame of reference which regulates the load current and never let it to increase than a prescribed value as the transformer-coupled loads are turned on. Laboratory test results obtained under various operating and loading conditions of the single-phase line-interactive UPS system verify the operation of the proposed system.

Quench Experiments of Conduction-Cooled Coated Conductors With Various Copper-Stabilizer Thicknesses

We experimentally studied the quench properties of REBa2Cu3Oy (RE-123) coated conductors with various plated-copper thicknesses (20 and 40 μm). A short sample of coated conductors was conduction-cooled to 45 K, a magnetic field (μ0H, up to 2 T) was applied perpendicular to its wide face to control the critical current, an operating current was supplied, and subsequently quench was initiated using a small heater. Normal zone propagation velocities (NZPVs) were measured at various operating currents, and the NZPVs of coated conductors with various copper thicknesses were compared with each other. To understand the impact of the copper stabilizer on quench protection, hot-spot temperatures were measured during the processes that simulate quench detection using voltage taps and protection using dump resistor. The maximum hot-spot temperatures were plotted against the operating current as well as the overall current density, and the impact of the thickness of the copper stabilizer on hot-spot temperature was examined. The impact of the initial temperature on hot-spot temperature was also studied.