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The power transmission system, in this age, is characterized by ultra- and extra-high voltage AC, and multi-terminal high voltage DC networks. It has a wide-area power network across the nation. It incorporates conventional and ultra-mega-power plants (UMPPs). It also has a submission of increasing penetration due to Renewable Energy Sources (RES). A crucial role is delivered by the system integrity and protection schemes (SIPS) in sustaining guaranteed and safe grid operation. A SIPS also assists efficient grid management during serious power system emergencies. In this article, thorough investigation of the performable capabilities of three influential SIPS in India is made. The shortcomings in ongoing SIPSs got revealed. A proposed methodology eliminates these obstacles. Apperception and vitality of the recommended technique get decided by simulation exercise on an IEEE 10 generators 39-bus test system ingrained with HVDC link in MATLAB. Simulation outcomes accomplished the credibility of the method in defending system integrity. Electrical Transient Analyzer Program (ETAP) is used for the validation of MATLAB results. ETAP has an organizing/investigation mechanism and it is a remarkably convenient interface. [ABSTRACT FROM AUTHOR]

An Indian power system is characterized by a conglomeration of ultra-high voltage AC and DC, multi-terminal DC, and extra-high voltage AC transmission networks. It consists of a large distribution network across the country along with conventional generation having Ultra-Mega Power Plants (UMPP) and increasing penetration of Renewable Energy Sources (RES). The System Integrity and Protection Schemes (SIPS) play an important role in maintaining a secure and reliable grid and assists in effective grid management during severe power system contingencies. This paper presents the operational experience of some SIPS implemented in India along with their performance evaluations. The operational experience of three important SIPS, one in the Northern Regional (NR) grid and another two in the Western Regional (WR) grid of India are presented. The drawbacks in existing SIPS are pointed out and an algorithm is proposed to overcome these drawbacks. The performance and effectiveness of the proposed algorithm are evaluated by simulation studies on the 39-bus New England system embedded with an HVDC link in MATLAB/Simulink. Simulation results consummated confirm the authenticity of the scheme in preserving system integrity. Results are validated using Electrical Transient Analyzer Program (ETAP), which is a very powerful design and analysis tool and has an extremely user-friendly interface. [ABSTRACT FROM AUTHOR]

Abstract—Industrial Energy Measurement System (IEMS) used for measurement of electrical energy consumed by high-tension industrial consumers. It consists of three current transformers (CTs) and three potential transformers (PTs). Cost of IEMS increases with improvement in its accuracy class. The contribution of this article is that, it adduces design and development of high accuracy class and cost-effective IEMS. To accomplish this, a novel Industrial Energy Measurement-Error Compensation Unit (IEM-ECU) is proposed. To realize this, first, the three different accuracy classes, viz. 0.2, 0.5, and 1.0 IEMS are fabricated in the laboratory. Characteristics of every CT and PT are determined. Second, the proposed error correction algorithm is implemented in real time to improve errors of IEMS. Finally, the experimental results are depicted in LabVIEW for mixed class of CTs and PTs. Various experimental tests have been performed and results are validated by comparing the results obtained from digital storage oscilloscope. These results clearly illustrate that the proposed IEM-ECU not only convert lower accuracy class IEMS to higher accuracy class but it also gives flexibility to use available class of CTs and/or PTs, if required under contingency. Thereby, considerable cost savings can be achieved as the performance of lower accuracy class matches with the higher accuracy class. [ABSTRACT FROM AUTHOR]

Current transformers (CTs) are extensively used for the measurement of electrical energy, and hence they play a crucial role in the revenue generation for power distribution utilities. The novelty of this paper is that it presents artificial neural network (ANN) application for the ratio and phase angle error corrections of CTs in the presence of harmonic distortions. In this paper, the behaviors of silicon iron alloy and nanocrystalline alloy CTs are examined by the means of a number of experimental tests under the sinusoidal and distorted waveform conditions. The relation between the nature of CTs secondary current waveforms (CTSwf) with their metrological properties, connected burdens, and nature of load currents (linear or nonlinear) is established. The training data are obtained by the nature of CTSwf in terms of amplitude errors, time shifts, and deviations caused by different harmonic contents between input and output quantities. The ANN is trained for various operating conditions. The implementation of the error correction system and data acquisition is done using dSPACE 1104 software. The experimental results illustrate that the proposed technique can be used for error compensation in case of sinusoidal and the distorted waveform composed of fundamental and many harmonics. [ABSTRACT FROM AUTHOR]

This article describes the development of an error compensation algorithm for a measurement current transformer (CT). The flux‐magnetising current loops are derived in the proposed algorithm to minimise the number of required loops for computation. At every sampling interval, the exciting current is obtained from these loops and then it is added to the measured secondary current to gain the corrected primary current. The performance is tested using MATLAB program and later, the same code is executed in LabVIEW environment. Performance analysis indicates that the proposed algorithm improved the accuracy of the measurement CT notably even with minimum loops. The experimental test results demonstrate that the compensator is capable to correct the accuracy of the measurement CT in remarkable manner. [ABSTRACT FROM AUTHOR]

An online approach based on application of search coil for transformer winding fault detection is presented in this paper. Earlier attempts report use of search coil for the detection of transformer interturn fault. This paper extends application of search coil for detection of winding displacement in addition to interturn fault identification. Experimental results based on specially designed 10-kVA transformer are presented to analyze search coil voltages during healthy and faulty conditions. The algorithm detects phase ($U$ , $V$, $W$), side (LV, HV), and precise location of the fault. Discrimination between interturn fault and winding radial displacement is also achieved by search coil voltage analysis. The results are experimentally verified based on impedance analyzer plots. Experimental analysis indicates that the proposed method is independent of load on the transformer, vector group, nature of winding, balanced or unbalanced source voltage, source voltage harmonics, inrush, and overexcitation conditions. [ABSTRACT FROM AUTHOR]

Interturn short-circuit faults are the leading cause of power transformer's failure. If not detected at the incipient stage, these faults usually develop into more severe faults that would result in irreversible damage to the transformer, unexpected outages, and consequential losses. This paper presents a transformer interturn fault detection system (TIFDS) for the detection of an interturn fault at the inception stage in power transformers. TIFDS is immune to supply voltage imbalance, constructional asymmetries, and instrumental errors. It also takes care of unequal load distribution. The TIFDS algorithm makes the transformer symmetrical in its entire three phases and sets primary-side neutral current to zero value. This is achieved by computing and applying various correction coefficients. However, under the interturn fault condition, TIFDS characterizes the behavior of neutral current. Simulation and experimentation studies are carried out on the 400/110-V, 3 \times 2.5 kVA power transformer. Presented test results demonstrate the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

The microgrid concept is a promising approach for injecting clean, renewable, and reliable electricity into power systems. It can operate in both the grid-connected and the islanding mode. This paper addresses the two main challenges associated with the operation of a microgrid i.e. control and protection. A control strategy for inverter based distributed generation (DG) and an energy storage system (ESS) are proposed to control both the voltage and frequency during islanding operation. The protection scheme is proposed to protect the lines, DG and ESS. Further, the control scheme and the protection scheme are coordinated to avoid nuisance tripping of the DG, ESS and loads. The feasibility of the proposed method is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

System islanding is often considered as the final stage of power system defense plans. The goal is to preserve stable areas of the faulted power systems. The islanding scheme plays an important role in the power system restoration phase as it can make the power system restoration less complex and reduce the overall restoration time. The basis for islanding is not standard but rather depends upon the nature of the utility. Even though the formation of islands is dominated by geographical proximity of the synchronous generators to maintain generation-load balance, there are some factors which can assist in designing a better islanding scheme. These factors are the type and location of the fault and the dynamic performance of every island on the system against the fault. This paper present the application of islanding scheme and its performance operation for the scheme commissioned at 132 kV Deepnagar Bhusawal Thermal Power Station (BTPS). The methods and constraints of islanding scheme are discussed in details. Case studies regarding performance of islanding scheme are also described. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach based on the loci of instantaneous symmetrical components called "Wing Shape" which requires the measurement of three input stator currents and voltages to diagnose interturn insulation faults in three phase induction motors operating under different loading conditions. In this methodology, the effect of unbalanced supply conditions, constructional imbalances and measurement errors are also investigated. The sizes of the wings determine the loading on the motor and the travel of the wings while their areas determine the degree of severity of the faults. This approach is also applied to detect open circuit faults or single phasing conditions in induction motors. In order to validate this method, experimental results are presented for a 5 hp squirrel cage induction motor. The proposed technique helps improve the reliability, efficiency, and safety of the motor system and industrial plant. It also allows maintenance to be performed in a more efficient manner, since the course of action can be determined based on the type and severity of the fault. [ABSTRACT FROM AUTHOR]

The high probability of a rotor winding failure in a three-phase wound rotor induction motor (WRIM) due to the complicated structure of the rotor necessitates developing efficient techniques for detecting rotor winding faults in their evolving stages. FFT-based motor current signature analysis (MCSA) is extensively used to detect the electric failures of rotors. However, it is complemented by implementing alternative techniques to prevent the failure indicated by the MCSA. Rotor current-based fault detection schemes have been scarcely investigated and implemented in industry. However, this experimental study investigates the rotor winding inter-turn short-circuit (ITSC) faults in a WRIM based on the loci of the symmetrical components of the three-phase rotor currents £ (ir1–ir2) that form a 'Wing Shape.' Hence, the technique is called the 'Wing Technique.' The proposed fault-sensitive and noninvasive approach investigated the effects of unbalanced stator voltages, constructional imbalances, and instrumentation errors on the measurement of rotor currents. It contributes to diagnosing the motor loading and to monitoring the insulation condition of the rotor windings even under lower fault levels. Experimental results presented for a 7.5 hp, 415 V, four-pole WRIM validate the competency of the proposed technique. [ABSTRACT FROM AUTHOR]

• A novel, non-pilot scheme to avail Accelerated Trip (AT) signal using local measurements for the distance relays. • Method based on total relative reactance change – not requiring any extra hardware for implementation. • Fast operation of a non-pilot method comparable with permissive transfer trip signal delays. • Testing of methods in varying types of contingencies to ensure correct operation such as evolving high impedance fault and remote-end breaker arc re-striking. • Confirmation of the tests with relay data record-timing diagrams discussed in the protection subcommittee meeting, NRPC, India. Challenges about the accurate impedance measurement comply pessimistic setting of distance relay reach. Hence, internal, remote-end faults from either end of the connected power system's protected line section are cleared with a prolonged time delay. Although carrier communication-aided protection schemes can accelerate the relay operation, latency in data transmission and link failure hampers the reliability of communication-assisted TRIP schemes. The present article analyzes the adverse effects of the inadvertently long fault clearing time due to the contingent communication-assisted transfer trips. To overcome the challenges by minimizing fault clearing time, the paper proposes a simple yet effective method of monitoring the total relative reactance change seen by the relay to discriminate between internal and external faults to the protected line section and consequently issue of Accelerated Trip (AT) signal for internal faults without communication assistance. The method monitors the total relative change of reactance over the specified time window and compares the same with the threshold to discriminate between internal and external faults. In addition, a steady state difference between the apparent values of the measured reactance is used to improve the robustness of the proposed algorithm further. The method has shown robustness against a wide range of fault resistance and fault types. Moreover, extensive unique tests are carried out and reported such as AT issue stability during remote-end breaker arc re-ignition for internal faults, sudden change in fault resistance during the detection window, and the fault on mutually coupled parallel line section. The method issues AT signal in 70 ms from the point of fault inception, comparable with the permissive transfer trip signal delay. Moreover, the AT signal issue is independent of the fault MVA for the remote end, internal faults, and the mutual inductance due to coupled parallel lines. The timings for the fault inception to clearing process are referred from relay data records presented in the protection sub-committee meeting of the Northern Region Power Committee (NRPC), India. The modeling and simulations are carried out using PSCAD software and the algorithm is tested with MATLAB. [ABSTRACT FROM AUTHOR]

This paper presents high step-up dc-to-dc converter for low voltage sources such as solar photovoltaics, fuel cells, and battery banks. To achieve high voltage gain without large duty cycle operation, combination of coupled inductor and switched capacitor voltage doubler cells are used. By incorporating active clamp circuit, voltage spike due to the leakage inductance of the coupled inductor is alleviated and zero-voltage switching turn on of the main and auxiliary switch is obtained. Due to the use of MOSFETs of low voltage rating and soft turn on of the switches, conduction loss and switching losses are reduced. This improves the efficiency and power density of the converter. The proposed converter can achieve high voltage gain with reduced voltage stress on MOSFET switches and output diodes. Design and analysis of the proposed converter is carried out, and finally, a 500-W experimental prototype is built to verify theoretical analysis. [ABSTRACT FROM PUBLISHER]

Summary: In this work, an isolated modular resonant circuit with effective voltage regulation is presented as front‐end for multilevel inverter system to interface renewable sources of energy with micro grid. Inputs of each module of the converter are connected to low‐voltage DC sources. Modular‐structured module outputs may be linked in sequence or parallel to attain the desired DC link capacitor voltage for multilevel inverter. The proposed converter overcomes imbalance in the capacitor voltage of diode‐clamped inverter structure. Interleaved phase shift of 90° is supplied among the gate pulses of all four modules that minimizes the input‐side current ripples. An effective zero voltage switching (ZVS) is achieved over wide load range using duty cycle and frequency‐duty cycle double control method to improve system performance at light load condition. Adopting powder core magnetics and low forward voltage insulated‐gate bipolar transistors (IGBTs) reduces magnetic and conduction loss. A 12‐kW prototype of the designed modular resonant converter was verified by experimentation with a different‐level diode‐clamped inverter structures. [ABSTRACT FROM AUTHOR]

An optimized resonant converter with zero-voltage switching over an extensive range of loading is proposed to integrate renewable energy sources to an onboard charger. In conventional resonant circuit, high-frequency transformer (HF) parasitic components are used as tank circuit, this degrades the performance due to non-optimal magnetic components. Here, the HF transformer is fabricated with optimized resonant tank circuit shunt branch inductance ($L_p$) as magnetizing inductance, hence eliminating the need for shunt branch inductance. The proposed resonant converter circuit design is optimized for minimum kilovoltampere rating and better voltage regulation with both duty cycle and frequency control (mixed control method). Furthermore, the performance of the converter at a very light load is improved using the proposed control method. Incorporating a low- $R_{\text{DS}}(\text{ON})$ silicon carbide mosfet and softly turning off the switches for a wide load variation minimizes conduction and switching losses and improves efficiency. Using powder core for the design of the tank circuit reduces magnetic losses. A 3-kW prototype of the converter is built to verify the performance from no load to full load. The highest efficiency of the proposed converter is 98.6%, attained at 50% full load. [ABSTRACT FROM AUTHOR]

An isolated four channel dc/dc converter with zero voltage switching is proposed as the front-end of multiple inverter structures to integrate renewable and other low voltage energy sources to micro grids. The interleaving technique is adopted to connect each module of proposed converter to a common dc source. This dc source can be a fuel cell stack, PV panels, battery, or any other low voltage dc source. All four channels are interleaved and a phase shift of $90^{\circ }$ is provided between the gate signals of each channels, which reduces the input current ripple. The output port of the proposed converter provide four isolated and regulated dc voltages. These isolated dc sources can be connected in series or parallel or series-parallel manner to obtain required dc-link voltage of various inverter structure. Issues like capacitor voltage balancing of diode clamped multilevel inverters can overcome through the proposed converter. By incorporating a coupled inductor for isolation and energy storage along with voltage multiplier circuit, the proposed converter can achieve higher voltage step up with lower turns ratio and lower voltage stress at moderate duty ratio. Hence, mosfets of low voltage rating (low $R_{DS}(\text{ON})$ ) can be utilized to reduce conduction loss. A 2 kW prototype of the proposed interleaved dc/dc converter is developed and tested with diode clamped three-level inverter, five-level inverter, and three-phase two-level inverter to verify the design. [ABSTRACT FROM AUTHOR]

A nonisolated soft-switched-integrated boost converter having high voltage gain is proposed for the module-integrated PV systems, fuel cells, and other low voltage energy sources. Here, a bidirectional boost converter is integrated with a resonant voltage quadrupler cell to obtain higher voltage gain. The auxiliary switch of the converter, which is connected to the output port acts as an active clamp circuit. Hence, zero voltage switching turn-on of the MOSFET switches are achieved. Coupled inductor's leakage energy is recycled to the output port through this auxiliary switch. In the proposed converter, all the diodes of the quadrupler cell are turned off with zero-current switching (ZCS). This considerably reduces the high-frequency turn-off losses and reverse recovery losses of the diodes. ZCS turn-off of the diodes also remove the diode voltage ringing caused due to the interaction of the parasitic capacitance of the diodes and the leakage inductance of the coupled inductor. Hence, to protect the diodes from the voltage spikes, snubbers are not required. The voltage stress on all the MOSFETs and diodes are lower. This helps to choose switches of low voltage rating (low R\text{DS}(\text{ON})) and, thus improve the efficiency. Design and mathematical analysis of the proposed converter are made. A 250-W prototype of the converter is built to verify the performance. [ABSTRACT FROM AUTHOR]