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In this paper, we present a new approach to protection of double-circuit transmission lines using modal transformation. The current differential principle is applied in the modal domain, and the relay characteristics are plotted in the alpha plane for numerical differential protection applications. Synchronized voltages and currents from both the ends are transformed to modal values. The transmission lines are modeled as equivalent π model in modal domain, and line charging current is compensated. Electromagnetic transient program EMTP-ATP is used to simulate the double-circuit transmission systems, and the algorithm is implemented in MATLAB. The extensive case studies demonstrate the utility and the superiority of the proposed current differential scheme. [ABSTRACT FROM AUTHOR]

The ever‐increasing power demand coupled with limited power transfer corridors and minimum redundancy have forced power system operation close to its security limits. Further, increase in renewable penetration, market deregulation, and mal‐operation of protective devices under stressed conditions has imposed serious threats to power system stability. To overcome these operational challenges, a new response‐based system integrity protection scheme (SIPS) is proposed here. The proposed scheme works towards preserving system integrity in two ways. First, an apparent impedance‐based relay security index (RSI) is introduced to prevent the zone 3 mal‐operations of distance relays under stressed situations and achieve accelerated zone 3 operation during faults. Second, a system stability index (SSI) computed from the generator rotor angles is forecasted using a predictive analytic to foresee system instability, if any, and take corrective actions in real time. The scheme can be used for area‐based monitoring and control of system stability, does not require coherency group identification, remains unaffected by changes in network topology, and can effectively function for first swing stable contingencies. The scheme is tested on IEEE 39‐bus New England system and the results obtained validate the reliability of scheme in maintaining system integrity. [ABSTRACT FROM AUTHOR]

The authors propose a novel algorithm to compute distance to fault on the transmission line. The loss of time synchronisation due to failure of global positioning system leads to synchronisation error. Time synchronisation error is computed non‐iteratively in phase domain using measurements available from two ends of the transmission line. The proposed algorithm computes distance to fault accurately even under current transformer saturation. Algorithm compensates the synchronisation error and estimates accurate fault location in a step. The proposed algorithm also works accurately for synchronised measurements. Simulations are carried on ATP/EMTP on IEEE 14‐bus system, and algorithm is implemented in MATLAB. Extensive simulation studies demonstrate the merits of proposed algorithm. [ABSTRACT FROM AUTHOR]

The segregated phase comparison technique is a notable form of differential protection which compares the phase angle of end currents of a transmission line. The literature shows that phase differential protection serves as a better option for transmission-line protection due to its simplicity, sensitivity, selectivity and comprehensibility. However, line-charging current causes a significant error in the phase angle of two end currents of a transmission line. This paper presents improved phase comparison which compensates error due to line-charging current and a function of a cosine scheme using the equivalent-\pi model of the transmission line. The phase differential function is developed using phase coordinates. The scheme is compared with the existing scheme like, conventional scheme based on line currents, the positive-sequence component of line currents and a mixed combination of line currents. The global positioning system is used for time-synchronised measurements and fiber optics are considered for data communication. Simulations are carried out in an Alternate Transients Program/Electromagnetic Transients Program on an IEEE 14-bus system, and a protection scheme is implemented on one of the tie lines. The results demonstrate the accuracy of the proposed approach over the existing schemes. [ABSTRACT FROM AUTHOR]

Considering electrical network as a continuum has become popular for electromechanical wave analysis. This paper reviews the concept of electromechanical wave propagation. Analysis of large number of generator ring system will be an easy way to illustrate wave propagation. The property of traveling waves is that the maximum and minimum values do not occur at the same time instants and hence the difference between these time delays can be easily calculated. The homogeneous, isotropic 10 generator ring system is modeled using electromagnetic transient simulation programs. The purpose of this study is to investigate the time delays and wave velocities using Power System Computer Aided Design (PSCAD)/Electromagnetic Transient Program (EMTP). The disturbances considered here are generator disconnections and line trips. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of Static Var Compensator (SVC) connected in transmission line on adaptive distance protection is studied. [•] The SVC is connected at three locations in transmission line. [•] Measured impedances by the relay with and without SVC is determined. [•] SVC connected at mid-point affects seriously on the characteristics of relay. [•] Discrete Fourier Transform (DFT) is used to estimate the phasors of the voltage and current at the relaying bus during fault. [ABSTRACT FROM AUTHOR]

We propose a new approach to current differential protection of transmission lines. In this approach, we transform the instantaneous line current(s) by using a moving window averaging technique. If the time span of moving window is equal to one-cycle time, then the steady-state value of the transformed current is zero for a periodic signal which is composed of fundamental and harmonic frequencies. Signal distortions (e.g., a fault) cause the transformed currents to deviate from the nominal zero value. This permits the development of a sensitive, secure, fast, and yet simple current differential protection scheme. The scheme can be applied in toto to series-compensated transmission lines. Results on a four-machine ten-bus system and comparative evaluation with state-of-the-art methods brings out promise of the proposed method. [ABSTRACT FROM AUTHOR]

Throughout the history of power system protection, researchers have strived to increase sensitivity and speed of apparatus protection systems without compromising security. With the significant technological advances in wide-area measurement systems, for transmission system protection, current differential protection scheme outscores alternatives like overcurrent and distance protection schemes. Therefore, in this paper, we address this challenge by proposing a methodology for adaptive control of the restraining region in a current differential plane. First an error analysis of conventional phasor approach for current differential protection is provided using the concept of dynamic phasor. Subsequently, we extend the methodology for protection of series compensated transmission lines. Finally, we also evaluate the speed versus accuracy conflict using phasorlets. Electromagnetic Transient Program simulations are used to substantiate the claims. The results demonstrate the utility of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is Bus Observability Index giving a measure of number of PMUs observing a given bus and SORI is System Observability Redundancy Index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: 1) optimal phasing of PMUs can be computed efficiently; 2) proposed method of modeling zero injection constraints improve computational performance; and 3) BOI and SORI help in improving the quality of PMU placement. [ABSTRACT FROM AUTHOR]

This paper presents a new protection algorithm for double circuit transmission lines using the sum of ratios of modal currents. Relay-operating characteristics is proposed using the complex ratio of modal currents. The proposed algorithm estimates modal domain line parameters and identifies the faulty phases for single pole-tripping applications even during inter-circuit faults. The scheme is sensitive to high resistance internal faults and also detects internal faults with outfeed. The proposed scheme is immune to mutual coupling and is found robust to uncertainties in parameter estimation due to measurement inaccuracies. The scheme is tested for its effectiveness to deal with current transformer saturation and synchronisation error. The scheme protects series compensated double circuit transmission lines even in the presence of current inversion. Exhaustive case studies in electromagnetic transient program (EMTP)/alternate transient program are performed on 400 kV, 300 km, double circuit transmission lines and the proposed protection algorithm is implemented in MATLAB. The results confirm the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper proposes an expert system approach to short-term expansion planning (STEP). The rules which drive STEP can be classified into MW, MVAR, and ampacity management rules. MW and ampacity management rules are for alleviating transmission line congestion. Reactive power management is required for voltage control at load busses, conformity to the capacity curve of the generators, and containing the MW losses within acceptable limits. Embedding reactive power management in STEP is a challenging task since ac load flow may not converge in absence of proper reactive power planning and load modeling. Therefore, we also propose enhancements to the fast decoupled load flow algorithm for on-the-fly reactive power management. The enhanced algorithm not only can detect divergent load flow scenarios but also self-correct it by restarting the whole process with greater degree of freedom in reactive power controls. The proposed approach leads to development of an automated tool for STEP which has the capability to work, even with incomplete information. A simple method for evaluating location and requirement of shunt reactor is also proposed. By analysis and comparative evaluation, we show that the proposed system can arrive at a solution which is close to optimal. Results on the Western Regional Grid of India with an approximate load of 28000 MW and 1200 nodes are presented to demonstrate effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This study presents a rotor structure, for a line start permanent magnet synchronous motors (LSPMSMs), which can be applied to other types of inverter driven motors, such as brushless dc and permanent magnet synchronous motors. In this development, the magnet configuration is a combination of both circumferentially (spoke) as well as radially magnetised (embedded) magnets which are so arranged that induced poles are generated in alternate positions in the heteropolar structure, thereby reducing the quantity of permanent magnets in the rotor. Both the transient as well as steady‐state performances of the machine have been analysed by using time‐stepping finite element method. For experimental demonstration a prototype which uses spoke magnets (P1), plus two prototypes (P2 and P3) of the proposed magnet arrangement have been built. The former (P1) is used for benchmarking the performance of the proposed configuration. Results have indicated that the rotor configuration reported here (P2) with reduced magnet volume gives better performance than the spoke magnet rotor LSPMSM. Also, the performances of prototype LSPMSMs are compared with that of the standard induction motor of the same frame size and physical dimensions. [ABSTRACT FROM AUTHOR]