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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]

Conventionally, transmission fixed cost allocation is carried out on postage stamp basis. Amongst various other ways of solving the problem, the cost allocation under the "usage-based" domain has also been suggested, namely, based on proportionate tracing and recently, by optimization based real power tracing. Changing the cost allocation regime from postage stamp basis to usage-based methods, though technically sound, can pose fairness issue. The fairness criteria in its simplest form would allocate cost in equitable manner oh per unit basis while meeting the constraints. The optimization-based tracing provides room for defining an objective, leading to tracing compliant postage stamp method, that strikes a balance in allocation between conventional postage stamp and proportionate tracing-based methods. In this paper, we address this complex cost sharing problem by suggesting a min-max fairness algorithm, using optimization-based real power tracing. The min-max algorithm achieves fairness by equalizing allocations within constrained space and reaching an equilibrium where further balancing cannot be achieved. We show that computing min-max fair solution simply corresponds to solving a sequence of sparse LP problems for real power tracing. The algorithm satisfies the property of aggregate invariancy. Results on actual data of central transmission utility of Western Regional Grid of India, as well as IEEE 30-bus system, validate the claims. The results are compared with the tracing compliant postage stamp method. [ABSTRACT FROM AUTHOR]

Postfault rotor angle oscillations lead to power swings. Both unstable and stable swings can induce distance relay tripping. For unstable swings, a new computational procedure to locate all of the electrical centers is developed. It simplifies the work associated with visual screening of all the R-X plots. For stable swings, a generic three-tier hierarchy of stability-related norms defined by branch norm, fault norm, and system norm is proposed. Ranking by branch norm leads to ranking of power swings. Ranking by fault norm leads to ranking of faults or contingencies. Magnitude and rate of change of system norm can be used to detect an out-of-step condition. Results on a ten-machine system and a utility system with detailed models are also presented. [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]