Analysis of faulted power systems in three phase coordinates- a generic approach

Analysis of faulted power systems in 3-phase coordinates is desirable when dealing with unbalanced networks and complex faults. Thevenin's model in 3-phase domain is well-known for shunt faults. However, lack of generic circuit model for series and simultaneous faults is an impediment, as it sacrifices both simplicity and computational efficiency. In this paper, we extend this approach to arbitrarily complex faults. Case studies with complex faults on two example systems demonstrate the claims made in the paper.© IEE

A simple and efficient approach to determination of minimum set of break point relays for transmission protection system coordination

Coordination of relays in a meshed system is an iterative process. It involves finding a set of break point relays. In this paper, we propose a new polynomial time approximation algorithm for computation of the minimum break point relay set. In turn, procedure for computation of minimum break point relays requires systematic enumeration of all possible simple loops in the system. Therefore, we also propose a simple method for enumerating all possible loops. The advantages of proposed approach are (1) simplicity and (2) reduced computational complexity. Case studies on various topologies demonstrate the utility of the proposed approach.© IEE

A simple and efficient approach to determination of minimum set of break point relays for transmission protection system coordination

Coordination of relays in a meshed system is an iterative process. It involves finding a set of break point relays. In this paper, we propose a new polynomial time approximation algorithm for computation of the minimum break point relay set. In turn, procedure for computation of minimum break point relays requires systematic enumeration of all possible simple loops in the system. Therefore, we also propose a simple method for enumerating all possible loops. The advantages of proposed approach are (1) simplicity and (2) reduced computational complexity. Case studies on various topologies demonstrate the utility of the proposed approach.© IEE

Optimal multistage scheduling of PMU placement: an ILP approach

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.IEE

Computationally efficient methodology for analysis of faulted power systems with series-compensated transmission lines: a phase coordinate approach

A capacitor in series with a transmission line is protected from overvoltage due to a large fault current by a nonlinear metal-oxide varistor (MOV) connected in parallel. Fault analysis, as well as the evaluation of performance of the transmission protection system, in the presence of MOV action becomes complex because 1) v-i characteristics of the MOV are nonlinear; 2) unsymmetrical MOV action for unsymmetrical faults will introduce coupling in sequence networks; and 3) MOV action will influence voltage or current inversion phenomenon. This paper presents a computationally efficient and simple methodology for fault analysis wherein the linear part of the network is modeled by an equivalent multiport Thevenin network. The proposed approach handles nonlinearity in fault analysis efficiently. It also provides an elegant approach to model unbalance in a network due to MOV action. The proposed approach can be used to determine relays prone to voltage or current inversion. Results on a real-life 716-bus Indian system illustrate the efficiency of the proposed approach.IEE

Min-Max Fair Power Flow Tracing for Transmission System Usage Cost Allocation: A Large System Perspective

Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage (TSU) cost and 2) loss (MW) cost for generator and load entities in the system. Recently, optimal power flow tracing methods have been proposed to "explicitly" model fairness constraints in the tracing framework. This paper, further, strengthens the tracing-compliant min-max fair cost allocation approach. The min-max model proposed in this paper is robust. It addresses concerns like scalability, numerical stability and termination in a finite number of steps while searching the optimal solution. We also propose a methodology to model DISCOMs and GENCOs as coalition within min-max framework. Case studies on an all India network of 1699 nodes and comparison with average participation and marginal participation methods bring out the better conflict resolution feature of the proposed approach. A method to model HVDC lines within the marginal participation scheme is also proposed. Quantitative and qualitative comparison of various TSU cost allocation methods on such a large system is another noteworthy contribution of the paper