Dedução de funções de alívio para estimar a influência de medidas de chaveamento na eliminação de sobrecargas a partir da técnica de injeção reversa

Abstract

Derivation and Tests of Relief Functions to Estimate the Influence of Switching Measures in the Elimination of Overloads by Using Backward InjectionEventually, violations of voltage limits at buses or admissible loadings of transmission lines and/or power transformers may occur by the power system operation. If violations are detected in the supervision process, corrective measures may be carried out in order to eliminate them or to reduce their intensity. Loading restriction is an extreme solution and should only be adopted as the last control action. Previous researches have shown that it is possible to control constraints in electrical systems by changing the network topology, using the technique named Corrective Switching, which requires no additional costs. In previous works, the proposed calculations for verifying the ability of a switching variant in eliminating an overload in a specific branch were based on network reduction or heuristic analysis. The purpose of this work is to develop analytical derivation of linear equations to estimate current changes in overloaded branches (due to switching measures) by means of few calculations. For busbar coupling, derivations will be based on Short-circuit the-

Impact of Corrective Switching in Wind Farms Operation

“…It produces power redistribution in all network branches. According to [6]- [10], it is possible to develop a relief functions based on circuit analysis. The equivalent circuit is presented in Figure 3.…”

“…Considering the circuit showed in this figure, it is necessary to calculate impedances Z der , Z ser , Z P and Z switch , since it is known I re (rerouted current), I re S (part of I re flowing to switching node S), I re V (part of I re S flowing through the circuit breaker that links bus-bar S and S'), Z AB (impedance on overloaded branch), V re AA' (voltage difference between nodes A and A' for overload rerouting case) e V re A'B (voltage difference between nodes A' and B for overload rerouting case). According to [6]- [10], circuit impedances in Figure 3 are obtained using (1), (2), (3), (4) and (5).…”

“…In this circuit, I switch is current flowing through the circuit breaker that links bus-bars on switching node S. This current is obtained from load flow calculation on base case. Current variation on branch A-B after switching variant realizations is calculated by (6), where impedance Z 1 is calculated using (7). In (8), it is calculated I AB ABTSN , current on branch after splitting buses S and S'.…”

“…It is noteworthy that the relief functions presented in [3]- [5] were heuristically developed, without considering the reactive power in the system. Later, the relief functions incorporating the reactive power were derived in [6]- [10].…”

“…Representation of a power system equivalent for simulating overload rerouting with bus-bars coupled.An evolution of [3]-[5] was developed in[6]-[10] which presented relief functions derived analytically, considering reactive power effects.Figure 2sketches this situation. In this figure, I AB is the loading of the overloaded branch in base case; I nom corresponds to the rated current of the branch; I sob means the branch overload; I re refers to the rerouted current, I Switch is the switching current, I s re refers to the part of I re flowing to node S; I v re is the part of I s re flowing through the circuit breaker.…”