One of the main factors that may limit the penetration level of distributed generation (DG) in typical distribution systems is the steady-state voltage rise. The maximum amount of active power supplied by distributed generators into each system bus without causing voltage violations can be determined by using repetitive power flow studies. However, this task is laborious and usually time-consuming, since different loading level and generation operation modes have to be evaluated. Therefore this article presents a method that, based on only one power flow solution and one matrix operation, can directly determine the maximum power that can be injected by distributed generators into each system bus without leading to steady-state voltage violations. This method is based on the determination of voltage sensitivities from a linearised power system model. In addition, this article proposes a numerical index to quantify the responsibility of each generator for the voltage level rise in a multi-DG system. Based on this index, utility managers can decide which generators, and in which degree, should be penalised by the voltage rise or rewarded by not depreciating the voltage profile. The method is applied to a 70-bus distribution network. The results are compared with those obtained by repetitive power flow solutions in order to validate the proposed method.

This paper presents a numerical method for observability analysis and restoration in power system state estimation based on Gram matrix factorization. A method to identify observable islands based on minimum norm solutions is also presented. The method has the advantage of being easy to implement because all information used for the new formulation can be extracted or adapted from operations that are present in conventional state estimation. The observability analysis and restoration are performed in a single step in which measurements and pseudo-measurements are processed. If the system is nonobservable, minimum norm solutions obtained with nonredundant measurements are used to identify observable islands and, in the sequel, with the results of Gram matrix factorization, a set of nonredundant injection measurements that restore the global observability of the system is obtained. This approach is an alternative to the classical observability analysis and results in methods that are robust and suitable to be used in real-time applications. Numerical examples to show the performance of the methods are presented.

This study presents an approach based on short‐circuit theory and on modern monitoring infrastructure for locating permanent and temporary faults in power distribution systems. The main innovative aspects of the proposed approach are: (i) no fault classification is required if phasor measurements are adopted, (ii) both current and voltage measurements may be included in the problem, (iii) in the fault location criterion the measurements are weighted according to their proximity to the fault location, (iv) a refinement scheme allows finding the fault on branches and not only at buses. The proposed approach can cope with magnitude measurements, synchronised phasors obtained via micro phasor measurement unit and unsynchronised phasors, which are being used for the first time for fault location purposes. Case studies are carried out considering a real 134‐bus feeder. Initially, the performance of the proposed approach is assessed with respect to fault location, fault type and fault resistance. Next, studies regarding the influence of the number, position and type of measurements are presented. Statistical simulations are performed for assessing the influence of the random errors inherent to measurements, load forecasting and distribution system parameters. The results indicate that the proposed approach is accurate and very promising.