Pre-fault Measurements Research Articles

A Real-Time Self-Healing Methodology Using Model- and Measurement-Based Islanding Algorithms

In this paper, a new real-time defensive islanding method, which is adaptive to the operating conditions is proposed. In the method, a number of candidate islanding schemes are generated using both model- and measurement-based islanding algorithms after detecting a severe fault in the system by means of a new severity index based on generator bus voltage frequency measurements. Of model-based algorithms, slow coherency-based islanding, in which the prefault measurements are utilized, is adopted. On the other hand, ${K}$ -means, hierarchical, and fuzzy relational eigenvector centrality-based clustering are employed as measurement-based islanding algorithms, where the postfault measurements of the evolving dynamics after the severe fault are utilized. A faster-than-real-time software platform is, then, employed to validate the success of the candidate schemes in healing the system. Among the successful schemes, the one resulting in the least load imbalance is chosen to be applied. All the computations from the detection of the fault to the application of islanding are performed in real-time, directly after the occurrence of the fault. The proposed method is demonstrated on the 37-generator 127-bus WSCC power test system, and on a model of the Turkish power system to assess the method’s performance.

Transient-Based Fault Location on Three-Terminal and Tapped Transmission Lines Not Requiring Line Parameters

In this paper, fault location on three-terminal and tapped transmission lines without requiring line parameters is presented, which mitigates the effect of line parameter variations due to weather and loading conditions on fault-location accuracy. For three-terminal lines, a fault-location method is presented, which utilizes postfault measurements of all three terminals. For tapped lines, two methods are presented. The first one uses postfault measurements of the main two terminals. The second one needs one cycle of prefault measurements at the main terminals as well. Synchronized transient-based measurements are used in methods proposed in this paper. In all of the presented methods, the fault-location problem is converted to an optimization problem and then solved to find the line parameters and the accurate location of the fault. The simulations are carried out by alternative transients program/electromagnetic transients program (ATP/EMTP) software, and the presented algorithms are executed by MATLAB. Simulation results assess the effects of fault resistance, type, and inception angle on the accuracy of the presented methods. Further discussion is also provided on the impacts of synchronization errors, noisy measurements, and nonresistive faults.

Indirect Power-System Contingency Screening for Real-Time Applications Based on PCA

This letter introduces the application of a data mining method with the purpose of contingency screening, by rapid recognition of hazardous, reoccurring power-system operating conditions. The method, suitable for real-time applications, is demonstrated on the north-western part of the Slovenian power-system, for first-swing stability issues. The presented demonstration consists of two steps: First, a database containing a set of prefault operating states and the corresponding critical clearing times of several contingencies is constructed. Second, the prefault measurements matrix is decomposed using the principal component analysis method and represented in a coordinate system, defined by the principal components. Since operating states form dense clusters of points in this coordinate system, the similarity between current and past conditions is established by identifying the shortest Euclidean distance metric. In this manner, the indication of each contingency impact is provided rapidly as long as a similar operating state exists within the database. Otherwise, the case is thoroughly investigated and included in the database. This approach is applicable to a wide spectrum of dynamic problems, providing that problem-relevant sets of input data are considered.

Locating faults in parallel transmission lines under availability of complete measurements at one end

Fault location in parallel transmission lines with availability of complete measurements from one end of the lines is considered. Generalised models of fault loops and faults are used for formulation of the fault location algorithm. The derived algorithm has a very simple first-order formula and does not require knowledge of impedances of the equivalent systems behind the line terminals as well as use of pre-fault measurements. Application of the fault location algorithm to impedance measurement of the adaptive distance protection is considered. An issue of improving the fault location accuracy by compensating for shunt capacitances of the lines is addressed. Results of the evaluation with use of ATP–EMTP simulations are reported and discussed.