Dynamic Thresholds for a Reliable Diagnosis of Switched Systems

Safety, availability and reliability are the main concern of many industries. Thus, fault detection and isolation of industrial machines, which are in most cases switched systems, is a primary task in many companies. The presented paper proposes a new diagnostic approach for switched systems using two powerful tools: bond graph and observer. A diagnostic layer detects model errors using bond graph, and a smart algorithm identifies and locates faults using observer. Although observers serve as fault detectors, they also have their own errors caused by convergence delay of calculations; even in the case of no sensor defect, the residue does not converge to zero. In this paper, we propose a new method to solve this problem by integrating dynamic thresholds in the detection procedure, which helped to avoid false alarms and ensure a highly reliable diagnosis.

Improvement of the technical excellence of multiparameter relay protection by combining the signals of the measuring fault detectors using artificial intelligence methods

The features of the dielectric rod defects and the rod-electrod defects of polymer insulators were investigated by using the developed complex method of contactless remote diagnostics of high-voltage insulators health, which includes the initial detection of local areas with elevated electric field gradients as well as measurement of a set of partial discharges characteristics. The radiation of extra-large partial discharges was detected and partial discharges features were investigated. According to the measurement results, a diagram was constructed for the electro-physical processes that accompany the emission of extra-large partial discharges; and the reasons for their occurrence were established.

Development of the logical part of the intellectual multi-parameter relay protection

The issues of increasing the sensitivity and reliability of multi-parameter relay protection by sharing more than one information feature (current module, voltage module and phase, active and reactive power) are considered. In this case, the response parameters of individual one-dimensional measuring fault detectors based on the accumulation of statistical data during simulation in the Matlab / Similink software package are determined. A method for combining the signals of one-dimensional measuring fault detectors to increase the sensitivity of protection is proposed. The reliability of the organization of the logical part of multi-parameter relay protection was estimated using the theory of Markov processes, the principles of “2 out of 3” and “1 out of 2”.

Fault Detection for Message Passing Systems

Many crucial dependable and secure services including atomic commitment, consensus and group membership, and middleware services (such as replica, communication and transaction services) use fault detectors. Through the use of fault detectors, the overlying service can be exempted from failure treatment and synchronization requirements. Fault detection is essential for proving that the services carried out are correct. In this paper, we first identify the necessary conditions to detect faults in a message passing system where multiple disjoint paths exist between each pair of endpoints. We then present the first fault detection protocol capable of detecting message meta-data modification in the presence of various message interferences in addition to other faults including omission faults, message replay and spurious messages using disjoint paths, where paths with faults are not known a priori. In addition, it authenticates message origins allowing Sybil attacks to be detected, identifies faulty paths, and classifies faults in the presence of multiple messages sent by various system processes. We establish the completeness and soundness properties of the proposed algorithm, i.e., it detects each considered fault and each detected fault is an actual fault, respectively. We also show that our algorithm does not yield a significant packet size and delay overheads. The algorithm shows the viability of the use of disjoint paths in fault detection.