A Novel Arc Fault Detector for Early Detection of Electrical Fires

Arc faults can produce very high temperatures and can easily ignite combustible materials; thus, they represent one of the most important causes of electrical fires. The application of arc fault detection, as an emerging early fire detection technology, is required by the National Electrical Code to reduce the occurrence of electrical fires. However, the concealment, randomness and diversity of arc faults make them difficult to detect. To improve the accuracy of arc fault detection, a novel arc fault detector (AFD) is developed in this study. First, an experimental arc fault platform is built to study electrical fires. A high-frequency transducer and a current transducer are used to measure typical load signals of arc faults and normal states. After the common features of these signals are studied, high-frequency energy and current variations are extracted as an input eigenvector for use by an arc fault detection algorithm. Then, the detection algorithm based on a weighted least squares support vector machine is designed and successfully applied in a microprocessor. Finally, an AFD is developed. The test results show that the AFD can detect arc faults in a timely manner and interrupt the circuit power supply before electrical fires can occur. The AFD is not influenced by cross talk or transient processes, and the detection accuracy is very high. Hence, the AFD can be installed in low-voltage circuits to monitor circuit states in real-time to facilitate the early detection of electrical fires.

Electroclinical features of lateral and medial orbitofrontal epilepsy: a case series

To better understand the electroclinical features and epileptic network of lateral and medial orbitofrontal epilepsy (OFE). We evaluated four patients who had undergone epilepsy surgery. Epileptic foci in two patients originated from the lateral orbitofrontal cortex, and those in the other two originated from the medial orbitofrontal cortex, which was confirmed by stereoelectroencephalography (SEEG). Time-frequency spectrograms were also provided for assistance, and the change in high-frequency energy was superimposed on the 3D reconstructed brain with a colour code in order to more intuitively show the transfer of high-frequency energy as the seizure evolves. All patients underwent SEEG-guided radiofrequency thermocoagulation (RF-TC) or focal resection and achieved satisfactory results. Lateral OFE and medial OFE were relatively independent with regards to clinical symptoms and epileptic network, however, lateral OFE was likely to propagate to the dorsolateral frontal lobe, whereas medial OFE (gyrus rectus) was more likely to propagate to the medial temporal lobe or insular lobe with long duration. There were significant differences in duration (21.17 ± 11.5 vs. 127.22 ± 235.05) and early propagation time (7.92 ± 4.44 vs. 29.0 ± 33.47) between the two origins. A better understanding of the electroclinical features of lateral and medial OFE is helpful to understand their epileptic networks and perform accurate resections in order to protect the cognitive and behavioural functions of patients.