Perikles D. Bourkas

A Wildfire Model for the Estimation of the Temperature Rise of an Overhead Line Conductor

Fires in open land covered with grass, brush, or timber are often called wildfires. During a wildfire, the overhead conductors of a passing through distribution line suffer a thermal stress that deteriorates their mechanical properties. This paper presents a fire model that allows the estimation of the temperature rise of the conductors if we know some characteristics of the fire. The knowledge of the temperature rise is necessary for the study of the effects on the overhead line conductors.

Thermal Effect of the Recloser Operation Cycle on Bare Overhead Conductors

A new calculation method of the temperature rise generated from multiple (consecutive) short circuits, to which bare overhead conductors are subjected, is proposed in this paper. Multiple short circuits are common in medium-voltage lines protected by reclosers due to their operation cycle. The proposed method treats each short circuit as a separate event. In additiony, the cooling between each short circuit is taken into account. The results of the proposed method are compared to the results given by the method of the IEC 60865-1 standard. The application of the proposed method results in greater temperature rises when the equivalent thermal current density is greater than a threshold. Furthermore, alterations to the recloser operation cycle are performed in order to investigate its effect on the generated temperature rise, namely, alterations to the reclosing interval between successive tripping operations and the ratio of fast to delayed trips. Finally, the proposed method was compared to an exact numerical solution of the heating process.

High-Voltage Lines in Fire Environment

This letter concerns the change in bending which can manifest in a high-voltage line, when it lies in a fire environment. It is shown that in the case where aluminum conductors steel-reinforced conductors attain a temperature of more than 500°C, a drastic fall of the steel core mechanical strength occurs, resulting in permanent elongation of the line which drastically decreases the clearance from the underlying vegetation.

Magnetic-Field Measurements Near Two-Pole-Type Distribution Substations

This paper presents the mean values of the resulting magnetic field in the low-frequency range, which were recorded during spring and summer near two-pole-type distribution substations in urban areas. The mitigation of the magnetic field that was achieved after covering the low-voltage (LV) fuse boxes with thin aluminum plates is also presented. The mean attenuation achieved is approximately 23% during spring and 18% during the summer at the region of up to 30 cm from the substations and at a height of 1.0 m from the ground, at the measuring points near the LV fuse boxes. All of the measured magnetic-field values that were observed were lower in comparison with those specified as limits and introduced by ICNIRP.

PROTECTIVE MEASURES AGAINST ELECTRICAL HAZARDS OF CONSUMER INSTALLATIONS

The protection system of a home electrical installation concerns exclusively the private consumer himself and all necessary measures insuring its proper and safe operation is his own responsibility. Electrical installations with an inadequate protection system in conjunction with unforeseeable events like the abruption of an overhead power line have often caused fatal accidents and property damage. The aim of this paper is to focus on such events and to propose measures to prevent similar accidents in the future.

Partial Discharges Measurements on Coated and Non-Coated Solid Dielectric in Air

In this work, high voltage pulses of the form 1.2/50μs were applied on a metal tip solid dielectric metal plate combination in the air using coated and non coated specimens in order to investigate the reduction of partial discharges. The measurements indicated the effect of the coating, as it reduces the partial discharges on the dielectric.