Abstract: A system for detecting a fault occurred within a substation and judging a location of the fault including optical current sensors each having a Faraday element arranged on a top of an insulator post of a bus disconnecting switch, a magnetic core arranged to surround a terminal plate of the disconnecting switch to generate a magnetic field corresponding to a current passing through the terminal plate, a laser diode for emitting a laser light beam, an optical fiber for guiding the laser beam to the Faraday element, a photodiode, and an optical fiber for guiding the laser beam transmitted through the Faraday element to the photodiode. The photodiode supplies a signal representing the current passing through the terminal plate to a fault location judging circuit in which the fault location within the substation is judged from the signals from the photodiodes.

Abstract: An excellent optical fiber built-in type composite insulator including at least two insulator bodies each having a penetration bore, at least one optical fiber inserted in the penetration bores, and sealing structures for the penetration bores of the insulator bodies and for a joining layer of opposing end surfaces of adjacent insulator bodies, is provided, which effectively prevents leakage of inner silicone grease, bending and breakage of the optical fiber, leakage of electric current along the penetration bores, short circuited trouble, and destruction of the insulator bodies, improves joining strength of the opposing end surfaces of the insulator bodies, and maintains the joining strength for a long period, affords a change of numbers of the insulator bodies, and facilitates the production. A method of producing such composite insulator is also provided.

Abstract: An excellent optical fiber built-in type composite insulator including at least two insulator bodies each having a penetration bore, at least one optical fiber inserted in the penetration bores, and sealing structures for the penetration bores of the insulator bodies and for a joining layer of opposing end surfaces of adjacent insulator bodies, is provided, which effectively prevents leakage of inner silicone grease, bending and breakage of the optical fiber, leakage of electric current along the penetration bores, short circuited trouble, and destruction of the insulator bodies, improves joining strength of the opposing end surfaces of the insulator bodies, and maintains the joining strength for a long period, affords a change of numbers of the insulator bodies, and facilitates the production. A method of producing such composite insulator is also provided.

Abstract: Optical fiber-containing insulators each comprises an insulator body having a through hole provided in its central portion and extending along an axial direction thereof, an optical fiber core wire passing through the through hole, an insulating material filled between an inner peripheral surface of the through hole and the optical fiber core wire, and arrangements for preventing the filled insulating material from axially protruding out of the insulator body even at high temperature or spacers for holding the optical fiber core wire at the central portion of the through hole of the insulator body.

Abstract: A work helmet for effecting an intercommunication between workers as well as between a central control room and respective workers, especially used for informing each workers of guide information adequate for emergency escape when a disaster occurs is disclosed. To this end, the work helmet includes a light-receiving element for receiving a light signal modulated with the guide information, an earphone for reproducing audibly the guide information, a light emitting element for emitting an outgoing light signal modulated with a speech signal supplied from a microphone, and an oscillator for generating a carrier having a frequency specific to the helmet, on which carrier said speech signal is modulated, so that the outgoing light signal is always modulated by the carrier serving as a helmet identifying signal by means of which the central control room can recognize and identify the worker wearing the helmet.