Abstract: A fault sensing electrical wire (411) utilized one or more sensor strips (407) which provide an impedance change when the wire is subject to an overtemperature condition or mechanical damage of the wire. A control unit (402) measures the impedance of the sensor strips of the fault sensing wire and provides a control signal (405) to initiate an alarm or protective action based on the severity of the condition. The control unit (402) may monitor a number of fault sensing sires simultaneously or in sequence. The apparatus may be used to sense an electrical arc occurring in the insulation of the wire.

Abstract: An optical fiber sensor, disposed in the insulation of a wire or cable, provides a means of detecting damage to the insulation of the wire or cable. An optical measurement device, such as an optical time domain reflectometer (OTDR), coupled to the sensor, detects the presence and location of a sensor fault or stress. The sensor is positioned between the conductor and the outside surface of the conductor so that the OTDR will sense damage before the conductor is exposed or contacted by a damage element.

Abstract: A fault sensing electrical wire (411) utilizes one or more sensor strips (407) which provide an impedance change when the wire is subject to an overtemperature condition or mechanical damage of the wire. A control unit (402) measures the impedance of the sensor strips of the fault sensing wire and provides a control signal (405) to initiate an alarm or protective action based on the severity of the condition. The control unit (402) may monitor a number of fault sensing wires simultaneously or in sequence. The apparatus may be used to sense an electrical arc occurring in the insulation of the wire.

Abstract: An electrical safety device comprises a sensor strip disposed in the insulation of a wire or in the insulation of a sheath enclosing a bundle of insulated electrical conductors. The sensor strip comprises a distributed overtemperature sensing portion comprising a conductive polymer having a positive temperature coefficient of resistivity which increases with temperature sufficient to result in a switching temperature. A mechanical damage sensing portion comprises a strip disposed in the sheath in a mechanical damage sensing pattern which becomes damaged or open upon mechanical damage of the sheath before the bundle of conductors are damaged. The overtemperature sensing portion and the mechanical damage sensing portion may be the same sensing strip disposed in the sheath and arranged in a helical relationship with a longitudinal axis of the sheath.

Abstract: An electrical safety device comprises a sensor strip disposed in the insulation of an electrical power cord or other electrical apparatus. The sensor strip is made of a conductive polymer with a positive temperature coefficient of resistivity which increases with temperature. The sensor strip forms a series connected loop connected to an impedance measuring circuit. A relay interrupts current to the conductors of the cord when the impedance of the sensor strip increases due to an overtemperature condition. The sensor strip is positioned between the conductors of the cord and the outside surface of the cord. The position of the sensor strip allows the strip to act as a mechanical damage sensor, opening the series connected loop before an energized conductor is exposed.