Fault indicator for three-phase sheathed cable
First Claim
1. A fault indicator for sensing a fault current in a three phase three conductor sheathed cable of the type having first, second and third electrical conductors enclosed within the sheath, comprising:
- first, second and third magnetic pole pieces arranged outside of the sheath and primarily in magnetic fields surrounding said first, second and third conductors, respectively;
first, second and third magnetic windings in a magnetic communication with said first, second and third pole pieces, respectively, for developing first, second and third signals indicative of the current level in said first, second and third conductors, respectively; and
indicator circuit means responsive to said first, second and third signals for indicating the occurrence of a fault current in said first, second and third conductors.
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Accused Products
Abstract
A fault indicator for three phase sheathed cables includes a flexible collar unit which fits over the cable. Magnetic pole pieces within the collar unit having associated magnetic windings are aligned with the three conductors within the cable to produce signals indicative of the current level in each conductor. An alarm unit receives the signals and sounds an alarm in the event the current in any conductor exceeds a predetermined threshold level to indicate the occurrence of a fault. The voltage level of the current indicating signals may be utilized to align the magnetic core assemblies with the conductors.
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Citations
30 Claims
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1. A fault indicator for sensing a fault current in a three phase three conductor sheathed cable of the type having first, second and third electrical conductors enclosed within the sheath, comprising:
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first, second and third magnetic pole pieces arranged outside of the sheath and primarily in magnetic fields surrounding said first, second and third conductors, respectively;
first, second and third magnetic windings in a magnetic communication with said first, second and third pole pieces, respectively, for developing first, second and third signals indicative of the current level in said first, second and third conductors, respectively; and
indicator circuit means responsive to said first, second and third signals for indicating the occurrence of a fault current in said first, second and third conductors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A fault indicator for sensing a fault current in a three phase three conductor sheathed cable of the type having first, second and third conductors enclosed within a single overlying sheath, comprising:
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first, second and third magnetic sensors, each providing an output signal indicative of the amplitude of a sensed magnetic field, said sensors being arranged around the exterior of said sheath whereby said sensors are primarily in magnetic communication with respective ones of said first, second and third conductors; and
indicator circuit means responsive to said first, second and third signals for signaling the occurrence of a fault current in one or more of said conductors. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. A fault indicator for sensing a fault current in a three phase three conductor sheathed cable of the type having first, second and third electrical conductors enclosed within the sheath, comprising:
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first, second and third magnetic pickup assemblies arranged generally at 120°
intervals around the circumference of the cable sheath, said assemblies each being aligned with a respective one of said conductors and each providing an output signal indicative of the magnetic fields associated with said conductors;
said magnetic pickup assemblies each comprising a generally U-shaped magnetic pole piece having poles extending to either side of its associated conductor and a central portion, a magnetic winding on said central portion, and a rectifier circuit connected to said magnetic winding for providing an output signal indicative of the magnetic field developed in the pole piece by the associated conductor; and
indicator circuit means responsive to said first, second and third output signals for signaling the occurrence of a fault current in the conductor. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification