Method and apparatus for the identification of a faulty conductor in a multiple supply line
AssigneeEnertec
InventorIsabelle Heller
Life of this patent
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Abstract
A method of and apparatus for determining which if any phase of duplex supply lines wherein each phase w is assigned two conductors w1 and w2. The method and apparatus use an asymmetry value, for example a function of the relationship (output of 9) of the difference Iw1-Iw2 (output of 5) to the sum Iw1+Iw2 (output of 6) of the currents in the conductors w1 and w2. If the asymmetry level exceeds in absolute value a threshold level K(see 12 and 13), the conductor passing the current having the lowest amplitude is indicated as being sound.
Claims12
In an electricity supply line of at least two polyphase groups the respective phases of which may be connected in parallel at least at one end of the supply line, a method for determining in which polyphase group of conductors of the supply line is a conductor having a fault present thereon, including the steps of:
- establishing at a measurement point on the line, first and second current signals proportional to instantaneous values of current passing in first and second conductors which, respectively, belonging to first and second ones of the polyphase groups, are the conductors associated with a faulty phase;
- combining the first and second current signals to obtain processed signals, each one of said current signals having a modulus and a phase angle;
- generating a reference signal having a threshold level;
- combining said processed signals to obtain an intermediate signal having an asymmetry value corresponding to an asymmetry of distribution of current, between the first and second conductors, in a faulty phase, wherein said asymmetry value is proportional to the product, given by the cosine of the phase angle between the difference and the sum of the first and second current signals, and the modulus of the difference of the current signals expressed as a function of the modulus of their sum;
- comparing said intermediate signal level with said threshold level;
- and
- deriving at least a first output signal indicating as being sound the conductor associated with the current signal having the lowest modulus provided that said asymmetry value exceeds, in absolute value, said threshold level.
For an electricity supply line having at least two polyphase groups, respective phases of which may be connected in parallel at least at one end of said supply line, apparatus for determining in which polyphase group of conductors is a conductor having a fault which is present on a phase of said electricity supply line, including:
- means for detecting first and second current signals, each of said current signals having a modulus and phase angle;
- combining means for providing processed signals representative of a combination of said first and second current signals that are proportional respectively to instantaneous values of current passing through first and second conductors which, belonging respectively to first and second ones of said groups, are the conductors associated with a faulty phase;
- means for comparing a threshold level defining a value of asymmetry expressed as a function of said processed signals and representative of an asymmetry of distribution, between the first and second conductors, of current in a faulty phase, said asymmetry value being proportional to the product, given by the cosine of the phase angle between the difference and the sum of the first and second current signals, and the modulus of the difference of the current signals expressed as a function of the modulus of their sum;
- and
- means for deriving at least a first output signal indicating whether the conductor associated with the current signal having the lowest modulus is sound, subject to said asymmetry value exceeding, in absolute value, said threshold level.
Dependencies are inferred from the claim text.