Method and device for detecting a ground-fault direction in an electric three-phase network
AssigneeNSE, Inc.
InventorAndreas Aebersold
Life of this patent
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Abstract
The invention relates to a method for ascertaining an earth fault and the earth-fault direction in a three-phase network which is operated in a compensated manner or in an insulated manner. Value pairs of a zero voltage and a zero current are measured, the active or reactive energy is calculated, and a voltage flag and a current flag are combined by a Boolean link, wherein the presence of a earth fault is ascertained depending on the result, and a decision is made as to whether the earth-fault direction is signalled as “forward” or “reverse” at least on the basis of the sign of the active or reactive energy.
Claims12
Method for ascertaining an earth fault and an earth-fault direction in a three-phase network operated in a compensated way, characterized by the steps of:
- a) using a measurement device adapted to do so, continuously measuring value pairs of a zero voltage and of a zero current with a given sample rate, wherein the value pairs are each attributed to a measurement time, and recording the determined value pairs and the attributed measurement time in a memory;
- and,
- using a calculation unit adapted to do so,
- b) continuously calculating an active energy by forming a product of the measured zero voltage and the measured zero current for each measurement time and forming a sum of a product which is attributed to the current measurement time and a number of preceding products,
- c) setting for the current measurement time a voltage flag to 1 if the attributed zero voltage is greater than a first threshold value and else to 0, and a current flag to 1 if the attributed zero current is greater than a second threshold value and else to 0,
- d) performing a Boolean AND-operation with the voltage flag and the current flag, for each current measurement time, wherein a result of the Boolean AND-operation is ON-delayed by a first time interval and release-delayed by a second time interval, wherein no earth fault is present in case of a result of 0 and an earth fault is present in case of a result of 1, and if an earth fault is present
- e) continuing to execute the steps a) to d) and verifying an algebraic sign of the active energy calculated up to the current measurement time, wherein a result of the verification is ON-delayed by a third time interval and release-delayed by a fourth time interval, and
- f) deciding at least on the basis of the algebraic sign of the active energy if the earth-fault direction is reported as “forward”, in case of a positive algebraic sign, or as “backward” in case of a negative algebraic sign.
Method for ascertaining a earth fault and an earth-fault direction in a three-phase network operated in an isolated way, characterized by the steps of:
- a) using a measurement device adapted to do so, continuously measuring value pairs of a zero voltage and of a zero current with a given sample rate, wherein the value pairs are each attributed to a measurement time, and recording the determined value pairs and the attributed measurement time in a memory;
- and,
- using a calculation unit adapted to do so,
- b) continuously calculating a reactive energy by forming a product of the measured zero voltage and the measured zero current for each measurement time and forming a sum of a product which is attributed to the current measurement time and a number of preceding products,
- c) setting for the current measurement time a voltage flag to 1 if the attributed zero voltage is greater than a first threshold value and else to 0, and a current flag to 1 if the attributed zero current is greater than a second threshold value and else to 0,
- d) performing a Boolean AND-operation with the voltage flag and the current flag, for each current measurement time, wherein a result of the Boolean AND-operation is ON-delayed by a first time interval and release-delayed by a second time interval, wherein no earth fault is present in case of a result of 0 and an earth fault is present in case of a result of 1, and if an earth fault is present
- e) continuing to execute the steps a) to d) and verifying an algebraic sign of the reactive energy calculated up to the current measurement time, wherein a result of the verification is ON-delayed by a third time interval and release-delayed by a fourth time interval, and
- f) deciding at least on the basis of the algebraic sign of the reactive energy if the earth fault direction is reported as “forward”, in case of a positive algebraic sign, or as “backward” in case of a negative algebraic sign.
Device for ascertaining an earth fault and an earth-fault direction in a three-phase network operated in a compensated way, characterized in that the device comprises at least a measurement device adapted to continuously measure value pairs of a zero voltage and of a zero current with a given sample rate, wherein the value pairs are each attributed to a measurement time, furthermore a memory for storing the determined value pairs and the attributed measurement time, and comprising a calculation unit, wherein the calculation unit is adapted
- to continuously calculate an active energy by forming a product of the measured zero voltage and the measured zero current for each measurement time and to calculate a sum of a product which is attributed to the current measurement time and a number of preceding products,
- to set for the current measurement time a voltage flag to 1 if the attributed zero voltage is greater than a first threshold value and else to 0, and a current flag to 1 if the attributed zero current is greater than a second threshold value and else to 0,
- to perform a Boolean AND-operation with the voltage flag and the current flag, for each current measurement time, wherein a result of the Boolean AND-operation is ON-delayed by a first time interval and release-delayed by a second time interval, wherein no earth fault is present in case of a result of 0 and an earth fault is present in case of a result of 1, and if an earth fault is present
- to verify an algebraic sign of the active energy calculated up to the current measurement time, wherein a result of the verification is ON-delayed by a third time interval and release-delayed by a fourth time interval, and
- to decide at least on the basis of the algebraic sign of the active energy if the earth fault direction is reported as “forward”, in case of a positive algebraic sign, or as “backward” in case of a negative algebraic sign.
Device for ascertaining an earth fault and an earth-fault direction in a three-phase network operated in an isolated way, characterized in that the device comprises at least a measurement device which is adapted to continuously measure value pairs of a zero voltage and of a zero current with a given sample rate, wherein the value pairs are each attributed to a measurement time, furthermore a memory for storing the determined value pairs and the attributed measurement time, and comprising a calculation unit, wherein the calculation unit is adapted
- to continuously calculate a reactive energy by forming a product of the measured zero voltage and of the measured zero current for each measurement time and to calculate a sum of a product which is attributed to the current measurement time and a number of preceding products,
- to set for the current measurement time a voltage flag to 1 if the attributed zero voltage is greater than a first threshold value and else to 0, and a current flag to 1 if the attributed zero current is greater than a second threshold value and else to 0,
- to perform a Boolean AND-operation with the voltage flag and the current flag, for each current measurement time, wherein a result of the Boolean AND-operation is ON-delayed by a first time interval and release-delayed by a second time interval, wherein no earth fault is present in case of a result of 0 and an earth fault is present in case of a result of 1, and if an earth fault is present
- to verify an algebraic sign of the reactive energy calculated up to the current measurement time, wherein a result of the verification is ON-delayed by a third time interval and release-delayed by a fourth time interval, and
- to decide at least on the basis of the algebraic sign of the reactive energy if the earth fault direction is reported as “forward”, in case of a positive algebraic sign, or as “backward” in case of a negative algebraic sign.
Dependencies are inferred from the claim text.