Disturbance detecting current sensor
A power distribution monitoring system is provided that can include a number of features. The system can include a plurality of monitoring devices configured to attach to individual conductors on a power grid distribution network. In some embodiments, a monitoring device includes a current sensing element comprising a Rogowski coil. The output of the Rogowski coil can be used by a fault detection circuit to determine if a fault or disturbance occurs on the conductor. Methods of using the monitoring devices are also provided.
1. A method of sensing a fault or disturbance on a conductor of a power distribution network, comprising:
inducing a voltage in a Rogowski coil of a line monitoring device to produce a raw output;
inputting the raw output from the Rogowski coil into an integrator circuit of the line monitoring device to produce an integrated output;
inputting the raw output from the Rogowski coil into an all-pass filter of the line monitoring device to produce a filtered output;
subtracting the integrated output from the filtered output to produce a fault detection output; and
indicating that a fault or disturbance has occurred on the conductor if the fault detection output is a non-zero value.
2. The method of claim 1 , further comprising, prior to the inducing step, mounting the line monitoring device on the conductor.
3. The method of claim 1 , wherein the raw output of the Rogowski coil is proportional to a rate of change of current in the conductor.
4. The method of claim 1 , wherein a frequency response of the integrator circuit has a sloping gain and a constant phase shift of 90° over a frequency band of interest.
5. The method of claim 4 , wherein a frequency response of the all-pass filter has a sloping phase shift, with a phase shift of 90° at a fundamental frequency of the conductor, and a constant gain over the frequency band of interest.
6. The method of claim 1 , wherein the subtracting step is performed at a fundamental frequency of the conductor.
7. The method of claim 6 , wherein the fundamental frequency is 60 Hz.
8. The method of claim 6 , wherein the fundamental frequency is 50 Hz.
9. A line monitoring device configured to detect a fault or disturbance on a conductor of a power distribution network, comprising:
a housing configured to be mounted to the conductor;
a Rogowski coil disposed on or within the housing, wherein a voltage is induced in the Rogowski coil to produce a raw output when current flows through the conductor; and
a fault detection circuit disposed within the housing and being electrically coupled to the Rogowski coil, wherein the fault detection circuit comprises:
an integrator circuit configured to receive the raw output from the Rogowski coil and produce an integrated output;
an all-pass filter configured to receive the raw output from the Rogowski coil and produce a filtered output;
a summation circuit configured to subtract the integrated output from the filtered output to produce a fault detection output;
wherein the fault detection output indicates a fault or disturbance on the conductor if the fault detection output has a non-zero value.
10. The device of claim 9 , wherein the raw output of the Rogowski coil is proportional to a rate of change of current in the conductor.
11. The device of claim 9 , wherein a frequency response of the integrator circuit has a sloping gain and a constant phase shift of 90° over a frequency band of interest.
12. The device of claim 11 , wherein a frequency response of the all-pass filter has a sloping phase shift, with a phase shift of 90° at a fundamental frequency of the conductor, and a constant gain over the frequency band of interest.
13. The device of claim 9 , wherein subtracting is performed at a fundamental frequency of the conductor.
14. The device of claim 13 , wherein the fundamental frequency is 60 Hz.
15. The device of claim 13 , wherein the fundamental frequency is 50 Hz.
16. A fault detection system, comprising:
a conductor of a power distribution network;
a housing configured to be mounted to the conductor;
a Rogowski coil disposed on or within the housing, wherein the conductor is configured to induce a voltage in the Rogowski coil to produce a raw output when current flows through the conductor; and
a fault detection circuit disposed within the housing and being electrically coupled to the Rogowski coil, wherein the fault detection circuit comprises:
an integrator circuit configured to receive the raw output from the Rogowski coil and produce an integrated output;
an all-pass filter configured to receive the raw output from the Rogowski coil and produce a filtered output;
a summation circuit configured to subtract the integrated output from the filtered output to produce a fault detection output;
wherein the fault detection output indicates a fault or disturbance on the conductor if the fault detection output has a non-zero value.