SENSOR VOLTAGE PHASE ANGLE CORRECTION
A monitoring system is provided for correcting phase angle errors using an accurate current sensor such as a current transformer, or Rogowski coil. Using an accurate source of time and communication, such as a cellular or mesh radio, this correction can then be applied across a fleet of sensors within a range (governed by wave propagation speed of electricity) and between transformers.
1 . A method of collecting and characterizing phase measurements of a power network, comprising:
receiving current magnitude and phase measurements from a plurality of line monitoring devices prior to an active switching event on the power network;
receiving current magnitude and phase measurements from the plurality of line monitoring devices after the active switching event on the power network;
estimating optimal phase angles for each phase of the power network;
determining an error correction value for the phase measurements; and
correcting the estimated optimal phase angles for each phase of the power network with the error correction value.
2 . The method of claim 1 , further comprising collecting current magnitude and electric field phase measurements from the power network with the plurality of line monitoring devices.
3 . The method of claim 2 , wherein collecting the phase measurements comprises measuring an electric field of conductors of the power network.
4 . The method of claim 2 , wherein collecting the phase measurements comprises measuring a current of conductors of the power network.
5 . The method of claim 2 , wherein collecting the phase measurements comprises measuring a voltage of conductors of the power network.
6 . The method of claim 1 , wherein the active switching event is the result of a capacitor bank operating on the power network.
7 . The method of claim 1 , wherein the active switching event is the result of a recloser operating on the power network.
8 . The method of claim 1 , wherein the active switching event is the result of a switch operating on the power network.
9 . The method of claim 1 , wherein the optimal phase angles are spaced 120 degrees apart.
10 . The method of claim 1 , wherein estimating optimal phase angles for each phase of the power network further comprises:
rotating each of the phase measurements by a rotation angle that places a B-phase value at 180 degrees;
averaging the rotated B-phase value, a rotated A-phase value, and a rotated C-phase value;
determining a new estimate for the B-phase value from the averaged rotated B-phase, A-phase, and C-phase values;
determining a new estimate for the A-phase value and the C-phase value from the new estimate for the B-phase value; and
removing the rotation angle from each of the new estimates.
11 . The method of claim 1 , where in the correction value is a constant phase error between an approximated voltage and a true voltage.
12 . A non-transitory computing device readable medium having instructions stored thereon, wherein the instructions are executable by a processor to cause a computing device to perform a method comprising:
receive current magnitude and phase measurements from a plurality of line monitoring devices prior to an active switching event on the power network;
receive current magnitude and phase measurements from the plurality of line monitoring devices after the active switching event on the power network;
estimate optimal phase angles for each phase of the power network;
determine an error correction value for the phase measurements; and
correct the estimated optimal phase angles for each phase of the power network with the error correction value.
13 . A power line monitoring system, comprising:
a plurality of line monitoring devices configured to collect current magnitude and phase measurements for each phase of a power network before and after an active switching event; and
a remote computing device configured to receive the current magnitude and phase measurements from the plurality of line monitoring devices, the remote computing device being configured to:
estimate optimal phase angles for each phase of the power network;
determine an error correction value for the phase measurements; and
correct the estimated optimal phase angles for each phase of the power network with the error correction value.