Fiber optic sensing system for grid-based assets
A sensor system includes a sensor network comprising at least one optical fiber having one or more optical sensors. At least one of the optical sensors is arranged to sense vibration of an electrical device and to produce a time variation in light output in response to the vibration. A detector generates an electrical time domain signal in response to the time variation in light output. An analyzer acquires a snapshot frequency component signal which comprises one or more time varying signals of frequency components of the time domain signal over a data acquisition time period. The analyzer detects a condition of the electrical device based on the snapshot frequency component signal.
1. A sensor system comprising:
a sensor network comprising at least one optical fiber that includes one or more optical sensors including at least one vibration sensor, the at least one vibration sensor disposed within a power grid electrical device and configured to sense vibration of the power grid electrical device;
at least one detector configured to generate an electrical time domain signal in response to a time variation in light output from the at least one vibration sensor; and
an analyzer configured to:
transform select sequential times of the electrical time domain signal into a plurality of frequency domain signals for each of the selected sequential times;
extract frequency components of the time domain signal from each of the plurality of frequency domain signals;
acquire one or more snapshot frequency component signals from the extracted frequency components, each snapshot frequency component signal comprising a time varying signal of the extracted frequency components of the time domain signal over a data acquisition time period; and
detect a presence or amount of a condition of the power grid electrical device based on the snapshot frequency component signal.
2. The system of claim 1 wherein the at least one vibration sensor or the optical fiber is rigidly attached to a component of the power grid electrical device.
3. The system of claim 2 wherein:
the power grid electrical device is an oil-filled transformer; and
the component of the oil-filled transformer comprises one of a core, an oil tank wall, an oil tank lid, a low voltage plate, and a frame of the oil-filled transformer.
4. The system of claim 2 wherein the at least one vibration sensor is mounted to two components of the power grid electrical device and arranged to sense relative movement of the two components.
5. The system of claim 2 wherein the optical fiber is mounted to two components of the power grid electrical device such that the at least one vibration sensor is disposed between the two components of the power grid electrical device.
6. The system of claim 5 wherein the power grid electrical device is a transformer and the two components are a first core and a second core of the transformer.
7. The system of claim 5 wherein the power grid electrical device is a transformer and the two components are a core and a frame of the transformer.
8. The system of claim 1 wherein the power grid electrical device is a transformer and the at least one vibration sensor is in oil within the transformer and is not rigidly attached to a transformer component.
9. The system of claim 1 wherein the sensor network also includes a temperature sensor.
10. The system of claim 1 wherein the power grid electrical device is an oil-filled transformer and the sensor network includes at least one temperature sensor positioned proximate to an oil tank wall of the oil-filled transformer.
11. The system of claim 1 wherein the power grid electrical device is and oil-filled transformer and the sensor network includes at least one temperature sensor positioned in a headspace above oil within the oil-filled transformer.
12. The system of claim 1 wherein the power grid electrical device is an oil-filled transformer and the sensor network includes at least one temperature sensor positioned proximate to a surface of oil within the oil-filled transformer.
13. The system of claim 1 wherein the power grid electrical device is an oil-filled transformer and the sensor network includes at least one temperature sensor positioned proximate to a bottom of an oil tank of the transformer.
14. The system of claim 1 wherein the power grid electrical device is a transformer and the sensor network includes at least one temperature sensor positioned proximate to a top of a coil of the transformer, proximate to a middle of the coil, and/or proximate a bottom of the coil.
15. The system of claim 1 , wherein the power grid electrical device is an oil-filled transformer and the sensor network includes an oil level sensor.
16. The system of claim 1 , wherein the sensor network includes one or more external sensors disposed external to the power grid electrical device.
17. The system of claim 16 , wherein the one or more external sensors comprise environmental sensors.
18. The system of claim 1 wherein the optical fiber is disposed on or in a rod inserted through an opening in a case of the power grid electrical device.
19. The system of claim 18 wherein the optical fiber includes at least one optical temperature sensor and at least one oil level sensor.
20. The system of claim 18 wherein the rod comprises polycarbonate.
21. The system of claim 18 wherein:
the power grid electrical device is a transformer;
the rod is mounted to an internal component of the transformer; and
the optical fiber exits the transformer through a plug fitting.
22. The system of claim 21 wherein:
a plug is disposed in the opening; and
the optical fiber is disposed through a hole in a plug.
23. The system of claim 22 wherein the opening is a national pipe tapered thread (NPT) opening and the plug is an NPT plug.
24. The system of claim 22 further comprising a hermetic seal configured to hermetically seal the hole in the plug.
25. The system of claim 1 , wherein the power grid electrical device comprises an oil-filled transformer, the oil-filled transformer comprising:
a transformer case configured to contain oil; and
insulation material including one or more oil ducts disposed within the transformer case; and
the at least one optical fiber extends at least partially through at least one of the oil ducts.