Directional UAV Localization of Power Line Ultraviolet Corona

The electrical transmission lines used to transmit power are optimized for 50 to 60 Hz waveforms, but are suitable for waveforms of higher frequencies, into the megahertz range. Therefore, powerline conductors are capable of transmitting signals which could be used for geolocation. Indeed, frequencies in the 100 kHz range are used for diagnostic purposes in contemporary power grids today. Signals transmitted in this band are used to verify the operation of sites along the power grid, are used to configure the power grid (for example, throw a circuit breaker). The technology takes advantage of the suitability of electrical conductors employed in power transmission for signal transmission in the sub-megahertz range, and, in the preferred embodiment, utilizes the existing diagnostics signals in this range for geolocation.

Langley has developed various technologies to enable the portable detection system, including: - 3-inch electret condenser microphone - unprecedented sensitivity of -45 dB/Hz - compact nonporous windscreen - suitable for replacing spatially demanding soaker hoses in current use - infrasonic calibrator for field use - piston phone with a test signal of 110 dB at 14Hz. - laboratory calibration apparatus - to very low frequencies - vacuum isolation vessel - sufficiently anechoic to permit measurement of background noise in microphones at frequencies down to a few Hz - mobile source for reference - a Helmholtz resonator that provides pure tone at 19 Hz The NASA system uses a three-element array in the field to locate sources of infrasound and their direction. This information has been correlated with PIREPs available in real time via the Internet, with 10 examples of good correlation.

The tester was designed to monitor electrical faults in either online or offline modes of operation. In the online mode, wires are monitored without disturbing their normal operation. A cable can be monitored several times per second in the offline mode, and once per second in the online mode. The online cable fault locator not only detects the occurrence of a fault, but also determines the type of fault (short/open/intermittent) and the location of the fault. This enables the detection of intermittent faults that can be repaired before they become serious problems. Since intermittent faults occur mainly during operations, a built-in memory device stores all relevant fault data. This data can be displayed in real time or retrieved later so maintenance and repairs can be completed without spending countless hours attempting to pinpoint the source of the problem. Hardware and algorithms have also been developed to safely, efficiently, and autonomously transfer electrical power and data connectivity from an identified damaged/defective wire in a cable to an alternate wire path. This portion of the system consists of master and slave units that provide the diagnostic and rerouting capabilities. A test pulse generated by the master unit is sent down an active wire being monitored by the slave unit. When the slave unit detects the test pulse, it routes the pulse back to the master unit through a communication wire. When the master unit determines that a test pulse is not being returned, it designates that wire as faulty and reroutes the circuit to a spare wire.

Increasing demand for smaller UAVs (e.g., sometimes with wingspans on the order of six inches and weighing less than one pound) generated a need for much smaller flight and sensing equipment. NASA Langley's new sensing and flight control system for small UAVs includes both an active flight control board and an avionics sensor board. Together, these compare the status of the UAVs position, heading, and orientation with the pre-programmed data to determine and apply the flight control inputs needed to maintain the desired course. To satisfy the small form-factor system requirements, micro-electro-mechanical systems (MEMS) are used to realize the various flight control sensing devices. MEMS-based devices are commercially available single-chip devices that lend themselves to easy integration onto a circuit board. The system uses less energy than current systems, allowing solar panels planted on the vehicle to generate the systems power. While the lightweight technology was designed for smaller UAVs, the sensors could be distributed throughout larger UAVs, depending on the application.

This technology utilizes the U.S. high-voltage power transmission grid system as an extremely large antenna to extract unprecedented spatiotemporal space physical and geological information from distributed GIC observations. GICs are measured using differential a magnetometer technique involving one fluxgate magnetometer under the transmission line and another reference magnetometer station nearby. The reference station allows subtraction of the natural field from the line measurement, leaving only the GIC-related Biot-Savart field. This allows inversion of the GIC amplitude. The magnetometer stations are designed to operate autonomously. They are low-cost, enabling large scale application with a large number of measurement locations.