Angel G. Mata

Direct Lightning Strikes to Test Power Distribution Lines—Part I: Experiment and Overall Results

The interaction of rocket-triggered lightning with two unenergized power distribution lines of about 800 m length was studied at the International Center for Lightning Research and Testing in Florida. A horizontally configured line was tested in 2000, and a vertically configured line in 2001, 2002, and 2003. The horizontally and vertically configured lines were equipped with six and four arrester stations, respectively, and, additionally, in 2003, the vertical line with a pole-mounted transformer. During the 2000, 2001, and 2002 experiments, arresters were frequently rendered inoperable by disconnector operation during triggered lightning strokes, but there was no disconnector operation during the 2003 experiment when the transformer was on the line. In all four years, there were commonly flashovers from the struck phase-conductor to the closest phase-conductor not subjected to direct lightning current injection. The self-consistency of measurements is assessed via comparison of the injected lightning current with: 1) the total current flowing to Earth through the multiple line groundings and 2) the total phase-to-neutral current flowing through the line arresters and line terminations. This paper is part one of two related papers.

Direct Lightning Strikes to Test Power Distribution Lines—Part II: Measured and Modeled Current Division Among Multiple Arresters and Grounds

The division of return stroke current among the arresters and groundings of two unenergized test distribution lines, one horizontally configured and the other vertically configured, was studied at the International Center for Lightning Research and Testing in Florida. The division of return stroke currents for the vertically configured line was initially similar to the division on the horizontally configured line: at the time the return stroke current reached peak value (after one microsecond, or so) the two closest arresters/grounds on both lines passed about 90% of the total current. However, the time during which the return stroke current flowed primarily through the closest arresters to the neutral conductor was significantly shorter on the vertically configured line. On that line, the arrester current was about equally divided among all four arresters after several tens of microseconds. The arrester current division as a function of time measured on the vertical line was successfully modeled using the published VI-characteristic, while the division on the horizontal line after some tens of microseconds was only successfully modeled if the residual voltage of the two arresters closest to the current injection point was reduced by 20%. Based on the triggered lightning current division observed on our line, the minimum energy absorbed in each of the two arresters closest to the strike point during a typical natural first stroke is estimated to be 40 kJ.

A new comprehensive lightning instrumentation system for pad 39B at the Kennedy Space Center, Florida

A new comprehensive lightning instrumentation system has been designed for Launch Complex 39B at the Kennedy Space Center, Florida. This new instrumentation system includes the synchronized recording of six high-speed video cameras; currents through the nine downconductors of the new lightning protection system; four dH/dt, 3-axis measurement stations; and five dE/dt stations composed of two antennas each. The instrumentation system is composed of centralized transient recorders and digitizers that are located close to the sensors in the field. The sensors and transient recorders communicate via optical fiber. Sensor outputs are sampled by fiber-optic digitizers, which transmit the digitized data to transient recorders via fiber optics. The transient recorders are triggered by the dH/dt sensors, the dE/dt sensors, or the current through the downlead conductors. The high-speed cameras are triggered by the trigger output of one of the transient recorders when any of the recorders perceive a qualified trigger.

Lightning Current Measurement with Fiber-Optic Sensor

A fiber-optic current sensor is successfully developed with many potential applications for electric current measurement. Originally developed for in-flight lightning measurement, the sensor utilizes Faraday Effect in an optical fiber. The Faraday Effect causes linear light polarization in a fiber to rotate when the fiber is exposed to a magnetic field. The polarization change is detected using a reflective polarimetric scheme. Forming fiber loops and applying Amperes law, measuring the total light rotation results in the determination of the total current enclosed. The sensor is conformable to complex structure geometry. It is also non-conductive and immune to electromagnetic interference, saturation or hysteresis. Installation is non-intrusive, and the sensor can be safely routed through flammable areas. Two similar sensor systems are described in this paper. The first system operates at 1310nm laser wavelength and is capable of measuring approximately 300 A - 300 kA, a 60 dB range. Laboratory validation results of aircraft lighting direct and in-direct effect current amplitudes are reported for this sensor. The second system operates at 1550nm wavelength and can measure about 400 A - 400 kA. Triggered-lightning measurement data are presented for this system. Good results are achieved in all cases.