Testing of the OBO Bettermann Peak Current Sensor System for Lawrence Livermore National Laboratory

Schoene, J ; Uman, M A ; Aurele, M ; Rambo, K J ; Jerauld, J E ; Schnetzer, G

Lawrence Livermore National Laboratory

关键词: Lawrence Livermore National Laboratory;    Testing;    Magnetic Fields;    Spark Gaps;    Lightning;   

DOI  :  10.2172/15014497
RP-ID  :  UCRL-SR-209203
RP-ID  :  W-7405-ENG-48
RP-ID  :  15014497

美国|英语

来源: UNT Digital Library

【 摘 要 】

During summer 2004 we studied the reliability of the OBO Bettermann peak current sensor (PCS) monitoring system - (1) credit card-type cards with magnetic strips and (2) a card reader. Three methods were used to generate current for testing the PCS system: (1) a Keytek current generator (2) a capacitor discharge, and (3) rocket triggered lightning. The data obtained from the cards were compared with oscilloscope measurements of the generated currents. Additionally, we tested for nearby natural and nearby rocket triggered lightning by placing cards on an airport runway lighting system lightning-protection counterpoise, on power line grounds, and on the lightning-protection system of an explosive storage igloo at Camp Blanding Army National Guard Base. In all experiments exposed cards were read multiple times to test the consistency of the measurement. Each card read zero before each experiment. The Keytek current generator produced a maximum peak current of 5 kA which was unrecorded by the PCS system despite the OBO Bettermann claim that currents larger than 3 kA could be recorded. Three cards were exposed to triggered lightning current and gave proper results (the PCS card measurement deviated less than +- 2 kA from the peak current value measured by research equipment). Cards exposed to the current of the capacitor discharge, which was initiated by triggering a spark gap, generally yielded current readings about four times higher than the actual value, but proper readings were observed with some card orientations and locations. Two of the 7 cards tested with the Keytek and 4 of the 17 cards placed on the explosive storage igloo and on the runway counterpoise yielded non-zero current on some readings and zero current on other readings, while all other cards in those locations produced zero current for all readings of the card. The cause of the apparently erroneously high current readings on the cards used in the capacitor discharge experiments is not understood, but the high values may well be related to (1) the direct electromagnetic radiation from the spark gap or from other parts of the current-carrying wire effecting the card's magnetic stripe in an unexpected way, and/or (2) the magnetic field from a potential short duration (nanosecond scale) breakdown current (not observable with our present instrumentation if indeed it does exists) in the current-carrying wire rather than from the oscillatory capacitor discharge current observed on the digitizing oscilloscope.