Lightning current tests on radars and similar structures

A lightning stroke presents a real challenge due to its potential to cause irreversible damage on electronics. Future systems are packaged in composite shielding materials, which give little or no protection with respect to the electromagnetic fields caused by a nearby strike. A direct lightning stroke is even a higher threat for densely packed electronics in composite housings. Our objective is to determine an appropriate level of protection for a direct stroke. From the military standard MIL-STD-464A - Severe Strike, peak currents of the discharge between 50 and 200 kA, for the A pulse, 2 kA for the B pulse and 200 to 800 Amps for the C pulse are re-created in a closed environment. Experiments have been carried out using a test setup that could duplicate these three discharge components on structures representative for radar housing

Lightning current test on radar system

With the extended use of very sensitive electronic components, in modern systems, the danger represented by a lightning stroke becomes something not to be neglected. The Long Range Radar requires protection not only against direct strike, but also against the indirect effects. The formulation of the military standard MIL-STD-464A Severe Strike confirms this need. The peak currents of the discharges are between 50 and 200 kA, for the A pulse, 2 kA for the B pulse and 200 to 800 Amps for the C pulse. For a radar system placed high on a ship, the chosen approach is the fictitious Rolling Sphere Technique in order to confirm the protection offered by the design. Experiments have been carried out using a test setup that could duplicate the three discharge components

Methods for estimation of the vacuum status in vacuum circuit breakers

In this paper several methods are described for the estimation of the pressure inside vacuum interrupters which have been in operation for many years. The methods are applicable without demounting the interrupters and use only electrical measuring techniques. According to these methods the vacuum circuit breakers are subjected to synthetic circuits, switch-off limited currents, either 10 A dc or 300 A ac. With the 10 A dc method the height of arc voltage spikes are measured and represented in a histogram. The shape of the histogram is discriminative for pressures below or above 10-2 Pa. Switching tests with currents of 200 to 400 A ac in inductive and capacitive circuits also showed different behavior for internal pressures below or above 10-1 Pa. A three phase 200 A test device with a 10 kV recovery voltage, fed from a standard 380 V supply, showed similar result

An optimized BSCCO/Ag resonator coil for utility use

AC coils made with BSCCO-2223/Ag tapes and operating in liquid nitrogen have a potential for power related applications, e.g., inductors, transformers and current limiters. High-Tc tapes are available from several producers, while access to the coil building know-help is still rather limited, The relevant knowledge and technology suitable for making HTS coils for 50-60 Hz operation is being developed as a part of the current project. To verify the technology, several test solenoids and a first full-scale sub-coil have been manufactured. Electromagnetic, thermal and mechanical analysis of the coils is performed. The electromagnetic analysis focuses on the reduction of the radial magnetic field component in the windings. Voltage-current characteristics and the AC loss data obtained from relevant short sample measurements are applied. A good agreement between calculated and measured V-I curves and losses of the coils is found. A remarkable increase of the critical current and the reduction of the AC loss at the coil edges are predicted and confirmed experimentally. With the losses defined, thermal analysis and optimization of the coil structure are performed numerically followed by measurements for verification. The paper reports on the series of coils developed and explains the features of the projec