Solar array test set-up proposed by CNES in the frame of European standardization: Prevention of secondary arcing induced by electrostatic discharge

The validation of new solar cell for geostationary satellite application sets the problem of arcing between solar cells triggered by electrostatic discharges (ESD(sup 1)). The main difficulty of a ground test is to properly simulate the transient behavior of one string from the first microsecond of an electrostatic discharge and to take into account all the energy stored on a panel that would be released during hundreds of microseconds. The test set-up to use, with all the physical data we need to take into account, to properly simulate the response of the string to an ESD, is presented in this paper. Since the power losses on the Tempo and Panamsat satellites attributed to electrostatic discharges in 1997 (15 percent of the power in three months), the international scientific community has looked into the problem of sustain arc on solar array. It was therefore necessary to draw up a discharge theory, with a sequencing of events, by taking into account the energy available at the moment of discharge on the satellite presented at the 7th SCTC as on this energy depends the amplitude of the primary discharge, and therefore the associated thermal effect, which totally conditions the arc. On the other hand, manufacturers, now encountering problems of electrostatic nature on satellites (section losses on high voltage solar arrays), present the problem in terms of efficient solutions. Manufacturers and laboratories still test solar array samples with their own assembly configurations which, for a single sample, can either be disastrous or have not the slightest effect. Indeed, depending on whether the energy developed in the primary discharge comes from a capacitor of 100 pF or one of 1 micro-F, the result with regards to the direct effects of the primary discharge and the sustained arc risk will be completely different. To test solar array samples a priori in the confinement of an enclosed vacuum, it is necessary to define a laboratory test set-up, which represents what the solar array comes across in the geostationary orbit. To finalize this test set-up, we had to know the error made when using a 4 cells sample instead of a real large solar array in terms of primary discharge representativity, available energy stored, and electrical response of the simulating circuit. This paper will present electrical circuit needed to be representative of the flight configuration. It will explain how to make your own test set-up depending on the solar cells you want to use. This test set-up take into account the energy stored in the coverglass and the way it has to be released. The solar array test set-up is proposed by CNES in the frame of the ECSS for the European standardization. It does not take in consideration any commercial aspects or feasibility by such-and-such manufacturers. So one could imagine disagreements even oppositions to those propositions whom all are based on pure technical aspects. Although, the draft proposed is based on seven years of experiments, last one of which was shared with Japan to set basis of an universal standardization.
資料番号: AA0049206048
レポート番号: JAXA-SP-05-001E