Impacts of Grounding Concepts in IT DC-Grids on SPD Safety

Conference: NEIS 2019 - Conference on Sustainable Energy Supply and Energy Storage Systems
09/19/2019 - 09/20/2019 at Hamburg, Deutschland

Proceedings: NEIS 2019

Pages: 6Language: englishTyp: PDF

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Schork, Franz; Brocke, Ralph; Ott, Daniel (DEHN SE + Co KG, Hans-Dehn-Str. 1, 92318 Neumarkt, Germany)

Modern DC-grids fed by DC/DC-converters can be built easily as isolated (IT) grids. To have a non-floating grid potential different grounding system are discussed such as capacitive or high ohmic grounding. In both cases residual currents can flow to ground. This current can be either a DC-current caused by asymmetric ohmic grounding or AC-current driven by high switching frequency of the DC/DC-converters. Both currents can cause a permanent arc once a spark gap based surge protective device (SPD) has been triggered. This paper deals with the possible range of residual currents due to different grounding systems. Derived from this the turn-off limits of spark gaps in DC-grids are discussed and possible protective measures will be shown.