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5 Are DC grids more dangerous than AC grids?

No, the same safety rules apply as for AC voltage. VDE 0100 and IEC 60364 allow up to 1000 V for AC and 1500 V for DC in low-voltage installations.

 

 

5.1 Where are the necessary protection measures for DC defined?

The basic safety standard IEC 61140 describes the protection measures up to DC 1500 V (and AC 1000 V). See here

5.2 What is an electrical arc?

An arc is a hot, conductive plasma, similar to a lightning bolt.   

5.2.1 Which types of arcs are there?

There are two types of arcs: 

  • Deliberately generated arcs, e.g. during electric welding or when opening switching contacts.
  • Fault arcs caused by a fault, e.g. cable break, insulation fault, foreign parts in switch cabinets.

5.2.2 Are there differences between AC- and DC arcs?

With DC, there are no current zero-crossings; therefore, additional measures must be imple-mented in the protective devices. In mechanical switches, these measures are, for example, magnetic fields and larger air gaps. Power electronics and hybrid switches are further options for preventing arcing in switchgear.

5.3 Can AC breakers be used for DC?

This cannot be answered in general – it depends on the specifications of the particular switch. Often AC switches are also approved for a certain DC voltage range according to the specific manufacturer's specifications and product standards.

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