Protective separation is an independent protective measure in which, in accordance with DIN VDE 0100-410 (VDE 0100-410):2007-06 section 413,
- basic protection is provided by basic insulation of the active parts;
- fault protection is assured by simply disconnecting the electrical circuit
from other circuits and earth.
Accordingly, protective separation derives its protective effect from the fact that the secondary circuit is separated galvanically from the mains supply and earth, or, in the case of a mobile generator, the output winding is separated from earth. When an active conductor is touched, the high insulation resistance and low system leakage capacitances (Ze very large) of the secondary circuit to earth means that virtually no current can flow through a human.
However, the size of the system leakage capacitance is negatively affected by the length of the wire and the number of loads or the resulting impedance between the active conductor and earth (Z becomes smaller). For this reason, the instruction to limit this protective measure to the supply of an electrical consumable applies generally, and the length of the wire must also be borne in mind. For fault protection, additional measures are still needed:
- The voltage of the circuit with protective separation must not exceed 500 V.
- The active parts of the circuit with protective separation must not be connected to another circuit, to earth or to a protective earth at any point.
- The exposed conductive parts of the circuit with protective separation must not be connected to the protective earth, to the exposed conductive parts of other circuits or to earth.
- Flexible cables and wires must be clearly visible along their entire length in places that are exposed to mechanical loads.
Provided they comply strictly with these requirements, protective separation with a load may also be used by individuals without an electrical engineering background. In practice, however, mobile generators are usually equipped with more than one socket-outlet. Therefore, the requirements of Annex C.3 of DIN VDE 0100-410 (VDE 0100-410):2007-06 apply as well.
Annex C.3 of this standard describes the protective measures with more than one consumable, which may only be operated and monitored by qualified electricians or individuals who have received electrical training.
- C.3.2 In the case of protective separation with more than one consumable, the requirements of section 413 (not including 413.1.2) and the subsequent additional requirements must be met.
- C.3.3 Take precautionary steps to protect separate circuits from damage and insulation faults.
- C.3.4 Connect the exposed conductive parts together by insulated, unearthed protective conductors. These conductors must not be connected to the protective conductors or other exposed conductive parts in other circuits or to any extraneous conductive parts.
- C.3.5 All socket-outlets must have an earth contact that is connected to the protective equipotential bonding system and meets the requirements of C.3.4.
- C.3.6 Flexible connecting wires must include a protective earth conductor that functions as a protective bonding conductor and also complies with the requirements of C.3.4.
- C.3.7 If one insulation fault occurs in each of two different items of equipment and various external conductors, shutdown must take place within the time shown in table 41.1 of DIN VDE 0100-410 (VDE 0100-410):2007-06.
- C.3.8 It is recommended that the product of the nominal voltage of the power circuit in volts and the length of the wires/cables in metres should not exceed a value of 100,000 and the total length should be limited to 500 m.