Office Building Solution

BU I LDI NG SOLUT IONS

20

— Permanent leakage current at mains frequency

Generally, the permanent leakage currents in a circuit are related to the deterioration of the insulation or to the presence of filters or capacitors between phase and earth.

— Table 2 – Stationary electrical equipment connected to a single-phase or polyphase system permanently or by means of plug-in receptacles having a current rating greater than 32 A.

If the total leakage currents are higher than 0,3 I dn , in order to avoid untimely interventions it is advisable to divide the protected circuit in sub-circuits, each protected by single differential devices. The total leakage current coming from different devices generally does not coincide with the arithmetic sum of the single currents due to phase differences so it is advisable to consider a multiplication factor equal to 0,7/0,8.

Rated current (In)

Maximum leakage current

In ≤ 7 A

3,5 mA

For an estimate of the permanent leakage current in the design phase, it may be useful to refer to the IEC 61140 standard which recommends the values shown in the table.

7 A < In ≤ 20 A

0,5 mA/A

In > 20 A

10 mA

— Table 1 – Electrical equipment connected to a single-phase or polyphase system via plug-in receptacles rated 32 A or less.

— Table 3 – Typical leakage current levels of common appliances.

Rated current (In)

Maximum leakage current

Devices

Maximum leakage current

In ≤ 4 A

2 mA

Appliances Computers

da 1 a 2 mA da 0,5 a 1 mA

4 A < In ≤ 10 A

0,5 mA/A

In > 10 A

5 mA

Printers

da 0,5 a 0,75 mA da 0,5 a 1 mA da 0,5 a 1,5 mA

Small portable devices

Copiers

Photocopiers

circa 1 mA

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