Filter
Top Products
Appendix: TN Systems
36 Symmetra MW 800 kW 3 × 400/230 V Installation - 990-1510D
The characteristics of protective devices and the circuit impedances shall be such that, if a fault of
negligible impedance occurs anywhere in the installation between a phase conductor and a protective
conductor or exposed conductive part, automatic disconnection of the supply will occur within 5
seconds (valid for distribution circuits), the following condition fulfilling this requirement:
In the condition:
If a fault occurs close to the UPS (before the power distribution) while the UPS system is in Battery
Operation and Bypass is unavailable, the available power is unable to activate the protective device.
In that situation the Inverter will shut down in five seconds (IEC 60364-4-41 413.1.3.5 norm). If a
residual current protective device is used, this device will disconnect the supply.
The four diagrams show the Symmetra MW installed in four different TN systems:
• Earthing arrangements and protective conductors - Symmetra
®
MW in “TN-S installation”
• Earthing arrangements and protective conductors - Symmetra
®
MW in “TN-S installation”
(Legal in DK - special cases)
• Earthing arrangements and protective conductors - Symmetra
®
MW in “TN-C-S installation”
• Earthing arrangements and protective conductors - Symmetra
®
MW in “TN-C installation”
is the impedance of the fault loop comprising the source, the live conductor up to the point of the
fault, and the protective conductor between the point of the fault and the source
is the current causing the automatic operation of the disconnecting protective device within a
conventional time not exceeding five seconds
is the nominal AC RMS voltage to earth
Z
s
I
a
× U
0
≤
Z
s
I
a
U
0