Max Zs
Revit Guides
Data Management
Themaximum value of earth fault loop impedance (Zs) that will allow the protective device in a circuit to disconnect an earth fault within the prescribed time.
Example: if themaximum earth fault disconnection time for a circuit is 0.4 s and a fault current Ia = 320 A is required to operate the circuit protective device in that time: Max Zs = (Cmin x Uo)/Ia = (0.95 x 230)/320 = 0.7188 Ω
The earth fault loop impedance, i.e., the path through which fault current will flow for an earth fault in the circuit under consideration. It comprises the sum of:Ze, the external impedance; Z1, the line conductor impedance;Z2, the circuit protective conductor impedance.
Zs = Ze + (Z1 + Z2).
pre-design process
construction process (3.3.2) determining construction properties (3.5.1) for the built environment (3.1.7) before it is designed[1] 1 Online
Secondary Supply – diverse cable route
This guidance covers the routing of secondary supply cables from a life safety generator to the ATS (Automatic Transfer Switch), and the final equipment with reference to:
BS 7671:2018+A2:2022, specifically Section 560: Safety Services
BS 8519:2020, with emphasis on Clause 7 (Cable Routing) and Clause 11 (Cable Selection)
The goal: clarify requirements for the diverse cable routing and maintain circuit integrity under fire conditions for systems that support life safety and fire-fighting applications, such as sprinkler pumps, fire-fighting lifts, and smoke control systems.
