The Zs for MTZ used to be done from the settings on the Micrologic X and using the following formula - Zs = 218.5/In x Ir x Isd x 1.1
Where - 218.5 is the 230 voltage to earth multiplied by the Cmin factor 0.95 divided by - In = Device rating x Ir = Long time dial setting x Isd = short time setting x 1.1 a 10% tolerance for the Isd short time setting.
Now it can be done easily by entering your figures into the attached (Related Tab) Excel file.
A 1000A example has been entered on Line 5.
Released for: Schneider Electric Ireland
