Max Zs For Tt System. TT Earthing System Detailed Explanation, Diagrams Asutpp The preferred means of earth fault protection on a TT is an RCD (411.5.2) and the maximum Zs value will be in accordance with table 41.5 As the circuit in question is protected by a 30mA RCD in a domestic setting, max RA is 1667 Ohms (50V/30mA)
PPT BS7671 Formula and Tips PowerPoint Presentation ID2810396 from www.slideserve.com
Just starting to look into TT systems a little more The maximum Zs when using RCDs for fault protection in a TT system is based on 411.5.3 and Table 41.6 applies
PPT BS7671 Formula and Tips PowerPoint Presentation ID2810396
Where the protective device is a nondelayed RCD, the maximum value of Zs can be found from Table 41.5 of BS 7671 Where the protective device is a nondelayed RCD, the maximum value of Zs can be found from Table 41.5 of BS 7671 Popped in today and did a quick Ze test and got 16.98 ohms
TT Earthing System Detailed Explanation, Diagrams Asutpp. protection requirements of Regulations 411.4.5 (TN system) or 411.5.4 (TT system) are considered to be met when the measured value of Zs does not exceed 80% of the applicable maximum value (such as that given in Tables 41.2, 41.3 and 41.4 of BS 7671) As the circuit in question is protected by a 30mA RCD in a domestic setting, max RA is 1667 Ohms (50V/30mA)
Max Zs Values Android Apps on Google Play. As RA will dominate Zs, should I enter 1667R or the figure for a TN system from the OSG or not applicable (N/A)? On the other hand a lot of people who are perhaps more used to TN systems often refer to the loop impedance at the origin as Ze and then try to do things like Zs = Ze + R1 + R2, whereas technically it should be Zs = Ze + R A + R1.