The values of maximum earth fault loop impedance (Zs) given in Tables 41.2, 41.3 and 41.4 in Chapter 41 of BS 7671: 2008, for commonly-used overcurrent protective devices, should not be exceeded when the conductors are at their normal operating temperature (such as up to 70 °C for thermoplastic insulated conductors).

For fault protection, the limiting values of earth fault loop impedances, Zs, are given in Tables 41.2, 41.3 and 41.4 of BS 7671, for many commonly-used overcurrent protective devices.

Maximum measured Zs values for fuses & circuit-breakers. BS 7671 compliance guide for electrical safety. Downloadable pocket reference.

The maximum earth loop Impedance figures can be found on the attached pdf files. The standard MCCB's used for ratings of 16A to 250A with part numbers beginning with "MGP..." are identical to the NSX with thermal magnetic trip units. The standard MCCB's used for ratings of 400A & 630A with part numbers beginning with "MGP..."

fault loop impedance (Zs) corresponding to a disconnection time of 0.4 s are stated in .2 for a nominal voltage (UI)) of 230 V. For types and rated currents of general purpose (gG) fuses other than those mentioned in "2, and for motor circuit fuses (gM), reference should be made to the appropriate British Standard to

How to determine the maximum Z S of the selected device. Following the selection of a device from the previous section, the maximum permitted Z S must be obtained to ensure compliance with the disconnection time as stated in Regulation 411.3.2 of BS 7671:2018+A2:2022.

These maximum Z s values in Tables 41.2-41.4 of BS 7671:2018+A2:2022 are useful when designing a circuit. The current carrying capacity tables, rating factors and volt drop values in BS 7671 are all comparative in keeping safely, yet economically, within the declared maximum permitted operating temperatures of any cable or equipment.

2019年1月19日 · Max Zs is the maximum permissible values of earth fault loop impedance (Ω), some maximum Zs values are listed in BS 7671, the maximum earth loop impedance values listed in the Zs tables are used to compare against the actual measured earth loop impedance values to ensure compliance with BS 7671.

The maximum Zs values given in Tables 41.2 to 41.4 are based upon the line conductors carrying load current and being at a temperature of 70 °C.

Maximum Earth Fault Loop Impedance (Zs) For Fuses, For 5 S Disconnection time with Uo of 230 V (see Regulation 411.4.8) (General purpose (gG) and motor circuit application (gM) fuses to BS 88-2 – fuse systems E