Fault loop impedance table

MAXIMUM EARTH FAULT LOOP IMPEDANCE VALUES FOR. OVERCURRENT PROTECTIVE DEVICES IN COMMON USE, FOR FAULT PROTECTION. For fault protection, the limiting values of earth fault loop impedances, Zs, are given in Tables 41.

Earth- fault loop impedance values. The over-riding requirement is that sufficient fault current must flow in the event of an earth fault to ensure that the protective device cuts off the supply before dangerous shock can occur.

Guide to the Wiring Regulations.

Maximum earth fault loop impedance (Zs) for fuses, for 0.

General purpose (gG) fuses to BS 88–2. Maximum measured values of earth fault loop impedance (Z )s. The table below provides maximum values of Zs for fuses and circuit breakers. It should be understood that the reading obtained relates to the applied nominal voltage.

Values for Earth Loop Impedance (Zs). In practice, the thermal setting also scales the magnetic setting and therefore the above values are the maximum. If the measured earth fault loop impedance is above the values in the table , it may be possible that it meets the requirements of the lEE Regulations if the thermal setting is . Zs is maximum earth fault loop impedance to operate the fuse element of the disconnection device (overload and short circuit) in the required disconnection time.

Earth fault loop impedance (Regulation 61). Earth Fault Loop Impedance (max Ze) is the impedance of the earth fault current loop starting and ending at the point of earth fault. Diagram 7: Insulation Resistance Test. The polarity test is carried out to verify: a) That all single-pole switches in lighting circuits are connected into the line . Certain Conditions apply for Automatic protection ( ADS) 411. Measuring earth- fault loop impedance and prospective short-circuit current.

Now we must find the maximum acceptable earth- fault loop impedance for the circuit. Zs is the earth fault loop impedance in ohms. Since the external loop impedance is 0. Ia is the current in amperes causing operation of the protective device within the.

The protective measure for RLV systems is automatic disconnection of supply ( ADS) and Regulation 411. Zs values can be calculated or the maximum Zs values in Table 41. Curcuit Breakers and HRC Fuses. Edition, which is reproduced below.

Where an RCD is employed to achieve the disconnection time required by.