Get Dzs 791 Part 3

ze is external. zs is external and internal impedance.

Therefore, where reliable measured values are available for the external earth loop impedance (Ze) and for the loop resistance of the line and protective conductors (R + R ) of the circuit, it is permissible to derive the loop impedance of a circuit by using the following formula: Zs = Ze + (R + R ).

The Earth Fault Loop test sequence: This is a live test so extra care is advised! Step 2. With the appropriate Earth Fault Loop Tester, connect the test leads to the Line, Neutral and Earth terminals.

If a Zs value is high, then you need to establish whether it is due to circuit conditions, supply conditions, or a fault. You can then descide the appropriate course of action. Just installing an RCD or RCBO may not be the solution in a deteriorating installation.

Earth fault loop impedance is the path followed by fault current when a low impedance fault occurs between the phase conductor and earth, i.e. earth fault loop . Fault current is driven round the loop by the supply voltage. ... This impedance is abbreviated to Zs.

Therefore, where reliable measured values are available for the external earth loop impedance (Ze) and for the loop resistance of the line and protective conductors (R + R ) of the circuit, it is permissible to derive the loop impedance of a circuit by using the following formula: Zs = Ze + (R + R ).

The main reason for earth loop impedance testing which is often simply called loop testing is to verify that, if a fault occurs in an electrical installation, sufficient current will flow to operate the fuse or circuit breaker protecting the faulty circuit within a predetermined time.

The highest measured Zs value for each circuit should not exceed 0.8 of the relevant value in the BS 7671 tables. ... This number should be higher than the highest measured Zs value for the given circuit.

Earth fault loop impedance (Zs) is the impedance in ohms of the circuit path formed during a fault between earthed metal work and live parts. It includes the external impedance circuit (Ze) and the resistance of the phase and circuit protective conductors (R1 + R2).

The main reason for earth loop impedance testing which is often simply called loop testing is to verify that, if a fault occurs in an electrical installation, sufficient current will flow to operate the fuse or circuit breaker protecting the faulty circuit within a predetermined time.