Earth Loop Impedance Testing ZS (in-house) Full Course

This is an In-house course which requires a minimum of 3 candidates to run

Prices exclude VAT. Prices shown are for the full course. 

Learners should leave understanding:

• What Ze, Zdb, R1 + R2 and Zs each represent.
• The complete earth-fault current path, including the supply transformer and distributor’s conductors.
• Why sufficiently low Zs is needed for automatic disconnection of supply.
• How to select the correct maximum Zs using the protective-device standard, type, rating and required disconnection time.
• Why BS 7671 design-table values and acceptable measured values are not necessarily identical.
• The effect of conductor temperature. IET guidance explains that Chapter 41 values relate to conductors at operating temperature, while measurements are normally made closer to ambient temperature; the commonly used 80% figures are a convenient screening method, not a substitute for proper calculation where results are marginal. IET inspection and testing FAQs
• How RCD protection affects the assessment of TT and other circuits, without treating an RCD as a cure for defective earthing or protective conductors.
• Instrument limitations, measurement uncertainty, parallel earth paths and why measured Zs may be lower than Ze + (R1 + R2).
• How electronic loads, surge protective devices, UPS equipment and sensitive equipment can affect the testing method.
• What to do when a result is high, fluctuating, unexpectedly low or inconsistent with previous records.