This does not mean that they will fail to achieve conformity with the relevant parts of the Electricity at Work Regulations 1989.

To quote precision that is not there when recording results is actually wrong as it misleads the reader about the accuracy of the measurement.I would like to express my great appreciation to the following individuals for their valuable contributions to this article. I suggest you go and measure Zs on a real system with a real meter early in the morning, then go out for lunch and polish the meter probes and re-test with the same meter at the same point in the afternoon. The equipment at the intake position is owned by the distributor and the meter and tails belong to the supplier. Where circuits comprise capacitance due to connected loads or due to long cable lengths, even after the RCD has operated, the capacitance in the circuit will continue to discharge influencing the result recorded by the instrument. When carrying out an earth fault loop impedance test at ambient temperature, it is necessary to adjust the value to take into account increased resistance of the conductors due to a rise in temperature caused by load current.

An EICR is a factual report on the condition of an electrical installation and suitability for continued use. If the Type A RCD setting is selected on the test instrument, the test current is increased by a factor of 1. A good simulation of our example with similar values, but giving readings in kΩ instead of Ω, can be made using six 47 Ω and six 120 Ω resistors to represent the line and cpc conductors of the ring final circuit respectively. The objective of this chapter is to provide requirements, such that, low-voltage electrical installations are compatible with the current and future ways to deliver safely the electrical energy to current-using equipment either from the public network or from other local sources. This section incorporates BS 7671:2018+A1:2020 together with other changes, such as, taking account of prosumer’s electrical installations (722.My point is not that we need to know all this, usually we cannot hope to, but more that if your design is close to the limit, and relies on a change of less than 5000 parts per million to put it one side of the line or the other, then it does not matter, as the last digits on the tester are about as helpful as a fruit machine. The following example is used to demonstrate how the differences in measurement between the cross-connection (usually at the origin of the circuit within the consumer unit or distribution board) and the mid-point in the ring occur.