Can you test Zs at the board?

Zs is your total impedence

impedence

Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage.

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Electrical impedance - Wikipedia

of the circuit including your sub main. There is only one Ze which is at the origin of the supply. The board fed by the sub main will have a Zs value at the board which will roughly equal Ze = R1 +R2. You measure the Zs at the incomming terminals of the sub board.

Where is a ZS test carried out?

Such a test is carried out between the circuit protective conductor and the associated line conductor and measures the series resistance of both conductors for the circuit under test.

Is a ZS test done live?

The presenter does live Zs testing at sockets with a plug top lead switching on the socket switch before taking the test. So this in the words of the Regulation would be "reasonable".

Are you allowed to calculate Zs?

You can obtain the Zs by calculation Zs=Ze+(R1+R2), or by measurement using an Earth Fault Loop Impedance Meter.

What is the source to check values of Zs?

For overcurrent devices not covered by those tables, another reliable source of information on the limiting values of Zs must be consulted, such as the manufacturer's data. Where the protective device is a nondelayed RCD, the maximum value of Zs can be found from Table 41.5 of BS 7671.

How to Carry Out Earth Fault Loop Impedance Test - Measuring Zs | PTT

How do you measure Zs at DB?

Zs is your total impedence of the circuit including your sub main. There is only one Ze which is at the origin of the supply. The board fed by the sub main will have a Zs value at the board which will roughly equal Ze = R1 +R2. You measure the Zs at the incomming terminals of the sub board.

What is the maximum ZS permitted by BS 7671?

​The 1.37 ohms value is the 100% max Zs value which should be recorded on the test certificate.

What if Zs is too high?

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.

What is the 80% ZS rule?

The 80% rule of thumb is only intended to be applied to a test result taken from an impedance test. You have to ensure that the tested value does not exceed 80% of the tabulated value.

Does ZS confirm polarity?

A Zs test confirms earth continuity, and with lighting circuits confirms polarity of the switches. Do not enter calculated values in the schedule of test results. An R1+R2 also confirms polarity.

How do you find the Zs of a circuit?

Zs=Ze + (R1+R2)

(R1+R2) - Sum of the resistance of Line and Earth for the tested circuit.

How do you measure ZS on a ring circuit?

To find the zs of a ring circuit you need to cross connect at the origin of the ring, ie, connect the incoming phase to the outgoing cpc and vice-versa, then measure between phase & cpc at all of the sockets, the one with the highest reading gives the r1+r2 figure, just add this to your ze figure and you`re there!

When carrying out a ZS test on a ring circuit which reading do you record on the test certificate?

Step 3: Press the TEST button. The measurement should be a low reading ohm value. Do not forget to record this value of `Ze` on the Electrical Installation Certificate.

What does ZS test prove?

A Zs test is not to prove an earth connection exists, although it would do so, but to prove that the CPD would operate within the time required by BS7671. Smpling should be of circuits, not equipment of a circuit that is being tested.

What is a high Ze reading?

High ZE readings essentially refer to earthing arrangements in the property. High readings could be due to a wiring fault on the earth cable.

How can earth fault loop impedance be improved?

Increase the size of the PE or PEN conductors and/or the phase conductors, to reduce the loop impedance.

How does Mccb calculate max Zs?

Max Zs for 60974-2 MCCB

Please ensure the tables are to the current version of the wiring regulations and factor in the Cmin factor @ 230V. The Cmin factor is 230 x 0.95 = 218.5 volts, therefore to calculate Zs: 230 x 0.95 = 218.5, 218.5 / la = Zs.

What should my Ze be?

We all know the 17th edition states that the maximum ZE should be 0.35 ohms. That figure is for TNCS, you said your supply is TNS which should be a max. of 0.80 ohms.

What does Zs stand for in electrical?

On the surface these units can look basic, but what do they truly stand for? Zs represent earth fault loop impedance and consists of Ze and (R1+R2). R1 is the phase and R2 is the CPC. These are measurements of the fault current from the supply transformer to the building. It covers the entire electrical cycle.