What is the purpose of a earth loop impedance test?

Should there be a fault in an electrical circuit, an earth loop impedance test is conducted to ensure the fault current will be strong enough to set off the circuit protection. If a fault current is undetected or not disconnected fast enough, circuits can overheat and catch fire.

What is the earth loop impedance?

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”. So in short it is the impedance of the earth fault current loop starting and ending at the point of earth fault. This impedance is abbreviated to Zs.

What is a loop tester used for?

Loop testers are used to measure earth fault loop impedance and determine prospective fault currents. Initially loop testers used a high current load to measure the voltage drop on the supply and measure the source impedance.

How do you test a loop impedance?

Step 1: Locate the furthest point on the circuit to be tested (such as the furthest socket) Step 2: With the appropriate Earth Fault Loop Tester, connect the test leads to the Line, Neutral and Earth terminals. Step 3: Measure and write down the test results on the Schedule Of Test Results.

What will a successful ZS test prove?

Zs represent earth fault loop impedance and consists of Ze and (R1+R2). If Zs are too high, not enough fault current can flow and the MCB may not trip at all. On circuits after 17th edition, RCDs will be more common and will trip before MCBs.

What do I do if my 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 an acceptable earth loop impedance reading?

It is generally accepted that, where the measured earth fault loop impedance of a circuit is not greater than 80\% of the relevant limit specified in BS 7671, the impedance can be expected to be sufficiently low under earth fault conditions to meet the relevant limit specified in BS 7671, and for the protective device …

What is a good fault loop impedance reading?

The value of external earth loop impedance (Ze) measured or otherwise determined in accordance with Regulation 313.1 may differ from the applicable typical maximum value declared by the electricity distributor, which is usually: 0.8 Ω for TN-S system. 0.35 Ω for a TN-C-S system.

How do you conduct an earth fault loop impedance test?

The Earth Fault Loop test sequence:

1. Locate the furthest point on the circuit to be tested (such as the furthest socket)
2. With the appropriate Earth Fault Loop Tester, connect the test leads to the Line, Neutral and Earth terminals.
3. Measure and write down the test results on the Schedule Of Test Results.

What is the difference between resistance and impedance?

The main difference between Resistance and Impedance is that resistance opposes the flow of DC & AC current whereas Impedance only opposes the flow of AC current. Impedance is having meaning only in AC circuit. Whereas resistance simply means resistance of a component.

What happens if earth fault loop impedance is too high?

If the resistance in the earth return circuit is too high, the fault current may be too low to be detected, and the fault current will continue to travel around the main circuit – causing a short circuit. If the resistance is too high, the circuit protection may not operate.

How do you reduce loop impedance?

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

What is the importance of earth loop impedance?

Why is Impedance Testing Important? An earth loop impedance test is conducted to make sure that, if a fault occurs in an electrical circuit, the fault current will strong be enough to set off the circuit protection . If a fault current is left undetected, circuits can overheat and catch on fire.

What is earth fault loop impedance?

“Earth fault loop impedance” is a measure of the impedance, or electrical resistance, on the earth fault loop of an AC electrical circuit, explains Alert Electrical. The earth fault loop is a built-in safety measure within electrical systems to prevent electric shock.

Why is impedance testing important?

Why is impedance testing important? Well, if you care about the ongoing quality of the circuitry in your building, it’s very important. In order to prevent overheating and fires , the loop impedance needs to operate at a certain level. The only way to maintain this optimum level is with regular testing.

What is a loop resistance test?

Loop resistance testing is an essential step in the manufacture and maintenance of safe bonding circuits; it should not be an inconvenient delay in putting aircraft into active use. Simple electrical bonds between two discrete elements are relatively straightforward to test.