Video: AMZC-306

Video transcript

What the AMZC 3 oh 6 measures in a low-voltage installation, how it is connected for each fault loop, and how the prospective short-circuit current tells you whether the protection will trip in time. When insulation fails, the fault current must be large enough to trip the protective device in the time the standard allows. That current is set by the impedance of the fault loop. So the loop is measured, and the result is checked against the device. Loop impedance with a resolution of 100th of an ohm, from 0.13 to 19 99 ohms.

Networks from 1 10 over 1 90 to 400 over 6 90 volts. And a mode that measures behind RC Ds of 30 milliamps and above without tripping them. The 3 test sockets, L, PE and N, are on the top edge. The rotary switch selects the loop. START runs the test, and the touch electrode next to it checks the protective conductor. SET holds the network settings.

It comes with a mains plug adapter, 1.2 metre test leads, probes and crocodile clips, a neck harness, the case, the USB cable, a rechargeable pack and its charger. Longer leads and three-phase socket adapters are options. This is a high current method. For 10 milliseconds the meter loads the loop with a current of up to 24 and a half amps at 230 volts, and up to 36.7 at 690. From the voltage drop it calculates the impedance, and splits it into resistance and reactance.

Before the first test, set the rated voltage of the network with SET, since the short-circuit current is calculated from it. Then choose the loop with the switch, set the length of the test leads so their resistance is taken into account, connect, and press START. For the LN loop, the L lead goes to the phase and the N lead to the neutral, or the plug adapter goes into the socket. For a loop between two phases, the same two leads go to two phases. For the LPE loop, the PE lead goes to the protective conductor

or to the exposed metal part, and the L lead to the phase. The N lead is optional. RC Ds in the circuit have to be bridged for this test, and restored afterwards. Before the test, touch the electrode next to START for about a second. If the protective conductor carries voltage, the meter shows it and beeps. Stop and clear the fault first. And if L and N are swapped, the meter says so and still measures. In circuits protected by an RCD, use the RCD position of the switch. Connect PE, N and L downstream of the device, or use the plug adapter.

The loop is measured without tripping RC Ds of 30 milliamps and above. The meter always measures impedance, and calculates the prospective short-circuit current as the voltage over the loop impedance. The protection works if that current exceeds the current that trips the device in time. For example, with a B 16 breaker, that is 5 times 16, 80 amps. A loop of two point oh 4 ohms at 230 volts gives about 113 amps. The condition is met.

Near the transformer, loop resistance is small and reactance becomes significant. Reading only resistance would then overstate the fault current. The meter shows R and XL separately, so the impedance, and the current, stay right. Results are stored in 990 memory cells, with 3500 entries, and transferred over USB to the PC for the inspection report. Measuring category 4 at 600 volts, IP 54, 2 kilos, and 4 LR 14 cells for more than 5000 measurements. Shock protection in low-voltage installations, industrial networks up to 690 volts,

circuits with RC Ds, and prospective short-circuit currents at distribution boards, all documented for periodic inspections. Fault loop testing, from Amperis.