c. Measurement between LINE-LINE
Connect the distribution board lead ACC064 to the instrument.
Press the Mode Switch(F1) and select L-N/L-L or PSC.
Connect the blue N lead of the ACC064 to the line of the distribution board,
the brown L lead to another line of the distribution board. (See Fig.26)
Carry out the initial checks
Press the test button. A beep will sound as the test is conducted and the
value of loop impedance will be displayed.
10.1 Principles of RCD Measurement
The RCD tester is connected between phase and protective conductor on the
load side of the RCD after disconnecting the load.
A precisely measured current for a carefully timed period is drawn from the
phase and returns via the earth, thus tripping the device. The instrument
measures and displays the exact time taken for the circuit to be opened.
An RCD is a switching device designed for breaking currents when the residual
current attains a specific value. It works on the basis of the current difference
between phase currents flowing to different loads and returning current
flowing through the neutral conductor (for a single-phase installation). In the
case where the current difference is higher than the RCD tripping current, the
device will trip and disconnect the supply from the load.
There are two parameters for RCDs; the first due to the shape of the residual
current wave form (types AC and A) and the second due to the tripping time
(types G and S). A typical RCD is AC-G.
▲
□
RCD type AC will trip when presented with residual sinusoidal alternating
currents whether applied suddenly or slowly rising. This type is the most
frequently used on electrical installations.
▲
□
RCD type A will trip when presented with residual sinusoidal alternating
currents (similar to type AC) and residual pulsating direct currents
(DC) whether suddenly applied or slowly rising. This type of RCD is not
commonly used at present, however, it is increasing in popularity and is
required by the local regulations in some countries.
▲ RCD type G. In this case G stands for general type (without tripping time
delay) and is for general use and applications.
▲
□
S
RCD type S where S stands for selective type (with tripping time delay).
This type of RCD is specifically designed for installations where the time
delay characteristic is required. In order to assure successful protection on
an electrical installation using RCD's they should be checked to test trip-out
time tΔ.
LOOP/PSC/PFC
10 RCD
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