Manual

8.7 Ramp test
The RCD trip current is measured by applying a test current of half the rated trip current and increasing this every
300 ms (or 500ms for type S RCDs) from 30% to 110% of the RCD current rating. When the RCD trips, the current
flowing is recorded and displayed in mA.
Making a measurement
1. Select the appropriate RCD rated current on the right hand rotary switch
30
= 30 mA etc.
2. Select the RAMP test on the left hand range knob.
3. Press the TEST button
The RCD should trip and the display show the trip current in mA.
If the RCD fails to trip, >***mA is displayed, where *** = 110% of the nominal RCD trip current.
8.8 Fast Ramp Test
Fast ramp test can be selected in Setup (See “11. Setup options” on page 53)
The fast ramp test tests that the RCD will trip between 1/2I and 1xI of the rated RCD trip current. This allows faster
testing and higher test currents to be used repeatedly, without overheating the instrument. The duration of each
ramp step is less than the 300ms required in EN 61557. As such this test should not be used if compliance to
EN61557 is required. Testing is the same as the standard ramp test.
8.9 Type A (DC Sensitive) RCD test
‘Type A’ RCDs are sensitive to pulsed DC as well as AC fault currents, and are tested with a pulsed waveform.
The RMS current is √2 x the rated operating current of the RCD. As with the normal RCDs, these should be tested
with 0° and 180° polarity.
1. To select a Type A RCD see “8.2 Selecting RCD type” on page 38
These are tested in exactly the same manner as those tested in 8.3 on page 39 to 8.7 on page 42.
NOTE : Type A RCDs should be tested at 0° and 180° on 1/2xI, 1xI and 5xI
www.megger.com
MFT1800 series
42
Residual Current Device (RCD) or Ground Fault Current Interrupt (GFCI) testing