PPrriinncciippllee ooff MMeeaassuurreemmeenntt –– RRaammpp
During RCD Ramp testing, the earth leakage current starts at 20% of RCD rated current and
increases by 10% of RCD rated current every 300ms up to a maximum of 110%. For example
a 30mA Ramp test runs from 6mA to 33mA.
The trip time is measured as in the normal case and the trip level calculated from it.
RRCCDD TTeesstt FFuunnccttiioonn
CAUTION
Although fully protected against over voltage to 550VAC this tester should only be used
on a 230V supply.
The Ethos 8400 will test all the most commonly encountered RCD’s of both standard (AC) type
and selective (ACS) type across the full range of tests required by the 17th Edition of the wiring
regulations.
Test requirements
Each RCD is tested to ensure that:
It is not prone to ‘nuisance’ tripping as does not trip when a fault of half its rated current
is introduced. This is referred to as the x1/2 test.
It operates with a maximum disconnection time of 300ms (AC type) when a fault at its
rated current is introduced.This is referred to as the x1 test.
In the case of an RCD rated at 30mA there is an additional requirement that it operates
with a maximum disconnection time of 40ms when a fault of five times its rated current is
introduced.This is referred to as the x5 test.
For the reasons explained below all of the above tests have to be conducted at both 0° and 180°
this means that four tests (or for 30mA RCD’s six tests) have to be made for each RCD.
The user friendly design of the Ethos 8400 simplifies the test process by enabling you to do any
of these tests by making just two function selections.
SSiinnuussooiiddaall ppoollaarriittyy ((tthhee 00°° oorr 118800°° tteesstt))
RCD’s often operate with different reaction times depending upon whether the fault is
introduced during the positive or negative half cycle of the AC waveform. Therefore to
accurately determine the maximum response time of an RCD it is necessary to test it twice at
each given fault current, firstly with the fault introduced during the positive half cycle and
secondly during the negative half cycle.
The Ethos 8400 takes care of this for you by alternating the start point of consecutive tests at
any given setting. If for example you have selected a test at the rated trip current (x1) of a
100mA RCD, the first press of the test button will apply a 100mA fault current starting on the
positive half cycle (0°) and display the result. A further press of the test button will carry out
another test at the same current but starting on the negative half cycle (180° ).
23
EETTHHOOSS 88440000
INSTRUCTION MANUAL
RRCCDD
WARNING
Leakage currents in the circuit following the residual current protection device may
influence the measurements.
Potential fields of other earthing installations may influence the measurement.
Special conditions in S-type residual current protective devices shall be taken into
consideration.
Equipment connected downstream of a residual current protective device (RCD) may
cause considerable extension of the operating time. Examples of such equipment might
be connected capacitors or running motors.
22
EETTHHOOSS 88440000
INSTRUCTION MANUAL
PPrriinncciippllee ooff MMeeaassuurreemmeenntt –– xx11//22,, xx11,, xx55
During normal RCD test an earth leakage current (I) is applied to unbalance the RCD.
During application of the current, VLN is monitored using voltmeter V1 for an RCD trip
signature.When trip occurs, the time from application of the earth leakage current to the trip is
calculated and displayed.
Additionally, VLE is measured using voltmeter V2 to monitor Fault Voltage. If excessive Fault
Voltage is detected, testing is aborted and a warning is displayed. This detection uses the actual
Fault Voltage occurring during the test and not the predicted fault voltage at the rated residual
current.
Application of the current is limited in duration. If no trip is detected during the application, an
over range reading is displayed. Note: when testing at x1/2, no trip is a PASS.
To Next Page
Loading...