Actual test voltage using RCD tester?

[silver surfer]

I hope i can word this so it makes sense...
When testing for instance a ring final for RCBO tripping times, is the test voltage within the test instrument reduced to 50Vmax to simulate the max permissable touch voltage? ie, is there a 1667 ohm resistor inside and 50 volts applied across it so 30ma can flow and then times taken etc,etc?

Thanks

 

[Deleted member 26818]

There isn't a test voltage per se.
The instrument uses the supply voltage, and then places differing resistances between the L&N conductors to produce various loads.
When conducting a ramp test, the instrument starts at maximum resistance, and then decreases the resistance untill the RCD trips.

 

[silver surfer]

There isn't a test voltage per se.
The instrument uses the supply voltage, and then places differing resistances between the L&N conductors to produce various loads.
When conducting a ramp test, the instrument starts at maximum resistance, and then decreases the resistance untill the RCD trips.

Would that mean that in proportion to 50v/1667ohms= 30ma
the instrument would now apply 230v/7668ohms= 30ma ?

 

[spark 68]

Hi Spin,

There isn't a test voltage per se.
The instrument uses the supply voltage, and then places differing resistances between the L&N

I thought this test was done between L&E, with the E being the variable ( as in different or unknown on each installation) lower half of a Potential divider, the tester being the upper half, and as you say it decreases the resistance values of the upper part of the potential divider until the required current flows, that is why if you have a crap earth (High resistance), if the upper part of the potential divider reaches a certain low enough resistance value WRT earths resistance value, ie. leading to =>50V (using ohms law) at the Potential dividers junction, the tester will inhibit the test, to stop the earths voltage rising any further up to dangerous levels, ie. higher than 50V

I hope this makes sense, I know what I mean, but it is difficult to get across in words Lol

 

[Deleted member 26818]

Yes, my post wasn't very good.
Should have been between L&E for 0º, and then N&E for 180º.