531.3.1.202

Legh Richardson:

gkenyon:

ebee:

I`m not admitting that it was me but a "Noise Reduction Plug" a k a a resistor betwixt L & E in a plugtop to cut power to teenagers rowdy party whilst parent in bed , prove quite effective a few years back

That's not really an external connection, but it is intentionally introducing a residual fault current.

Where does that place the use of RCD testing?

Legh

Note 2.....531.3..1.201

Or loop impedance / pfc testing for that matter ... it leaves those in the hands of electrically skilled persons, to be carried out using test instruments to a suitable [specified series of] standards that apply test conditions for limited times etc., and to be carried out only once basic safety tests have been undertaken.


If carried out without some of the safeguards in BS EN 61557 series, the "upstream/downstream" method could inadvertently connect an upstream live conductor to downstream conductors that are supposed to be disconnected by the RCD for prolonged periods. And similarly, if carrying out the test to the associated protective conductor, currents in excess of those that can lead to serious electric shock effects might be applied for too long if an instrument to BS EN 61557 series is not used. Hence the inclusion of Note 2 (Part 6 calls out BS EN 61557).


The RCD test button itself operates in this way, albeit through a high value resistor, which is why I guess the term "external connection" is used.  Interestingly, some RCDs have a disconnector contact for the test switch too, some don't - the current version of BS EN 61008-1, Clause 8.11, states "It shall not be possible to energize the circuit on the load side by operating the test device when the RCCB is in the open position and connected as in normal use." but it is not specified whether the in-built mechanism for achieving this is electrical or mechanical (or indeed a control interlock).

Legh Richardson:

gkenyon:

ebee:

I`m not admitting that it was me but a "Noise Reduction Plug" a k a a resistor betwixt L & E in a plugtop to cut power to teenagers rowdy party whilst parent in bed , prove quite effective a few years back

That's not really an external connection, but it is intentionally introducing a residual fault current.

Where does that place the use of RCD testing?

Legh

Note 2.....531.3..1.201

Or loop impedance / pfc testing for that matter ... it leaves those in the hands of electrically skilled persons, to be carried out using test instruments to a suitable [specified series of] standards that apply test conditions for limited times etc., and to be carried out only once basic safety tests have been undertaken.


If carried out without some of the safeguards in BS EN 61557 series, the "upstream/downstream" method could inadvertently connect an upstream live conductor to downstream conductors that are supposed to be disconnected by the RCD for prolonged periods. And similarly, if carrying out the test to the associated protective conductor, currents in excess of those that can lead to serious electric shock effects might be applied for too long if an instrument to BS EN 61557 series is not used. Hence the inclusion of Note 2 (Part 6 calls out BS EN 61557).


The RCD test button itself operates in this way, albeit through a high value resistor, which is why I guess the term "external connection" is used.  Interestingly, some RCDs have a disconnector contact for the test switch too, some don't - the current version of BS EN 61008-1, Clause 8.11, states "It shall not be possible to energize the circuit on the load side by operating the test device when the RCCB is in the open position and connected as in normal use." but it is not specified whether the in-built mechanism for achieving this is electrical or mechanical (or indeed a control interlock).