RCD's not tripping with TL transformers

[BruceB]

Or install in way that does not require an rcd. Normally relatively easy to do unless TT.

 

[grandfortune]

As a spark i find it almost impossible to install anything with a depth of 50mm, even in trunking i usually goes though some sort of wall or floor and the cable becomes less than 50mm somewhere along the line.

 

[BruceB]

A cable just going through a wall or floor from one side to another (say a wall from outside to trunking inside) does not bring in the 50mm rule. What I was suggesting was surface run swa, or solar cable or T&E in surface trunking. The only times I have 'had' to install rcds has been TT.

 

[SibertSolar]

Hmmm.....

TypeAC trip coil will saturate with any DC component, pulsed or pure
TypeA trip coil will saturate if the pulsed DC component is greater than 6mA but will saturate with any pure DC component
TypeB trip coil(s) will not saturate with either pulsed or pure DC component, regardless

Interesting thread. I shall monitor and try to offer assistance if required. For anyone needing pricing/stock of TypeA or TypeB RCDs then feel free to get in touch,

Andy

 

[SibertSolar]

Btw....if anyone's planning on visiting the SolarPowerUK show in B'ham in October then we'll have representatives from Doepke with us along with a demo unit to show how TypeA and TypeB RCDs operate.

 

[sparkatus12]

Can somebody explain why dc prevents rcd tripping. Also is it true that capacitors in appliances can cause rcd to go over range with trip times. If so why? Thanks.

 

[SibertSolar]

Basically, the DC component of the AC waveform "magnetises" the trip coil of the RCD and prevents it from functioning normally under AC leakage current fault conditions (magnetisation of the trip coil stops its ability to sense changes from phase to ground)

Your second question relates more to "nuisance tripping" which is a separate issue to DC leakage/sensitivity. PV array frames can generate parasitic capacitive AC leakage currents (especially on moist mornings...) which, when combined with the inverter's inherent AC leakage current, can exceed the minimum tripping level of the installed RCD on the AC side, even when a ground fault doesn't exist.

 

[SibertSolar]

Apologies, just re-reading and perhaps I didn't answer your 2nd question actually! Not entirely sure about capacitors in electrical appliances other than perhaps the same principal applies regarding excessive AC leakage current being generated by the capacitors.....

 

[sparkatus12]

No I was told capacitors released dc back into the system preventing rcd from tripping in correct times.

 

[SibertSolar]

Hmm, not sure about that on typical AC electrical appliances to be honest. Anywhere there's frequency conversion or DC/AC inversion, and no galvanic isolation, tends to be an area where DC onto AC is a concern but I've no experience with standard electrical appliances incorporating capacitors causing issues.

 

[danesol]

HI all,

getting some info though that there is problems with Transformer less Inverters and RCD's not tripping.

thought id check one of mine and low and behold it didnt trip.

It is the first time ive tested it with the PV on though so i would never normally pick it up. Looks like the the Inverter is injecting DC into the RCD toroid and saturating it.


ill try and get some more info as this now has gone above my head lol

Cheers
Crofty

Did you not know this at installation stage when you did the electrical tests for customer documentation ???

 

[grandfortune]

Yes, i dont test RCBO's or RCD's with the load connected.

 

[grandfortune]

No I was told capacitors released dc back into the system preventing rcd from tripping in correct times.

you dont test a trips timings with the load on so it should never affect the times on a test meter

Cheers
Grand

 

[grandfortune]

A cable just going through a wall or floor from one side to another (say a wall from outside to trunking inside) does not bring in the 50mm rule. What I was suggesting was surface run swa, or solar cable or T&E in surface trunking. The only times I have 'had' to install rcds has been TT.

True, im probably speaking from a sparky point of view as working with mostly T&E, so basically without worrying about the 50mm rule you just RCD it and be done with it