Short-circuit current of multiplus II is limited? what to do in off grid/island modus

DIY
,
1

I currently have a Victron system that functions solely as an ESS (connected only to the main distribution board via AC input).

Now I would like to use my Victron (3-phase Multiplus) as emergency power as well for when the net goes out.

So, the entire main distribution board need to be put on the AC output of the multiplus.

However: the short-circuit current of the multiplus is only 40-80A compared to 3kVA for the grid. In other words, the circuit breakers will not trip in the event of a short circuit in the socket.

What should I do to resolve this?

Ik heb momenteel een victron systeem dat louter functioneert als ESS ( enkel aangesloten op hoofdbord via AC in )

nu zou ik mijn victron ( 3 fase multiplus ) ook als noodstroom willen gebruiken.

Dus heel de hoofd kast op de AC out.

Echter : de kortsluitstroom is slechts 40-80A ten opzichte van 3kva voor het net. Maw de C automaten gaan niet springen bij kortsluiting in stopcontact.

Wat moet ik doen om dit op te lossen ??

2

Ik zie eerlijk gezegd geen problemen, bij sluiting knalt ie er gewoon uit

Maar wat is de reden dat je c automaten hebt?

3

Hey Marc, ja geen idee.. zijn allemaal C automaten.. is een kast van 2001… meeste 16A C curve

volgens mijn elektricien zouden die automaten niet springen bij een kortsluiting aan de stopcontacten/lichten omdat de kortsluitstroom van de multiplus vele malen lager is dan de kortsluitstroom van het net ?

Dit weliswaar in off grid modus…

Foutieve info ?

4

Is het in NL of in BE?

5

Als we dit in het Engels houden, dan hebben meer mensen baat bij deze vragen en antwoorden.

In English this post may be useful for the whole world.

That said, this Dutch video is very informative. https://www.youtube.com/watch?v=rs1P5VaKlKk

6

BELGIUM

I understood that a short circuit in the socket can cause the Multiplus to deliver maximum power… and if the circuit breaker doesn’t trip, the Multiplus will continue to supply current, which could cause the cables to start melting and/or pose a risk of electrocution/fire (admittedly in exceptional circumstances, but still).

Ik begreep dat kortsluiting in stopcontact ervoor kan zorgen dat de multiplus max vermogen kan gaan leveren… en als de automaat niet springt gaat de multiplus stroom blijven leveren waardoor de kabels zouden kunnen beginnen smelten en/of gevaar op elektrocutie/brand ( weliswaar in uitzonderlijke omstandigheden, maar toch )

7

I’m sorry.. I’ll add the English translation later today.:

translation added

8

thank you.. will watch tonight.. seems exactly what I need

9

The multiplusses will go in overload and switch off pretty fast, preventing fire. Both B and C fuses will (most likely) not trip.

In case of the grid being present, both B and C fuses will trip as long as you don´t use long extension cables.

2 Likes
10

thanks, was an interesting video to see the protection in action…

I wonder, though, is this safety in the multiplus enough to pass inspection ?

1 Like
11

Why not? On grid there is no problem in case of short circuits, and the Victrons have internal short circuit protection in island mode.

Victron inverters are conform to European harmonized specs (CE-mark):

And more precise, safety of uninteruptable power supplies (UPS), NEN-EN-IEC 62040-1:2019 en;fr, so why worry? Others have done the worrying for you.

1 Like
12

Thats not treu, breakers will trip faster then mutli going in overload, my whole house is on 3 phase mp2, and have that happen in off grid mode

13

What breakers do you have ? Because in the video the multiplus wasn’t able to trip a B16

14

i have 12x B16 single phase on 3 rcd’s

and 2x 3 phase B16 rcbo’s (schneider electric)

all on 3 phase output of mp2 5k’s

15

Its good that you contemplate such things, but you clearly do not understand electrical protection. You mention “3kVA for the grid” - I expect you mean 3kA. But perhaps you misunderstand this too. Its likely your CBs have a fault current rating of 3kA, which is (hopefully) higher than your actual fault current at your point of supply. Your CBs are designed to trip at about 1.2 x their nominal protection value, such as 10A or 20A or 40A etc. The wiring to the sockets etc will cope with this current flowing 24/7. The real problem with normal protection is if you have a fault that is less than a full short, well within the rating of the wiring and CB, but its still enough heat to start a fire in the socket, or more likely, in an extension cord.

16

I have also seen this video, but…

Our 3 x Multiplus 6K5 is connected to a 3 x 25A grid. The output is also limited in settings to max 25A. This begs the question if our inverters are capable of tripping a B16 breaker. My best guess is it won’t. However. As already pointed out. The Multiplus will shutoff. Taking over the job of the MCB’s. The thing is. NEN1010 specifically states that a failure in one circuit may not trip the rest. Or whatever wording should be used here.