My solar panel provider changed their datasheet recently and I was wondering if the system I designed still passes as safe. I am currently working on a PV system utilizing the Victron Multi RS Solar 48/6000/200 hybrid inverter and would appreciate your input.
The proposed configuration is as follows:
Inverter: Victron Multi RS Solar 48/6000/200
PV Modules: Jinko 620 W bifacial modules
Total PV Modules: 10
MPPT Configuration: 2 independent MPPT trackers
String Layout: 5 modules in series on each MPPT tracker
The key electrical parameters are summarized below:
Victron Multi RS Solar 48/6000/200
Maximum PV Open-Circuit Voltage (Voc): 450 VDC
Maximum PV Short-Circuit Input Current (Isc) per MPPT: 16 A
Jinko 620 W Bifacial Module
STC Ratings:
Voc: Approximately 49.5 V
Isc: Approximately 16.08 A
Pmax: 620 W
BNPI Ratings:
Voc: Approximately 49.7 V
Isc: Approximately 17.77 A
Pmax: Approximately 682 W
For the PV protection, each string is protected by:
16 A DC circuit breaker
20 A DC fuse
Is this system still safe? Is my Multi RS at risk of failure/warranty void?
Could you please also confirm that this configuration and the selected protection devices are suitable for continuous operation under bifacial conditions, and advise whether any additional design considerations or limitations should be taken into account?
Location: United Arab Emirates
Ground-mounted system.
Multi RS is operating in an air conditioned environment.
Thank you for your support.
Best regards,
A
EDIT: I would like to mention that changing the PV modules is not currently an option.
Do you have pictures of the circuit breaker (there is too much crap on the market, good ones are not cheap!!!).
Also which DC fuse are planned (there are special PV fuses, mind the arcing!!)
the best idea could be to contact a local Victron representative for further contacts (look at victronenergy.com, where to buy) or further planning and/or certification with local sparkies.
If that is done already, to get a second opinion or get some additional knowledge you can ask further questions here, of course.
P.S. Do you have the exact nameplates or nameplate data of the modules?? Photos?? Nominal serial fuse rating (with 2 strings that is ok, but from 3 strings+ you have to make sure there can no dangerous shortage currents accumulate!)?? String plan of the system (wiring plan of the array!)??
For the max Voc theres an additional limit, which is battery float voltage x8. So for example for a 16s LiFePo this would be 54V x 8 = 432V
However, your 5S strings are far away from that.
The Isc is limited by the internal reverse voltage protection, which is only rated for 16A. In the event of a reverse polarity event, like it can happen during initial installation, the MPPT could not protect itself. Since you also intend to use an external 16A MCB this should be fine however.
But keep in mind that even though the Isc is limited to 16A, the Imp is further limited to “only” 12A. So even if your panels can achieve a higher output due to bifacial conditions, the MPPT can only ever convert up to 12A.
if so, the serial fuse rating is 35A (by the way, chrigu that is the max. reverse current protection fuse in parallel configuration, not 16A) for 2 strings ok. The Isc is 17,77 for the 620Wp modul.
But the regulator is at its current limits!!
check the voltage rise when it is cold in the desert to be save than sorry (sunrise in a cold morning)!!
the PV Fuses are ok (you should not operate them at max current, they get hot)
Max. operational current 12 A/Tracker → Jinko 66HL4M-BDV 620W Impp=15.22A nach STC. Nach BNPI Impp=16.81A
Max. short circuit current is 16A/Tracker → Jinko 66HL4M-BDV 620W Isc=16.08A nach STC. Nach BNPI Impp=17.77A
P.S.
The serial fuse which should be used when the number of strings is increased over 3 (possible accumulating the reverse currents in case of string failure in the generator array and more than 3+ strings) is max. 35A
I think you need to go back to first principles here. Your design is nearly there but you have misunderstood the function/behaviour of several of your components.
You must choose a panel that has a Isc of less than or equal to 16A at STC. You must not use a panel with a higher Isc than specified in the datasheet. This is not advice, it is mandatory.
You cannot provide any protection for the RS6000 with a fuse here. The reason is because that is the maximum that the panel can produce (@STC) and so it cannot blow a fuse of 20A which would require a current of approximately 1.25x the rated value to blow. This would be 1.25 x 20A = 25A.
For this reason string fuses are not used to protect the inverter/mppt, you must adhere to the max input current of 16A.
String fuses are used when there are three or more strings, if a fault occurs on one string where current from the other two strings may back feed into the damaged module, a string fuse can reduce the likelihood of a fire. Two strings each with a Isc of 16A can provide enough current to blow that 16A fuse. The maximum series fuse is specified by the manufacturer of the panels and is often around double the Isc. They have determined, in your case that a faulty module can withstand 35A for a short time before that fuse is blown. By implication, four strings would be the typical maximum in an array designed with these panels.
The 16A circuit breaker is similarly not needed. Although a MCB will trip under high thermal load under overload, or sometimes with a sudden magnetic effect from a short circuit, it still will require more than 16A to trip, so your mppt is cooked by then anyway!
If you want to use the MCB as a point of isolation, that would be OK, but there are cheaper and more reliable isolators specifically designed, so I would use one of them. They are often black/grey can be locked in the off position and can only have the lid removed once isolated.
Good luck hunting for some more modules.
Jona
Q: I wonder if I might get another AI flag for my post??
As the panels are not a changeable option and are over the limit for the rs, have you considered going seperate mppt’s & inverter which have a higher amperage limit / but have a lower voltage limit.
Could go 2x 250/70Mppt + 1x 150/35Mppt +mp2gx to get over the issue to make 2x 4S into 2x 250/70 + 2S into 150/35, plus could go with higher rated mppt’s if future upgrades may be considered.
