# Thread: COC's on Solar PV and DC installations

1. ## COC's on Solar PV and DC installations

How do you go about doing a COC on a solar system with 8KW inverter and a couple batteries? My understanding is that it would be 3 seperate testes done on each of this sections such as the voltages, and Earth Fault Loop Impedance, what else needs to be tested on the solar panel side? Inverter side?, Battery side and Grid side? on p263 it talks about the Prospective short circuit current test on DC, What is meant by "total resistance of the upstream network"? it also says you can use the PSCC that the manufacturer used at the terminals (8.4.6.4) would you write down the manufacturer's rating on 1 battery or add up all the batteries and use that as the PSCC?

2. Hi

There was a previous thread on PV and DC which will provide some pointers

https://www.theforumsa.co.za/forums/...+Installations

PSCC on batteries would be for the bank - Rule of thumb is 12 x Amp hour rating of battery bank -Don't trust me on that. There is a calculation that you can do and it is found in SANS10142-1 ED2 Clause 8.4.6.3
There is also a draft document out for public comment on PV systems and the tests required that may be useful
There was a previous thread on PSCC and I have put the link further down

8.4.6.3 The prospective short-circuit current of batteries in ampere (A) can
be calculated using the following formula:
PSCC =Eb/Rbbr

where
EB is the open-circuit voltage of the batteries; if this information
is not known, then use
EB = 1,05 x UNB V (where UNB = 2,0 V/cell);
RBBr is the total resistance of the upstream network, in ohms (Ω),
including the internal resistance of the battery and the
resistance of the conductors;
RBBr = 0,9 x RB + RBL + Ry Ω (see figure 8.1);
RB is the internal resistance of the battery;
RBL is the resistance of the battery connections;
Ry is the resistance of the conductors.
NOTE The internal resistance of the battery can be obtained from the manufacturer's
data.
Figure 8.1 — Resistance components in a battery power source circuit
8.4.6.4 Alternatively the estimated PSCC at the battery terminals, as
supplied by the manufacturer of the battery, may be used.

https://www.theforumsa.co.za/forums/...highlight=PSCC