Hi all.

Have a friend who has installed a 5KVA system. They were just approved for SSEG by the City of Cape Town. The notice says however that they have an export limit of 3.45 KVA. What is the reason for the limit? Is is based on inverter size? The street infrastructure? Is this a hard limit on all installations? Is this a 3 phase thing? (they have 3 phase)

I'm just about to press go on a much larger system (12kW), and am wondering if I'll run into something similar, so would be very keen to hear how the export limit is calculated. 3.45 is nowhere near the capacity of the breaker.

48 minutes ago, display_Name said:

Hi all.

Have a friend who has installed a 5KVA system. They were just approved for SSEG by the City of Cape Town. The notice says however that they have an export limit of 3.45 KVA. What is the reason for the limit? Is is based on inverter size? The street infrastructure? Is this a hard limit on all installations? Is this a 3 phase thing? (they have 3 phase)

I'm just about to press go on a much larger system (12kW), and am wondering if I'll run into something similar, so would be very keen to hear how the export limit is calculated. 3.45 is nowhere near the capacity of the breaker.

It's normally calculated as 25% of the Notified Maximum Demand, where he'd have basically a 60A circuit breaker, which at 230V will have a notified peak output of 13.8kW. And 25% of that is 3.45KVA. Not sure how the 3-phase scenario fits in. Does he maybe have a limit of 3.45kVA per 60A phase?

If you ever find out definitively technically why that limit is so, I'd love to know. There are some old threads if you search the forum with some thoughts of grid stability. Bear in mind if you're exporting full power, it's not impossible that a cloud comes over and the grid suddenly has to pick up the slack for whole neighbourhoods in short time. Extract from the NMBM SSEG doc reads: "As most domestic, commercial and small industrial LV supplies are fed from a shared LV feeder, the maximum individual generation will be limited to approximately 25 % of the customer’s NMD"

In reality more folks these days are buying hybrid inverters in the 8-12kW range or more because of loadshedding. I wasn't even sure if these rules are still being applied. Last chats on the forum I heard just that the inverter's power rating should be lower than the grid power capacity.

39 minutes ago, GreenFields said:

It's normally calculated as 25% of the Notified Maximum Demand, where he'd have basically a 60A circuit breaker, which at 230V will have a notified peak output of 13.8kW. And 25% of that is 3.45KVA. Not sure how the 3-phase scenario fits in. Does he maybe have a limit of 3.45kVA per 60A phase?

If you ever find out definitively technically why that limit is so, I'd love to know. There are some old threads if you search the forum with some thoughts of grid stability. Bear in mind if you're exporting full power, it's not impossible that a cloud comes over and the grid suddenly has to pick up the slack for whole neighbourhoods in short time. Extract from the NMBM SSEG doc reads: "As most domestic, commercial and small industrial LV supplies are fed from a shared LV feeder, the maximum individual generation will be limited to approximately 25 % of the customer’s NMD"

In reality more folks these days are buying hybrid inverters in the 8-12kW range or more because of loadshedding. I wasn't even sure if these rules are still being applied. Last chats on the forum I heard just that the inverter's power rating should be lower than the grid power capacity.

woooow.... this COMPLETELY changes the economics of my planned install.

It's in the SSEG requirements, section 3.1

https://resource.capetown.gov.za/documentcentre/Documents/Procedures, guidelines and regulations/Requirements for Small-Scale Embedded Generation.pdf

You guys just saved me a TON of anguish before proceeding with a completely oversized install. I'm going to need to rethink some things. This is definitely something that I would have expected my installer to flag after having a TON of discussion / planning with them.