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WHAT IS a Type 1: Passive standby UPS utilised as off-grid hybrid SSEG:

=======================================================
Implication is that the SSEG has an Off-Grid Mode and a Passive UPS mode,
the requirement is to have a transfer switch but the documentation does not say what the transfer switch must do
What States are allowed in this type of system and what activities are allowed in which State ?
 
STATE 1 = OFF GRID
Nothing/Genset ——>Input to SSEG—> Output from SSEG—>E.L.—>MCB—> Load   .AND.   GRID—>Nothing or Unprotected / High Power Loads Only 
                                          invert   
BATTERY—————————>|
SSEG can do what it wants as it is Off-Grid
 
STATE 2 = Passive Standby UPS, Charging Allowed and Passthru Allowed, Inverting Not Allowed >> must switch to State 1
GRID——> Input to SSEG—> Output from SSEG—>E.L.—>MCB—> Load
                          charge   
BATTERY<———|
Same as a load shedding system when it is in charge mode with Passthru
 
STATE 3 = Passive Standby UPS (charging allowed but No passthru allowed,... SSEG is a.n.other load that charges the battery... grid connects directly to all loads)
GRID——> Input to SSEG—> Output from SSEG—>NOT Connected to Any Load      .AND.     GRID——>E.L.——>MCB——>All Loads      
                          charge   
BATTERY<————|
Implication = No load = No demand for power = No Inverter activity = No Feed-In = Electrical Safety
 
STATE 4 = No Charging allowed and No Passthru Allowed
Nothing/Genset ——> Input to SSEG—> Output from SSEG—>NOT Connected to Load      .AND.     GRID——>E.L.——>MCB——>All Loads      
                           charge   
BATTERY<———————|
Implication = SSEG Must charge with its own resources, Solar or Generator, it remains Off-Grid permanently
 
When the transfer switch detects loss of Grid or the SSEG starts the solar day it initiates STATE 1
When the SSEG reaches the end of the solar day or a Dark Day depletes the battery it initiates STATE 2 or 3 or 4 (whichever is allowed)
 
Assuming State 1 is allowed
Q) Which of states 2,3,4 are allowed and what are the conditions for allowing them
     (N.B. State 2 is how all Existing Load Shedding Systems are connected, so if this is not allowed then all Load shedding systems in CoCT are illegal)
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4 hours ago, CCC Telecom said:

WHAT IS a Type 1: Passive standby UPS utilised as off-grid hybrid SSEG:

=======================================================
Implication is that the SSEG has an Off-Grid Mode and a Passive UPS mode,
the requirement is to have a transfer switch but the documentation does not say what the transfer switch must do
What States are allowed in this type of system and what activities are allowed in which State ?
 
STATE 1 = OFF GRID
Nothing/Genset ——>Input to SSEG—> Output from SSEG—>E.L.—>MCB—> Load   .AND.   GRID—>Nothing or Unprotected / High Power Loads Only 
                                          invert   
BATTERY—————————>|
SSEG can do what it wants as it is Off-Grid
 
STATE 2 = Passive Standby UPS, Charging Allowed and Passthru Allowed, Inverting Not Allowed >> must switch to State 1
GRID——> Input to SSEG—> Output from SSEG—>E.L.—>MCB—> Load
                          charge   
BATTERY<———|
Same as a load shedding system when it is in charge mode with Passthru
 
STATE 3 = Passive Standby UPS (charging allowed but No passthru allowed,... SSEG is a.n.other load that charges the battery... grid connects directly to all loads)
GRID——> Input to SSEG—> Output from SSEG—>NOT Connected to Any Load      .AND.     GRID——>E.L.——>MCB——>All Loads      
                          charge   
BATTERY<————|
Implication = No load = No demand for power = No Inverter activity = No Feed-In = Electrical Safety
 
STATE 4 = No Charging allowed and No Passthru Allowed
Nothing/Genset ——> Input to SSEG—> Output from SSEG—>NOT Connected to Load      .AND.     GRID——>E.L.——>MCB——>All Loads      
                           charge   
BATTERY<———————|
Implication = SSEG Must charge with its own resources, Solar or Generator, it remains Off-Grid permanently
 
When the transfer switch detects loss of Grid or the SSEG starts the solar day it initiates STATE 1
When the SSEG reaches the end of the solar day or a Dark Day depletes the battery it initiates STATE 2 or 3 or 4 (whichever is allowed)
 
Assuming State 1 is allowed
Q) Which of states 2,3,4 are allowed and what are the conditions for allowing them
     (N.B. State 2 is how all Existing Load Shedding Systems are connected, so if this is not allowed then all Load shedding systems in CoCT are illegal)

The question comes down to what the CoCT envision is being switched with CoCT power by the transfer switch, the SSEG AC INPUT, the SSEG AC OUTPUT or BOTH and what they permit in an application that makes your system fit into this category

INPUT implies that Passthru is OK and Charging is OK, the input to the SSEG is switched between CoCT Power and a Generator, the output is the load DB Board with two sections sacrificial loads and protected loads, Normal ATS functionality applies here, they are probably thinking to only use the SSEG on power failure only and that anything else is classified as a grid tied SSEG, but the user is thinking to disconnect the CoCT power every solar day to operate Off-Grid and resume CoCT power at Night

OUTPUT is the way they normally think, where the entire DB Board is switched between the SSEG Output and CoCT Power, and that the SSEG acts as backup power supply in passive UPS mode to the CoCT Grid in case of power failure, I am not sure what their thoughts will be on deliberately disconnecting CoCT power to operate OFF Grid all day 

BOTH implies that CoCT expect their grid to be disconnected from both the SSEG AC Input and load DB Board when the SSEG is operational using a 4 pole ATS for single phase power (i.e. 8 input wires and 4 output wires to switch CoCT power on and off from the SSEG input and the Load DB Board simultaneously), feed-in is impossible when disconnected and that when connected they expect the load DB Board to be directly powered by CoCT power and that any SSEG input is for battery charging only

So if anyone can shed any light on what the CoCT thinks a "Type1: Passive standby UPS utilised as an off grid hybrid SSEG" is and how it connects and disconnects, because it all seems to be a bit hit and miss to me, you put your application in and if your project engineer thinks it isn't possible for there to be any grid feed-in you are good to go, if anyone has been refused this Type1 classification because they are not switching the OUTPUT with an external switch, or they have had their application refused because they intend to deliberately disconnect CoCT every day and not on power failure, that would be useful information

Edited by CCC Telecom
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This is what I understand about the CoCT Passive standby UPS requirements:

A Passive standby UPS is one in which the inverter doesn't run (i.e. produce it's own AC output) while the grid is present. In other words, the loads are switched to the grid through some sort of changeover switch, which could be the internal passthrough and the inverter is basically off. The UPS is allowed to charge the battery during this time subject to the AC current limit of 25% of your main breaker size. The switch that disconnects the load from the grid (internal or external) must comply with SANS 60947-6-1. As far as I know the changeover must be a break-before-make, with at least 20ms break so that the inverter can never feed into the grid.

I am using an MLT Inverters Oasis, which is of this type (done intentionally as this type of inverter doesn't require NRS certification) and MLT have this declaration that you can submit with your off-grid SSEG application.

https://www.mltinverters.com/documents/Oasis-SSEG-Suitable-Contactor-v1.1.pdf

 

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  • 3 months later...

I have a Mecer Axpert 4kW/5kW inverter and some batteries and solar panels. I don't intend to feed power into the grid at all. I'm not sure about the internals of the inverter, but I'm pretty sure it operates in two distinct modes: Solar priority supplemented by Grid and/or batteries should the load be insufficient OR Grid Priority where PV only charge the batteries. (And of course Grid-fault mode where it is a PV/UPS setup).

PV definitely gets limited by the load under normal operating conditions - i.e. if the load is low, the PV will only match that and not produce exported energy.

Does this sort of setup qualify as a SSEG?

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