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Hybrid inverters with emergency back up circuits island mode. Inverter backup PFC

justinneedham

Domestic PEI and islanding mode PFC

Hybrid inverters having DC PV inputs, DC battery inputs, and a limited output to feed "emergency" loads in islanding mode appear to be getting very commonly available. I am receiving enquiries from my domestic customers, but am struggling with a seeming lack of significant info. 

Pulling up data sheets for numerous hybrid inverter models, I can't find any data for any of them relating to inverter PFC during "islanding mode" when the emergency loads are supplied directly, during network power failures, or presumably during planned periods. 

Reference 826.1.2.1. "Overload and short circuit currents shall be determined at every point..." And  I am getting no response from manufacturers I have emailed in this regard. 

I appreciate the PEFC might well be related to the local earth rod (assuming a situation of an otherwise connected external TN earth failure), and the short circuit PFC might be related to the chosen battery internal impedance characteristic in some way..

The inverter data sheets typically state only the power output capability/current (steady and peak values) for the emergency/backup load supply. How is one supposed to take these to and plan appropriate protection? The lack of info seems to be quiet universal with these devices. 

 

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    OK, let's try for an example. A random example (Givenergy) suggest 2600W output (~ 11.3A) with and this particular one, unusually it seems to me, does quote maximum fault current output 40A. It tells us nothing about for how long this fault current might  be able to be produced. - Hence the only safe thing is to presumably not to rely on that being a limiting factor and assume for "as long as it takes" .

    Let's suggest we aim to run a lighting system on it using B6 breaker. At 40A this would break in ~ 20 seconds, and by Adiabatic, require in excess of 1.5mm conductors. - Fair enough.

    Another random brand (Solis) provides no maximum current at all but just says in the data "output short circuit protection - YES."

    Another (Solax this time) 5KW output rated one simply says "Maximum AC output Current" 23.9A. - (Presumably a steady state operating current), again without any figure for short circuit max or short circuit time before internal protection kicks in. 

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  • 0

    OK, let's try for an example. A random example (Givenergy) suggest 2600W output (~ 11.3A) with and this particular one, unusually it seems to me, does quote maximum fault current output 40A. It tells us nothing about for how long this fault current might  be able to be produced. - Hence the only safe thing is to presumably not to rely on that being a limiting factor and assume for "as long as it takes" .

    Let's suggest we aim to run a lighting system on it using B6 breaker. At 40A this would break in ~ 20 seconds, and by Adiabatic, require in excess of 1.5mm conductors. - Fair enough.

    Another random brand (Solis) provides no maximum current at all but just says in the data "output short circuit protection - YES."

    Another (Solax this time) 5KW output rated one simply says "Maximum AC output Current" 23.9A. - (Presumably a steady state operating current), again without any figure for short circuit max or short circuit time before internal protection kicks in. 

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