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Design Standards / compliance options

Updated

This page lists the calculations or design restrictions which are applied in SolarPlus when you select various compliance options under Business Settings.

CEC design guidelines (Version 14, May 2022)

For grid-connected PV systems without batteries, this inverter-array oversizing limit (warning) will apply: “the inverter nominal AC power output cannot be less than 75 per cent of the array peak power.”

Please note that when you begin designing a hybrid system, you will generally select the inverter and modules first, and so this oversizing limit will apply. It will automatically be removed after a battery is added to the system design, enabling you to go back and add more modules to an inverter.

The CEC oversizing limit does not apply to Off-grid systems, or systems with DC-coupled batteries. It does apply to systems with AC-coupled batteries.

AS/NZS 4777

  • In the design/compliance section of Business Settings, check the box marked “Limit residential string voltage to 600V”

  • The 600V limit will not be applied if the Contact/Site is marked as Commercial, or if ‘Off-grid’ is selected under ‘Grid Configuration’ on the Design Page.

AS/NZS 5033:2021

 

  • Maximum voltage limits - 3.1.

    • 1000V d.c. for domestic electrical installation and 1500V d.c. for other electrical installations.

    • Hard limit does not allow for string design which exceeds these values - site is designated as domestic or commercial.

 

  • Inverter backfeed current - 3.4.1

    • We have contacted all of the inverter manufacturers on the Australian market, and those who have replied confirmed that when installed as per instructions, IBF TOTAL = 0. Therefore unless we have specification provided by a manufacturer, in which case this value with be applied as per the Standard, we have assumed that for all inverters, IBF TOTAL = 0.

 

  • Maximum string current - 3.4.2.1

    • String containing no DCUs:

      • ISTRING MAX = 1.25 x KI x ISC MOD

    • Full support for non-SolarEdge optimisers will be provided in coming releases.

    • Note that SolarEdge are compliant with IEC 62548, ie limited by the inverter, and so IDCU string max = maximum input current of the inverter.

    • String containing partial DCUs: the greater of

      • ISTRING MAX = IDCU string max WORK IN PROGRESS

      • or ISTRING MAX = 1.25 x KI x ISC MOD WORK IN PROGRESS

    • Strings with DCUs on all modules: TESTING IN PROGRESS

      • ISTRING MAX = IDCU string max

    • IDCU string max = smaller of the installed fuse, or the IDCU OCPR

Note that some inverter manufacturers may choose to show ‘Number of strings’ on their datasheets however this is contrary to industry best practice where string current in calculated based on Inverter and Module current specifications. We believe this number is stated as a generalised suggestion only. We do not support the method of fixing a maximum number of strings across all types of panels for a particular inverter series. Anyone wishing to design in strict accordance with that method for such inverter is advised to work with System Pre-build Packages where you can set that configuration.

  • DC Optimisers (DCUs)

    • 4.3.10.3 The PV input of DCUs shall have an ISC PV rating of at least 1.25 x KI x ISC MOD except where overcurrent protection is provided that is rated to protect the DCU.

    • SolarEdge:

      • Exempt from this requirement, because SolarEdge complies with IEC62548.

    • Non-SolarEdge Optimisers: 4.3.10.3 effectively means that the only PV modules currently on the market that are compatible with DCUs are the SunPower Maxeons, which come with an option for integrated micro-inverters. For now, as at June 2022, we have not updated our code to give compliance support for non-SolarEdge Optimisers.

 

Users have the option to disable this check in More Settings > Admin > My Business > Design & RoI Preferences.

  • Bifacial modules - KI

    • New bifacial modules added to the product library will have their ISC BNPI and bifaciality factor recorded.

    • If an older bifacial module is selected and there is no record of its ISC BNPI and bifaciality factor, a default, conservative KI value of 1.125 is applied, or alternatively, Isc BNPI = Isc STC *(1+0.135*BF).

    • 3.4.2.1 Max. string current includes factor for KI: ISTRING MAX = 1.25 x KI x ISC MOD, where KI = ISC BNPI / ISC MOD.

    • Bifaciality will only affect the Isc if the panel is on tilts.

 

  • Potential fault currents

    • String fault current - 3.4.2.2 IF STRING = (SA-1) × ISTRING MAX. Where there is only one string, IF STRING = ISTRING MAX

    • Sub-array fault current - 3.4.2.3 IF S-ARRAY = (SA- SSA) × ISTRING MAX

 

  • Requirements for overcurrent protection - 3.4.3.1

    • Strings: required if IF STRING + IBF TOTAL > IMOD MAX OCPR

    • Sub-array: “Where no overcurrent protection is provided, the cable size shall be as specified in Clause 4.2.2”. We have left the inclusion of Sub-array overcurrent protection as a design decision.

    • Array: “Where no overcurrent protection is provided, the cable size shall be as specified in Clause 4.2.2” We have left the inclusion of Array overcurrent protection as a design decision.

 

  • Overcurrent protection ratings

    • String containing no DCUs: 1.2 x ISTRING MAX < In ≤ IMOD MAX OCPR

    • String containing partial DCUs: (Work in progress )

      • 1.2 x ISTRING MAX < In ≤ IMOD MAX OCPR

      • and In ≤ IDCU OCPR

    • Strings with DCUs on all modules:

      • ISTRING MAX < In ≤ IDCU OCPR

    • The 1.2 multiplier is only required for string fusing, not circuit breakers. However, as circuit breakers are not recommended for overcurrent protection, the multiplier is always applied for string overcurrent protection rating calculations

    • Sub array: In ≥ SSA x ISTRING MAX

    • Array: In ≥ SA x ISTRING MAX

 

  • PV d.c. circuit current calculation 4.2.2.2

    • Components selections (isolator recommendations, PCE string input limits, and cables) are calculated by this method.

    • String

      • single string array, string overcurrent protection not provided: the greater of ISTRING = ISTRING MAXa or IBF TOTAL

      • multiple string array, string overcurrent protection not provided: ISTRING = Inb + IF STRING

      • string overcurrent protection provided: ISTRING = In

    • Sub array

      • Sub-array fuse not provided: IS-ARRAY = Inb + IF S-ARRAY

      • Sub-array fuse provided: IS-ARRAY = Inb + IF S-ARRAY

    • Array

      • PV array overcurrent protection not provided: The greater of the following: IARRAY or IBF TOTAL

      • PV array overcurrent protection provided: IARRAY = In

 

  • Initial inverter-module configuration is made before selections of fusing. If a fuse is selected which exceeds the maximum DC input current rating of the PCE, a warning message will appear.

 

  • PV d.c. circuit maximum voltage calculation - 4.2.1.3

    • No DCUs: PV array maximum voltage = VMOD MAX x M

    • Systems containing DCUs: All non-SolarEdge DCUs on the market do not increase the voltage above VMOD MAX therefore the same calculation is used as for No DCUs.

    • Note that SolarEdge are compliant with IEC 62548, ie limited by the inverter, and so PV array maximum voltage = maximum input voltage of the inverter.

 

  • Current and voltage ratings for switch disconnectors - 4.3.4.2.3

    • Current ratings for switch disconnectors include minimum ratings for both Normal Operation (Ie), and Fault conditions I(make) and Ic(break).

    • Advice provided for switch disconnectors on PV String cables only, not Sub-array or Array cables.

 

  • Commissioning checklist - 6.3

    • 6.3. The following checks have been added to commissioning checklist:

      • Before commencement of the installation of PV system, check that radio and TV reception in the key broadcast stations (essential services) are in normal operational and record irregularities.

      • Check that radio and TV reception in the reception of key broadcast stations (essential services) are not degraded when the installation is fully operational.

 

  • Site Map - 5.6.1

    • 5.6.1 Creation of Site Map PDF feature which contains all required features, including:

      • (a)  be legible and be sufficiently durable for the location, i.e. be laminated or protected by a solid clear sheet (Perspex, etc);

      • (b)  be fixed permanently in a manner appropriate for the location;

      • (c)  be in English;

      • (d)  be labelled “PV (Solar) site information” in white letters with a red background;

      • (e)  show the location address as recorded for the installation;

      • (f)  contain a plan view of the building showing the location of the PCE, the PV array(s);

      • (g)  contain a legend for the map or clearly label to identify key components and building reference points;

      • (h)  identify the location of the site information sign with the words “you are here”;

      • (i)  be as accurate as practicable ensuring the various components on the drawing are indicative of the actual installation; and

      • (j)  installation date

 

  • Circuit Current Calculations

    • As per Table 4.2 Current calculation of circuits

 

  • PV DC Voltage drop

    • 4.4.3.4 Warning appears on Install page when voltage drop between the most remote PV module in the array to the input of the PCE exceeds 5 % of the Vmp (at STC). (shall) “WARNING: DC Voltage Drop Limit”

    • 2.2.3c Warning appears on Install page when voltage drop between the most remote PV module in the array to the input of the PCE exceeds 3% of the Vmp (at STC). (should) “WARNING: DC Voltage Drop Limit”

    • Voltage drop/rise calculations are done for the longest DC cable run in a system, using the simplified method, for copper: VDROP = 2 x L x IMP x 0.0183 / ACABLE

 

  • PV Maximum DC Voltage

    • 4.2.1.2 The PV module maximum voltage is equal to VOC MOD corrected for the lowest expected operating temperature, as follows:

      VMOD MAX = VOC MOD + γv (Tmin - TSTC)

    • The minimum temperature is derived from MeteoNorm weather data, and is visible on the Design page by clicking the Site Information icon.

       

    • 4.2.1.2 (c) allows that “Where manufacturer’s instructions are not available for crystalline and multi-crystalline silicon PV modules, multiplying VOC MOD by a correction factor according to Table 4.1, using the lowest expected operating temperature as a reference.” Often people use the correction factors in Table 4.1 as a short cut, even when module data is available, and because it is a simplified method, the exact result may be slightly different than when using the equation above.

 

Inverter PV input Pmax

A warning will show if the PV array exceeds the maximum PV input power for the inverter. Please note that some inverter manufacturers have an additional power limit that applies to each MPPT, which is not checked in SolarPlus.

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