Glossary · Climate
Climatic region (DSTU-N B V.1.1-27)
A region of Ukraine by building climatology; for PV it gives the absolute minimum air temperature used to check string voltage.
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Definition
DSTU-N B V.1.1-27:2010 "Building climatology" divides Ukraine into climatic regions (Table 1 and Figure 1). A PV plant needs one number from it: the absolute minimum air temperature of the site. DSTU HD 60364-7-712:2022 (Annex B) calls it Tmin and puts it into the UOC MAX formula.
| Region | Name | Tmin, °C (in Solispec) |
|---|---|---|
| I | North-western | −40 |
| II | South-eastern | −42 |
| IIIA | Carpathian | −38 |
| IIIB | Transcarpathian | −32 |
| IV | Southern coast of Crimea | −20 |
| V | Crimean mountains | −27 |
For regions I and II, Table 1 gives a range (−37…−40 °C and −32…−42 °C). Solispec takes the colder end: a lower temperature means a higher open-circuit voltage, so the result errs on the safe side. Example: Kyiv lies in region I, so Tmin = −40 °C; Odesa is in region II, Tmin = −42 °C. The I/II boundary was read from Figure 1 by eye, so near the line itself the accuracy is about 0.2–0.3°.
Do not confuse the climatic region with the snow and wind districts of DBN V.1.2-2:2006: these are different maps from different norms, and their boundaries do not coincide.
Where the boundary runs in practice. The north and west of the country, including Kyiv, Zhytomyr, Chernihiv, Rivne and Lutsk, lie in region I. The south and east — Odesa, Mykolaiv, Kherson, Zaporizhzhia, Dnipro, Kharkiv — are in region II, and there the Solispec minimum is even lower, −42 °C, because the cold end of the table range is used. This surprises many people: for the string voltage check, southern Ukraine is not 'warmer' than the north. The Transcarpathian lowland (IIIB, −32 °C) is the notable exception. If your site lies near a region boundary, it is safer to enter Tmin by hand from the colder region: spare voltage margin costs at most one panel per string, while a shortfall can cost an inverter.
How Solispec applies it
The Solispec engine finds the region from the site coordinates (climateRegion): Crimea first, then the Transcarpathian lowland and the Carpathian belt, then the I/II boundary. If you have not set Tmin yourself, the string check uses that region’s minimum and shows the source "DSTU-N B V.1.1-27:2010, Table 1". Your own value always wins. For a project with no site placed on the map no region is assigned, and the 1.2·UOC STC rule applies.
Norms and clauses
- DSTU-N B V.1.1-27:2010, Table 1, Figure 1
- DSTU HD 60364-7-712:2022, Annex B
Related terms
- Site minimum temperature TminThe lowest ambient air temperature at the PV site; it sets the maximum open-circuit voltage of a string, U_OC MAX.
- Maximum open-circuit voltage UOC MAXThe open-circuit voltage of a panel or string at the site minimum temperature; inverters, fuses and isolators are selected by it.
- PV stringA chain of panels connected in series: voltages add up, the current is shared; frost and the inverter MPPT window limit its length.
- MPPT and the inverter voltage windowThe inverter’s maximum power point tracker; its voltage range sets the minimum and maximum number of panels in a string.
- DSTU-N B V.1.1-27:2010: climatic regions and Tmin for PV stringsNorms explained
- DSTU HD 60364-7-712:2022: the electrics of PV systemsNorms explained
Solispec’s calculation is preliminary: for a design it has to be checked by an engineer. The values and clauses follow the current editions of the norms on the date of the page.