According to strings

Method

The collector width is divided into strips whose strings switch off independently. The strips are the strings on one rack (Racking tab), one when the input is blank, when they are stacked across the width. Strings side by side along the row form one strip, since a shadow on the row reaches every one of them. As the shadow climbs a strip, the strip's loss ramps from zero to the whole strip over one cell width, because a partly shaded cell limits the current of the whole string. With the geometric closed form of the Near shading step the ramp is not applied. The extra loss beyond the light the shadow removes is recorded as the electrical shading row, scaled by the fraction for electrical effect. Every width below is measured up the slope of the collector.

The math

$$f_{elec} = f_{frac}\left(\frac{\sum_k \ell_k}{W_{tot}} - F_{sh}\right),\qquad \ell_k = s_k + \min\!\left(\frac{s_k}{c}, 1\right)(W_{strip} - s_k) \tag{1}$$

where

Symbol	Meaning	Unit
$f_{elec}$	the extra fraction of the direct light lost to the electrical effect	—
$f_{frac}$	the fraction for electrical effect	—
$\ell_k$	the width of strip $k$ counted as lost	m
$W_{tot}$	the total row width	m
$F_{sh}$	the shaded fraction of the row	—
$s_k$	the width of strip $k$ the shadow covers	m
$c$	the width of one cell	m
$W_{strip}$	the width of one strip, the collector width over the number of strips	m

References

1. PVsyst 8 help, Electrical effect according to module strings

API

array.shade_mode = electrical

Symbols follow the symbol registry.