Factor Table 10, trefoil groups

Calculation factor according to German Standard VDE 0276-1000 (1999), Table 10, single cables, applicable to single-core cables in air grouped in trefoils with spacing of two cable diameters between the groups.

The factors are according to CENELEC Report R064.001 for Standard HD 384.5.523:1991.
A cable tray is a continuous plate with walls on the side but without a cover.
A cable tray is considered with holes when the holes cover at least 30 % of the total plate surface.
In case of grouped cables, no reduction of rating is necessary if the horizontal or vertical spacing between cables is at least four times the cable diameter.

Symbol

$F_{T10,3}$

Unit

p.u.

Choices

arrangement	layers	groups 1	2	3
on the surface	1	0.98	0.96	0.94
tray without holes	1	0.98	0.96	0.94
	2	0.95	0.91	0.87
	3	0.94	0.9	0.85
	4	0.937	0.894	0.84
	5	0.934	0.887	0.83
	6	0.93	0.88	0.82
tray with holes	1	1.0	0.98	0.96
	2	0.97	0.93	0.89
	3	0.96	0.92	0.85
	4	0.957	0.914	0.844
	5	0.954	0.907	0.837
	6	0.95	0.9	0.83
horizontal ladder	1	1.0	1.0	1.0
	2	0.97	0.95	0.93
	3	0.96	0.94	0.9
	4	0.957	0.937	0.89
	5	0.954	0.934	0.88
	6	0.95	0.93	0.87
vertical supports	1	0.94	0.91	0.89
	2	0.94	0.9	0.86