These tests shall be made in principle on three-pole switchgear and controlgear but may be
made on a single pole or on a single unit provided the influence of the other poles or units is
negligible. This is the general case for non-enclosed switchgear. For three-pole switchgear
and controlgear with a rated normal current not exceeding 1 250 A, the tests may be made
with all poles connected in series.