According to Ignoramus22178 :

Actually, a similar (but broader) statement applies to polyphase
circuits, such as three phase circuits. The sum of currents going
through hot conductors must be zero at all times.

Slight correction: through all _current_carrying_ conductors.
Eg: the hot conductor current in a 240/120V circuit (eg: stove
or dryer or "kitchen split receptacles") doesn't balance very often -
the GFCI has to sum the neutral current too.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.