danger electric power electricity electricity power lines insulators power power pole power pylon strength Tension wiring advice advising alert black communicate communication concern electric-power electrical electricity-power-lines energy equipment height high high-voltage information informing overhead power-lines power-supply protect protection risk risks risky safety sign supply warning wires yellow cutter cutting power disconnecting house wiring arches cables current lines towers voltage blue ice snow sunshine transformer winter electricity poles high voltage high voltage equipment light street light transformers electricity-poles high-voltage-equipment power-poles sub-station