Min Separation Between 25kv Power and LV Control Cable

Whats the min separation needs to be maintained when LV control cables will cross perpendicularly on top of power cables which are (25 kv power cables) inside concrete duct. power cables are running east west direction inside concrete duct and top of concrete duct to top of ground (before placing insulating gravel) is 600 mm. LV 120V-240V control cables running north south direction (direct buried) require to cross duct of power cable. Whats the separation I need to maintain for this crossing. I checked CSA, NEC and IEC code and all code mentioned about the separation when both cables run parallel in same tray or trench. Nothing mentioned about crossing. Any advise in this regard is appreciated.