High Voltage, 30kv and Low Voltage Cable 400 Volts

Any national standard will do. I suggest you run MV circuits in seperate cable trays & if possible cover the tray & provide "HV" warning signs every 10m of the cable run. For 30kV distance to the LV cable tray would at least be 30cm. For buried HV cables it's the same principle regarding distances, but better take a bit more space. Provide either ducting/or direct burying on sand layer in the bottom of the trench & at least 100cm depth + red warning sheet. Intra unit/factory, most customers require tiles also. Generally buried HV cables will be signalled with small concrete markers or PVC signalling at ground surface level.

Design Engineering Books/reference manuals dealing with underground power distribution and raceways readily provide for the seperation distances.

One reference available with me says that " Power cable to power cable clearance not necessary, however, larger the clearance, better should be current carrying capacity".

My experience is that conventionally a minimum seperation of one foot is maintained between HT and LT power cables.

→ British Standard 7671.

If you are from India (where mosquitoes are more, I presume) please refer to IS 1255.