Medium Voltage Cable

I would like to know the minimum acceptable insulation resistance for a 300m cable PVC /XLPE/PVC ,3*150mm^2, SERVICE VOLTAGE IS 6.6KV.
this cble is now isolated from both ends and have 3Mohm resistance measured by 5000v megger.please support your answer by a technical reference.
thank you in advance

My rule of thumb was always 1 Megohm per KV + 1 Megohm. That would give a minimum resistance of 7.6 megohm. I see that you are using a cross link PE which in itself can create some problems. In addition, I would never rely on 5,000 volts on a cable carrying more than 6,600 volts. This is a case for DC hipotting a cable using a graduated scale to chart the resistance overtime. Since this is more than megging a cable and not left to novices and definitelysomething I would not explain in an email, I would suggest that you contact the cable manufacturer for help or hire an expert in this field. This is really nothing to take lightly.