Hi

Running native gels in general require low voltage, the reason for that the high voltage generates heat which may denature your protein So try as low as 100V at 4 C and keep an eye on the tracking dye (of sample buffer) till it reach near the bottom !-2cm then turn off power pack this may take up to or more than 90 min. If you are looking for activity such of enzymes then electrophoresis should be carried at 4 degree C.

I used to insert my (empty) gel rig in suitable ice box and fill the box sides with ice and run it on bench.

Good Luck 

I usually run my acidic native gel at 150 to 200V using chilled buffer inside refrigerator 

I normally run it at 120V, under 40C, and it should work well. 

If this your first gel with that specific sample, I suggest starting with 100V until the sample enters the separating gel and then shift the to 150V for the remainder of the run. Keep the unit in an ice bath or in the fridge.