wire from combiner box to elect panel

Billy

Running wire from combiner box that is grounded to my electrical panel that is also grounded do I need to run a ground wire with my positive and common wire ?

BB.

There are two (major) reasons for grounding electrical systems.

The first is to reduce the chances of electrocution. Say you have a solar array mounted to a metal racking (metal panel frames, etc.). If there is a short circuit from "hot" to "local ground". And a squirrel chews a positive cable insulation and it touches the frame (panel, ground mount, pole, etc.) and charges the frame to Voc-array (can easily be a 100 to 600 VDC depending on array wiring). Even if you have a local ground rod (2nd reason for grounding is lighting)..

The framework is now "energyized" and the local earth grounding is not enough to pop a circuit breaker or fuse) and the grounding is not "low enough resistance" to keep the "hot frame' "short circuited" to near zero volts (with respect to "dirt"). For example, wet grass in dirt, somebody walks up to "hot frame" and you have an electrocution risk from frame to wet grass.

The general solution is to run a "ground wire" from your battery/power shed/power room in home to the ground rod at the base of the array.

The ground rod (6 AWG minimum from ground rod to racking/solar panel metal frames) provides a path for lightning, and the ground lead from the power shed provides a return path for any short circuit voltage/current to the battery return bus (and AC safety ground too).

This does assume that your battery (typically) negative bus is grounded to the local shed/home ground rod, and the AC ground (and usually AC neutral for TSW/PSW inverters are tied together in the main panel, and a 6 AWG minimum cable from panel ground bus to the same ground rod as the battery bus).

That way any short circuit from Panel/Battery/AC inverter "hot" to local metal (electrical boxes, plumbing, DC or AC) has a save return path.

If you have lightning issues, then surge suppressors are suggested too:

https://www.solar-electric.com/search/?q=mnspd

Grounding is a complex issue (lightning, electrical safety, cathodic corrosion protection, etc.)... Following electrical code is a start--But even NEC (national electric code for USA) does not alway do a good job for lightning.

-Bill