Moe Joe

I believe that I have built the largest domestic plant in SA.
26 Panels ==> <=13kw Pv
3 phase supply
2x Solar Evt solar water heating, equivalent to 10kwh and 6.5kwh per day
4 x instant water heaters
1 solar to gas fan induced Gas water heater
3 dwellings, the main dwelling is capable of running off-grid indefinitely

If the distance is too long, maybe this solution will work for you:
https://www.sunsynk.org/post/eastron-meters-do-you-need-one

Yes the 1st try is with Cat 5/6 cable. 
If no luck then as per the link provided earlier by @PowerUser
Just don't use 2 pairs to get a thicker wire as the 2 pairs will loose the essential twisted affect. 

Further news to the whole CT coil extension. We abandoned the Meter control because the meter simply does not communicate back to the Inverter. We are confident that the Sunsynk sends it's RS485 signal but the meter even though selected does not talk back. We had 2 of these examples on site & they both did not work. The other meter that is supported according to Sunsynk is the Enstrom meter. 
I will reach out to Sunsynk support to see exactly why this meter does not work . We extended the CT coil wiring & actually cut the coil wiring off to as small as possible & used Shielded CAT5e cable over a distance of 42m & it worked beautifully. This should give all others trying to do this some confidence. 
So for the record the Chint DDSU666 meter is a no go at the moment for Sunsynk 8kW inverter.