Hello good people,
i'm dealing with a big probleme of my RS485 network on a photovoltaïque power plane.
I make Modbus communication with over 26 slave in RS485 in the photovoltaïque field (between inverter and junction box) , everything works fine in the 03 first mouths.
Then we notice that the communication begin to interrupts over the day , and losing the communication for 1hour, 2 hours, sometimes all the day...
We investigate the situation , we found that there is big AC voltage between the wire A or B and the commun , or A and the PE ground, or the Shield of the RS485 and the PE ground , we mesured up to 143 VAC , this voltage has a fast variation from 1V to 40VAC or 60VAC or 100VAC up to 143VAC (max mesured , the max value follow proportionaly the the power generated by the inverter.
We conclued that this is a 'Noise' in the signal , we make the proper cabling (Shield to the ground in one point) , we did the insulation test of all the equipements we found that everything is ok and probleme still aprear.
We mesured the voltage between two ground wire in different location on the field , we found a potentiel difference up to 24VAC !
I conclude that it's a common mode noise that affect the communication cable.
i'm still searching for a solution to this probleme and also i'm searching for the exactly source of the probleme !
I will be appreciated if someone can help me understand this problem.
Regards.
i'm dealing with a big probleme of my RS485 network on a photovoltaïque power plane.
I make Modbus communication with over 26 slave in RS485 in the photovoltaïque field (between inverter and junction box) , everything works fine in the 03 first mouths.
Then we notice that the communication begin to interrupts over the day , and losing the communication for 1hour, 2 hours, sometimes all the day...
We investigate the situation , we found that there is big AC voltage between the wire A or B and the commun , or A and the PE ground, or the Shield of the RS485 and the PE ground , we mesured up to 143 VAC , this voltage has a fast variation from 1V to 40VAC or 60VAC or 100VAC up to 143VAC (max mesured , the max value follow proportionaly the the power generated by the inverter.
We conclued that this is a 'Noise' in the signal , we make the proper cabling (Shield to the ground in one point) , we did the insulation test of all the equipements we found that everything is ok and probleme still aprear.
We mesured the voltage between two ground wire in different location on the field , we found a potentiel difference up to 24VAC !
I conclude that it's a common mode noise that affect the communication cable.
i'm still searching for a solution to this probleme and also i'm searching for the exactly source of the probleme !
I will be appreciated if someone can help me understand this problem.
Regards.