Questions about Communication Protocols

[F.ono]

I work as a project engineer of electrical equipment for substations.
More and more I have to deal with the communication of these equipment with PLC and other equipments. But I really don't know much about this area.
For example, we have Modbus, Profibus, IEC-61850... every now and then I have to verify if we have the components required to connect some equipment to some network.
So the following questions arise:
- What type of connector do I need? When do I use RS232, RS485, DB9, etc?
- What type of cable do I need? When do I use fiber optic, twisted pair or whatever?

I have searched and read parts of books about it, but they don't really get straight to the point.
I would really appreaciate if someone could give me an introduction about it.

 

[anorlunda]

Your answers depend on the bandwidth and environmental requirements, and more important on the historical accidents of convention. RS232 for example, has been implemented with dozens of connector and cable combinations.

An "accident" might be that a manufacturer chose to use DB9 connectors. You have to accommodate that even if he had no good reason for choosing DB9 over alternatives.

I'm afraid that my answer amounts to no answer of your question.

 

[berkeman]

I work as a project engineer of electrical equipment for substations.
More and more I have to deal with the communication of these equipment with PLC and other equipments. But I really don't know much about this area.
For example, we have Modbus, Profibus, IEC-61850... every now and then I have to verify if we have the components required to connect some equipment to some network.
So the following questions arise:
- What type of connector do I need? When do I use RS232, RS485, DB9, etc?
- What type of cable do I need? When do I use fiber optic, twisted pair or whatever?

I have searched and read parts of books about it, but they don't really get straight to the point.
I would really appreaciate if someone could give me an introduction about it.

I googled Modbus, Profibus, IEC-61850, and got some good hits on summary pages. I'd suggest reading through some of them, and following some of the reference links at the Wikipedia pages. That should start to give you a better understanding. If you have specific questions about that reading, please do post them here so we can help out. :-)