Field Application: B&B Electronics Solves RS-485 Problem
for Electricity Company

Salt River Project ("SRP") supplies power to the rapidly growing suburbs of Phoenix, AZ and outlying areas. As one of the fastest growing counties in the USA, the area's electrical grid is constantly and rapidly expanding.

Challenge

Different substations in SRP's grid use differing SCADA systems from multiple vendors. Each vendor implements different circuits and recommendations on how to wire, ground, bias and terminate RS-485 ports. Ongoing communication glitches were a source of stress and concern for SRP for years as erroneous data errors and trouble reports threatened to mask real substation problems.

Application

A B&B Electronics engineer made an on-site visit to SRP and reviewed RS-485 concepts with the customer. Lab testing validated the concepts could be used to measure RS-485 data signals at the substation where minor adjustments were made to termination and biasing. This was easy since SRP uses B&B Electronics' model 485DRCi converter with switchable biasing.

Looking at the scope's data also indicated errant relay slave nodes on the multi-drop RS-485 system weren't consistently replying to their polls. Random delays were causing bus contention. A follow-up call to the relay manufacturer led to a software update - problem solved!

Product - Model 485DRCi

• RS-232 to RS-422/485 optically isolated converter
• 2000V isolation on input/output and power
• 10-48 VDC operation
• Modbus ASCII/RTU compatible
• Approvals: CE, CUL Class1 Div2

Click here for more information on Model 485DRCi.

See all of B&B Electronics’ RS-485 converters at: www.bb-europe.com/485converters