Westinghouse Digitrip RMS 800 trip units Comm Protocol?


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James Wilk

Does anyone know what protocol a Westinghouse Digitrip RMS 800 Circuit breaker trip units would talk? I have seen these in the field talking to a Cutler Hammer D725 Industrical PC and then modbus back to Wonderware. I want to check on the protocol so I can have a software solution when the D725 dies. Thanks alot in advance for any info. Jim [email protected]
The protocol is called INCOM. You can download a copy of the protocol manual from the Cutler-Hammer web site at https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/FILES/IL17384V30/IL17384V30.HTM.

The signal coming out the DT800 is a two wire, 1200 baud FSK signal. 110 kHz represents a binary 1 and absense of tone indicates a binary zero. Data is send in 33-bit packets, so you will need a converter that works with something you will find on a PC. One way is to convert this 33-bit FSK signal into an 10 or 11-bit (1 start, 8 data, none or 1 even parity, 1 stop bit) asynchronous RS-232 signal. The catalog number for this converter is MINT. MINT stands for Master INCOM Network Translator. See https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/PRODUCTS/MINTII/MINTII.HTM for more information on the MINT. There is a less expensive version of the MINT called the PMCOM5, but it only works on with the newer 9600 baud products. The older 1200 baud products require the MINT.

Another solution is to install an ISA bus card in the PC and use a device driver from Cutler-Hammer to interface your software with this card. The card is called a CONI (Computer Operated Network Interface). See https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/PRODUCTS/CONI/CONI3.HTM for more information on the CONI-III. The device server communicates to other programs using DDE or OPC. Visual Basic is probably the easiest to interface with this DeviceServer since you can define a variable in VB to have a "application, topic, item" DDE name and the tag will automatically update with the DDE value without writing any code.

If you have a MINT or CONI, you can download a free version of some old "Series III" software that includes the DDE interface. The download point is https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/FILES/EIGHTLIVE/S38LIVE.zip. Then just write your VB or VC++ to access the data points as described in the INCOM protocol manual. See https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/PRODUCTS/PowerNet/manual/version3/apxb.pdf for a listing of all the DDE tags (called Device Objects). Note that the application for both PowerNet or the older Series III software was always "IMPACC". The topic for Series III was always "values". The topic for PowerNet was "xxxx" where, xxxx is the name of the DeviceServer (PowerNet is a client server architecture, so you will possibly have many DeviceServers). The "item" will be DxYYYY, where x is the device number (1 through 1000 and corresponds to how many Digitrips or IQ devices you have connected to the same blue hose) and YYYY is the information you find from the Device Objects table listed in the https://www.ch.cutler-hammer.com/docs/Fred/apscpgh/htmL/PRODUCTS/PowerNet/manual/version3/apxb.pdf URL.

Lastly, you can always directly hack out the code yourself to talk to the serial port and directly read the MINT. Just read the protocol manual to learn out. Just a word of caution, unless you have written some complex, object oriented device drivers, I would expect that a VB programmer without serial port experience would need about 1 man-month to develop the code. If the VB programmer already was proficient with writing serial port code (knew how to send binary data, new how to develop CRC or checksum algorithms, etc.), then I think it would only require about 2 man-weeks to develop. With the Series III program, it should talk about 4 man-days to develop it cold. As an example, it would take me about 1 hour to write a VB application that populated a screen with 40 variables fetched from the same number of IQ devices. Once you get proficient, the coding is very fast.

If you want more help on this subject, call the Power Management Product Center (PMPC) help desk at 800-809-2772 and press option 1.