Breaker with modbus component

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anbm

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We specify draw out, electronic breakers with modbus communication as standard feature, vendor asked for modbus specification. What is modbus specification does anyone know? Modbus is communication device do the client can monitor amp, voltage draw through breaker, breaker status remotely. Thank you.
 
Mod bus is a communication protocol, which has been around for about 30 years. If your vendor does not have a Modbus driver you will be their guinea pig, or need to use some type of gateway/convertor. What is your vendor's native protocol?
 
jim dungar said:
Mod bus is a communication protocol, which has been around for about 30 years. If your vendor does not have a Modbus driver you will be their guinea pig, or need to use some type of gateway/convertor. What is your vendor's native protocol?
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Dont know, will ask... as elec. designer, I have not dealed with this kind of vendor's question in past. Thought it is an IT/Computer related question.
 
I've never seen any kind of breaker in Modbus communications cabling. Are they asking for the breakers between the Modbus-enabled meter where it monitors the voltage of the circuit, or in the communications cabling itself?
 
anbm said:
We specify draw out, electronic breakers with modbus communication as standard feature, vendor asked for modbus specification. What is modbus specification does anyone know? Modbus is communication device do the client can monitor amp, voltage draw through breaker, breaker status remotely. Thank you.
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This question is confusing enough that maybe a drawing is in order?

As others have said, Modbus is a protocol, and there are multiple transports -- low voltage RS-485 on differential untwisted pair, TCP, UDP, and for some people who are masochistic, ASCII.

The protocol was originally developed by Modicon ages ago, but has since been pretty much open source for ages. There are different protocol documents depending on the transport, so, what's the transport medium?

What you will need to know is going to be the transport (what kind of communications cabling is involved) and the register map with the kinds of registers, and the function of each register. I'm guessing that's what the vendor needs to know?
 
anbm said:
Dont know, will ask... as elec. designer, I have not dealed with this kind of vendor's question in past. Thought it is an IT/Computer related question.
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Kinda? Most "IT / Computer people" don't know this end of the business. If you ask in "Controls & Logic" you might find people with the relevant knowledge.
 
tallgirl said:
I've never seen any kind of breaker in Modbus communications cabling. Are they asking for the breakers between the Modbus-enabled meter where it monitors the voltage of the circuit, or in the communications cabling itself?
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Unlike Molded Case Circuit Breakers, Power Circuit Breakers almost always have some sort of communications options available.

More and more though, MCCBs with electronic trip units are able to have accessories added to them for communications, so we will be seeing it showing up on specs.
 
tallgirl said:
I've never seen any kind of breaker in Modbus communications cabling. Are they asking for the breakers between the Modbus-enabled meter where it monitors the voltage of the circuit, or in the communications cabling itself?
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Many electronic breakers have Modbus communications.
 
tallgirl said:
I've never seen any kind of breaker in Modbus communications cabling. Are they asking for the breakers between the Modbus-enabled meter where it monitors the voltage of the circuit, or in the communications cabling itself?
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It is very common with especially larger breakers to have a communications module on the breaker.
 
jim dungar said:
Many electronic breakers have Modbus communications.
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Yes, but meters also have breakers between the meter and the circuit being monitored, which is why I asked for a drawing. He also mentioned monitor the circuit. If he'd not done that I wouldn't be so confused!
 
tallgirl said:
Yes, but meters also have breakers between the meter and the circuit being monitored, which is why I asked for a drawing. He also mentioned monitor the circuit. If he'd not done that I wouldn't be so confused!
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I have often seen both meters and breakers communicating because they provide slightly different information.
I think his 'building automation' or SCADA vendor is not used to power systems equipment.
 
This was copied from a report of a job I did for GE. The communication cards were installed on the ATS units and programmed to talk to the building BMS system. Note that the settings in the table below were provided by the systems engineer in charge of the BMS system.

ATS-1 GE-Zenith Controls ZS1DB16031-05E601X, SN 1630289-3, 72A-2000
ATS-2 GE-Zenith Controls “ , SN 1630289-1, “

ATS-3 “ “ SN 1630289-2, “

ATS-R “ ZS1DB20031-05E601X, SN 1630290 “

  1. New/ Billable.
  2. To install and program (4) Modbus cards.
  3. BACKGROUND The customer reported that he wanted Modbus cards installed and programmed in the four ATSs in order for them to be included in the BMS network using the GE Cimplicity software.
  1. WORK DONE
    • Time was spent locating the proper Modbus Converter and shop testing the Modbus cards on a spare MX250 controller.
    • The cards were installed on the (4) ATSs and programmed according to the procedure listed in the GE-Zenith O&M Manual 71R-2200.
    • The Modbus USB to RS-485 Converter was connected between the laptop and the Modbus card. The Configuration Program 50P-1111 was accessed and the following settings were provided by John Xxxxxxx of GE Energy:


Baud Rate
19,200​
Protocol

RTU​

Parity​

None​

Data Bits
8​
Stop Bits
1​


  • All cards were re-programmed and testes using the above procedure.
5. WORK DONE continued

  • The MX250 controller settings were noted and recorded.
  • All systems were returned to their normal standby mode.


6. RESULTS AND RECOMMENDATIONS

  • The Modbus communication cards have been installed on the four ATS, programmed and tested. The results of the tests indicate that the cards are operating as designed. No starting of the generators or load transfer tests could be performed at this time.
  • John Vandriel tried to connect into the network as the cards were being installed but was unable to communicate with the Cimplicity program on his laptop.
  • TECI spent the rest of the day in assisting John but all attempts were unsuccessful.
  • The following day John contacted TECI and advised them that he had found a checkbox in his program that was not checked. He made the proper change and everything is now working properly.
  • TECI recommends that each ATS be transfer tested on a monthly basis and that the tests be initiated by a command through the Modbus network of each ATS to verify proper system operation.
Hope this answers some questions.
 
Jraef said:
The likely want to know if you want Modbus RTU, which is typically over an RS-485 connection, or Modbus TCP/IP, which would be over an Ethernet connection.
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You are correct, it was Modbus RTU and has cat 5 cable to connect to a gateway, gateway then communicate with remote monitoring system via Ethernet.
 
jim dungar said:
I have often seen both meters and breakers communicating because they provide slightly different information.
I think his 'building automation' or SCADA vendor is not used to power systems equipment.
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Most of what I've used Modbus for was talking to either power meters or power conversion equipment. Modbus is pretty much all over the place. Very nice protocol. Very easy to implement. Very hard to implement correctly ...
 
petersonra said:
What is hard about it?
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I think getting some of the timers right has to be the hardest, followed by making sure the transmitter FIFO is kept full when it's supposed to be full. At lower bit rates there's plenty of time, and things like the T3.5 timer is fairly long. The last Modbus stack I wrote I made sure to test all the way to 460kBaud to make sure it would work properly at saner speeds.

The problem is increased reliance on general purpose operating systems as the platform, rather than a small RTOS on a dedicated microcontroller.

My personal peeve is using TCP instead of UDP. Datagrams are so much nicer than byte streams, and multicast UDP seems like a natural approach to doing Modbus on a large network with lots of devices.
 
tallgirl said:
I think getting some of the timers right has to be the hardest, followed by making sure the transmitter FIFO is kept full when it's supposed to be full. At lower bit rates there's plenty of time, and things like the T3.5 timer is fairly long. The last Modbus stack I wrote I made sure to test all the way to 460kBaud to make sure it would work properly at saner speeds.

The problem is increased reliance on general purpose operating systems as the platform, rather than a small RTOS on a dedicated microcontroller.

My personal peeve is using TCP instead of UDP. Datagrams are so much nicer than byte streams, and multicast UDP seems like a natural approach to doing Modbus on a large network with lots of devices.
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But, encapsulating an RTU packet inside a TCP/IP packet means you don't have to write all that much code.
 
petersonra said:
But, encapsulating an RTU packet inside a TCP/IP packet means you don't have to write all that much code.
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The same can be said for UDP datagrams, but with datagrams and multicast you can get the network gear to do more work and you know you have the entire packet because it's a datagram.

With TCP you have to decapsulate the header to know how much more there is to read. With UDP you just read a datagram, and there you are -- by definition you have the entire packet. If you want all of some class of devices to respond, create a net group and have all of that class of devices subscribe to that group. That's something you can't do with TCP unless you want to use broadcast, but then you can't limit the recipients like you can with a net group.
 
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