The Net is the Automation.
|-> home > question and answers > common >
1. Is an RTU a device or a function?
2. What does seamless communication in utility systems mean?
Modern approaches like the IEC 61850 draft standard and UCA are designed in a way that the application information (information models for real world information, e.g. transformer or circuit breaker), the services to access this information (e.g. reporting, control, logging), and the communication stacks (MMS, TCP/IP, Ethernet, ...) are more or less independent of each other.
Seamless means that the information of a device can be accessed independent were the device is installed. To explain the concept of seamless communication, the following cases are discussed:
Case 1 (From Control Center directly to Device)
Location of information Device installed in a substation
Case 2 (From Control Center through a proxy to Device image)
Location of information Proxy computer in a substation representing device information
Case 3 (From Control Center directly to Device - different stack)
Location of information Device installed somewere
Seamless in the context of utility applications means:
Seamless does NOT mean:
3. Is DNP3 Protocol a property of GE Harris or is it open?
This question is easy to answer: The dnp user group's web site says:
"DNP3 was developed by Harris, Distributed Automation Products. In November 1993, responsibility for defining further DNP3 specifications and ownership of the DNP3 specifications was turned over to the DNP3 Users Group, a group composed of utilities and vendors who are utilizing the protocol."
There are multiple answers to the second question (DNP3 or IEC 60870-5-104?) depending whom you ask. A technical comparison of the two can be found under: //news/51.html
This comparison will help you at least to understand the commonalities and differences.
The real interesting question is: What will be the future standard in telecontrol and - more general - in power systems automation? A new standard just arrived: IEC 61850 (Communication networks and systems in substations). Read what independent experts like John McDonald from KEMA recomment: "If your timeframe is one to two years, you should consider IEC 61850 and UCA2 MMS as the protocol." [Remark: UCA2 MMS is a crucial input to IEC 61850; UCA is now an umbrella: IEC 61850, ICCP/TASE.2, ...]
Gustavo Brunello from General Electric wrote recently in an article titled MICROPROCESSOR-BASED RELAYS AN ENABLER TO SCADA NTEGRATION: "The flexibility provided by the IEC61850/UCA-MMS protocols has the potential for saving millions of dollars in development costs for utilities and manufacturers, manufacturers, since it eliminates the need for protocol converters and lengthy, complex database mapping when integrating devices from different manufacturers..."
A first public draft "companion" standard to IEC 61850 has recently been published by IEC: IEC 61400-25 (Communications for monitoring and control of wind power plants). This standard relys on IEC 61850 and extends IEC 61850 mainly in the following two areas:
1. adds a comprehensive wind power plant information model including current process, statistical, and historical information of some 150 "information points" like "rotor speed".
2. adds to the MMS mapping (IEC 61850-8-1) other mappings: to IEC 60870-5-104, OPC XML-DA, web services, and DNP3 (keeping the information models!!)