/rapid61850

Rapid-prototyping protection and control schemes with IEC 61850

Primary LanguageJava

Rapid-prototyping protection schemes with IEC 61850

The goal of this software is to automatically generate C/C++ code which reads and writes GOOSE and Sampled Value packets. Any valid IEC 61850 Substation Configuration Description (SCD) file, describing GOOSE and/or SV communications, can be used as the input. The output code is lightweight and platform-independent, so it can run on a variety of devices, including low-cost microcontrollers and the Raspberry Pi. It's ideal for rapid-prototyping new power system protection, control, and automation systems that require communications.

This readme file describes how to set up the software, and its basic use.

The code is meant to be a proof of concept, and some parts are experimental. It has not been tested on many SCD files. Some features may be incomplete.

Features

  • Implements sending and receiving GOOSE and Sampled Value packets
  • Lightweight and fast, and suitable for low-cost microcontrollers and the Raspberry Pi
  • Platform-independent, and any C/C++ compiler should work
  • Performs validation of the SCD file, and reports any problems
  • Can optionally support fixed-length GOOSE encoding, which reduces GOOSE encoding time by approximately 50%
  • Supports initialisation of data type values, and instance-specific values
  • Simple API. The platform can be used in two ways:
    • As part of a native C/C++ program. This approach would be used where deterministic real-time performance is important, or where the network interface is custom (such as on a microcontroller). It also works well with the Qt C++ GUI framework.
    • As part of a Python or Java program. This approach uses additional C code (with winpcap/libpcap) to automatically handle the communications and data model, with SWIG wrappers to link to a Python or Java program. All the communications is handled behind the scenes. It is useful for any application where sub-millisecond performance is not needed, because it offers the comfort and convenience of writing your control logic code in a high-level language.
  • An HTTP and JSON-based implementation of the IEC 61850-7-2 ACSI. A very lightweight HTTP/HTTPS stack makes the rapid61850 data model self-describing and accessible at run-time, on-demand. This is a significantly simplified alternative to the MMS protocol or the mapping to SOAP-based web services as in IEC 61400-25-4. The use of JSON as the data format is easily supported by several programming languages, and especially JavaScript-based web applications. Therefore, it is simpler to create multi-vendor IED monitoring and control applications.
  • Open source, under the GPL 2

You can read more about the motivation and benefits of the project here.

Installation

This process has been tested on Windows and Ubuntu, but other Linux flavours and OS X should work too. Most steps only need to be completed once.

The software requires Eclipse, with the Eclipse Modeling Framework (EMF). Java Emitter Templates (JET) is needed for development, but not to run the code. It's easiest to start with the version of Eclipse that comes with the Modeling Tools bundle (see here: http://www.eclipse.org/downloads/). (If you are planning on using the Python or Java interfaces on Windows, it is best to use the 32-bit versions of Eclipse, and the JDK.)

There are two source code trees: emf (in Java), and c (obviously written in C). Each should be a separate project in Eclipse. The Java emf project directory is organised as follows:

  • src/
    • rapid61850/: code that does the bulk of the conversion from an SCD file to C code. The class Main contains the main() function for the project, and contains the filename for the input SCD file.
      • templates/: template classes that are generated by JET.
    • ch/: the EMF Java model implementation. These files are all automatically generated by EMF, but are included in the repo for convenience.
  • model/: the IEC 61850 XML Schema files. EMF uses these to generate the model.
  • templates/: the template source files used by JET.

EMF import process

  1. Start Eclipse, with the Workspace set to the root of the repository directory, e.g., /home/user/rapid61850 on Linux.
  2. Create an "EMF Project" called "emf", at the location of the repository code.
  3. Select "XML Schema" as the Model Importer type. Select all the IEC 61850 XML Schema documents in the emf/model directory.
  4. Select the three root packages that are imported (although, only scl is used). Click "Finish". This will re-generate some files in emf/model: scl.ecore, lcoordinates.ecore, lmaintenance.ecore, and SCL.genmodel.
  5. Create a new project of type "Convert Projects to JET Projects", and select the emf project. For the emf project, go to Project Properties > JET Settings, and set Template Containers to "templates", and Source Container to "src". Delete the rapid61850/templates directory in the root of emf that was created before JET was configured correctly.
  6. Open SCL.genmodel and right-click on the root of the model tree. Select "Show Properties View" and ensure that "Compliance Level" is set to "6.0". Right-click on the root again and select "Generate Model Code". This should re-generate the model implementation files (in the emf/src/ch directory), and set up the project properly for using the generated code.
  7. Two additional JAR libraries must be included for the project to compile. In the Project Properties for emf, go to Java Build Path > Libraries. Click on "Add External JARs..." and find com.ibm.icu_4.4.2.v20110823.jar and org.eclipse.emf.query_1.2.100.v200903190031.jar (or similar versions). These should be located in the "plugins" directory within the Eclipse installation.

C code project example

An example SCD file and a main.c file are provided. Many of the other C files are generated automatically. For the C code to compile with Eclipse, you should:

  • If you plan to use the native, low-level C/C++ interface (as shown in the next section), exclude the two interface*.c files from the build in Eclipse: right-click on the files > "Resource Configurations" > "Exclude from Build...", and then choose "Release" or "Debug" or another build. Also, exclude the main_SV_LE.c file, which provides an example implementation of IEC 61850-9-2LE Sampled Values, using scd_LE.xml as the SCD file. Otherwise, if using the high-level interfaces, exclude the existing main.c and main_SV_LE.c files.
  • Install MinGW and add C:\MinGW\bin; to PATH in the Project Properties > C/C++ Build > Environment options. (Other compilers should work too.)
  • In Project Properties > C/C++ Build > Settings > GCC Compiler Includes, set "${workspace_loc:/${ProjName}/Include}" as an include path.
  • In Project Properties > C/C++ Build > Settings > MinGW C Linker, add wpcap and ws2_32 (assuming you are using Windows) to "Libraries" and add "${workspace_loc:/${ProjName}/Lib}" and "C:\MinGW\lib" to "Library search path".
    • With Linux, use pcap instead of wpcap, and just add "${workspace_loc:/${ProjName}/Lib}" to the "Library search path".
  • The WinPcap library files and header files (from http://www.winpcap.org/devel.htm) have been included in the repository for convenience. The PC must also have the WinPcap driver installed (either by installing Wireshark, or from http://www.winpcap.org/install/default.htm).
    • With Ubuntu, libpcap can be installed using sudo apt-get install libpcap-dev.
    • Remember that, on Linux, libpcap needs to run as root, so either start Eclipse or run the compiled binary from the Terminal with sudo. Alternatively, you can grant the binary the capability to access the network interface using: sudo setcap cap_net_raw,cap_net_admin=eip /path_to_project/rapid61850/c/Release/c.

Using the code with a new SCD file

First, open the file Main.java. In the Main class, set the value of SCD_FILENAME to the filename of the SCD file. The SCD file should be in the same directory as the Main.java file. Run the Java project to generate the C implementation. If the SCD parser complains, ensure that the first two lines of the SCD file exactly match those from the example scd.xml in the repository. It's usually best to refresh the C project in Eclipse, to ensure that Eclipse knows about the new or modified files.

A basic C main() function will look something like:

#include "iec61850.h"

int length = 0;
unsigned char buffer[2048] = {0};

int main() {
    initialise_iec61850();                                         // initialise all data structures

    // send GOOSE packet
    E1Q1SB1.S1.C1.TVTRa_1.Vol.instMag.f = 1.024;                   // set a value that appears in the dataset used by the "ItlPositions" GOOSE Control
    length = E1Q1SB1.S1.C1.LN0.ItlPositions.send(buffer, 1, 512);  // generate a goose packet, and store the bytes in "buffer"
    send_ethernet_packet(buffer, length);                          // platform-specific call to send an Ethernet packet


    // in another IED...


    // receive GOOSE or SV packet
    length = recv_ethernet_packet(buffer);                         // platform-specific call to receive an Ethernet packet
    gse_sv_packet_filter(buffer, length);                          // deals with any GOOSE or SV dataset that is able to be processed

    // read value that was updated by the packet (it will equal 1.024)
    float inputValue = D1Q1SB4.S1.C1.RSYNa_1.gse_inputs_ItlPositions.E1Q1SB1_C1_Positions.C1_TVTR_1_Vol_instMag.f;

    return 0;
}

The data structures used for generating GOOSE and SV packets are stored within LN0. GOOSE packets are generated by calling the appropriate send(buffer, statusChange, timeAllowedToLive) function, where statusChange should be 1 if any value in the dataset has changed, and where timeAllowedToLive is the time in milliseconds for the receiver to wait for the next re-transmission. SV packets are sent by calling the update(buffer) function, which returns 0 if the next ASDU was written, but other ASDUs are free. It returns the size of the packet when all ASDUs have been written (and buffer contains the packet data). Clearly, a real implementation might include the use of platform-specific timers, interrupts and callbacks, where needed.

The generated C code implements all IEDs specified in the SCD file. You can use the code to emulate the communications between several IEDs, or just use one IED's implementation.

Set the local MAC address

In ctypes.h, set LOCAL_MAC_ADDRESS_VALUE to the local network interface's MAC address. This must be done for each physical device.

Callbacks after a dataset is decoded

Callbacks should be set up in the form:

void SVcallbackFunction(CTYPE_INT16U smpCnt) {
    ;
}

void GSEcallbackFunction(CTYPE_INT32U timeAllowedToLive, CTYPE_TIMESTAMP T, CTYPE_INT32U stNum, CTYPE_INT32U sqNum) {
    ;
}

//...

D1Q1SB4.S1.C1.exampleMMXU_1.sv_inputs_rmxuCB.datasetDecodeDone = &SVcallbackFunction;
D1Q1SB4.S1.C1.RSYNa_1.gse_inputs_ItlPositions.datasetDecodeDone = &GSEcallbackFunction;

where D1Q1SB4.S1.C1.exampleMMXU_1 is a Logical Node defined in datatypes.h (and ied.h). rmxuCB is the name of the SampledValueControl, in a different IED, which sent the SV packets. After being initialised, the callback function will be executed after this dataset is successfully decoded, to allow the LN to deal with the new data. For example, by default, only one packet of data is saved for each GSE or SV Control - and is overwritten when a new packet arrives. Therefore, it may be useful to use the callback to log the data to a separate memory buffer.

Fixed-length GOOSE encoding

To enable fixed-length GOOSE encoding, in ctypes.h set the value of GOOSE_FIXED_SIZE to 1. Otherwise, it should have a value of 0. This can only be enabled globally for all GOOSE encoding, rather than on a per Control basis.

Platform-specific options

All platform-specific options can be edited in ctypes.h or ctypes.c. For example, for a big endian platform, change:

#define LITTLE_ENDIAN       1

to:

#define LITTLE_ENDIAN       0

All CTYPE_* definitions must map to local datatypes of the correct size and sign.

In ctypes.c, the basic library function memcpy() is used to copy bytes in order (according to platform endianness), and reversememcpy() copies the bytes of multi-byte data types in reverse order (for converting between endianness). Although these will work, they can be replaced with platform-specific alternatives for better performance.

The value of TIMESTAMP_SUPPORTED should be set to 0, unless generating timestamps has been implemented for your platform. An implementation for Windows has been included by default.

Using the HTTP and JSON interface

This functionality is experimental. Some data types and ACSI services have not been fully tested yet. Support for Windows and Linux has been verified; OS X should work too. The JSON interface can run on an embedded (i.e., non-POSIX) platform, but an alternative web server is necessary.

An "index" of the data model provided by rapid61850 is generated automatically. This fully exposes the data model, including all metadata (such as data types and functional constraints), at run-time. A JavaScript object notation (JSON) data format, with an interface which is exposed via HTTP (or HTTPS), has been provided for implementing the IEC 61850-7-2 abstract communication service interface (ACSI).

Mongoose, which is embedded in the repository and has an open source GPL 2 license, provides a simple and lightweight web server. As with the rest of rapid61850, the JSON interface "implements" all IEDs specified in the SCD file. By default, a new thread is spawned for each IED; this allows multiple IEDs to be tested together from a single application. (Note: no locking has been implemented for the data model, but different IEDs should not modify each other's data directly.) As well as the HTTP server for each IED, there is a basic facility for an HTTP client, for IEDs to perform GET and POST operations on other IEDs - whether local or remote.

API details

There are examples of how to use each command from C code in main_json.c. JSON prettification (formatting with whitespace) can be enabled at compile-time.

Either . or / can be used to separate items in the object reference, but the separator between the Logical Device and the object reference must be /. All URLs are case-sensitive.

Associate

Explicitly creates an ACSI association, using the IP address and port of the requester as the ID. ACSI_AUTO_ASSOCIATE can be set to 1 to automatically associate any client that requests data. Alternatively, this command can be completely ignored for convenience. If using HTTP authentication (with SSL), the username and password act as the authentication parameters for the association.

HTTP GET with: /associate

Release

Releases an ACSI association.

HTTP GET with: /release

Abort

Aborts an ACSI association.

HTTP GET with: /abort

Get value

Returns the value of the specified element and all sub-elements, if applicable. The is effectively the default response for the server; if no Logical Device is specified, then all data for the entire IED will be returned.

HTTP GET with: /<LD>/<ObjectRef>

Example: GET http://localhost:8001/C1/LN0.NamPlt.configRev

Returns: {"configRev":"Rev 3.45"}

Example: GET http://localhost:8001/C1/exampleRMXU_1.AmpLocPhsB

Returns: {"AmpLocPhsB":{"instMag":{"f":1.024000},"q":0}}

Get definition

Returns the data definition of the specified element.

HTTP GET with: /definition/<LD>/<ObjectRef>

Example: GET http://localhost:8001/definition/C1/LN0.NamPlt.configRev

Returns: {"name":"configRev","type":"VisString255","FC":"DC"}

Example: GET http://localhost:8001/definition/C1/exampleRMXU_1.AmpLocPhsB

Returns: {"name":"AmpLocPhsB","type":"simpleSAV","CDC":"SAV"}

Get directory

Returns the definition of the full hierarchy, starting from the specified element. I.e., does the same as "get definition", except that it recursively seeks out all leaf nodes.

HTTP GET with: /directory/<LD>/<ObjectRef>

Example: GET http://localhost:8001/directory/C1/LN0.NamPlt.configRev

Returns:

{
    "name" : "configRev",
    "type" : "VisString255",
    "FC" : "DC",
    "items" : []
}

Example: GET http://localhost:8001/directory/C1/exampleRMXU_1.AmpLocPhsB

Returns:

{
    "name" : "AmpLocPhsB",
    "type" : "simpleSAV",
    "CDC" : "SAV",
    "items" : [
        {
            "name" : "instMag",
            "type" : "myAnalogValue",
            "FC" : "MX",
            "items" : [
                {
                    "name" : "f",
                    "type" : "FLOAT32",
                    "items" : []
                }
            ]
        },
        {
            "name" : "q",
            "type" : "Quality",
            "FC" : "MX",
            "qchg" : true,
            "items" : []
        }
   ]
}

Set value

Attempts to set the value of the specified element.

HTTP POST with: /<LD>/<ObjectRef> and with the new data value encoded as a string in the message body

Example: GET http://localhost:8001/C1/exampleMMXU_1.A.phsA.cVal.mag.f, 123.456

Returns: ok if successful

Building the JSON interface code

Two JSON examples are provided in the repository:

  1. A generic testing application, using scd.xml with main_json.c, and
  2. A simplified multi-vendor IED monitoring application, using ied_monitor.xml with main_json_ied_monitor.c.

To run the IED monitoring application:

  1. Generate C code for the ied_monitor.xml SCD file included in the repository. You may need to alter the JSON_WEB_SERVER_START_PORT variable in SCDCodeGenerator.java to control the TCP port range used for web server instances.
  2. In the C project build settings, add "${workspace_loc:/${ProjName}/src}" as an include path. This ensures the JSON code can access the other header files.
  3. Ensure that the *.c files in the c/src/json directory and main_json_ied_monitor.c are included in the build, and that the other main*.c files are not included.
  4. In ctypes.h, set JSON_INTERFACE to 1.
  5. Build and run the C project. On Windows, this step can take a long time, depending on the size of the data model.
  6. Open a web browser and go to http://localhost:8001/C1 to confirm that the web server is working.

Using SSL to encrypt all connections

  1. Install OpenSSL for your operating system.
  2. In the C project build settings:
    1. define the symbol USE_SSL
    2. link to the library ssleay32
  3. Link with SSL library
    1. Copy the file ssleay32.dll from the OpenSSL bin directory (e.g., "C:\OpenSSL-Win32\bin" on Windows) to the c/Lib directory in the repository.
    2. Rename the DLL to libssleay32.a.
  4. Ensure that the SSL certificate (ssl_cert.pem) is in the appropriate directory: typically at the root of the C directory if running from Eclipse. WARNING: the included certificate file is for testing only. Generate or purchase a new certificate for production purposes.
  5. If you wish to use HTTP authentication, set USE_HTTP_AUTH to 1 in json.h. Create your password file called htpasswd.txt, in the same directory as the SSL certificate. Mongoose (as well as various web sites) can be used to help create the MD5 hash: see main_json.c for an example.

Using the Python or Java interfaces

So far, this readme has described how to use the native C/C++ interface. It's also possible to use SWIG to automatically generate wrappers for high-level languages from C/C++ header files. At the moment, Python and Java interfaces on Windows and Linux have been tested, but other languages (such as C#, Lua, Perl, Ruby, etc.) should work too. (You can also use the high-level interface from C/C++ too, but not alongside the native interface.)

Four C files, with filenames interface*, are generated along with the rest of the GOOSE/SV code. These files, and the SWIG interface file rapid61850.i, are used as the input to SWIG. They contain functions to start a (platform-dependent) network interface using winpcap/libpcap, and functions to send GOOSE or SV packets using that network interface. All of the interaction with pcap is done in C, and is hidden by the interface given to SWIG.

Note that this interface can also be used within a C/C++ application - this is shown in the example main.c file, if HIGH_LEVEL_INTERFACE is defined as 1. If your are not using this high-level interface, and are using the plain C interface, you may need to exclude the two interface*.c files from the build in Eclipse.

Building on Windows

If using MinGW as the C compiler (as described above), this process is significantly simpler if the 32-bit versions of Eclipse and the JDK are used. The following instructions assume this. It's also assumed that the Python or Java application exists within a directory at the same level as the emf and c directories.

  • Generate the C code for your SCD file, as described above.

  • Download swigwin, which is a pre-compiled binary of SWIG for Windows. Once unzipped, there are two options for using this:

    • Add the location of swig.exe to the Windows PATH environment variable.
    • Or, copy the contents of the swigwin directory (i.e., copy swig.exe and all the sub-folders) to the c/src directory. You will need to tell Eclipse to exclude these directories from the build.

  • Create the directory for your Python or Java program called, for example, python_interface or java_interface. You may wish to make this an Eclipse PyDev or Java project.

  • Open a command prompt at the c/src directory, and run SWIG using one of the following commands:

    For Python:

     swig -python -outdir ..\..\python_interface rapid61850.i

    For Java:

     swig -java -outdir ..\..\java_interface rapid61850.i

The following subsections explain how to change the compiler settings for the c project to generate a dynamic library, instead of an executable. This differs for Python and Java. It may be helpful to create different build configurations in Eclipse if you need to use more than one of the C/C++, Python, or Java interfaces. You may also need to exclude the existing main.c file from any Python or Java builds.

Python interface C compiler settings

  • In C/C++ Build > Settings > Build Artifact:

    • set Artifact Type to Shared Library
    • set Artifact name to rapid61850
    • set Artifact extension to pyd
    • set Output prefix to _

  • In C/C++ Build > Settings > Tool Settings > Includes, use the following Include Paths (adjust these to match the exact version and location of Python on your system):

    • "C:\Python27"
    • "C:\Python27\include"
    • "C:\Python27\Lib"
    • "${workspace_loc:/${ProjName}/Include}"

  • In C/C++ Build > Settings > Tool Settings > Libraries, use the following Libraries (-l):

    • wpcap, python27, and ws2_32. (Again, adjust python27 to the correct version.)

  • In C/C++ Build > Settings > Tool Settings > Libraries, use the following Libraries search paths (-L):

    • "${workspace_loc:/${ProjName}/Lib}"
    • "C:\Python27\libs"

  • Build the C project, and copy the _rapid61850.pyd file from the Release folder to the python_interface project directory.

  • Create and run your Python code, e.g.:

    import rapid61850
from rapid61850 import *

rapid61850.start()

rapid61850.interface_gse_send_D1Q1SB4_C1_MMXUResult(1, 512)     # send GOOSE packet

rapid61850.cvar.E1Q1SB1.S1.C1.LPHDa_1.Mod.stVal = MOD_ON_1      # interact with IED data model
print rapid61850.cvar.E1Q1SB1.S1.C1.LPHDa_1.Mod.stVal

    Note that all C global variables appear within rapid61850.cvar.

Java interface C compiler settings

  • In C/C++ Build > Settings > Build Artifact:

    • set Artifact Type to Shared Library
    • set Artifact name to rapid61850
    • set Artifact extension to dll
    • leave Output prefix blank

  • In C/C++ Build > Settings > Tool Settings > Includes, use the following Include Paths (adjust these to match the exact version and location of Java on your system):

    • "C:\Program Files (x86)\Java\jdk1.7.0_03\include"
    • "C:\Program Files (x86)\Java\jdk1.7.0_03\include\win32"
    • "${workspace_loc:/${ProjName}/Include}"

  • In C/C++ Build > Settings > Tool Settings > Libraries, use the following Library search path (-L):

    • "${workspace_loc:/${ProjName}/Lib}"

  • In In C/C++ Build > Settings > Tool Settings > Miscellaneous, add -Wl,-add-stdcall-alias to the Linker flags

  • Build the C project, and copy the rapid61850.dll file from the Release folder to the java_interface project directory.

  • Create your Java code, e.g.:

    public class Main {
    static {
        System.loadLibrary("rapid61850");
    }

    public static void main(String[] args) {
        rapid61850.start();

        System.out.println(rapid61850.interface_gse_send_E1Q1SB1_C1_Performance(1, 512));                 // send GOOSE packet

        rapid61850.getE1Q1SB1().getS1().getC1().getMMXUa_1().getMod().setStVal(Mod.MOD_ON_1);             // interact with IED data model
        System.out.println(rapid61850.getE1Q1SB1().getS1().getC1().getMMXUa_1().getMod().getStVal());
    }
}

  • To run the Java program, you first need to specify the path to the native library. In Project Properties > Java Build Path > Libraries, expand the "JRE System Library" tree and select "Native library location". Click on "Edit..." and enter the project name (e.g., java_interface) as the Location path. Note that if the interface changes, such as due to changes in the SCD file, then all .java and .class files generated by SWIG should be deleted before a new dynamic library is compiled and used by the Java program.

Building on Linux

On Linux, it's easier to create the Python or Java interface with the Terminal, rather than with Eclipse. The steps below assume Ubuntu (and have only been tested on 11.10 64-bit), so it may differ on other distributions. *Note that because the following scripts compile all .c files, the example main*.c files may need to be deleted from the C source code directory.

Install the following packages:

sudo apt-get install libpcap-dev
sudo apt-get install swig
sudo apt-get install build-essential
sudo apt-get install python2.7         # other Python versions should be ok
sudo apt-get install openjdk-6-jdk

Open a Terminal at the rapid61850/c/src directory.

Python

# attempt to clean up any previous files
rm *.o *.so *_wrap.c rapid61850.py rapid61850.pyc

# run SWIG, output goes in current directory
swig -python rapid61850.i

# compile and link the C library
gcc -fPIC -c *.c -I/usr/include/python2.7
gcc -shared *.o -lpcap -o _rapid61850.so

# run Python. sudo is needed for the network interface
sudo python2.7

# example Python program:
>>> import rapid61850
>>> rapid61850.start()
>>> print rapid61850.interface_gse_send_D1Q1SB4_C1_MMXUResult(1, 512)
332
>>> exit()

Java

# attempt to clean up any previous files
rm *.o *.so *_wrap.c java/*.class java/*.java

mkdir java    # only needed once

# run SWIG, and put the .java files (there will be a lot) in the "java" sub-directory
swig -java -outdir java rapid61850.i

# compile and link the C library
gcc -fPIC -c *.c -I/usr/lib/jvm/java-6-openjdk/include -I/usr/lib/jvm/java-6-openjdk/include/linux
ld -G *.o -lpcap -o librapid61850.so

# compile all .java files, including the sample program
javac -d java/ java/*.java ../../java_interface/Main.java

# run the sample Java program. sudo is needed for the network interface
cd java
sudo java -Djava.library.path=/home/steven/rapid61850/c/src/ Main    # this path must be set correctly

Software documentation

Validation

SCDValidator.java performs semantic validation of the SCD file, prior to code generation. It checks for the following constraints:

  • Where necessary, the names of IEDs, logical nodes, data sets and data types are unique.
  • Each Control instance has matching DataSet and ControlBlock instances.
  • Each logical node “Input” has a corresponding source in a data set (typically in another IED).
  • No circular sub-data object (SDO) references occur.
  • Data attributes, basic data attributes and SDOs must map to valid types that exist in the SCD file.
  • Data type definitions appear in a hierarchical order, that will result in valid generated code.

As shown in Main.java, the validation process is separate from the code generation process. Therefore, it's possible to reuse the validation process in other software, if needed.

The validation process extensively uses the EMF Model Query framework for searching and filtering SCD data. It uses a SQL-like syntax. For example, to find all IEDs in the SCD document object root:

public void checkForDuplicateNames(DocumentRoot root) {
    // describe a condition: is the object an IED (called `TIED` in EMF)?
    final EObjectCondition isIED = new EObjectTypeRelationCondition(
        SclPackage.eINSTANCE.getTIED()
    );
    
    // build and execute a query
    IQueryResult iedResult = new SELECT(
        new FROM(root),
        new WHERE(isIED)
    ).execute();

    // loop through results
    for (Object o : iedResult) {
        TIED ied = (TIED) o;
        String iedName = ied.getName();

        // ...
    }
}

Augmented IEC 61850-6 SCL model

SCDAdditionalMappings.java uses hash maps to explicitly link parts of the Java representation of the SCL model. This greatly simplifies the code generation process. (In the SCL, these links are implicit and are achieved by string-matching.) Each mapping is as follows:

  • Each DAI is mapped to an AbstractDataAttribute, which has the sub-type of either DA or BDA, which defines the type of the DAI value.
  • Each Control, which has the sub-types GSEControl and SampledValueControl, is mapped to the matching DataSet for convenience.
  • ExtRefs are mapped to all DataSets, typically in other IEDs, which satisfy the ExtRef.
  • Instances of BaseElement, which is the super-class of DO, DA, and BDA, are mapped to Strings which contain pre-calculated C code.
  • FCDAs are mapped to:
    • The data item to which the FCDA refers, which may be a DO, DA, or BDA (all of which are sub-classes of BaseElement). Therefore, the type of the FCDA can be inferred.
    • The LN instance which contains the source data.
  • A String which is the unique name of the FCDA used in C code generation.

Code generation

The following UML class diagram illustrates how a generic representation of a C file is used by the code generation process:

Java Emitter Template (JET) files (CSourceTemplate and CHeaderTemplate) are used to define the generic structure of C source and header files. This approach allows several header files, which specify function prototypes, to be generated automatically from the CSource objects.

Notes and possible features

  • Some data types are not supported yet. However, the main useful data types (integer, floating-point, and boolean) are supported.
  • FCDAs and ExtRefs cannot use the syntax vector.mag.f as values for data object or data attribute references.
  • Data types cannot contain arrays.
  • According to the standard, SV datasets should only contain primitive data types, and not constructed types. However, because SV encoding involves fixed-length value fields, it is always possible to reconstruct the data, if encoded and decoded consistently. Therefore, this library will allow constructed types to be encoded in SV packets. Semantically, SV datasets should only contain data values that have been sampled at the specified sampling rate. Again, for practicality, this library allows any DA or DO to be used in SV datasets.
  • Support for trigger options is not implemented at present.