Henri Kujala

Integration of programmable logic into a network front-end of a telecontrol system

Supervisor: Professor Patric Östergård

Instructor: Jouni Meriläinen, M.Sc. (Tech.)

Organization: Netcontrol Oy

Contents

• Objective of the thesis• The field of electricity distribution

– Related subjects: network front-end, programmable logic

• Implementation– I/O devices and data types

• Configuration constructed for verifying results• Fault clearing application for testing purposes• Summary

Objective of the thesis

• The purpose of integration of programmable logic into a network front-end of a telecontrol system is to offer a programmable logic platform– Aid in the automatization of the environment of remotely

controlled stations, namely substations

• Automatization for economical reasons and also to improve the usability of the network by increasing the level of reliability

• The aim is to make the programmable logic environment co-operate with the front-end device

Field of electricity distribution

• The field is geographically distributed– Unmanned remote stations

• Telecontrol is defined as the remote transmission of operating information

• Telecontrol applied in electricity distribution networks– Control and command of relays, breakers and switches

• A master/slave model, where the control centre is the master and the slave stations are called substations

• The key parameters of an electricity distribution network are voltages and currents

Front-end of a telecontrol system - NFE

• A device resembling computers– CPU, memory, ports for communications, database for storage

• Located at node points in the network• Front-end devices pre-process information exchanged

between substations and the control centre• Used as protocol converters and data concentrators• An example of a front-end device is the NFE (Network

Front-End) from Netcontrol– NFE504 is the specific NFE unit used throughout this thesis

Programmable logic – PLC and softPLC

• Programmable logic is used in the control of traffic lights, for example

• Programmable logic controller – PLC– PLCs execute tasks in a loop, called the scan cycle

• softPLC – software-based control– softPLC means that the functions of a PLC are executed on a PC

platform in software

• The selected softPLC application is ISaGRAF from ICS Triplex and it is used throughout this thesis as the softPLC environment– Other platforms also available

ISaGRAF environment

• Hardware independent – portable• Consists of a workbench and a target• Workbench for programming the applications and target

for executing these• Target: one virtual machine for one resource• Different target models: multi- and monotasking; medium

(16-bit) and large (32-bit)• Project database is a Microsoft Access database

ISaGRAF input and output devices

• There are two types of I/O-devices– Simple devices– Complex devices

• Simple devices are one-way (input or output)

• Complex devices are combinations of simple devices

• An I/O-driver consists of a multiple of ISaGRAF devices

Implementation

• ISaGRAF communicates with the NFE using NFElink protocol

• Also an interface module called NFElinkITF is used in the communications process– NFElinkITF is an interface, which facilitates

communications between ISaGRAF and NFElink

• I/O interface for the connection between ISaGRAF and NFE was constructed

Implementation (2)

• The structure of NFE data types is taken into account when constructing ISaGRAF I/O-devices– A dedicated ISaGRAF I/O

device and data type for each NFE data type was created

• The correspondence of the data types is almost one-to-one

• The I/O interface constructed uses the created ISaGRAF data types to access the corresponding data types at the NFE

NFE data type ISaGRAF data type

NPCBIN ISABIND

NPCBIND ISABIND

NPCINT ISAINT

NPCFLOAT ISAFLOAT

NPCCMD ISACMD

NPCSTRING ISASTRING

NPCLINE ISALINE

NPCREG ISAINT

NPCLOG ISALOG

NPCTIME ISATIME

Cross-reference

• Due to differences in addressing notation, cross-referencing is needed

• ISaGRAF notation is of type %(I/Q)AX.Y.Z– I/Q stands for input/output, respectively– A is the type of channel

• U for user generated and D for integer, for example– X.Y.Z is the channel number consisting of ISaGRAF device index

(X), the index of the simple device inside the complex device (Y) and the channel number (Z)

• NFE database addressing is as follows:– Group structure of 16 bits identifies the NFE channel and data

type– A hexadecimal 32-bit index identifies the I/O point inside the group

Cross-reference (2)

• One ISaGRAF channel is mapped into a combination of one NFE channel, one data type and one index in the group of data types

• Example:– NFE channel 2, data type NPCCMD and index

0x02000003 (hex notation) is mapped into ISaGRAF data type ISACMD, channel 2, which here, in correct notation format is %QU0.2.2

Advantages of the implemented model

• Advantages:– Easy to expand and improve– Benefits from NFElink– Redundancy of NFE’s handled by NFElink

• Disadvantages:– One additional layer between the NFElink and

ISaGRAF caused by the NFElinkITF

Configuration

• A real-life environment• Process simulator based on Mitsubishi’s PLCs• Netcontrol’s Netcon 500 substation

– NFE504 as the front-end device– IO64 cards for input/output

• ISaGRAF softPLC environment• iFix industrial automation software for controlling and

visualizing the demo configuration• NFElink + NFElinkITF for accessing the NFE database• PC computer for programming and executing the

ISaGRAF logic

Configuration (2)

Application example

• The application is an automatic fault clearing application

• The fault clearing process is automatic, but the starting of the application has to be triggered (currently manually)

• When clearing is finished, the trigger is reset

• The automation of the starting of the fault clearing process is possible to accomplish with little effort

Fault clearing

• The exchange of triggering information benefits from CMT (Connection Manager Test) module

• The triggering information itself is virtual

• Fault clearing in this process is sequential:– Open the switch– Open and close disconnectors for line testing– Close the switch to test if the fault still exists– Continue until the fault is separated from the energized

line

Fault clearing (2)

Summary and suggestions for the future

• Summary:– Programmable logic is executed with ISaGRAF– ISaGRAF is located on a PC platform and connects to the NFE for

data transfer– The created data types correspond to the NFE data types– The application example proves that the co-operation of ISaGRAF

and NFE is functioning properly

• Suggestions for the future:– Implement the redundancy of the logic in order to improve

reliability– Port the logic into the same functioning environment with the NFE

or at least execute the logic on a real-time operating system