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
Henri Kujala
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, crossreferencing 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