DIGITIZED COPPER – ADVANTAGES, DISADVANTAGES AND

OUTLOOK OF A POWER AND PROCESS INTEGRATED CONTROL

SYSTEM USING IEC 61850
Copyright Material PCIC Europe
Paper No. PCIC Europe BER-79

Laya Sathyadevan Janne Starck Shailesh Chauhan

ABB UK ABB Oy Shell P&T
St Neots Vaasa Stavanger Area
United Kingdom Finland Norway

Abstract - The safe and reliable supply of electricity for time synchronization, file transfer and engineering tool
ensuring a continuously running process, and the access on one physical cable.
feedback and data exchange from the one side to the
other, is of crucial importance to the Oil & Gas II. MODBUS RTU
Segment. It is typical that Transformers, HV, MV and
LV distribution equipment as well as the wells, field Modbus RTU communication interface normally
compressor stations and central processing plants with perform in a master-slave configuration. The master or
their motors and pumps are physically spread across a PLC sends “Query messages” to the slave device and
large area. Traditionally, ensuring a safe, reliable and receives response from the slave in “Response
continuously running plant, came hand in hand with a messages”. The standard structure of a Modbus
large amount of hardwired cabling and the site ending message is:
up with two or more automation system for process • Device address – address of the message receiver
control and power distribution, with several protocols • Function code – this code defines the message type
and interfaces. Although IEC 61850 is well known a • Data – Data block with additional information
standard, it has just recently emerged as and will take • Error check – Numeric check value to test for
further steps in fully enfolding its benefits via the communication errors
seamless connection of the electrical and the process
side. The unification of both power and process If there are a number of slaves connected to the
automation via one Ethernet Standard enables one master device, the address in the message header
centralized and optimized main control system for determines which slave responds to the message. The
monitoring and protecting an entire plant. This paper slaves whose address field doesn’t match the address
compares two model project set-ups – one using the field in the message ignores the message.
traditional power and process automation approach, the The device addresses range from 0….247, where 0 is
other based on a common IEC 61850 technology – In the broadcast address and 1…247 are assigned to
terms of safety and flexibility, performance and individual Modbus devices. The function codes contain
reliability, time and costs. one byte of information which defines the message type
and the type of action required by the slave
Index Terms — IEC 61850, interoperability, GOOSE
01 read coil status
I. INTRODUCTION 02 read input status
03 read holding register
In industries like Oil & Gas, uninterrupted power 04 read input register
supply is of vital importance. The critical operations 05 force single coil
involved in the functioning of oil & gas platforms call for 06 preset single register
better energy management through process and power 07 read exception status
automation systems. Traditional platforms achieved 15 force multiple coils
this through extensive hard wiring which is both costly 16 preset multiple registers
and complicated due to the amount of cabling and 17 report slave ID
engineering efforts involved. Modern Industrial Ethernet
standards such as IEC 61850 can now be utilized to For example, when a slave receives a Modbus
provide better visibility of assets, large amounts of message with function code 01, it collects the
diagnostic data and an integrated alarm/event and necessary output values and constructs an answer
asset management system. message. The length of this message depends on the
The integrated control and safety system (ICSS) number of values to be returned to the master.
provides a single operator interface to control and Modbus RTU uses RS-485 connections for
monitor process and power systems in the oil & gas communication between Master and Slave. This speed
platform. By using IEC 61850 communication protocol limitation makes the protocol unsuitable for time critical
to define the communication between field devices and plant operations like load shedding. The typical speed
ICSS, hardwired interfaces and serial cabling can be of a Modbus link is 19200 baud. Furthermore, the
replaced with an intelligent interface which provides Modbus interfaces does not provide redundancy to

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enhance the safety and reliability of the plant as only data via IED-IED GOOSE messages and is capable of
one client can be connected. intelligent decisions based on the system status. They
can work efficiently in a decentralized control
III. PROFIBUS architecture or a centralised one.

In a Profibus interface, cyclic or acyclic data collected

from the actuator is fed back to the PLC. It supports
cyclic as well as acyclic data exchange, diagnosis,
alarm-handling and isochronous messaging. Profibus
DP is a performance optimised version of the interface
that is used for time critical communication between
master and slave. The Profibus master is a main
controller which exchanges information cyclically with
the slaves. A slave is a peripheral device such as a
sensor or actuator which collects data. The data
transfer between the master and the slave consists of
three phases – parameterization, configuration and
data transfer. The master device follows the sequence
below during startup to exchange data with a slave: Fig. 1 IEC 61850 Logical Node structure

• Station address The data is exchanged using functions residing in the

• Request for diagnostics devices. The exchanged data is grouped into Logical
• Slave parameterization Nodes (LN) belonging to functions. The IEC 61850
• Diagnostic request check before cyclic data exchange standardises the name and the data contained in a
• Cyclic data exchange particular logical node. Logical devices (LD) groups the
• Global control logical nodes that can be managed together. For
example, the standardized data for motor temperature
When the master and slave devices are connected supervision is STMP.Alm.stVal, where STMP is the
using RS 485, 32 devices can be connected per Logical node, Alm is the data and stVal is the attribute.
segment without the use of repeaters. The devices may IEC 61850 engineering is based on standardized
be daisy chained and each segment must have a XML language which guarantees interoperability when
termination resistor at the end. Each element of the configurations are transferred between software tools,
network has an associated GSD file or configuration file for example, between protection relay and station
that defines the characteristics of each equipment. The controller tools.
data read from the Profibus device is in bytes which is Additionally, IEC 61850 has a wide set of
then unpacked by using suitable code in the controller communication services defined: object–oriented data
and identified by comparing it with the device manual. model browsing, event reporting, horizontal
Profibus interfaces have communication speeds of communication GOOSE, file transfer, time
about 1Mb, which is faster than Modbus RTU but still synchronisation among many. This enhances
slower than Ethernet links. The devices can have only interoperability and standardized behaviour. IEC 61850
one client or process controller and therefore does not standard also supports multiple vertical MMS clients
support redundancy. allowing easy application of redundancy concept at the
client or process controller level.
IV. IEC 61850
V. COMPARISON
The IEC 61850 standard uses Ethernet for data
transmission. It is fast and reliable and provides the If we consider a simple compressor motor connected to
basis to use new and evolving technologies. As IEC the ICSS, the diagnostic data and control available to
61850 is based on Ethernet technology it allows large the operator is significantly better when the
set of different network topologies which can be used communication interface between the motor and ICSS
depending of the system architecture. IEC 61850 is an Ethernet based IEC 61850 interface rather than a
standard technical report 90-4 gives network hardwired interface. An IEC 61850 interfaced motor can
engineering guidelines to help users to select communicate to the ICSS using vertical MMS
appropriate network design by describing different communication or horizontal GOOSE messages. In
reference topologies. Intelligent electronic devices or vertical communication, an IEC 61850 OPC server
IEDs is the main component of IEC 61850 interfaces. collects data from the intelligent electronic device (IED)
They not only collect data from field devices but also controlling and monitoring the motor. This data is then
acts as the control interface which can execute transferred to the ICSS in the form of regular OPC data
commands issued by the control system. The IEDs can items.
either communicate with the process automation The ICSS has direct access to time stamped voltage
system through an OPC server via MMS and current measurements, alarms and events and can
(Manufacturing Message Specification) or they can send control commands to the IED. The MMS
communicate to process controllers directly through telegrams are acknowledged and normally, no data is
high speed GOOSE (Generic Object Oriented lost as telegrams with errors are re-sent. In time critical
Substation Event) messages. The IEDs also transfer operations, vertical communications might provide a

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slower response than necessary. In such situations, unpacking of data involves careful mapping of bits and
horizontal GOOSE messages can be employed for if a device type is changed, new configuration file is
transferring analogue values needed in controller required to set up the communication link. The
applications and for fast tripping of field devices. engineering of Profibus interfaces is somewhat
GOOSE provides a high speed IED to IED data automated due to the use of GSD files, but signal level
transfer. Control and protection information can be engineering is still required at the controller. Modbus
transferred between IEDs or between IED and the interfaces behave in a similar way due to the unpacking
controller in less than 10ms using GOOSE messages. and mapping of received data that is required at the
Instead of data being sent to ICSS through OPC link, Master level. The engineering requires accurate coding
GOOSE messages can be sent directly from the IED at the controller level and is prone to human errors. Any
monitoring a field device to a process controller. To changes to the data registers will cause major changes
achieve the same level of control and monitoring, the in the engineering of the serial link. If a new device is to
amount of hardwiring required is extremely high, if not be added in between an existing set of devices, it
impossible. Furthermore, the diagnostic data available requires a rearrangement of register addresses of all
at the ICSS provides a wider perspective to the operator successive devices which will ultimately result in higher
to take informed decisions. Additionally, as all GOOSE engineering effort.
connections are continuously monitored, the receiving Securing the oil & plant platforms from malicious
device can identify anomalies as soon as they arise and outside interference is essential in today’s world as web
take corresponding action such as shifting into fail safe connectivity plays an important role in plant operations.
mode or blocking some functionality. If GOOSE messages are used for high priority data
In hardwired communications, hard wired signals must transfer, it can act as an additional security measure for
go through an output contact on the sending relay and critical data. GOOSE messages are sent at layer 2 of
then an input contact on the receiving relay. In IEC the ISO/OSI model and cannot be transmitted through
61850 communications using IEDs, the IED can be routers or firewalls. This makes the system immune to
programmed to send a report to the ICSS as soon as it rouge messages from outside the firewall. This is an
detects a change in the monitored data. As the data is important feature of IEC 61850 horizontal
transferred over Ethernet link operating at 100 Mbit/s, communication and is something that segregates the
exchanges of Sequence of Events (SoE) and GOOSE data transfer from the local network traffic.
commands between devices are faster than In the case of Modbus interfaces, the registers are
hardwired/serial/field bus protocols. Furthermore, mapped to particular devices and each bit is mapped to
special network switches can be used to prioritize a particular signal. This is vendor specific and project
GOOSE telegrams to pass critical real time data ahead specific and there is no standardized mapping which
of other network traffic. One additional benefit with IEC can be used across the various vendor devices.
61850 is the possibility to standardized redundant Similarly for Profibus devices, the GSD configuration
Ethernet using PRP and HSR protocols. Redundancy at file is vendor specific and will result in the same plant
the device level coupled with redundancy at the process having different criteria to unpack the data received
controller level improves reliability and availability of the from different Profibus devices. Utilizing IEC 61850
plant. communication technology helps the standardization of
During the lifecycle of the plant, if the communication substation configuration, control logic and operational
philosophy needs to be changed, the mapping from the procedures. The standardized substation configuration
data model to the full MMS stack is the only component language (SCL) helps in defining standardized libraries.
to be revised. This ensures long term adaptability to It saves commissioning time and a redundant
future technological developments. In such scenarios, configuration provides high levels of availability and
data modelling remains but underlying communication reliability. All data – both process and power system
technology can change to Gigabit wireless or fast data - required by the plant operator to take strategic
Bluetooth without changing the IED application. There decisions is available at the operator workstation. This
is also a life-cycle benefit that Ethernet being a stable increases the productivity as well as make the plant
technology, we can easily connect to older 10Mb half- better resistant to human errors.
duplex networks if needed. Interoperability of IEDs
throughout the plant is another advantage of the IEC VI. CONCLUSIONS
61850 communication. IEC 61850 protocol allows IEDs
from different manufacturers to be used in the same The IEC 61850 standard replaces the numerous
plant, as per client requirement, without the need of buses and links used today by a hierarchy of well
protocol converters or human interpretation. specified switched Ethernet networks. The long term
During the lifecycle of a plant, different instruments will benefits of IEC 61850 lies in its object oriented
need replacement and new components may get added hierarchical data modal approach with its use of
to the plant. IEC 61850 communication interface mainstream communication technology. The
ensures that interoperability can be maintained under standardization of substation configuration, control
such circumstances. This is possible as domain related logic, control libraries and operation procedures
model for both data and communication services are supports efficient running of the plant. This can also
separated from the protocol in IEC 61850. Data model reduce the engineering and commissioning effort
mapping to communication stack is also standardized thereby reducing the time and cost involved.
to ensure interoperable communication. In a Profibus IEC 61850 provides the customers the functional
interface, any change in the sequence of data sent by freedom in their process definitions and control
the device at some point in the plant lifecycle will philosophies and assures independence from any
require rewriting the code at the controller level. The single supplier. IEC 61850 not only delivers savings by

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way of substation design, installation, commissioning, VII. ACKNOWLEDGEMENTS
and operation, it also supports new capabilities that are
not practical or cost effective using legacy approaches. The authors would like to thank Thomas M.
On one hand there are numerous advantages of fully Schmidtchen, ABB Ltd., for his support in preparing this
utilizing the IEC 61850 protocol, but on the other hand, paper.
it has some challenges as well. VI. REFERENCES
IEC 61850 standard specifies the data model to be
followed for this communication protocol. However, the [1] A. Carvalho, J. Hansson, “Refined Integration”,
extent to which this is followed by specific ABB Review, 2009
manufacturers varies and this sometimes result in the [2] L. Sathyadevan, “Electrical Integration in Oil &
requirement of interface data management between Gas Integrated Control and Safety System using
different vendors. This is an area where greater IEC 61850”, 2014.
manufacturer collaboration will be advantageous to [3] “Special Report IEC 61850”, ABB Review, 2010
reduce engineering efforts. If we compare IEC 61850 to [4] J. Vasel, “An Introduction to integrated process
Profibus or Modbus, the amount of data management and power automation”
required is still smaller for IEC 61850 due to formal [5] J. Orth, “Future power plant control – Integrating
standardized engineering language. process & substation automation into one system”,
IEC 61850 is a comparatively young communication Power-Gen Europe, Track 7, Session Electrical
protocol and the oil & gas industry has a shortage of System, 2007.
relevant experience in this technology. The learning [6] Hakala-Ranta, Rintamäki, Starck, “Utilizing
curve for operators can be steep while trying to meet possibilities of IEC 61850 and GOOSE”, Paper
the high reliability and availability expectations of the 0741, CIRED 2009.
asset. At the same time, this is a valid point for all new [7] J. Starck, Dr. W. Wimmer, K. Majer, “Switchgear
technologies and technological advancement is Optimization Using IEC 61850-9-2”, Paper 0225,
inevitable in the modern world. While it will require CIRED 22nd International Conference on Electricity
extra efforts to introduce IEC 61850 protocol to Distribution 2013.
established brown field projects, it will be well suited for
green field projects with state of the art technologies VIII. VITA
where it can be a part of a new and improved working
environment for the operator.
Laya Sathyadevan graduated from Imperial College
The reliability of an Ethernet network depends on the
London in 2012 with an MSc degree in Control
speed and reliability of the hardware components like
Systems. She is an OGP Systems Engineer at ABB
Ethernet switches. This decides the effectiveness of the
UK. She is a member of IET and has authored three
complete system. Even though many new installations
previous papers. She worked on QGC project in
use industrial grade Ethernet in power and process
Australia and BP Caspian project where IEC 61850
automation, this aspect might force the traditional users
communication is used to integrate process and power
to adopt hardwired signals at least for critical trip
automation systems. Laya.Sathyadevan@gb.abb.com
functions.
The IEC 61850 devices are interoperable irrespective
Janne Starck works at ABB Finland as product
of the manufacturer. As interoperability is the basic
manager for distribution automation solutions. He has
philosophy of IEC 61850, interchangeability has not
15 years of experience with SCADA, protection relays,
been in scope of the standard so far. If the user wants
cyber security, substation automation and development
to replace a particular IEC 61850 device in the plant, it
of embedded devices. Janne is member of IEC TC57
will require some engineering effort at the automation
WG10. Janne.Starck@fi.abb.com
system level. The ‘plug and play’ concept is not yet
available as a part of this standard. Version update of
Shailesh Chauhan graduated from the University of
currently installed software or hardware may not
Rajasthan (Now known as National Institute of
support co-ordination with the existing versions from
Technology- Jaipur, India) in 1997 with a BE (Electrical)
different manufacturers. This could lead to a need for
degree. He has been working in the Oil & Gas industry
updating the complete zone of functions which includes
for more than 19 years. He has a lot of field experience
many devices of various manufacturers. It is important
under his belt from various electrical engineering
to note that version handling is a challenge that is
maintenance, operation and projects roles. In past he
common to all solutions based on different protocols.
has delivered papers in EXPIC and PCIC conferences.
EMI immunity, environmental challenges for outdoor
Since 2006 he is working for SHELL where he started
installation, cybersecurity, cost and complexity aspects
as a consultant electrical engineer. His most recent
of IEC 61850 communication protocol are some topics
assignment was as a Head of Electrical at Russia’s first
on which further study is required. This is presently
LNG plant. He has started his current assignment as an
outside the scope of this paper.
Electrical Engineering Team Lead at Shell P&T,
Stavanger, Norway since early 2014.
Shailesh.Chauhan@shell.com