Paper RTU
Paper RTU
Paper RTU
, NARVAEZ,
LUIZA., MELENDEZ, LUIS. RTU. 1
AbstractThe development of this project pretend expose also as these data exchange of the elements in the red. The
important points about the Remote Terminal Unit (RTU). All protocol specification defines the transmission modes: ASCII
based on research and prior consultations, with the purpose to and RTU. The modes define how the bytes of the message
expanding the knowledge on Industrial Communication Systems.
are transmitted. It is not possible to use the two transmission
modes on the same network. In RTU mode, each transmitted
Index TermsRTU. word has 1 start bit, 8 data bits, 2 stop bits, no parity. Thus,
the bit sequence for the transmission of a byte is as follows:
I. I NTRODUCTION
gramming languages, among other characteristics. Like, delve In RTU mode, each data byte is transmitted as a single word
into some specific vendors and referrals, to get a vision of the with its value directly in hexadecimal. The SRW 01 only uses
devices that are facing in the market. this mode of transmission for communication, thus not having
March 4, 2017 communication in the ASCII mode.
The Modbus-RTU network uses the master-slave system for
message exchange. Allows up to 247 slaves, but only one
II. W HAT ARE RTU S ?
master. All communication starts with the teacher making a
Remote terminal Units are data acquisition and field control request to a slave, and the slave responds to the teacher who
devices, whose main function is to interface between local was asked.
instrumentation and control equipment and the data acqui-
sition and monitoring system. A remote terminal unit has
the capability to monitor a number of I / O related to a B. Distributed Network Protocol (DNP 3.)
process, analyze and maintain data in real time, execute user- Non-proprietary communication protocol that must comply
programmed control algorithms, communicate with the master with IEC 60870-5 and must optimize transmission of data
station, and in some Cases, with others remote. It is a device acquisition and control of instructions from one station to
based on microprocessors, which allows to obtain independent another station in Supervisory Control and Data Acquisition
signals of the processes and to send the information to a (SCADA) applications between an RTU Local and / or remote
remote site where it is processed. Generally this remote site is and a master station. Presents important functionalities that
a control room where there is a central SCADA system that make it more robust, efficient and compatible than other older
allows visualizing the variables sent by the RTU. protocols, such as Modbus, with the counterpart of being a
much more complex protocol.
III. RTU C OMMUNICATION P ROTOCOLS The frame format used is based on IEC 60870-5 specifications
A RTU may be interfaced to multiple master stations and and uses the Cyclic Redundancy Check (CRC) for error
IEDs (Intelligent Electronic Device) with different communi- detection.
cation media (usually serial (RS232, RS485, RS422) or Ether-
net). An RTU may support standard protocols (Modbus, IEC C. IEC 60870-5-101, IEC 60870-5-104
60870-5101/103/104, DNP3,IEC 60870-6-ICCP, IEC 61850
etc.) to interface any third party software. The IEC protocol is an international standard prepared to
monitor energy systems, control systems and their associated
communications. The IEC 60870-5-104 protocol is the exten-
A. The MODBUS-RTU PROTOCOL sion of the 60870-5-101 protocol. Both are similar but the IEC
The Modbus protocol was developed by Modicon, part of 60870-5-104 version incorporates changes. The IEC 60870-
Schneider Automation. In the protocol are defined the format 5-104 protocol allows the communication of control stations
of the messages used by the elements that are part of the with substations via TCP / IP. The TCP protocol is oriented to
Modbus network, services that can be offered via red, and transmit data in a secure way. The IEC 60870-5-104 protocol
UNIVERSIDAD DEL CAUCA. VELASCO, LINA., NARVAEZ,
LUIZA., MELENDEZ, LUIS. RTU. 2
limits the data being transmitted and the configuration param- LAN or WAN, ensuring encrypted and authenticated Point-
eters defined with IEC 60870-5-101, which means that not all to-Point communication. SSL VPNs are used to establish
functions supported by the IEC 60870-5-101 are compatible an encrypted HTTPS tunnel to a Web server on the remote
with IEC 60870 -5-104. device. OpenVPN is a VPN technology that also allows to
establish encrypted VPN tunnels and allows authentication.
This protocol can be found in RTU Control devices, it is based
D. IEC 60870
on the SSL standard.
In electrical engineering and power system automation, the The advantages of using a VPN technology in RTU control
International Electrotechnical Commission 60870 standards devices are, for example, that any communication protocol
define systems used for telecontrol (supervisory control and regardless of its weakness can travel through a VPN in
data acquisition). Such systems are used for controlling electric complete safety and that the information travels encrypted and
power transmission grids and other geographically widespread can not be altered by a bad user deliberate.
control systems. By use of standardized protocols, equipment
from many different suppliers can be made to interoperate. V. P ROGRAMMING LANGUAGES
IEC standard 60870 has six parts, defining general informa- The industry has standardized on the IEC 61131-3 func-
tion related to the standard, operating conditions, electrical tional block language for creating programs to run on RTUs
interfaces, performance requirements, and data transmission and PLCs, although nearly all vendors also offer proprietary
protocols. The 60870 standards are developed by IEC Techni- alternatives and associated development environments.
cal Committee 57 (Working Group 03).
A. IEC 61131-3
IV. B UILT- IN TECHNOLOGIES
Part 3 of IEC 61131 deals with basic software architecture
A. GSM and GPRS and programming languages of the control program within
GSM [Global System for Mobile Communications] and PLC. It defines two graphical and two textual programming
GPRS [General packet radio service] can be used for data language standards:
transfer for industrial application. It is one of the cheapest
means of wireless communication, but at the cost of reliability. Ladder diagram (LD), graphical.
Though cheap it has a recurring cost and depends on public Function block diagram (FBD), graphical.
wireless communication domain. However, due to GSM and Structured text (ST), textual.
GPRS technology user can achieve wireless communication Instruction list (IL), textual.
up to far greater distances as compared to point to point Sequential function chart (SFC), has elements to organize
communication at a very low competitive cost. programs for sequential and parallel control processing.
Communication via GSM technology is at the middle of the
GSM radio modem can be interconnected with the PLC / VI. R EFERENCES
SCADA and RTUs. The data can be transmitted and received Among references of different brands were:
between PLC / RTU and SCADA using a GSM modem
with SIM cards of any public network that supports GSM ADAM-3600:
technology. Data can be transferred via two ways:
By sending and receiving Short messages-via short message
service (SMS) facility. * By Data calling user can connect to
remote location via dial up to transfer data serially i.e. By
creating Dial Up connection between SCADA /PLC and RTU
In the communication via technology GPRS the GPRS radio
modem can be interconnected with the PLC / SCADA and
RTUs. The data can be transmitted and received between PLC
/ RTU and SCADA using GPRS modem with SIM cards of
any public network that supports GSM technology.
Fig. 1. ADAM-3600
http://www.directindustry.es/prod/advantech/product-4657-1782415.html
SIEMENS
B. VPN Technology
In those cases in which the recommendations to obtain High Performance CPU Cortex A8 600MHz.
an ideal scenario mentioned above can not be applied, it Low Power DDR3L 256MB RAM.
is necessary to protect the communications between Control Embedded Real-time Linux Kernel.
Center and Remote RTU, regardless of the protocol used. Domain Focused Onboard IO -8AI / 8DI / 4DO.
The solution requires applying two different technologies to 4-Slot I/O Expansion.
Firewall and VPN tunnels. High I/O Flexibility with 4-slot I/O Expansion.
Virtual Private Network (VPN) tunnels allow you to es- Multiple wireless options for Zigbee/ Wi-Fi/ 3G/ 4G/
tablish IP communications over unsafe networks such as GPRS.
UNIVERSIDAD DEL CAUCA. VELASCO, LINA., NARVAEZ,
LUIZA., MELENDEZ, LUIS. RTU. 3
SICAM AK:
SICAM CMIC
Though it has a limited number of I/O modules, the standard, since there are some parameters that are not exactly
WAGOs ECO Telecontroller(750-880/025-002) is cost met, or doesnt give many information about them.
effective and the best alternative to complex control
VIII. C OMPARISON R EFERENCES
units. Nonetheless, not all applications in the telecontrol
sector requires a large number of I/O modules. This 1) SICAM A8000 is modular: the Z-miniRTU is GSM and
telecontroller only connects to a maximum of four I/O GPRS.
modules.
GSMZ-miniRTU.
6-Run AutoPILOT PRO XL.
DGCM.
C2363A-0-0.
SPRECON-E-C.
IX. C ONCLUSION
RTUs are devices that allow better performance of
industrial processes in terms of control, monitoring and
acquisition of data through communication protocols
that allow a secure and real-time communication with
the control center.
This unit has advantages over the PLC, since the RTU
has evolved in the electrical industry, and other branches,
where large SCADA systems, require the management
of a large number of signals with milli-second precision,
which is impossible with the PLCs.
R EFERENCES
[1] Gonzales Barbosa, Herman Dario. O. Supervision de las Unidades de
Transmision Remota de la electrificadora de Santander S.A. ESP mediante
protocolo IEC 60870 5 101 Bucaramanga, Colombia. 2016.
2
[2] Direct Industry. Available:www.directindustry.es/fabricante-
industrial/unidad-terminal-remota-95772.html
3
[3] COMITE DE NORMALIZACIN DE PETROLEOS MEXICANOS
Y ORGANISMOS SUBSIDIARIOS. PROTOCOLOS DE COMUNI-
CACION EN SISTEMAS DIGITALES DE MONITOREO Y CON-
TROL. MEXICO.2012.
4
[4] MOTOROLA SOLUTIONS. Available:www.motorolasolutions.com
5
[5] Wireless Systems for Automation.ISA Std. 100. 2005. Available:
https://www.isa.org/isa100/
6
[6] Industrial Automation and Control Systems Security.ISA Std. 99. 2002.
Available: https://www.isa.org/isa99/
7
[7] INDUSTRIAL NETWORK AND SYSTEM SECURITY. ISA Std. IEC
62443. 2007