What is scada? Definition and Details paessler com/it-explained/scada it explained: scada back to index Content

SCADA network communications and protocols
SCADA systems rely on a complex communication network between system elements
and the central SCADA control hub. Communication options include hardwired options
like Ethernet, telephone lines, and optic fiber lines, wireless options like wi-fi, radio,
microwave, and cellular.

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Some of the most popular protocols used in SCADA system are standard Modbus,
Ethernet/IP, Profibus, Conitel, RP-570, IEC 60870-5 (on which T101 is based), and
distributed network Protocol (DNP3).
Modbus RTU is the de facto standard protocol for serial communications between
industrial electronic devices.
IEC 60870-5 is a suite of specifications developed by the International Electrotechnical
Commission (IEC) to provide an open standard for the transmission of SCADA data and
is used extensively in electrical-based applications.
T101, also called IEC 60870-5-101, is an international standard for communication and
control mainly in power systems.
DNP3 is used widely by process automation applications, like water and energy
industries.
HMIs
People view, regulate, and report on data through HMIs which serve as central
processing hubs and graphical user interfaces (GUIs) in SCADA systems.
The difference between an HMI and GUI is that while the main function of a GUI is to
provide a user-friendly interface that allows people to navigate an application efficiently,
the main function of an HMI is to allow an operator to perform control tasks using a
variety of interfaces, not only visual ones. HMIs do not rely on eye-pleasing interfaces
and may comprise a basic console with knobs, buttons, and levers to perform control
tasks.
HMIs do not collect data but report on data collected by RTUs, PLCs, and IEDs. While
SCADA systems can theoretically operate without an HMI, in most cases it would be
pointless as operators wouldn’t be able to see the data or receive reports. HMIs are
designed to automatically monitor processes and equipment, notify operators about
routine maintenance requirements, send out alerts in the event of system or device
failure, and trigger modifications to equipment where necessary, like switching a machine
off.
HMIs provide an organization's management with trends, which are graphical illustrations
of historical and real-time data.
In the field, operators access SCADA data for example via PCs, PDAs, mobile phones, or
OTIs.
Storage devices
Data in a SCADA system may be stored in an on-premise or cloud database. Databases
in SCADA are sometimes called data historians. A data historian is optimized to efficiently
gather, store, and process time-series data which is used to display trends in SCADA

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systems.