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

SCADA evolution
Centralized protection and control systems (CPS)
The predecessors of modern SCADA systems were CPSs. They were developed in the
early 1900s and allowed remote, although hardwired through telephone lines, sensing of
the power status at power substations. 
The term SCADA was first used by the Bonneville Power Administration (BPA) in the
1960s. The BPA is a federal agency created in 1937 to market electric power and develop
power facilities in the Pacific North West. The 1960s saw the introduction of telemetry for
monitoring remote hardware components. The term SCADA was officially defined in 1987
in ISA RP60.6, a document that identified methods and terminology for components in
control centers. The term SCADA became common parlance in the 1970s in tandem with
the increased use of microprocessors and PLCs.
The popularity of modern SCADA systems rose out of a need by industrial enterprises,
utilities, and manufacturing businesses to be able to remotely control machines over long
distances and automate processes.
The first definition of a SCADA system described it as having three main components: a
master station, a communication transport system, and a remote station. While the
technologies that make up these components have changed over the years, the
functionalities remain the same.
SCADA generations
There are four generations of SCADA systems.
The first generation (1960s) of SCADA systems had a monolithic system architecture. A
monolithic computer system has a single-tier architecture where functional components
like communication, data processing, the user interface, and error handling are all
managed by one application on one platform. SCADA systems during this period ran on
standalone mainframe computers, using networks only to connect with field RTUs. Most

---

13/16
of the equipment used was proprietary. The functionality of monolithic SCADA systems
was limited to monitoring sensors, responding to alarms, and controlling setpoints
(desired metrics). 
The second generation (1970s) of SCADA systems had a distributed system architecture.
In this model, SCADA functions were distributed across multiple stations which were
connected through a local area network (LAN). Each station was dedicated to a particular
task, for example providing I/O capabilities or managing the operator interface, and
sharing information with the other stations in real time. Multiple stations provided more
processing power, improved redundancy, and made the system more reliable.
Neither first nor second-generation SCADA systems used standard network protocols.
Referred to as sealed systems because they were not connected to the internet, security
was less risky. The main difference between first and second-generation SCADA systems
is that first-generation systems had no connectivity to other systems.
Networked SCADA system architecture, the third generation (1980s) of SCADA systems,
connected system devices over a process control network (PCN). A PCN is made up of
multiple LANS and provides a wide area network (WAN) infrastructure for the
management and control of components on a network.
The main difference between second and third-generation SCADA systems is that third-
generation systems make use of open system rather than proprietary components.
Fourth-generation (2000s) SCADA systems harness cloud computing and IoT
technologies, for example using a web browser instead of a traditional HMI. Cloud
environments enable the use of complex control algorithms across geographically-
dispersed systems anywhere in the world. Fourth-generation SCADA systems require
less capital outlay for equipment but are subject to subscriptions. Cloud-based SCADA
systems allow virtually unlimited scaling, monitoring and remediation service from
professionals, and faster response times.