Introduction

The definition of SCADA is ‘Supervisory Control and Data Acquisition’. The
major function of SCADA is for acquiring data from remote devices such as
valves, pumps, transmitters etc. and providing overall control remotely from a
SCADA Host software platform. This provides process control locally so that
these devices turn on and off at the right time, supporting your control strategy
and a remote method of capturing data and events (alarms) for monitoring these
processes. SCADA Host platforms also provide functions for graphical displays,
alarming, trending and historical storage of data.
Historically, SCADA products have been produced that are generic with a ‘one
shoe fits all’ approach to various markets. As SCADA has matured to provide
specific solutions to specific SCADA markets it has provided solutions for wide
area network SCADA systems that rely on tenuous communication links. These
types of SCADA systems are used extensively throughout the Oil & Gas market
due to the fact that assets are spread over large geographical areas.
Looking at the overall structure of a SCADA system, there are four distinct levels
within SCADA, these being;
i. Field instrumentation,
ii. PLCs and / or RTUs,
iii. Communications networks and
iv. SCADA host software.
We will discuss each of these levels in detail, describing their function, how
SCADA has changed over the past 30 years and the impact of security
requirements and regulatory compliance on SCADA system operations.