What is SCADA system?
Generally, a SCADA system has three layers, SCADA master, communication media, and local control system.
SCADA is an acronym for "Supervisory Control And Data Acquisition", meant to explain the very essence of the system.
SCADA is a technology permitting to collect and process data received from the remote (in terms of distance from the Control Center) objects, and transmit commands via cable or radio communication systems.
SCADA may either eliminate the necessity of the on-going technological process personnel's presence, or drastically reduce the number of inspection visits to the system's objects.
SCADA is a technological control and management system providing for highly efficient cost effective production.
SCADA enables a technological process operator to monitor and control equipment status, to open and shut valves or motors, to view each of the technological process parameters all from a single Central Control Room.
SCADA systems are based on modern microprocessor and networking technologies enabling the system designer to implement a scalable application that can grow with expanding needs.
The SCADA master is set up at central locations (multiple masters can be established) of your operational organization. SCADA master consists of three main parts, SCADA console, SCADA server, and MTU (Master Terminal Unit). The console is HMI (Human Machine Interface) for your operation. The server contains database(s) for historical trend of pipeline state and other relevant data. MTU is a terminal that communicates with RTUs (Remote Terminal Unit) at local site of the pipeline. Each piece of SCADA master equipment is a node in SCADA master LAN (Local Area Network). The number and locations of SCADA master are determined for each application, depending on operation plan, total system reliability and other design terms.
For the data communication between MTU and RTU, communication media will be chosen from leased line, microwave radio, UHF/VHF radio, fiber optic transmission, or satellite communication. If you need to own new communications by yourself, installation cost of communication media tends to have a large impact on your total investment. Before you choose the best one for your pipeline, it is important to consider your requirements, local installation constraints, communication service availability, and total system reliability. Back up circuits using different communication media from the main circuits are sometime provided to increase the strength of communication circuits.
Local control system
The local control system includes all necessary control functions required for a local station on your pipeline and communication capability with SCADA masters. For a relatively small station such as a block valve station, a small RTU is suitable. On the other hand, a DCS (distributed control system) is often adopted to a terminal or booster station. It is crucial to design a local control system to safely continue controls in case of communication circuits failure with SCADA master(s). If your pipeline is running cross-country, the power supply for stations often poses a problem. In such case, solar cells or a small power station is built to a local station.