DCS & SCADA System

SCADA - Supervisory Control And Data Acquisition is an industrial automation system that performs control, monitoring, and data acquisition functions. The SCADA system became the backbone of many modern industries when programmable logic controllers (PLCs) were developed and integrated in the early 1970s.
Since then, it has provided a technological foundation for businesses to enhance their management and control capabilities in automated processes. Additionally, it enables operators to accurately analyze data and make timely decisions, thus facilitating the implementation of important decisions.

                                                      Hình 1. Giải pháp ứng dụng SCADA trong giám sát hệ thống lưới điện toàn nhà máy

Thien Tan specializes in the construction and development of PLC/SCADA and DCS software based on Siemens devices:

  • PLC: S7 1200, S7 1500, S7 400.
  • SCADA: WinCC, TIA Portal.
  • DCS: PCS7, Cemat, Simatic Batch, Route Control.
  • Safety Matrix.

Control Applications in Reality

In an industrial or civil production system, control applications can be divided into the following three types:

  • Sequential Logic Control
  • Regulatory Control
  • Supervisory Control and Data Acquisition (SCADA)

The requirements for these applications may vary depending on the nature of the process. Some processes primarily involve sequential logic control applications, such as in assembly workshops, while others primarily involve regulatory control applications, such as in continuous production chemical plants. However, the need for monitoring, operation, and data collection exists in almost all, if not all, systems, at least up to the present time.

DCS (Distributed Control System)

- A distributed control system is based on hardware and software for control and data collection using a high-speed communication channel. The system consists of distributed modules organized in a specific structure with individual functions and tasks. The communication devices on this high-speed channel allow easy integration with PLCs, controllers, and other supervisory control computers.
- Control functions are distributed throughout the system rather than centralized on a single computer. A typical DCS system has independent control stations that control specialized components of the plant.
- The ability to process analog signals and execute complex sequences is a strength of DCS systems.

SCADA (Supervisory Control And Data Acquisition)

- SCADA is a system used in process control applications, industrial automation, chemical production, power transmission, etc. It relies on a central processing unit (server) where data collected from sensors placed in workshops, buildings, or remote stations is sent for management and control (with a limited number of predefined control commands sent to the actuators).

From the perspective of programming and system execution methods:

This section will help readers understand the differences between SCADA and DCS in terms of programming and system execution methods. First, let's describe the steps involved in programming a SCADA system:

  • Based on the Process and Instrumentation Diagram (P&ID), programmers create a mapping table between variables in the PLC and the SCADA software (Figure 3a).
  • Then, programmers proceed to program the control for the PLC based on the designed control principles (Figure 3b). The choice of PLC type depends on various project criteria.
  • Engineers configure and program the Remote I/O devices (Figure 3c).
  • Another group of engineers configures the field devices (Figure 3d).
  • SCADA engineers program the SCADA application (Figure 3e) using selected tools based on various project criteria.
  • Finally, all groups together verify the connections between the SCADA-PLC-Remote I/O-Field Devices relationships (Figure 3f).

For DCS systems, the process is more streamlined:

  • The system is established by a DCS server and multiple engineering stations (Figure 4a, highlighted in blue).
  • The DCS system encompasses hardware, software, technology, and communication, all provided by a single vendor.
  • Engineers create a unified project that includes both the PLC program and SCADA program, tightly integrated.
  • Once the programming of the project is completed, the next step is project execution (Figure 4b): The control program is loaded into the PLC, the SCADA program runs on SCADA computers, and the configuration and programs for Remote I/O devices and field devices are loaded onto those devices.

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