In order to satisfy all the needs of supervision, monitoring and control of a production plant through a SCADA system, not only is the development stage carried out by the programmers important – it is also important that the features of the applications used comply with the requirements of the installation.
There are several programs dedicated to the design and development of SCADAs, each having a series of characteristics that make it ideal for a specific set of applications. In this article, we will briefly explain the characteristics of one of them: WinCC Open Architecture.
What is WinCC Open Architecture?
SIMATIC WinCC Open Architecture, hereinafter WinCC OA, is one of the Siemens solutions for the implementation of SCADA systems that satisfies the aforementioned basic needs (supervision, control and monitoring of facilities).
Some of its main characteristics are the following:
- “Manager” concept and client-server architecture.
- Distributed systems and redundancy.
- Flexible and scalable.
- Multilingual projects.
- System oriented to events.
“Manager” concept and client-server architecture.
With WinCC OA the “Managers” concept is introduced. The Managers are autonomous programs that communicate with each other through TCP/IP to configure the SCADA system. Each of the Managers is responsible for executing a series of specific functions.
A Manager could be, for example, the module that is responsible for reading and writing the data of the variables in the system’s database (Database Manager). Another Manager could be that which is in charge of communicating the SCADA system with the control systems of the installation (S7 Driver, S7Plus Driver, etc.).
The introduction of the Managers makes it possible, among other things, to differentiate between client and server. Thus, we can have the following architecture:
- Server(s): Managers for processing information and installation events (connection to database, communication with automation systems, execution of scripts).
- Client(s): Managers for processing information for the visualization of the current status of the installation, with the server being in charge of communicating with the clients and transmitting the information.
An example of a SCADA system with WinCC OA and client-server network would be as follows:
Distributed systems and redundancy
In this last figure one of the most remarkable features of WinCC OA can also be seen – the SCADA system can be made up of one or more servers.
For example, each server can be responsible for a production facility or plant or be part of a server network, in which the client can view everything that happens in their facilities, simply by connecting to a central server which is in communication with all plants, or plant servers directly.
Making use of this concept, a system can be made up of up to 2048 subsystems. This feature allows, among other functions, to execute actions on some subsystems from others and synchronize shared data throughout the system.
On the other hand, each server provides the system with additional functionalities, or duplicates existing ones for security (known as redundancy).
The redundant server assumes the functionality of the main server when a critical failure occurs in the latter, which compromises its functionality. An example of redundancy is shown in the following figure.
Flexible and scalable
WinCC OA allows adding, modifying and eliminating functions of the SCADA system through its own programming language: CONTROL.
In addition, as it is structured through the Managers seen in the previous points, the system is perfectly adaptable to the size of the installation. For larger installations, it is enough to add the number of Managers necessary to cover the needs of the project.
WinCC OA supports the monitoring of installations in multiple languages, so that operators can select their preferred language among those available in the project.
Finally, one of the fundamental characteristics of WinCC OA is that it is completely event-oriented, in other words, in general data processing only occurs when there is a change in the system.
The Manager in charge of managing the events (changes) received is the Event Manager, the “main engine” of the system.
This feature allows to greatly reduce the consumption of resources of the server or servers used, as it is not necessary for the SCADA system to continuously process data.
In another post, we will look in more detail at the practical guides on how to apply the points seen in this article to a WinCC OA project.