flashback of Building Automation

  flashback of Building Automation

  1.  Centralization of Operations

 

Before the Second World War, the technical installations in commercial buildings were completely manually operated. Large control panels were built to centralize the flow of information from the technical installations and enabled remote operation.

 

These panels took up a lot of floor space and required extensive and expensive cabling as each data point (field input or output signal) was wired individually to the control panel. To enhance the transfer of information these control panels were sometimes equipped with mimic diagrams depicting the technical installations. The mimic diagrams contained indicators to reflect the actual state of various process parameters and control elements for remote control purposes.

 

 

2.    Selective Data Presentation

In the nineteen sixties the complexity of the technical installations grew considerably. Consequently the central control panels became so large that these were no longer manageable. To overcome these problems, selective data presentation systems were introduced.

These systems used the switching methods employed by telephone switchboards. The mainly digital signals(status indication and switching commands)were no longer wired directly to the control panel but were collected in so-called data gathering panels(DGP's), or also called substations. These DGP's were connected to the central control panel via multi-core cables. The number of conductors in the cable links was lower than the number of data points being relayed. This was made possible by connecting the data points to multiplexed system with selection options.

 

he beginning of the nineteen seventies, developments in electronics and communications led to the internal transformation of these so-called Building Automation systems.

Although the external structure remained the same, the matrix switching relay techniques in substations were replaced by digital switching techniques. This made it possible to replace the multi-core cables with two or four core serial links that could also be used to transmit digitized analogue signals. The central control panel was replaced by a computer system with a monitor display and keyboard, and a printer replaced the analogue recorders. Computer systems and software were developed especially for this purpose.

As a result of the limited processing capabilities, the functionality of these systems was limited to the presentation of process statuses and values and alarm reporting functions.  As a replacement for the mimic diagrams slide projection systems were sometimes added, on which process diagrams and floor layouts could be displayed.

3-  Energy Saving

After the energy crisis of 1973 there was an urgent need to reduce energy consumption as far as possible. Making use of the capabilities the central computer of the Building Automation Systems could provide,  many  energy  saving  functions  were developed  and  integrated  into  the  Building Automation  Systems.  Functions such as optimization, night purging and time- and event- triggered switching programs. Also, the reporting capabilities of the system were enhanced to provide information regarding energy usage and to show the effects of energy conservation measures.

4-    Management Functions

The need for more detailed information grew as building management efficiency became more important. It became clear that a Building Automation System offered more potential than simply reducing energy costs.  The reporting functions were considerably expanded and other management tasks such as fire and intruder detection and access control were added to the Building Automation Systems.

The most important reason for this integration was the use of the expensive central computer system as efficiently as possible.

The building management tasks are now being distinguished as follows:

-          Installations management:

The operation and control (from a central point) of technical installations and the collection of information for management and maintenance purposes.

-          Energy management:

The implementation of energy-saving measures and the collection of information on the results, for control and adjustment purposes.

-          Risk managements:

The complete and systematic management of risks posing a threat to the business or organization, in an economically responsible manner.

5-    Standard Computer Systems

As a result of the expansion of management tasks, it became necessary to connect more and sometimes specialized operator stations. In addition, there was a requirement to be able to collect data such as alarm reports and measurement results over a given period and store these for later analysis. This required special provisions such as hard disk storage facilities. Systems that previously used the dedicated computer systems were altered so that standard mini-computers could be used as the central system. Later on color graphic displays were added to replace the slide projection equipment to display process diagrams and curve plots. Out of this, a distinctly hierarchical system structure evolved with the central computer (the master) at the highest level and below that, the substations (the slaves).

6-  Intelligent Substations

Up to this time the main function of the substations was to collect data at the local level, digitize these and relay them to the central computer through serial link. In the second half of the nineteen seventies micro-processors were being implemented in the substations to provide local processing capabilities. A number of functions, until then still carried out by the central computer, were transferred to the substations. This marked the birth of the intelligent substation. At first this intelligence was mainly restricted to the detection of alarms and deviations from analogue alarm limits, or the conversion and sometimes linearization of analogue measurements into digital signals. To utilize the still expensive microprocessor technology efficiently these substations had a modular construction, enabling connection of as much as possible input and output functions (I/O modules).