While intelligent building management is becoming the norm rather than the exception in a security and energy-conscious economy, the management of prisons and their infrastructure requires some special approaches and considerations rarely found in other applications.
Wonderware's InTouch HMI (human machine interface) scada application is being used in a number of maximum-security prisons in South Africa in order to provide operators with the level of control they need to run their facilities more efficiently.
One such maximum-security facility is located in Natal and gives an insight into the complexity of the necessary supervision and control system to do the job. The system integrator involved with this implementation was Delcon Marine Industrial (DMI). The system requirements included having one generic and universally standard application such as InTouch that could be changed at will and that would also be updated regularly. DMI's approach was to minimise Ethernet bandwidth and CPU usage during normal use in order to handle the bursts of data flow that occur periodically such as at meal times - this is a typical characteristic of building automation applications that predominantly consist of discrete I/O events. To test the system's ability to handle data bursts, InTouch had to detect and handle 200 simultaneous I/O analog variables (done using a Delphi I/O simulator). One of the most important requirements of the system was that each station must act as a server in its own right for purposes of failure and redundancy.
17 000 tags provide the scada system access to several integrated systems that include camera switching systems, UPS (uninterruptible power supply) units, surge arrestors, tape recorders, access control, generators, door control, lights and audio control. In this way, a total of 28 000 I/O could be controlled and monitored by using the ability of InTouch to dynamically reference tags. The front-end operator interface consists of eight InTouch scada stations all connected via an Ethernet backbone. These HMIs are connected in a redundant manner providing four high-level stations, two lower level stations and two management stations. To conform with one of the primary system requirements, any one of the four high-level stations can act as a hot standby for the other three. This is also true for the lower level and management stations.
Network response from each PC is monitored continuously. In this instance, hot standby didn't just mean providing redundancy. The standby PC also has the tricky job of instantly taking over the realtime control status of the failed system. The management machines are also responsible for datalogging and the configuration of user-access information.
One of the more difficult functions to implement was the switching of the audio matrix. 38 users of the system have access to various audio routes from different locations with different levels of authority and different switching possibilities. The switching possibilities are also a function of the front-end user logon configurations. Camera control is done by interfacing InTouch with a NetDDE camera server (written in Delphi) that controls a Video Allegiant via a serial bus. The camera server acts like a buffer taking care of the different data transmission speeds.
The system can handle several thousand alarms if required as well several hundred interlock groups. All this, while providing operators the ability to navigate at will through the prison's various sections. "This level of sophistication is providing prison administrations with the tools they're looking for to achieve new levels of efficiency, security, access control and equipment usage," says Alwyn McDonald, Design Engineer, Delcon Marine Industrial. "Because of the very nature of the system, existing staff not only have the ability to be more effective but they can also detect potential sources of trouble such as equipment malfunctions before these become critical."
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