Design and development of an optimised telemetry control system
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Designing an optimised telemetry control system will improve the quality of service for Supervisory Control And Data Acquisition (SCADA) systems implemented by CSE-W. Arthur Fisher and enable system expansion thus minimising revenue for their future system designs. The telemetry control system ensures a high degree of data reliability and integrity to meet SCADA operational requirements. This thesis presents the design and development of an optimised telemetry control system using Kingfisher Remote Terminal Units (RTU’s) with Kingfisher Series 2 protocol. To determine the system response for data transmission over the bandwidth, quantitative research methods were undertaken to evaluate communication blocks within the Kingfisher protocol. There are usually different techniques used to collect data from remote stations. The Kingfisher S2 protocol implements two techniques namely “Exception Reporting” and the “Polling” technique for data acquisition. The polling technique was the most efficient in terms of bandwidth utilization for transferring data therefore the system was designed using a pure polling system approach. It also enabled the communication links for remote stations to be monitored and enabled a deterministic system design approach to be implemented. Research focused on polling system optimization whereby efficient polling frequencies were calculated based on theory presented by (O. J. Boxma, Levy, & Weststrate, 1991). The aim was to efficiently allocate the limited bandwidth resource to a number of remote stations thus optimising the system performance. The proposed theory was implemented for system optimisation. It enables efficient polling frequencies to be calculated for a polling cycle hence optimising the bandwidth utilisation and eliminating fairness problems for the medium access control. Bandwidth optimisation enables system expansion thus reducing the networks need for additional resources. A pure polling telemetry communication system was implemented in this design using point to multipoint network topology over half duplex radio channel. Empirical data modelling enabled the design of the service duration period to allow for time sharing between the remote stations to share the bandwidth. The bandwidth was designed to share real time data and event log for SCADA systems monitoring and control. Queuing analysis was performed to establish system parameters and enable system optimisation. From the literature review the implemented design methodology uses the “mean delay approximation” method which was used to calculate efficient visit frequencies and enabled the optimisation of the bandwidth to the remote stations based on the workload of each remote site. The software for the telemetry control system was developed and tested using ladder logic. The results prove that the bandwidth utilisation can be efficiently controlled thus optimising the telemetry control system. The implemented design improves the quality of service for the SCADA system by providing regular real time system status poll requests for control purposes and was given the highest priority for medium access. It also performs a polling of individual sites according to the “mean delay approximation method” to efficiently allocate bandwidth amongst the remote stations depending on their workload thus optimising the system. The system was designed to be responsive to high priority event log data thus enabling system flexibility.