SIGMA – Specialist On-line Monitoring Sub-system Specialist System for Diagnostic and Prognostic
The Sub-systems are based on mathematical models that execute the processing of measurements obtained from equipment sensors, transforming the raw data into useful maintenance information. As a result, the Sub-systems become tools that enhance maintenance-engineering activities, allowing specialists more time to concentrate on important tasks, by not having to process large quantities of data.
The SIGMA Specialist Monitoring Sub-system is a software module that provides an additional tool to deal with information processing. Whilst other Sub-systems indicate the existence of a problem, the SIGMA Specialist cross-refers information, provided by the sensors, as well as mathematical models (processed information), in order to diagnose the probable cause of the problem, recommending corrective action and supplying a prognosis of future complications, if the defect is left uncorrected.
To accomplish these functions, the SIGMA Specialist uses a Specialist System, an Artificial Intelligence technique that consists of a set of decision rules that discard hypotheses and thus enables it to arrive at a problem’s most probable cause. This set of rules is flexible, allowing the user to tailor it to his/her own experience. In this way, the System Specialist constitutes a tool that permits the accumulation and consolidation of knowledge from various human specialists, thus contributing to its dissemination. This table represents a possible reply from the SIGMA Specialist:
Problem: Low efficiency of the cooling system.
Diagnosis (probable cause): One or more fans are out of operation.
Recommended Procedures: Repair the failed fans. Reduce the load to avoid over-heating.
Prognosis: High loads can cause over-heating, decreasing insulation life.
SIGMA Specialist permits remote access to on-line diagnostics and prognosis and to historical data, stored in data banks. Remote access is carried out over the Intranet or Internet network, using a standard Internet browser. The system can also send alert messages by e-mail or text messaging to mobile phones (SMS) when the system diagnoses an abnormal condition, freeing operators from the need for permanent supervision of the system.
SIGMA Monitoring Systems and Sub-systems architecture
The SIGMA monitoring system is based on a Decentralized and Modular architecture, in which Intelligent Electronic Devices (IEDs) are used as sensors (data sources) interconnected to the SIGMA monitoring system over a communication network. Frequently these IEDs are pieces of equipment that are essentially used in transformers in protective, supervisory and control functions, supplying information to the monitoring system through one of their serial ports. This makes centralizing units at the body of the transformer unnecessary, this architecture eliminates the necessity for specific sensors, resulting in a significant reduction in the cost of the system. This is the case with SIGMA Ageing Sub-system, as shown in the diagram.
SIGMA monitoring software, obeying the same philosophy as the Treetech IEDs, is composed of independent and scalable modules called Sub-systems, allowing the user to build their own monitoring system, according to their needs. As such, the Treetech modular systems allow the monitoring of small-scale transformers, eliminating the financial barriers that previously limited the application of monitoring systems to large-scale equipment only.
The Sub-system SIGMA Specialist utilizes both the IEDs’ measurements and the processed information supplied by other SIGMA Sub- systems.