SIGMA – Fan On-line Monitoring Sub-system Assistant for Maintenance of the Cooling System

Adequate cooling of a transformer is fundamental for its safe operation and the prevention of accelerated aging and reduction in the useful insulation life under high loading. Thus, it is essential that the forced cooling equipment, such as fans and oil pumps, function perfectly. The total or partial failure of the cooling equipment can activate the temperature protection or limit the loading of the transformer, leading to a total or partial unavailability.

For this reason, the normal wear and tear of the fans and oil pumps should be monitored, which is traditionally carried out off-line, through preventive maintenance as recommended by the manufacturers. These interventions are generally based on the service period of the equipment, including the exchange of components (for example, bearings).

SIGMA Fan Monitoring Sub-system is a software module, which, together with the Treetech Data Acquisition Module DM1, allows the exact monitoring of working time of every fan and pump, ensuring interventions at the appropriate time well before or after their specifications as defined by the equipment condition. Optionally, SIGMA Fan provides on-line monitoring of the torque developed by the motors, through transducers to measure electrical power, moving the time based maintenance to a system based on the condition of the equipment. Information provided by SIGMA Fan necessary to support maintenance of the cooling equipment includes:

• The total service period of the fans and pumps, since the start of operation, and the period since the last maintenance, with a register of the starts and stops of the motors;
• Daily average working period of the fans and pumps;
• The time to the recommended inspection or maintenance intervals, based on the daily average period of operation of the fans and pumps;
• Programmable advanced warnings, for the inspection or maintenance of equipment, based on the period of operation;
• Optionally, torque developed by the motors, allowing the detection of failures before they impare the transformer’s cooling efficiency.

SIGMA Fan permits remote access to on-line diagnostics and prognostics and to historical data, stored in data banks. Remote access is carried out over the Intranet or Internet network, using standard Internet browser. The system can also send alert messages by e-mail or text messaging to mobile phones (SMS) with maintenance notices or 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.