SIGMA-Simulation On-Line Monitoring Sub-System Temperature Forecasting Simulation
One of the principal factors limiting the loading of power transformers is the temperature attained by the equipment, as a result of its loading and the ambient conditions. High operational temperatures, while accelerating the loss of insulation life can increase the risk of failures (for example, the risk of bubble formation).
SIGMA Simulation is a software module which, together with the Treetech Temperature Monitors TM1 and TM2, provides the tools the user to carry out simulations of transformer loading. This will verify the evolution of the oil and winding temperatures and the associated loss of life. In this way, SIGMA Simulation becomes a tool for operational planning and not only for maintenance. The simulations can be carried out in two distinct modes:
- Based on current conditions – In this simpler mode, the real measurements of temperature and loading are used as the initial conditions for the simulation. The user only introduces a new percentage loading value, obtaining as a response the oil and winding temperatures evolution curves;
- Based on hypothetical conditions – In this mode, all the simulation conditions are introduced by the user for a period of 24 hours: evolution of ambient temperature and load, type of loading (cyclical or not) and initial temperature conditions and loading, if the loading is not cyclical. Result-The oil and winding temperature curves are provided for the 24-hour period, as well as the percentage daily life loss and the estimated life remaining.
In each of the simulations the user can modify the commands for cooling (switching off, automatic or manual control), the temperatures for activating and hysteresis of the cooling.
The SIGMA Simulation permits remote access to the simulations, on-line temperature and load measurements and to historical data, stored in data banks. Remote access is available 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 alarm condition in the on-line temperature measurements, 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.