The parallelism system for power transformers equipped with shunt taps under load has traditionally been done by an electro-mechanic panel, with analog indication of TAP position and manual tap change.…
At every three years, the Braskem industrial plant of polyethylene stops its activities for general inspection and maintenance of its premises. Machines and structures are inspected, in addition to the conditions of the electrical system, which receive special attention with specific activities, especially in the electrical power substation.
As the electrical power is a fundamental input for the factory production, it is necessary that all the substation assets are in perfect operation conditions. Thus, each detail is checked, including switchgears (circuit breakers and disconnecting switches), isolators (CTs and PTs), especially the power transformer.
The Cubatão plant’s substation has a single transformer, 88 kV / 13.8 kV, 20 MVA, which should not present any inconsistency, as this may represent losses to the company. The unit produces Low-Density Polyethylene (LDPE) and its production reaches 140 tons/year of the material.
The action of the technical and maintenance team of the company has the aim of keeping the safety of collaborators, achieving higher performance from the assets, in addition to uninterrupted power supply to support the ongoing production growth.
Modernization of the system at Braskem Cubatão unit
In March 2011, during plant shutdown for maintenance processes, the Braskem Cubatão unit, in partnership with Treetech Sistemas Digitais, performed the modernization of the thermal protection system of a transformer and implemented the on-line monitoring system for complete equipment management.
By initiative of the Reliability Engineer, Mr. João Luiz G. Neto, interested in assuring power supply to the plant, a solution has been searched for in order to improve quality of the own system (by increasing the asset’s operation reliability) and make the maintenance work more assertive and smart.
The project included the utilization of a set of IEDs (intelligent sensors) for monitoring of the transformer’s variables, with support of the Sigma expert software for real time diagnostics and forecasts. With these tools, the maintenance team achieves reliable information to assist the decision-making process.
The designed system includes the complete monitoring of capacitive bushings, removal and replacement of old analog thermometers by digital temperature monitor, automatic voltage adjustment and monitoring of the overload switch, in addition to on-lines supervision of the gas (H2) and moisture dissolved in the insulating oil.
These pieces of equipment are interconnected and send information (measurements) to a Data Center located in the substation’s command room. This information will be remotely accessed by the Braskem team via asset monitoring and management software Sigma4net™ (available for the computers interconnected over the company’s corporate network).
“We are able to follow all the measurements taken in the main transformer of the computer, in addition to quickly viewing diagnostics and forecasts provided by the software. The system also assists us in the better maintenance of the machine, fast consultations of graphics and trends on their operation,” states Eng. João Luiz Gonçalves Neto, responsible for the implementation and operation of the new system.
From now on, the entire maintenance team will be provided with the same information. Thus, they will be able to follow the transformer’s performance, and then prepare efficient plans for its maintenance. By its turn, there was great interaction with the new system during installation, as pointed out by João, “the Treetech team has supported us with all the information required to leverage the maximum system efficiency. Our experience, combined with the support from Treetech, will place us at the forefront of predictive maintenance in power substations”.
“As this is a fundamental equipment for production continuity here at Braskem, it was very important the monitoring system installation, which evidences the concern and care with the equipment. The entire team is aware that the new tool will help both in maintenance actions and to determining new investments based on the operating conditions of this transformer,” emphasizes José Moitinho, application engineer at Treetech.
Then, the benefits are not limited to providing corrective or preventive actions to keep the transformer operation. By using the monitoring system, the maintenance and operation teams can indicate to the finance and planning area when the replacement of purchase of new equipment will be required to meet the increasing demands of the plant.
By using Sigma, the Braskem Cubatão unit will be able to perform:
- On-line diagnostic of the transformer conditions;
- Viewing of alarms and alerts a perform in accordance with norms and procedures applicable to the normal and contingency operating conditions;
- Maintenance, operation and planning actions;
- Standardization of actions and communication in the maintenance area;
- Identification of asset efficiency optimization opportunities;
- Effective management of maintenance by periodical asset performance and status reports.
Shown below is the list of equipment and solutions that integrate the transformer TR1 (20 MVA) 88 kV at SS Braskem in Cubatão:
- TM1 – Temperature Monitor
- BM (Bushing Monitor) for HV
- AVR – Voltage Regulation Relay
- IDM – Switch Torque Monitor
- GMP – Gas and Moisture Monitor
- Sigma4net™ Software
- Complete training on the system utilization and operation.