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.

This project is time intensive for panel construction and installation, with maintenance being done periodically.

Modernizing the parallelism system to operate under a digital system renders the parallelism panel unnecessary and the equipment can be installed in any existing panel in the control room. Digital systems make it possible to achieve parallelism with transformers from different manufacturers and different commutation times. Systems can be expanded simply by acquiring new equipment and connecting them to the existing networks. Maintenance is simple and fast since it usually is merely visual. The system sounds alarms in the presence of any form of abnormal condition in the parallelism operations. This is an indication of the flexibility and economy generated by digitizing parallelism systems.

The product – Synchronous Parallelism Supervisor – SPS

Treetech’s Synchronous Parallelism Supervisor incorporates the functions of the different equipment that used to be used in the past for controlling transformer parallelism, such as selector switches Master/Slave/Individual, Manual/Automatic and
Local/Remote, tap position indicators, auxiliary relays for electro-mechanic logic, among others. For this reason, command wiring and number of components
have been extremely reduced, increasing considerably overall reliability and reducing labor time requirements during installation and testing, in addition to greatly simplifying maintenance.

See in the article below how Treetech’s Parallelism Supervisor can facilitate the parallelism between transformers.

The modernization of the auto-transformer banks replaces manual system with analog reading by digital systems.

The Electro-mechanic Maintenance Division (DSMI.O), subordinated to the São Paulo Production Department (DRL.O), concluded in October the modernization of the TAP control system for the banks of autotransformers and regulators series AT01/RS01, AT02/RS02 and AT03/RS03 of the Tijuco Preto Substation (SP). This implementation procedure involved redesign of the entire tap control system for the substations 500KV sector. The new system offers remote tap control, which previously was done manually and with analog indication.

In modernizing the system, the five-staff team readapted the transformer cabinets and removed from operation the regular commuter under load cabinets (OLTC).

According to engineer Luis Carlos dos Santos, this measure will add gains to the plug systems that will be installed, since it creates compatibility among the command circuits of regulating autotransformers from three different manufacturers, making additional modifications unnecessary when replacing any one phase in the transformers by a back-up unit.

The activity required 30 days of work in each regulating autotransformer. During this period, work was done in designing the system, preparing wiring and cabling, installing the new devices and two days for switching off each bank and energizing the new system. “Because of replacing the TAP existing system by a digital one, maintenance has been facilitated and the monitoring process has become interactive, since it is carried out by controller logic through software”, explains technician Sérgio Luiz Mistura.

The team received support from the departments of Electrical Engineering (DEL.T) and South Transmission Construction (DTS.T), of the Protection, Control and Supervision Engineering Division (DPCS.T) and the Mogi Construction Office (ECMO.T).

Source: Furnas Magazine, November 2005