Monitoring of High Voltage Bushing

Monitoring of High Voltage Bushing

In operation since October/2005, Teetech’s BM Bushing monitoring System in place at CEMIG’s Mesquita SS carried out online monitoring of capacitances and tangent deltas for three 500kV bushings manufactured by HSP, installed on a three-phase 500-230kV 400MVA auto-transformer (see previous article about this facility). Taking advantage of modularity feature of the BM bushing monitor, this system was expanded to cover monitoring for the 3 230kV bushings for this same auto-transformer (HSP) as well as the three single-phase 500kv current transformers manufactured by Haefely-Trench.

The interface module (MMI) for the existing system is installed in a panel on the casing of the auto-transformer, together with the existing measuring, which receives the signals from the 500kV bushings. On this same panel, the measuring module for the signals from the 230kV was installed, with the measuring module for the single-phase CTs was installed in the central CT panel, located in the structure of the phase A CT, about 70 meters from the power auto-transformer.

This architecture, with measuring modules installed on the singlephase CTs, was associated to the interface module already installed on the auto-transformer, this was only possible due to the linkage between modules be performed by way of a twisted-pair cable, RS485 serial communication standard, which allows for distances of up to 1300 meters.

With this new set up, CEMIG confirms once again its tradition of modernity in taking another step towards online monitoring and statebased maintenance for its equipment.