The Intellix BMT 330 Bushing Solution
The Intellix BMT 330 continuously monitors the condition of bushings in real-time and provides end users with the information they are used to receiving from off-line tests, namely changes in capacitance and power factor (tan delta), to assess the bushing dielectric efficiency and insulation integrity.
Using custom made adaptors connected at the bushing tapping points, the Intellix BMT 330 measures:
- The change in bushing leakage current compared with the original values calculated from the bushing nameplate information.
- The timing differences between the 3 bushing current phases, which translate to phase angle differences relative to each other.
The Intellix BMT 330 measures both oil and ambient temperature. It correlates capacitance changes linked to thermal expansion of the bushing and compensates for the measurements being made at actual bushing operating temperature compared with nameplate values obtained off-line.
Partial Discharge (PD) Detection
PD is a localized breakdown of a small portion of a solid or fluid electrical insulation system that is under high voltage stress, which does not completely bridge the space between two conductors. PD results in localized gradual erosion of the insulation system that eventually leads to failure of the critical insulation between transformer windings. Using the same bushing adaptors, the Intellix BMT 330 offers the added advantage of measuring high frequency signals in order to monitor PD activity, giving an added level of protection for the main tank of the transformer.
The amplitude of the PD pulses, as well as the number of pulses, are recorded and used to calculate an overall measure of PD activity. Several methods are used to discriminate between internal PD and external noise (corona discharge).