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These sensors are installed on bushings capacitor/potential taps. These sensors are used to monitor and detect problems with the bushing and winding insulation systems. Both the power frequency current from the bushing tap and the PD signals from the bushings and/or winding are detected.
The cap with a standard ½" liquid tight connection and the body of all sensors are identical. All protection is built into the body. Only the interchangeable bushing adapter is different, based on the bushing tap mechanical design. This allows for a quick turn around for new tap designs.
Unlike many bushing sensors in the current market, the EDI bushing sensor has three levels of protection built in to the body of the sensor. The sensor must be able to survive surges from switching, lightning, through faults etc. The BAU can withstand up to five full BIL hits.
Normally the bushing taps are grounded. If left ungrounded, voltage will build up at the tap which is a safety concern to personnel and can also cause a bushing failure. Normally the BAU is connected to a shorting switch or a continuous monitor such as the BHWM or any of our Partial Discharge Analyzers such as the R2100,VV Tester and the Continuous Partial Discharge Monitor (PDM). If an open circuit occurs downstream of the BAU, the built in open circuit protection operates. This protection will limit the output voltage to less than 20 volts.
The third and final level protection is a fail-safe circuit. In the unlikely event either the Surge or Open Circuit Protection fails, the fail safe circuitry operates and grounds the bushing at the tap.
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