Typically used for hydro-generators, PDA couplers detect stator winding PD activity. In the last two decades Epoxy Mica Capacitors (EMCs) have become the industry's choice due to reliability and the relative ease of installation. EMCs installation usually requires about 3 to 4 days of effort per machine.
Typically, on machines rated less than 100 MW, only 6 couplers are installed. On large machines, sometimes more than 6 PDA couplers are installed. The standard package includes a set of 6 couplers, a termination box and installation hardware.