The 1.5KE91CA_R2_00001: For a 77.8 V nominal rail, the 125 V clamping voltage (at 12 A peak pulse current) means the protected circuit sees a maximum of 125 V across the TVS during the surge event, which keeps downstream components within their voltage tolerance.
Bidirectional and through-hole — fit and polarity
The single bidirectional channel means the device clamps equally on positive and negative transients — no polarity marking needed on the PCB silkscreen, and it can be inserted either way into the axial lead holes. The DO-201AE package is a standard through-hole axial leaded form factor, 9.1 mm body length, with leads that solder into 1.0 mm diameter plated through-holes.
Obsolete — sourcing through independent channels
Panjit has marked the 1.5KE91CA_R2_00001 as obsolete.