Obsolete status and what it means for supply
The P6KE30A-T: The functional replacement is a different package or part number — a board spin may be required if the original footprint must be matched.
600 W peak pulse — the clamp that decides the protection level
The reverse standoff voltage is 25.6 V — this is the working voltage below which the diode stays transparent on the rail. The 28.5 V minimum breakdown voltage means the device starts conducting between 28.5 V and the 41.4 V clamp — a 25.6 V nominal rail sees no leakage under normal conditions, but a transient that pushes the line above 28.5 V is shunted to the clamp limit. Unidirectional — one channel in a DO-15 axial package. The anode and cathode are marked; polarity matters on the board. Through-hole mounting suits point-to-point wiring or prototype builds where a surface-mount TVS is not preferred.