What this TVS diode protects and how it clamps
The STMicroelectronics 1.5KE180CA is a bidirectional Zener-type transient-voltage-suppression diode from the 1.5KE TRANSIL™ series, designed to clamp voltage spikes on a 154 V nominal rail. The DO-201AA axial package suits through-hole mounting on boards where leaded components are preferred for mechanical robustness or thermal mass.
The 1500 W peak pulse power rating (8/20 µs waveform also specified at 31.5 A) tells you the device can absorb a single high-energy transient without failing. For a 154 V rail, the 171 V breakdown gives a comfortable margin above the operating voltage, so the diode stays off during normal conditions and only conducts during an overvoltage event. The 317 V clamping voltage is the maximum voltage the load sees during the surge — ensure your downstream components are rated for at least that peak. Capacitance of 362.5 pF at 1 MHz is typical for a TVS of this power class; it is not designed for high-speed data lines but is fine for power and general-purpose I/O protection.