Peak pulse power and clamping performance
The 1.5SMCJ30A absorbs 1500W during a 10/1000 µs transient — the standard IEC 61000-4-5 surge waveform for AC and DC power rails — clamping the overvoltage at 48.4V maximum before the protected load sees it. At that clamping voltage the peak pulse current is 31A, so the clamping knee is the governing spec for downstream MOSFET or regulator gate-survive ratings on a 24V nominal rail.
Standoff and breakdown — the protection window
Reverse standoff of 30V means the TVS idles as an open circuit on a nominal 24V rail with normal headroom to spare — it does not clip the supply under normal conditions. The breakdown threshold sits at 33.3V minimum, so the protection window between standoff and breakdown is tight: the device triggers fast, before the transient propagates to downstream ICs.
Junction temperature and thermal resilience
For a board running near the top end of its ambient range, verify that the transient energy absorption during the worst-case surge does not push Tj past 150°C on your thermal pad.