An electrical device like this requires a reverse leakage current of 500nA @ 137V.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 190V.For operation, diode reaches 1.2V @ 1A at the maximum voltage - Forward (Vf).
1N5387B Features
reverse leakage current of 500nA @ 137V 500nA @ 137V is the maximum voltage (Tol)
1N5387B Applications
There are a lot of Microsemi Corporation 1N5387B applications of zener single diodes.