An electrical device like this requires a reverse leakage current of 1μA @ 150V.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 200V.For operation, diode reaches 1.2V @ 200mA at the maximum voltage - Forward (Vf).
BZD27C200P MHG Features
reverse leakage current of 1μA @ 150V 1μA @ 150V is the maximum voltage (Tol)
BZD27C200P MHG Applications
There are a lot of Taiwan Semiconductor Corporation BZD27C200P MHG applications of zener single diodes.