This Article is about details of the Fluke-1550C discharge rate.
The specifications for the discharge rate for capacitive load is 1.5 s/uF.
The 1550C does have a dedicated discharge circuit to dissipate stored charge in the device under test (e.g. a cable with inherent capacitance).
Below is a high-level schematic. By default, the switch is engaged for discharge state. It disengages to allow an insulation resistance test or charging mode to commence.
The discharge rate is controlled by the 1550C’s input impedance which is in the range of 750kohms to 1Mohms.
The 1.5s/uF represents approximately 2-time constants from my observations. However, the number of time constants is unspecified.
It's worth noting that the 1550C will display the remaining voltage.
Best practice is to discharge until near zero voltage is present and continue to discharge for additional time to account for dielectric absorption.