Dell PowerVault 500 Systems Guide De Mise En Route page 13

Install the Power Cord Retention Bracket
Attach the power cord retention bracket on the right bend of the power
supply handle. Bend the system power cable into a loop as shown in the
illustration and attach to the bracket's cable clasp. Repeat the procedure
for the second power supply.
Plug the other end of the power cables into a grounded electrical outlet
or a separate power source such as an uninterrupted power supply (UPS)
or a power distribution unit (PDU).
11
Getting Started With Your System