10.1.3.3
24/48 V dc Power Protection
Characteristics of the 24 V dc power protection system are as follows:
•
24 V dc power distribution is a utility system using a 24 V nominal dc battery. A typical ac system uses one or more dc
power supplies for contact wetting and relay outputs.
•
The maximum allowable battery voltage is 36 V dc. The Mark VIeS controllers can initiate over-voltage shutdown when
the battery output voltage exceeds the allowable limit.
•
The 24 V dc input to 28 V dc output powers Mark VIeS control electronics.
•
The 24 V dc battery has no hard ground on either the positive or the negative dc bus. A high resistance from the positive
and negative dc is applied to earth to center the bus on earth. A single ground fault applied to this system can pass current
defined by centering resistor value and dc bus magnitude. The shift in voltage, with respect to earth, can be detected and
signal the presence of a ground fault.
•
The JPDE board provides centering resistors selected by using JP1. In the event the battery has external centering
resistors on the battery bus, JP1 could be eliminated to avoid higher ground fault currents.
•
The JPDE board is designed application using dc input filtering. Additional input filters are not needed.
•
The JPDG power distribution board provides distribution of 28 V dc (control power) and 48 V/ 24 V dc (wetting power)
to other boards within the control system. For both control and wetting power, the JPDG supports dual redundant power
supply inputs through external diodes. The JPDG provides fuse protection for all 28 V dc and 24/48 V dc outputs. The
voltage at common 24/48 V bus is monitored by the JPDG, and it supports feedbacks for 14 fuses in the 24/48 V dc
distribution section.
For the 48 V dc power protection system, the JPDE may be configured to operate correctly using 48 V dc input power for
power distribution.
PDM Power Distribution Modules
GEH-6855_Vol_II System Guide 305
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