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DC power distribution protection
Noark provides comprehensive DC system protection solutions to guarantee the safety of DC
systems. In the meantime, Noark also provides “Ex9MD DC dedicated moulded case circuit breaker”
based on the unique features of DC systems which is widely used in the following industries:
●
Mechanical supporting industry
●
DC power supply
●
Rail transportation and electric locomotive
●
Ports and ships
●
Communication system
●
Photovoltaic power generation
Difference between DC protection and AC protection:
●
There is no natural zero-crossing point in DC applications, therefore it is more difficult for DC arc
breaking.
●
If used in DC application, the instantaneous release value of AC circuit breaker will be increased.
The instantaneous release value of AC circuit breaker is set according to effective value, but
actually the instantaneous release of AC circuit breaker operates based on peak AC current. DC
current is equivalent to the effective value of AC current, therefore there is a big different between
these two currents. When an AC circuit breaker is used in DC system, its instantaneous release
current will be bigger than that in AC system, therefore it will be more difficult for AC circuit breaker
to cut off short circuit current in a DC system.
Wiring method in DC applications
Functions
Functions
Load
Load
Load
Load
Load
Load
Load
Note: 1. Both top and bottom cable entry are
available, here is bottom entry.
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Circuit diagram
Fault influence
Fault A
maximum short circuit current Isc
maximum short circuit current Isc
no influence
Fault B
Fault C
Fault A
no influence
maximum short circuit current Isc
no influence
Fault B
Fault C
≤DC500V
DC500~750V
DC750~1000V
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Note: 1. Both top and bottom cable entry are available,
here is bottom entry.
Note: 1. Both top and bottom cable entry are available,
here is bottom entry.
U
B
A
R
C
i
+
-
a
b
U
B
A
R
C
i
+
-
a
b
Note: 1. Both top and bottom cable entry are available,
here is bottom entry;
2. Make sure the installation method will not
cause secondary grounding fault.
Note: 1. Both top and bottom cable entry are available,
here is bottom entry;
2. Make sure the installation method will not cause
secondary grounding fault.
Note: 1. Both top and bottom cable entry are available,
here is bottom entry;
2. Make sure the installation method will not cause
secondary grounding fault.
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