Ground Fault Monitoring in Marinas and Shore Power

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Ground Faults in Marinas

Poor wiring on a boat or dock, a shorted water heater, water intrusion, and mechanical damage are examples of causes for low level AC leakage current. The harsh and corrosive environment present at marinas may also cause wire insulation to age much faster than expected. Many times, this leakage current may be at levels too low to trip a fuse or circuit breaker. The 2011 National Electric Code (article 555.3) now requires a ground fault protection device at either the main feeder or at the branches going out to the individual pedestals. The MarinaGuard provides a complete solution for ground fault monitoring shore power at marinas, by providing options for both feeder monitoring as well as individual branch monitoring.

Figure 1: Possible ground fault paths in a shore power application

How Does a MarinaGuard Detect Ground Faults?

In a typical shore power application, the secondary of the shore power transformer provides grounded 240/120 VAC power. When monitoring the feeder, the MarinaGuard will be connected to a current transformer. The current transformer will be placed around both hot conductors and the neutral (the ground conductor is not placed through). The MarinaGuard will detect faults downstream of the current transformer, including any leakage current between the transformer and wiring to the pedestals, or to a connected boat. Ground faults are detected by looking for a net imbalance of current between the phases - this correleates to an equivalent amount of leakage current downstream.

Branch monitoring works in a similar manner, however each individual branch leading to the pedestals is monitored seperately. Notification can be provided as to the particular branch that has the ground fault.

Figure 2: Typical monitoring points for a MarinaGuard system