APC PMH3XS-B ユーザーズマニュアル

The SPD

 

has leakage current to ground when energized and can present a 

hazardous touch voltage.

The device has SPD elements connected from phase to ground. To prevent 
hazardous touch voltage on the SPD enclosure during normal operation or 
during SPD end-of-life, it is critical that there be a robust and effective 
connection to the building grounding structure. The grounding connection must 
utilize an equipment grounding conductor run with the phase and neutral (if 
present) connection of the power system. The SPD should not be connected to 
a separate isolated ground.

When metallic raceway is used as the wiring method, an insulated grounding 
conductor should be run inside the raceway and sized in accordance with all 
applicable codes. Maintain electrical continuity at all raceway connections using 
appropriate bonding devices and do not install isolating bushings to interrupt a 
metallic raceway run.

For best overvoltage suppression by the SPD, use a single-point ground 
system where the service entrance grounding electrode system is connected to 
and bonded to all other available electrodes, building steel, metal water pipes, 
driven rods, etc. (for reference, see IEEE 142-2007). The ground impedance 
measurement of the electrical system should be as low as possible, and in 
compliance with all applicable codes.

SPDs rated for use on solidly-grounded power systems must not be connected 
to resistance-grounded (for example HRG) or ungrounded power systems. 
Such a connection can result in damage to the components within the SPD.

• Connect the SPD ground terminal to the building grounding grid 

structure.

• Use an appropriately sized equipment grounding conductor.

• When using metallic raceway or conduit:

— Do not use the SPD ground unless augmented with an insulated 

equipment grounding conductor installed inside the metallic raceway or 
conduit.

— Do not use isolated bushings to interrupt the metallic raceway or 

conduit.

— Maintain electrical continuity at all raceway and conduit connections 

using appropriate bonding devices.

• Do not use a separate isolated ground for the SPD.

• Verify proper equipment connection to the grounding system.

• Verify ground grid continuity by performing regularly scheduled 

inspections and testing as part of a comprehensive electrical 
maintenance program.