Colleagues:
I have been saying for some time that we need to rethink PV ground fault
indicator systems. The fundamentals of existing GFI systems is for the
bond between the grounded-conductor and the grounding-conductor to be
opened upon a ground fault. This bond is important for safety and it is
ludicrous to open it at the time it is most needed.
There are patents awarded for systems to detect ground faults and then
disconnect PV source circuits at the source. This is the best idea I can
think of at this time. There are more patents to be had for those that can
innovate in this area. Until there are better systems on the market,
regulators can not require better alternatives.
William Miller
At 01:04 PM 9/6/2010, you wrote:
Wrenches all,
I 100% second Bill B's comment Correct that... I 200% second it. It should
be the law.... "Don't begin to troubleshoot a faulted PV circuit without a
reliable DC clamp meter."
The MOST DANGEROUS PV system is a wounded PV system. This includes danger
to persons and property. Safely and efficiently troubleshooting a faulted
PV circuit requires a voltmeter AND an ammeter. And PPE. And adequate
knowledge and understanding of operational and non-operational
characteristics of PV systems.
The simple reason for this is that, when one or more circuit conductors
are faulted to a short condition, the voltage between the faulted elements
is zero. Relying on just a voltage reading to determine whether or not to
open a circuit under this condition will result in an arc. The amount of
energy in that arc will depend on the amount of available sunlight and the
amount of PV that is feeding into it. The amount of potential hazard will
correspond to these factors as well.
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