High-Resistance Grounding
All planning should start with a well grounded system. Pun intended. How about a floating ground, or more specifically the proper ground in the floating arena, e.g. ships and platforms? A couple of good starting points are an IEEE paper “The Grounding of Marine Power Systems: Problems and Solutions” (Paper No. PCIC-2004-17) and the “IEEE Recommended Practices for Installation on Shipboard” (IEEE Std 45 -2002). One of the best solutions with respect to safety appears to be the high resistance ground. While the insulation and surge requirements are slightly higher, 1.73X that in a solid ground, a High-R appears to be a good overall grounding solution for shipboard and floating platform applications. I’d like to gather some practical “lessons learned” insight into High-Resistance grounding. Can anyone help me here?
Brett Wilson
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Control & Safety System Power & Grounding
Control and Safety System Power & Grounding isn't anywhere near as sexy as just about anything else (i.e., Foundation fieldbus, Wireless, network-security, etc.) but I still argue it's the Rodney Dangerfield of control and safety system design and installation - It Don't Get No Respect!
A few years ago David Brown, Roger Hope and I collaborated on a book titled "Control System Power and Grounding Better Practice." It provides a no-nonesense approach to ensuring control & safety system reliability by applying the correct power & grounding practices.
The book is available from:
http://www.elsevierdirect.com/product.jsp?isbn=9780750678261
http://www.amazon.com/exec/obidos/tg/detail/-/0750678267/qid=1098364764/...
http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=mHu14...
Best wishes and remember to always stay grounded.
Dave
High Resistance Grounding
I do not have any experience with offshore grounding systems. I have done some projects at our manufacturing facilities of designing and installing sub stations (15 KV/480 V) which included high resistance grounding. Typically high resistance grounding offers the flexibility to the user of being able to continue to operate even if a ground fault exists (but it also puts the burden of detecting and clearing out the fault back on the user/owner). With so many cables running in conduits, cable trays, poor terminations etc, it is not unusual to see a ground fault appear on a system. However finding the fault and clearing it out takes some efforts. On a typical 480 Volts secondary system a 5 amp ground current is the maximum allowable. The grounding resistors can get very hot with that much current flowing into ground. I have seen one incidence of a fire occuring when transformer oil leaked out and fell on the hot resistor. So, it is very critical to find ground faults quickly and correct them.