Presumably the latteradded as part of the cycle of revisions initiated in 1987.
On 7/19/11 3:29 PM, "Hans Frederickson" <[email protected]> wrote: > David, > Thanks for the interesting history on GFPDs. My copy of the 1987 NEC does not > have 690-5, and it's not missing any pages. Either my code book is an > incomplete printing or perhaps John Wiles was referring to a 1987 proposal > that didn't make it into the code until the 1990 NEC. > > Regards, > -Hans > > > From: [email protected] > [mailto:[email protected]] On Behalf Of David Brearley > Sent: Tuesday, July 19, 2011 12:57 PM > To: RE-wrenches > Subject: Re: [RE-wrenches] 1987 NEC > > Hans, > > John Wiles described the evolution of this standard for a Home Power article > that we referenced later in a SolarPro on PV System Ground Faults: > > http://solarprofessional.com/article/?file=SP2_5_pg60_Mync > > ³As described by John Wiles, program manager for the Institute for the Energy > and the Environment, in the February/ March 2008 Home Power article > "Ground-Fault Protection Is Expanding," Article 690.5 was added to the NEC in > 1987. One of Wiles¹ first projects in the PV industry was to develop > ³prototype hardware² to meet the new Code requirement. "The basic concept (of > the original GFPD prototype)," writes Wiles, "was to insert a 0.5- or 1-amp > circuit breaker in the dc system-bonding conductor." This small circuit > breaker senses any current between the grounded current-carrying conductor and > the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By > mechanically linking this smaller breaker to larger capacity breakers that are > installed inline with the ungrounded current-carrying array conductors, it is > possible to detect, interrupt and indicate that a ground fault has occurred, > and to disconnect the fault. > > These early GFPDs were manufactured for 48 V or lower PV systems. According to > Wiles, ³As higher voltage, utility-interactive PV inverters became available > in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the > inverter¹s control electronics to monitor the fuse was more cost effective.² > While the sensing equipment may have changed, in general the role of the > modern GFPD remains the same as it was in 1987: > > 1. Detect ground faults in PV arrays. > 2. Interrupt the fault current. > 3. Indicate that a ground fault has occurred. > 4. Disconnect the faulted part of the array. > > These four GFPD requirements for grounded PV arrays are spelled out in NEC > 690.5(A) and 690.5(B). The former requires ground-fault detection and > interruption (GFDI), which includes the provision to indicate the presence of > a ground fault. The latter requires that faulted circuits be isolated either > by disconnecting the ungrounded conductors of the faulted circuit or by > shutting down power to the output power circuits of the inverter or charge > controller. > > A final GFPD requirement is found in Article 960.5(C), which calls for a > visible warning in the proximity of the ground-fault indicator. The warning > could be an LED, an LCD or both. In general, the manufacturer provides this > electric shock hazard warning as part of the listed grid-tied inverter or > charge controller. However, where a PV system includes batteries, the > installer must apply a duplicate warning label near the batteries, stating: > > WARNING > ELECTRIC SHOCK HAZARD > IF A GROUND FAULT IS INDICATED, NORMALLY > GROUNDED CONDUCTORS MAY BE UNGROUNDED > AND ENERGIZED > > One change in the GFPD requirements introduced in 1987 is that it is no longer > necessary to short-circuit, or ³crowbar,² the PV array in the event of a > ground fault. This added step had the effect of reducing the PV array voltage > to zero, minimizing shock hazard. The requirement was dropped in a subsequent > Code cycle, as leaving the array in a short-circuited condition created > several other issues.² > > > If you¹re a Home Power subscriber, you can access the original article in the > HP archives. If not, it is summarized above. > > Best, > > David Brearley, Senior Technical Editor > SolarPro magazine > NABCEP Certified PV Installer > [email protected] > Direct: 541.261.6545 > > > On 7/19/11 2:19 PM, "Hans Frederickson" <[email protected]> wrote: > >> Kent, >> I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. >> 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. >> There is no 690-5 or mention of ground fault detection/interruption in the >> 1987 NEC. >> >> In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 >> NEC. Here's the complete text from 1990: >> >> "690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic >> arrays located on dwellings shall be provided with ground-fault protection >> to reduce fire hazard. The ground-fault protection circuit shall be capable >> of detecting a ground fault, interrupting the fault path, and disabling the >> array." >> >> The handbook for 1990 goes on to say that the gfp device must: >> 1) detect the ground fault >> 2) open the grounded conductor to interrupt the ground fault >> 3) open the ungrounded conductors and short the photoltaic array source to >> disable it >> >> For some reason, I've never heard of item #3, specifically the part about >> shorting the array. Can anyone shed light on this? >> >> Regards, >> -Hans >> >> >> >> From: [email protected] >> [mailto:[email protected]] On Behalf Of Kent >> Osterberg >> Sent: Monday, July 18, 2011 10:07 PM >> To: [email protected]; RE-wrenches >> Subject: Re: [RE-wrenches] 1987 NEC >> >> Gary, >> >> No one else has come up with a 1987 NEC. If you can get a copy of 1987 >> section 690.5 (I think it was 690-5 back then), I'd appreciate it. >> >> Kent Osterberg >> Blue Mountain Solar >> >> >> >> Gary Willett wrote: >> >>> Kent: >>> >>> I am a member of the International Association of Electrical Inspectors >>> (IAEI), and they're headquartered here in the Dallas area. >>> >>> If you aren't successful getting the info from a Wrench with the 1987 code >>> book, let me know and I am sure I can request a FAXed copy of 1987 section >>> 690.5. >>> >>> >>> >>> >>> >>> Regards, >>> >>> Gary Willett, PE >>> [email protected] >>> >>> On 7/15/2011 4:30 PM, Kent Osterberg wrote: >>> >>>> I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. >>>> If any of you geezers have kept copies that old, please contact me off >>>> list. Thanks. >>>> >>>> Kent Osterberg >>>> Blue Mountain Solar >>>> _______________________________________________ > > > > > > >
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