<GPS vs. Gridzilla, Episode 100> Very interesting controversy raging about this.
FactFinder works in utilities with Y2K and is a regular contributor to
EUY2K. This was an interesting post of his. - Roleigh
>From: bboard@greenspun.com
>Subject: Response to First time post - NERC Report - Excel spreadsheets dated 7/10
>Date: Sun, 01 Aug 1999 02:00:56 GMT
>Reply-To: FactFinder@bzn.com
>Message-Id: <iss.a02.37a3ab4d.8e06c.1@mhub2.tc.umn.edu>
GPS vs. Gridzilla> > >
GPS vs. Gridzilla, Episode 100
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Sorry Tim, Bonnie, I don't buy it. This is just more GPS and the Grid nonsense, with a slightly different twist.
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GPS is not essential to grid synchronization, and is not typically used for generator synchronizers, if at all. Typical synchronizers use phase angle comparisons for synchronizing. GPS is not essential to SCADA, they have their own clocks and GPS if used at all, is used to keep them accurate. GPS is normally used for improved accuracy, total dependence on it for critical applications would be ludicrous, since the signal may be lost for numerous reasons (receiver failure, etc).
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The devices listed for power utilities on the Truetime Website at truee time.com/DOCS/TTprod_litFRM.html are mostly accurate "clocks" using GPS, but also include the Model XL-AK GPS Synchronized Time and Frequency Receiver, with the following listed functions:
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Power Utilities -- Frequency and time measurement, precise time and frequency outputs to SERs, fault locators and voltage phase angle systems. >
Range Timing -- Precise timing for data acquisition and time codes for range distribution and data time tagging.
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Reviewing the datasheet for this receiver, it has its own internal oscillator and provides a stability value for when it is not tracking satallites – it too will work without GPS. This device is of course NOT a stand alone synchronizer.
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Dick Mills wrote an excellent article "Another Myth, We Need Computers to Synchronize" at y2ktimebb omb.com/PP/RC/dm9849.htm. Specifically discussed is the mythical GPS grid synchronization "problem". And here is an excellent web page on synchronization: nebulaee net/calypso/article10.htm
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There have been numerous threads in the EUY2K forum that have discussed generator/grid synchronization and/or GPS, here are two of my favorites:
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Please keep in mind that the information that quotes from the Bonneville Power Adminstration concerning its use of GPS technology came from an "ad" on the TrueTime site. Sure GPS can improve accuracy for time functions. But is GPS really "required" by BPA? Is BPA concerned about GPS?
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See "BPA is Y2K Ready!" at bpa.gg ov/corporate/kcc/y2k/y2k.shtml and one of my new "favorite title" press releases (thanks for the lead, Bonnie!), "Y2K arrived today. . . and nothing happened " at > bpa.gov which details BPAs Columbia River Y2K Readiness.
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The only GPS information I could find on the BPA Y2K site was from the Dec. 14, 1998 Fact Sheet at http:/// www.bpa.gov/corporate/kcc/nr/99nr/y2kfactx.shtml :
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"Are there other dates that may cause problems other than 1/1/00?
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Part of BPA's methodical process for Y2K testing involves looking at several dates. January 1, 2000, isn't the only date potentially affected by Y2K. Here are some other priorities for BPA's Y2K testing:
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8/22/99 - GPS rollover: The Global Positioning System is a constellation of 24 low-orbiting satellites that transmit data used by some cellular telephones, devices that track the location of freight shipments, and some navigational equipment. The clocks on this system report the time as the number of weeks since the launch of the system. On August 22, 1999, this counter will overflow and return to 0000 (as would happen on the odometer of a car that traveled 1 million miles). "
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Huh? None of those critical utility GPS uses listed??? Don't these guys have a clue??? ;)
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By the way, the effects of the GPS rollover, like the effects of the Y2K rollover itself, is way overblown when it comes to embedded system equipment. Many devices will handle the GPS rollover fine (this rollover was in the GPS specifications by the way, but I guess not all vendors read it good enough). Other devices, like some navigation equipment, that are not "rollover" compliant are subject to interruptions for short periods of time, and then will work fine again. As stated earlier, SCADA and other computers typically have their own clocks and if GPS is used for time accuracy, it's typically supplemental |
