Wind Speed Interference From Callaway

1
Wind Speed InterferenceFrom Callaways Aviation
Beacon

• Tim Waldron, Met Associates
• Kip Barbour, Callaway Plant
• October 9, 2003

2
Wind Speed Interference at Night

• In early April 2002 while validating Callaway
  Plant's meteorological data for the Annual
  Effluent Release Report, Tim Waldron of Met
  Associates, Inc. performed differential analysis
  of the Primary Tower 10M WS data compared to the
  Secondary 10M WS data. This analysis identified
  an approximate 3 m/s bias on the Primary Tower
  data, but only at night.

3
Illustrations of Differential Analysis

• The following slides provide some examples of the
  differential analysis used by Met Associates to
  identify the intermittent bias found in the
  Callaway Plant wind speed data.

4
Wind Speed Interference at Night

• Tim speculated that the data was being affected
  by some kind of dusk-to-dawn circuitry at the
  Primary Tower shelter.
• The only circuit controlled by a photocell at the
  Primary Tower was the single aviation beacon
  located at the top of the tower.

5
Single Strobe Aviation Beacon
A Flash Technology FTB 310-4 strobe beacon was
installed in September 1997.
6
Flash Technology Power Converter
Cable to beacon
Conduit to Photocell
7
Initial Troubleshooting

• The IC FIN team verified the beacon was the
  source of the interference by removing the 10
  meter level cups and manually placing the beacon
  controls in night mode.
• The strip chart recorder immediately jumped to 3
  m/s when the beacon was placed in night mode, and
  pulsed to 5 m/s with each flash of the strobe.

8
Immediate Actions Taken

• Manually placed the beacon controls in day mode.
  The strobe intensity is about 20,000 candles vs.
  2,000 for night mode.
• Wrote operability evaluation for WS with the
  beacon controls kept in day mode.
• Contacted the nearest flight service station
  concerning strobe in day mode.
• Wrote a Night Order for Operations.

9
Other Actions Taken

• Submitted Special Report 2002-002 to the NRC.
• Submitted an Operating Experience report through
  INPO.

10
Obstruction Marking and Lighting

• Federal Aviation Administration Advisory
  Circular, AC 70/7460-1K
• 23. Light Failure Notification
• b. Any failure or malfunction that lasts longer
  than thirty (30) minutes and affects a top light
  or flashing obstruction light, regardless of its
  position, should be reported immediately to the
  nearest flight service station (FSS) so a Notice
  to Airmen (NOTAM) can be issued.
• FAAs website www.faa.gov/ats/ata/ata400

11
Obstruction Marking and Lighting

• This report should contain the following
  information
• Name of persons or organizations
• The type of structure
• Location of structure
• Height of structure above ground level
• A return to service date.
• FCC Antenna Registration Number, if app.

12
Obstruction Marking and Lighting

• 24. Notification of Restoration
• As soon as normal operation is restored, notify
  the same AFSS/FSS that received the notification
  of failure. The FCC advises that noncompliance
  with notification procedures could subject its
  sponsor to penalties or monetary forfeitures.

13
Investigation of Interference

• I contacted the following sources
• Innovative Flash, the contractor for Callaways
  cooling tower lights
• Flash Technology, the beacon vendor
• NUMUG e-mail list server

14
Innovative Flash

• Richard Schawba of Innovative Flash stated that
  he was only aware of one case where the flash
  head itself was creating an RFI field on a
  communications tower. They finally corrected the
  affect by installing a wire mesh around the flash
  head.

15
Flash Technology

• The Flash Technology representative stated that
  they do not endorse installing a mesh over their
  flash head. He recommended moving the beacon
  cable away from the sensor cables. He stated
  that they had had similar problems on
  communications towers when the beacon cable was
  installed too close to the communications lines.
• However, he also gave me the name and phone
  number of a competitor that sells a wire mesh
  made to fit their flash head

16
Some NUMUG Feedback

• One, ensure that your signal cable and strobe
  cable are not co-located they should especially
  not be tied to the same junction box. Two, make
  sure that your power source for the met system
  and for the strobe are separate. Both the met
  system and strobe should be grounded to your
  tower grounding network.
• Matt Parker, W Savannah River Company

17
Some NUMUG Feedback

• If the Wind Speed data is only being biased from
  dusk until dawn, it may not be RFI. We had a
  problem years ago that required us to jumper out
  the surge suppression on the ground return from
  the tower sensors into the Climatronics computer.
  we were getting errors on our wind direction
  sensors causing them to read lower than
  expected.
• Tom Payne, Waterford 3

18
Some NUMUG Feedback

• I would imagine that if the cause of your
  problem is, indeed, RFI related proper grounding
  and shielding techniques for both the sensor and
  lamp cable as well as re-routing of the lamp
  power cable should mitigate it.
• Bob Pickwoad, Palo Verde

19
Some NUMUG Feedback

• If I can add a note here, the shields need to be
  used. Send each of them through the cable run
  separately, and terminate them at the tower grid
  in the shelter (floating the sensors is
  important). Keep in mind that the analog
  translator circuits with the F460 system can pick
  up the RF, as well as the cable run.
• Ralph Heistand, Turkey Point

20
Summary of Possible Causes

• RFI from the beacon flash head.
• EMI from the high voltage cable.
• 60 Hz noise on tower ground.
• Inadequate instrument cable shield grounding.
• Shared a/c power source.

21
Cables at the Base of the Tower
Beacon cable.
Retired cables and waveguides.
Instrument cables.
110 VAC power.
Tower ground cable.
22
Conduit Supports to the Shelter
23
Possible Source of Interference
110 VAC in flex conduit
Beacon cable
Instrument cables
24
Review of Callaway TB Drawings

• The drawings for the rack TBs showed the sensor
  shields grounded at the rack TBs.
• The drawings for the tower TBs showed a jumper
  between the sensor shields and the tower ground.
  Possible ground loop?
• The Climatronics vendor manual drawings showed
  them ONLY grounded at the rack.

25
Extra Jumper from Shields
26
Corrective Actions

• FIN Electricians removed the jumper in the tower
  TBs to float the sensor shields. This did not
  fix the interference problems.
• Planned work documents to move the beacon cable.
  Put on 12-week schedule!
• An Unexpected Discovery
• The sensor cable shields were cut off at the rack
  TB,
• and were not grounded as shown on the rack
  drawings.

27
Corrective Actions

• IC FIN team re-lugged the sensor cables and
  grounded their shields at the rack. Grounding
  the sensor cable shields at the rack corrected
  the interference.
• The work document to move the beacon cable was
  cancelled.
• Health Physics and Met Associates had to resubmit
  several Effluent Release Reports