Utility LocatingCable Fault Locating IMSA BC Fall 2005

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Utility Locating/Cable Fault LocatingIMSA BC -
Fall 2005

• Gord Parker, C.E.T.
• Radiodetection Canada (Calgary, AB)
• Copy of this pres _at_ www.radiodetection.ca/docs

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Main Topics

• An Introduction to Modern Locate Needs
• Theory of Locating
• Cable Fault Locating
• Earth Faults
• Ducts Opens
• All this in 55 minutes, buckle up.

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A couple problems you face

• Locating isnt your core business
• You need to locate accurately but efficiently
• Locating is much tougher now with more and new
  utilities underground
• Multiple Telecom, fibre, CATV, SCADA,
• Power primary, secondary, streetlights
• Abandoned plant

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Abandoned and not marked
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If you hear one complaint

• It is that users feel modern equipment is
  difficult to use (too many buttons).
• BUT - Locating is getting tougher.
• Used to be just Gas water underground.
• You cant plan where congestion will or will not
  affect your locators.
• Simpler locators dont cut it anymore.
• BUT Still needs to be User-Friendly !!
• Users need to see the benefits get used to it.

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Locating is Tougher EVERYWHERE

• Both pictures taken from the same corner,but
  showing old and new neighborhoods.

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To find them
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Why there is a 1-3m hand expose

• Note Gas Line
• Note position of tracer wire
• Note congestion !

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Common Locate Situation
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Less-Common Locate Situation
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The Basic Theory of Locating

• Electromagnetics ???
• What the heck is that
• It it the flow of current
• We can all make a light bulb work and that is ½
  of locating
• Current flows down conductors
• Current stops towards open circuits
• insulated unions/meters, ends of main/cables

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Omni Markers

• Permanent, identifiable markers designed to be
  buried at features you may need to come back to.
• Different frequencies / utilities.
• Future time savings is primary reason
• (backhoe goes through C15 pretty quick)
• Mark valves, stubs, future expansion,
  right-of-way edges, concrete below-grade vaults,
  etc
• Walk a S shape or along pipe in null

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Passive Location

• The main purpose is for avoidance.
• Uses existing signals
• Quick
• Relatively easy
• Difficult to identify
• Can follow it - SLOW
• CPS is unique to pipe

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Active Signal Application
Clips first choice 100x the current Clamp
connect to live connectors (10x) Spill
(ghosting)
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Connection
Newer equipment confirms Tx is ready. A
successful connection to the metallic pipe or
cable will be indicated by a change in the
transmitter audio or visual indicator. Always
make the best possible connection for reliable
signal.
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Connection
Badly positioned remote ground causes more signal
transfer. Where possible, place ground rod away
from known adjacent utilities which may act as
return paths. Or if unsure, re-do locate after
moving ground.
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Connection
Grounding to a structure which is also grounded
can produce multiple signals. The signal returns
on every conductor that shares the same ground.
(I.e. Water Pipe Power, Tel, CATV)
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Connection
After making a connection, sweep a complete
circle around a signal source measure and mark
all occurrences of signal. Repeat to assure
accuracy.
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Connection
Energizing in the street and tracing toward the
bonding point can be more reliable.
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Induction
Often induction will energize every metallic
conductor close to the transmitter. This is
useful for checking an area for buried
conductors, but not useful for finding specific
conductors in congested areas.
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Peak / Null
Null antenna gives a sharp response which gives
the impression of good accuracy, but can be
less accurate than Peak.
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Peak / Null
Peak coil response is less sharp, but actually
more accurate.
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Peak / Null
Null response in an area with congested plant is
often useless and misleading.
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Locating Problems

• Null response in an area of congested plant is
  often useless.
• Peak response is much more reliable.

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Locating Problems

• All brands of locators can give bad depths and
  L/R errors.
• Field distortion can be checked by verifying the
  agreement of peak and null responses.
• Key part of RD locator and training (peak/null)

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Locating Problems
Twin aerials and signal processing reduce errors
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Distortion
You likely dont give out depths BUT it can be a
very useful tool for US to use in confirming a
locate.
Expect distortion and hence, bad depths near a
tee..
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Distortion
or near a depth change,
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Which Frequency? (and Why?)
High frequency signal quickly escapes from target
line and may return on an adjacent line. Lines
in close proximity will readily accept signal.
This can lead to field distortion and poor locate
information.
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Which Frequency?
Higher frequency shorter range (greater
capacitive signal loss to ground). This
frequency is better for induction onto small or
short length conductors, such as gas services and
ends-of-mains.
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Which Frequency?
Low frequency long range (minimum capacitance
signal loss to ground). This frequency is better
for connection and locating longer metal pipes or
cables.
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Which Frequency?
High frequency may locate service drops which are
not grounded at the termination point but range
on main line is reduced and may induce onto
crossing services.
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General Locating
When pinpointing the signal, keep the bottom of
the receiver blade close to and parallel to the
ground. You can pivot receiver to ensure maximum
signal is received. This is particularly true
prior to taking a depth reading.
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General Locating problems
Lost signal must be either End of line,
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General Locating problems
OR a T lateral, or a bend (90),
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Locating Hint
Searching for laterals. Use Peak and Highest
Frequency. Search 2 paces away from and parallel
to the main line.
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Locating Hint
Get aerials away from small fields on re-bar.
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Sondes
Just so you know they exist To locate
non-metallic pipe, insert inside. Harder to use
but more controlled and rock-solid signal at
10-20 of cover.
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New Abilities in Locators

• Low frequency is a must to avoid ghosting
• Transmitter ground indication confirms good
  signal launch
• Built-in Self-tests and Web-Enabled features
  save the user maintenance costs
• Optional Current Direction indication is an
  important tool to identify cables picking up a
  signal due to common bonds

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Depth Calculation

• Just as two eyes can judge distance, a receiver
  with a twin aerial antenna can measure depth.
• The signal strength at the bottom aerial is
  compared to that on the top aerial. The receiver
  does the arithmetic to provide a depth reading.

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Current Measurement (CM)

• Why do we need CM?
• The diagram shows the conventional locator
  response for the same signal on three adjacent
  conductors buried at different depths.
• It is only when CM is used that the correct
  target line can be identified.

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Current Direction (CD)

• Current Direction recognition is a Radiodetection
  technique for increasing the information
  available at difficult locates.
• Receiver identifies if user is detecting a signal
  that has jumped / ghosted onto adjacent lines,

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Current Direction (CD)

• The receiver displays the CD using either a
  forward or backward facing arrow on the LCD.

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THE EVOLUTION OF CONFIRMATION
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Summary

• Locating is tougher than it was even 10 years
  ago. There are new utilities (i.e. fiber and
  power) and more abandoned plant in the ground.
• The tools exist to confidently work through any
  congested areas.
• When I say tools, we mean the methods and
  features in modern equipment.
• This does mean there are more buttons and modes.
• Training is more of an issue now than ever.

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Fault Locating

• There are two kinds of faults on 110/220/347 and
  lower voltage cables.
• Earth Faults
• Where conductor(s) in contact with dirt.
• Opens or not-to earth
• Conductor burned open circuit.
• Cable in duct (may be faulted to earth but not
  the dirt right near it).
• Conductor shorted to another conductor in cable.

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Typical A-frame

• A-frame attachment for typical cable locator
• Doubles ability of locator.
• Points need to be in contact with earth but not
  deep.

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A-Frame Fault Finds
Both Signal Strength and Direction Arrows
indicate the fault.
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8 Deep !
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(No Transcript)
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Grow Op
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My Boss

• (from Toronto)
• Had to call army out for for this fault

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Opens Inside Duct

• Time Domain Reflectometers (TDRs)
• Sends out a pulse (10 volts)
• Shows the pulse returning
• Time is proportional to distance
• TDR calculates and gives distance
• Usually still need a locator to find accurate
  cable path for accurate measurement.

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Typical Streetlight cable fault.

• From opposite end of cable
• Cursor 1 is at start of cable
• Cursor 2 is at open (upwards reflection)

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Opposite End

• Cursor 1 is at start of cable
• Cursor 2 is at open (upwards reflection)

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(No Transcript)
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TDR Range (mile )
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Quality Value

• Terasen Gas found 1/8 as many repairs with modern
  equipment
• Look for value not price as the short term cost
  savings of lower priced equipment will be more
  than erased by any one of the following
  situations
• One repair (when shipping and down time included)
• One near miss, never mind even a minor hit.
• A technician taking an extra 5-10 minutes per
  locate on average for a year.

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RD 4000 Improvements

• Much cleaner user interface
• Modes shown on screen
• 4 buttons (from 9)
• Depth/Current combi
• Sonde mode moved to sub-menu
• Auto backlight (std)
• 4 D-cells (was-12 AA)
• Improved sealing

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Training and Support

• Included free hands-on, onsite training.
• Free repeat trips if necessary.
• Cell phone is always on (exc. during training)
• Local support (Langley/Calgary) .
• Free support to company trainers industry
  associations

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Radiodetection

• Contact Gord Parker, C.E.T.
• Telephone [phone] / c 606-5464
• Facsimile [phone]
• E-mail gord_at_radiodetection.ca
• Website http//www.radiodetection.ca

Eecol Electric Ltd.

• Contact Paul Warman
• Telephone [phone] / c 786-4780
• Facsimile [phone]
• E-mail warmansp_at_eecol.com
• Website http//www.eecol.com