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VON SST15-832, Operating Instructions Manual

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VON SST15-832 Operating Instructions Manual Download Page 21

VON MODEL SST15-832 ARC REFLECTION SECTIONALIZING SYSTEM    Page 19

1.

Connect the radar to a cable of known length, size, insulation type, shielding type and
condition.  Unburied cable is best since the actual cable length can be measured
accurately.  Buried cable lengths are less accurate due to the allowances that must be
made for cable depth and coils of wire put at the ends to handle future expansions.

2.

Use the turn on velocity factor or set the propagation velocity factor to an assumed
value or the value of a similar cable obtained from a chart such as that found in the end
of this section.

3.

Short to the cable neutral at both the near end HV lead connection point and the far
end to identify these points on the radar screen.

4.

Determine the total length to the end of the cable being measured. 

5.

To determine the true propagation velocity or propagation velocity factor, multiply the
assumed propagation velocity for propagation velocity factor by the actual cable length
and divide by the measured cable length.

True  

     Assumed propagation velocity x actual cable length = 

Propagation

 Cable length measured with the radar                Velocity

6.

Reset the radar with the True Propagation velocity determined above.  Repeat steps 3
and 4 to verify that the measured cable length equals the actual cable length

.
The propagation velocity factor is determined by dividing the actual velocity of propagation in
feet/microseconds by 983.  Some representative values are shown below.

INSULATION TYPE

INSULATION THICKNESS PROPAGATION

& CONDUCTOR SIZE

AND TYPE      

VELOCITY

                                                 

FACTOR

XLPE- 1/0 

175 mil insulation

.562

XLPE- 1/0 

260 mil insulation 

.555

XLPE- 1/0

345 mil insulation

.623

XLPE- 1/0

345 mil water impervious

.582

EPR-  1/0

345 mil 

.588

XLPE- 400kcmil

260 mil water impervious

.643

XLPE- 600kcmil

260 mil

.598

XLPE- 750kcmil

345 mil-CN

.562

XLPE- 1000kcmil

260 mil-CN or Jacketed

.600

XLPE- 1000kcmil

260 mil water impervious

.541

air-  most common sizes

.98

PILC- most common sizes

.38      

EPR-  range of sizes 

.55-.62

HMWP- range of sizes

.52-.58

XLPE- range of sizes

.49-.64  

The fault can be located by the following two methods even when the velocity of propagation
is not known.

The comparative method of locating a fault using radar utilizes the fact that an overall length
of the cable is known or a specific distance is known to a splice or landmark such as a
transformer.  Determine the distance to the fault with the radar.  Then determine the distance
to the known point with the radar.  Using the following formula, the actual distance to the

Summary of Contents for SST15-832

Page 1: ...OPERATING INSTRUCTIONS FOR MODEL SST15 832 Arc Reflection Sectionalizing System THE VON CORPORATION 1038 LOMB AVENUE P O BOX 110096 BIRMINGHAM AL 35211 TELEPHONE 205 788 2437 FAX 205 780 4015 ...

Page 2: ......

Page 3: ...CONTROLS AND INDICATORS 6 VI F SECTIONALIZING URD LOOP SYSTEMS 8 VI B HINTS AND TYPICAL TRACES 10 VI E TESTING AN ISOLATED CABLE 13 VI G RADAR OPTIONS MENU 13 VII IN CASE OF DIFFICULTY 13 VIII TEST LEADS BATTERY MAINTENANCE AND STORAGE 14 IX CIRCUIT DIAGRAM AND PARTS LIST 15 X RADAR THEORY 16 XI THEORY OF ARC REFLECTION METHOD 17 XII CABLE DISTANCE MEASUREMENTS 18 ...

Page 4: ...l with us so that we may share them with all VON users through application notes and instruction manual changes Please keep us informed of the names of personnel to receive application notes and instruction manual changes For any questions concerning this equipment or its application write or call The VON Corporation SHIPPING ADDRESS P O Box 110096 1038 Lomb Avenue S W Birmingham Alabama 35211 Bir...

Page 5: ...ead and the beginning of the test cable If the left marker does not already line up with this point consult with the factory 2 Now connect the conductor at the far end of the reel of test cable to its neutral or shield with a jumper Observe the leftmost point at which the two traces diverge The up blip at the open end will have an identical down blip from the short The leftmost point where the two...

Page 6: ...g the equipment to an energized cable causes severe equipment damage While using this equipment all exposed terminations of the cable being worked on must be roped off or otherwise protected so that the unaware can not come in contact with them In sectionalizing grounding is the most important concern and safety precaution The heavy green ground lead must be connected to same ground system to whic...

Page 7: ...ally shown on the screen The initial turn on value of 53 0 can be increased or decreased to the desired value The velocity factor can be set from 25 0 to 99 0 Screen LCD 3 5 8 9 cm x 4 5 11 4 cm with 320 x 240 dot matrix providing both trace and text The display can be easily read in direct sunlight A backlight is provided so the screen can be viewed in total darkness Memory Fifteen memories are p...

Page 8: ...pointing When in Thump mode the TDR screen will go blank to indicate this VOLTAGE ADJUSTMENT knob adjusts the discharge voltage from a low value to the maximum voltage of 15kV GAIN button Provides manual vertical gain adjustment from 0 to 20 dB by using the up and down arrow keys OPTIONS pushbutton Pressing the OPTION key presents a menu of available options such as delay and left starts This butt...

Page 9: ...rol circuit and motors The fuses are intended to limit and damage due to a component failure or short to the case Remove the fuses and unplug the unit when taking the unit out of it s case for maintenance VI A BASIC OPERATION Practice in a test situation with the radar before field use is very important Be sure that you know how to locate the end of the units test lead with the radar before connec...

Page 10: ... of the cable will not show past such a low resistance fault 5 The maximum voltage can be adjusted using the VOLTAGE ADJUSTMENT knob It is recommended that except on 5kV and below cable the VOLTAGE ADJUSTMENT be kept at or near maximum as the transformers in the loop dissipate much of the energy With the entire section on the display push the START button until the sentence WAITING FOR THUMPER app...

Page 11: ...ce the SST15 832 can then be connected to the faulted cable and the distance to the fault determined using traditional methods Some customers have expressed concerns that putting an arc reflection pulse on the source side or transformers feeding customers would send damaging pulses into the customers system Only a small percent of the energy can go through the transformer Since the SST15 832 is ra...

Page 12: ...t where the trace changes direction 5 Notice that locating the beginning of the cable by shorting it to ground requires the most skill Everything past the fault changes 6 Notice that a short at the end of the cable is easy to find and locate 7 Remember that the first major divergence between the reference trace and the active trace is what you are looking for The down blip at the fault may not be ...

Page 13: ...ow the right marker is at the point where the upward movement of the trace begins Figure 2 shows a typical faulted trace Notice that the right marker has moved to the beginning of the downward movement of the lower trace The distance now shows being approximately 355 feet from the hook up point to the fault Figure 3 shows another typical faulted trace This time the fault is at approximately 387ft ...

Page 14: ...ted trace Notice that the fault is close to the far end of the cable Instead of measuring from the current end to the fault it may be easier to measure from the far end The distance from the far end can be determined by subtracting the distance to the fault 948 ft from the previously determined length of the cable 1022 ft This gives you an approximate distance of 74 feet from the far end of the ca...

Page 15: ...u VII IN CASE OF DIFFICULTY Opening the unit should only be done by trained and qualified individuals under consultation with the factory To Open Unit remove the hex head screws from around the edge of the unit There are ten 10 screws total around the edge This is most easily done with a 5 16 nut driver Take care to save the screws lock washers and flat washers The unit pulls straight up and out o...

Page 16: ...lead acid battery should be kept charged to at least 11 5 volts during storage since it can be severely damaged if stored below 10 5 volts The internal battery charger regulates the voltage at approximately 13 6 to 13 8 volts so the unit should be left connected to 120 240 volts AC to store between uses To check battery voltage at any time use battery check switch The battery can also be charged b...

Page 17: ...VON MODEL SST15 832 ARC REFLECTION SECTIONALIZING SYSTEM Page 15 IX CIRCUIT DIAGRAM AND PARTS LIST To Be Added Later ...

Page 18: ...Pulses are generated and put on a cable that must have consistent distributed capacitance A reflection will result when a discontinuity or significant change of impedance occurs An upward reflection or blip would indicate a higher impedance discontinuity such as the cable ends or a place where the cable neutral is missing A downward reflection or blip will result from a lower impedance discontinui...

Page 19: ...most never occurs in the field Distance is figured by a radar using the time delay which is based on how fast the radar pulse travels along the cable The distance to the fault is related to the time the pulse takes to get to the fault and return The accuracy of the speed of the pulse in the cable called the velocity of propagation determines how accurately the distance to the fault can be calculat...

Page 20: ...hat an approximate location can be determined looking at the screen 4 Provides the conductor distance to the fault Only the conductor distance is displayed Actual ground distances are subject to variations caused by the cable route and the cable depth The accuracy of any distance determined by the radar is dependent on the correct velocity of propagation and the operator s skill XII CABLE DISTANCE...

Page 21: ... radar with the True Propagation velocity determined above Repeat steps 3 and 4 to verify that the measured cable length equals the actual cable length The propagation velocity factor is determined by dividing the actual velocity of propagation in feet microseconds by 983 Some representative values are shown below INSULATION TYPE INSULATION THICKNESS PROPAGATION CONDUCTOR SIZE AND TYPE VELOCITY FA...

Page 22: ...e end of the cable to the fault Measure out the distance with a wheel and drive a stake b Without changing the propagation velocity on the radar take a reading from the opposite end of the cable Again measure out the distance with a wheel and drive a stake c The fault will lie between the two stakes By using the following formulas the fault location can be determined Where D1 Distance to the fault...

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