Atec High-Voltage-CDS Series - Manual (Page 2)

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HVI – The Cable Testing & Fault Locating Company
HVI has extensive knowledge and field experience in fault locating and cable testing along with the best tools for the job. Fault
locating requires more than just a thumper. Efficient fault locating requires the convergence of knowledge, methodology, and
the right hardware. A total approach is needed to get the job done quickly to minimize customer outage time and damage to the
cable system. This includes knowledge of the cable systems design, construction, and history, accurate maps, proper fault locat-
ing procedures, the right thumper, some cable burn down method, use of tdr/radar, and a top level acoustical & electromag-
netic listening device. HVI can assemble the best system and approach possible to meet all needs from 5kV – 230kV cable.
Q.
Why Choose HVI Thumpers?
A.
HVI Thumpers Offer All the Features Needed.
When fault locating, remember this: do no harm. Don’t harm you insulation and accessories by thumping your 15kV cable
at 25kV for hours looking for a fault. Use proper methods and technologies. The goal should be to thump at the lowest possible
voltage yet deliver the highest possible energy to find the fault. Locate the fault without making more. To do this you need a
thumper with a variable hipot output, multiple full energy discharge outputs, and ample burn current to condition a fault
to arc at a lower voltage. HVI thumpers offer all the features and power necessary: many others don’t. Don’t handicap your
fault finding efforts by spending the same or more for ½ a thumper. HVI thumpers provide all the tools needed.
• Fully Variable Hipot Output On All Three Voltage Settings
Needed to identify faulted cable, show breakdown voltage to help choose tap, burn fault, hipot cables after repair
• Highest Burn Current
Burns down faults to permit thumping at lower, less damaging voltage levels. Some vendors offer no hipot/burn
• Three Output Voltage Taps All At Full Energy
Allows thumping at lower voltages. Noise of maximum joules @ 5kV = noise of maximum joules @ 20kV
• Variable Discharge Rate: 6 – 10 second discharge/thump rate. Faster and slower discharge rates are not advisable
• TDR/Radar Ready
Use your old TDR or buy a new one. A separate TDR box is advantageous over a TDR built-in to the thumper:
greater flexibility, versatility, ease in service, use without thumper, take to office for downloading and training, etc.
• Battery Operation
HVI thumpers are not battery operated. Thumpers of this class that are battery operated must sacrifice other necessary
features, like variable hipot outputs and cable burning, missing half of what a thumper should be. In addition, some
have a long 15 seconds between discharges, greatly slowing the fault locate. Also, battery charge times are short, as-
suming that you remembered to keep it charged between uses. To get battery operation is not worth the sacrifice.
Controlled Energy Thumpers With Burn Capability a Necessity
Due to the known problems associated with DC cable testing, most utilities worldwide have abandoned DC testing of solid
dielectric cable (many have switched to VLF AC testing), or greatly reduced their test voltage levels, yet they then thump cables at
voltages of 2 – 3 times normal line-to-ground voltage. They find the fault but make more in the process. This is avoided by using
HVI thumpers with three output voltage taps, and high burn currents used to reduce fault impedances to permit lower voltage
thumping. HVI thumpers can thump at voltages below normal line-to-ground voltage yet still deliver maximum joules, thereby
minimizing damage to the cable system while delivering full energy to the fault needed for rapid location.
Energy = Watt Seconds = Joules = ½ CV 2 = Fault Arc Intensity = Noise = Electro-Magnetic Discharge
Problem: To deliver the full joules of energy possible to a fault, the capacitors within a thumper must be charged to the maxi-
mum voltage. With the wrong thumper, this often results in thumping a cable at an excessive voltage, causing significant dam-
age to insulation and accessories. Since the applied voltage is a square function (½ CV²), if the thumper is at 2/3 voltage, only
45% of the joules are delivered to the fault. At half voltage only 25% energy is delivered, making the fault hard to hear. Either
fault locating takes far longer than necessary or the crew gets impatient and turns the voltage all the way up to get the loudest
bang. The fault is found but more are made. This practice can and should be avoided.
Solution: Use a multi-tapped, “controlled energy” thumper like those from HVI. With three output voltage taps and ample burn
current to condition faults, thumping can be performed at voltages far lower than before. Find your fault quickly while avoiding
damage. Wouldn’t you rather thump at 5kV instead of 20kV, as long as the discharge energy, or noise, was equal? The measure of
a good thumper is not the maximum voltage it can discharge, but the minimum voltage still capable of delivering the full
energy. For instance, our 5/10/20 kV output model is a far better choice than the 12.5/25kV model from others.