Atec High-Voltage-CDS Series - Manual (Page 6)

6
MV & HV Cable Fault Locating & VLF Testing
VLF + Thumper = Ease In Fault Locating HV Cables
5 kV – 25 kV Cable Systems
The VT33 VLF Thumper Combination is the best approach: VLF test cables, use VLF output for diagnostic
cable testing, use VLF Cable Burner to reduce fault voltage, fault locate with 13 kV @ 760 joules, use TDR/radar
for sectionalizing and for pre-locating faults. If a conventional thumper is desired, the CDS-2010U is the most
complete and full featured device available.
35 kV Network Systems
For 35 kV cable, solid or fluid filled, a popular combination of
products is the VLF-6022CM VLF hipot and the CDS-3632U
Thumper. Cable reels containing high voltage, return, and ground
cables are also supplied, with various MC connector attachments.
The VLF-6022CM is designed to VLF hipot cable rated up to 35kV.
It can also be used as a voltage source for Tan Delta and Partial
Discharge cable diagnostic testing. The CDS-3632U, with its 3200
joule discharge energy, offers the power needed to make good use of
electro-magnetic and acoustic detection devices as well as work very
effectively for Current Impulse locating on PILC.
69 kV - 230 kV Cable Fault Locating
For high voltage cable fault locating on cables up to 230 kV, there are not many options. One very good approach
is to use a Very Low Frequency AC hipot and the CDS-3632U. The VLF is used to burn down the cable fault to a
voltage arc-over level less than the discharge rating of the surge generator. Once a fault is made to arc over at less
than ~30kV, then the 36kV @ 3200 joules discharge of the CDS-3632U is sufficient to find the fault. The VLF hipot
can then be used to perform a VLF AC withstand test after the repair to verify the AC integrity of the cable and
the repair. Either a 120kV or 200kV VLF can be used.
Using a VLF hipot designed for cable burning is the most effective means of reducing the impedance of a
fault to reduce its arc-over voltage to enable the use of smaller and more conventional thumpers. A combination
of VLF, needed for AC hipoting the cable and as a voltage source for tan delta and partial discharge testing, and
our CDS-3632U is the best way to go. In the VLF Burn Mode, the VLF applies its output voltage to the cable. The
VLF voltage rises until the cable arcs. The VLF continues to operate, causing the cable to arc in the other polarity.
This continued arcing in successively opposite polarities rapidly burns down the fault. The arc current of the VLF
combined with the stored energy of the cable dumped into the fault every half cycle gets the job done far faster
than DC burn down sets.
VLF-6022CM
0-60kVac peak @ 0.1 – 0.02 Hz
Load rated to 5.5 uF
VLF-200CMF
0 – 200kVac @ 0.10 - 0.02Hz
Load rated to 3.75 µF
VLF-12011CM
0 – 120kVac @ 0.10 - 0.01 Hz
Load rated to 5.5 µF
VLF-90CM
0 – 90 kVac @ 0.10 – 0.02 Hz
Load rated to 2.75 µF
Other VLF models are available, as well as Tan Delta and Partial Discharge test equipment.
69kV cable 69kV – 138kV cable 138kV – 230kV cable