Atec High-Voltage-CDS Series - Manual (Page 5)

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!"11?LC?M Cable Fault Locators / Thumpers - Surge Generators
Very Low Frequency (VLF) AC Cable Testing
Most of the world has quit testing cables with DC voltage. It is well known that testing cables at the
historically applied 4 – 5 times normal voltage causes solid dielectric cables to fail prematurely. Also, DC
leakage currents tell little about the true condition of a cable’s insulation and even less so about its accessories.
With DC out of favor, something else had to be found. Enter VLF withstand, VLF Tan Delta, and VLF
Partial Discharge testing.
A VLF AC test set is just an AC hipot but with an output frequency of 0.1 Hz or lower, rather than
50/60Hz. The lower the frequency the lower the current and power required to apply an AC voltage to a
high capacitance load like cable. It requires 600 times less power to AC hipot a cable at 0.1 Hz as at 60Hz.
With the present day VLF products available from HVI, it is now possible to AC hipot a cable to verify its
integrity. The VLF hipot enables users to AC test long cables in the field with relatively portable and affordable
equipment. There is no better way to verify the integrity of a cable following repair than to apply 2 – 3 times
normal AC voltage for a period of time. The other methods used don’t get the job done: DC hipoting, a 5kV
megohmmeter test, hot stick adaptors that apply far less than the cables operating voltage, and/or a soak test.
Don’t be back in the same neighborhood a week after a repair because of additional damage resulting from the
original in-service failure, damage to adjacent cables, damage inflicted to the repaired cable by over voltage
thumping for hours, or because of a faulty repair. VLF it before re-energizing for the maximum assurance that
the cable is healthy.
HVI offers VLF products from 28kV to 200kV. Let us help you with all your cable test and fault location
needs. In addition to using the VLF to proof test a cable, add a Tan Delta and Partial Discharge accessory to
perform cable diagnostic testing. HVI is the cable test company.
Input: VT33: 120V, 60 Hz, 10A
VT33F: 230V, 50/60 Hz, 5A
VLF Hipot Output: 0 – 33 kVac peak @ 0.1 Hz
Load Capability:
1µF or more than 1 mile of 15kV cable
Discharge Output: 0 – 13 kVdc @ 760 joules
Discharge Rate:
Every 8 seconds
VLF Burner: Arcs cable every few seconds
TDR Interface: Arc Reflection & Current Impulse
Size & Weight: 28”w x 26”d x 44”h, 245 lbs.
711mm w x 660mm d x 1118mm h, 111kg
Cable Outputs: 50’ (15m) shielded HV cable & ground
VLF Thumper Combination - VT33(F)
VT33 - Complete Cable Care For 5 – 25kV Cable
With cable diagnostic testing becoming more common, the need for fault locating will rise. If
a cable cannot withstand the test voltage, failure will occur, requiring fault locating. If you’re in
the market for a thumper, why not get one with a VLF hipot built-in to test the AC integrity of
the cable following repair. The VT33 incorporates a powerful VLF hipot, a VLF Burner that
rapidly reduces a faults impedance (arc-over voltage), TDR/radar capability, and continuous
discharge for pinpointing the fault. Suitable for cables up to 25 kV. HVI puts all the tools
needed in one box.
• VLF test cables per IEEE400.2, VDE 0276, CENELEC, etc.
• Pre-locate faults using a connected TDR/radar
• VLF Burn faults to lower arc-over voltage
• Pinpoint fault with continuous thumping