Seba SWG 1750 Surge Wave Generator for Fault Location in Cables SWG1750 SWG1750C SWG1750CI SWG1750C-4 SWG1750CD

• SWG 1750C with 8 - 16 - 32 kV / 1750 J
• SWG 1750 CI with 8 - 16 - 32 kV / 1750 J, incl. leakage current measurement
• SWG 1750 C-4 with 2 - 4 kV / 1150 J and 8 - 16 - 32 kV / 1750 J
• SWG 1750 CD with 8 - 16 - 32 kV / 3500 J 

Together with reflectometers, surge generators are the central

component for cable fault location. They are used for both prelocation

and also pinpoint location.

Prelocation

Prelocation can be divided into transient methods and Arc

reflection prelocation, which differentiates between passive,

semi-active and active methods.

ICE - Impulse Current Method

(ICE-Method = Impulse Current Equipment)

This method is ideal particularly for fault location in long ground

cables and wet splices.

The surge wave generator ignites an arc at the fault. This

results in a transient, i.e. a spreading and repeatedly reflected

travelling wave between the fault and the surge wave generator.

An inductive coupler records this transient wave with a

reflectometer, the Teleflex. The length of one full oscillation

wave corresponds to the direct distance to the fault.

A coupler for recording the transient current wave is fitted as a

standard feature in all surge wave generators with a surge

energy of 1000 J or more.

ARM - Arc Reflection Method

(HV-supported reflection method)

All reflection prelocation methods offer the advantage of a very

detailed measurement result corresponding in principle to the

picture of a normal reflection measurement. So these are the

preferred fault location methods. Differences arise with the

different technologies, which can have a relatively simple

structure resulting in weight advantages. More complex technologies

are more efficient, but also have to be integrated in a

measuring system.

The simplest method is the passive ARM method (used to be

called arc stabilization or short-term arc method). This extends

the discharge of the surge generator and with it the burning

duration of the arc by means of a series resistor in the

discharge path.

In the semi-active ARM method, the discharge is extended

by an inductivity. Use of inductivity means that the level of

voltage is not affected, making it much easier to locate faults

also with a high ignition voltage.

With the LSG 3-E, SebaKMT offers an active ARM method

with an integrated 2 kV surge unit for excellent extension and

stabilization of the arc. At the same time, this device permits

an independent use as a 2 kV prelocation and surge unit.

Pinpoint location

For a precise location of the fault it is essential to confi rm its

position along the cable, because pre-location with the Telefl ex

only visualizes the absolute distance. But the position and path

of the cable in the ground, and thus the actual position of the

fault, is only relatively inaccurately known. An absolutely precise

pinpointing is necessary to limit expensive excavation

work and resulting surface damage to an absolute minimum.

Here, a direct discharge of the surge generator produces an

arc at the fault position. The direct connection means that this

discharge takes place very quickly, generating a loud fl ashover

sound which can be located without any problems using a

corresponding acoustic receiver at the surface, such as the

digiPHONE+.

It is important to always use the maximum available surge

energy, given the proportional behaviour of volume and

discharge energy. All SebaKMT SWG surge wave generators

have switchable surge stages.

The basic equation of the surge energy is: W = 0.5 x C x U²

Example with a required surge voltage of 8 kV: The full 1000

Joule surge energy is obtained with 100% surge voltage in the

8kV surge range. A setting of 25% surge voltage in the 32 kV

surge range ( kV) would be useless, producing only 62 Joule

surge energy.

Therefore it is always recommended as follows: First select the

optimum range, i.e. the lowest necessary voltage level, and

then adjust the SWG to the maximum possible voltage. This is

the only way to guarantee the maximum energy and sound at

the arc. If only half the voltage range is used, then only one

quarter of the surge energy is available.

digiPHONE+ - receiver for combined acoustic and

electromagnetic pinpoint location

The digiPHONE+ works according to the principle of the

coincidence or difference method. It automatically measures

the time differencebetween the electromagnetic signal of the

surge voltage and the acoustic bang of the arc fl ashover.

The digiPHONE+ operates like a stopwatch. The electromagnetic

pulse starts a counter and the much slower propagating

sound stops the counter afterward. The displayed time, or the

time difference between the sound and the magnetic pulse,

corresponds to the distance to the fault. The shorter the time,

the closer you are to the fault. The display shows the difference

in time as a numerical value, while a bar graph shows the

electromagnetic fi eld strength. The fi eld strength display also

acts as a locating facility of the cable position. The bar graph

display is broken down into individual segments to permit a

very accurate defi nition of where the cable is running. As long

as you keep your bearings on this maximum, your longitudinal

axis is already exactly on top of the cable. As a result, the

position over the cable is so precise that you almost cannot

miss the fault, even when faults are very diffi cult to hear.

This location principle also works for secondary noises and is

particularly useful in situations where cables are installed in

protective ducts or under solid road surfaces (concrete,

asphalt, etc.).