Technical description
9
2
Technical description
2.1
System description
The indicator unit can be used for different measuring tasks depending on the
measuring accessories connected. Which of the following sensors and antennas
actually belong to the delivery (see page 9) depends on the set purchased:
Surge wave receiver DPP-SU2 for the accurate pinpointing of
flashover faults in buried cables
A discharge generator feeds surge voltage pulses into the end of the
faulty wire. These cause voltage arc-overs at the fault location. The
resulting flashover noise propagates in the ground and is recorded with
the surge wave receiver on the surface. The distance to the fault
location can be calculated using either the volume of the flashover noise
or the time difference between the arrival of the magnetic pulse and the
flashover noise.
Audio frequency receiver iFS for route tracing and fault location on
buried metallic lines.
With the aid of the antennas, the alternating current flowing in metallic
lines can be recorded, converted into a signal and transferred to the
indicator unit. In this way, as well as metallic lines which are transmitting
a signal from a suitable transmitter (491 Hz … 33 kHz), cables that are
operational (50 / 60 Hz) and pipelines carrying a current of 100 Hz /
120 Hz current for protection from corrosion can be located and traced.
For lines carrying an active signal generated by an audio frequency
generator not only the path but also the laying depth, the current
strength and the direction of signal flow (in case of a SignalSelect
encoded signal) can be determined.
Earth spikes for accurate pinpointing of sheath faults on plastic
insulated PE and VPE medium voltage cables
Sheath faults are pinpointed using the step voltage method. The
measuring current flowing into the ground at the fault location forms a
potential gradient forms at the point of escape, which is measured using
earth spikes and the downstream indicator unit. The step voltage rises
when both earth spikes are situated in front of the fault position. If the
fault position is passed by, the step voltage polarity changes, which then
subsides again the further away you go.
Reader coil IFA for identifying a cable among several accessible
cables
As with the iFS receiver, the reader coil is used to detect audio
frequency signals within the frequency range of 50 Hz to 33 kHz. In
contrast to the receiver, the coil is applied directly onto the accessible
cable, thus increasing the measurement accuracy. Thanks to
SignalSelect compatibility, this method also ensures the reliable
identification of a cable on which a SignalSelect signal is transmitted
(e.g. when a cluster of cables is exposed after excavation work).
Description