Cable fault locator TDR-109 for power lines


TDR-109 is a high-precision 3-channel digital reflectometer designed to determine the distances to all types of faults in the power cable lines: open, short, sleeve, cable splice, parallel branches, wet cable, high-resistance faults, intermittent breakdown and etc.


TDR-109 provides the following measurement methods:

  • Time Domain Reflectometry (TDR);
  • Arc-Reflection;
  • Oscillatory discharge (ICM, Decay);

Time Domain Reflectometry (TDR) – the most accurate and safe – is effective for the diagnosis of low-resistivity cable faults, searching open and short-circuits.

Time Domain Reflectometer (TDR) is a cable device that uses the principle of a radar. The short probing pulse is supplied to the cable line. The signal propagates along the cable and reflected partially or completely at the cable impedance heterogeneity and finally returns back to the input of the device. After processing a received signal device displays the result (waveform signature) in the metric system on the screen.

Heterogeneity of the impedance are result of cables production technology violations, as well as due to mechanical and electrical defects during the construction and maintenance of the lines. The heterogeneity as usual arises in the other devices connection points to the line (coupling, tap, splice cable, coil Pupin, etc.) or in the location of the fault (open, short, soaking core of the cable, current leak to the ground, the leakage to the adjacent wire , broken steam, etc.). Time Domain Reflectometry (TDR) method allows  fixing of multiple inhomogeneities both discrete and multiple, depending on the ratio of their length and the  pulse width.

 TDR-109 is most effective with external High Voltage Pulse Generator (HVPG):

ARC-REFLECTION METHOD (ARM)- in complex with the high-voltage pulse generator  TDR-109 can detect high impedance faults with an accuracy of a TDR method.

Localization of faults with high resistance in the fault point is usually difficult using low-voltage TDR method. One of the solutions is to localize faults on power cables is ARM method.

The essence of the ARM method is in creating conditions (using HPVG)  for the occurrence electric arc (breakdown)  for a short time (few milliseconds) in the point of the fault. Synchronously with the burning arc (sync signal obtained from HPVG) reflectometer performs sensing. The TDR’s probe pulse is reflected from a low resistance of the arc with inverted polarity (like shorted circuit waveform). The method does not require the prior isolation burning and particularly effective when working on polyethylene sheath.



OSCILLATORY DISCHARGE METHODs: Impulse Current (ICM) and Decay Methods are based of the oscillation process period measurement which occurs due breakdown of a charged cable.

There are two ways to create an oscillatory process in the cable: a voltage wave (Decay method) or current wave creation (ICM method).

To create current/voltage wave,  high-voltage pulse generator (HVPG) raises the voltage in the cable to the moment of breakdown occures or discharge internal capacitor to the cable.


The defect of the insulation causes a breakdown at the injury point with a spark, which has a small  resistance, and the oscillatory discharge proceeds. Knowing the speed of propagation of electromagnetic waves along the cable and the period of oscillations process, we can calculate the distance to the breakdown:

where X – the fault distance , m;  v – velocity of propagation of electromagnetic waves in the cable, m/ms; tnn – the half-period oscillation process, ms, c – speed of light, which is equal to 300 m/ms; VF – the value of the velocity factor. To achieve the best accuracy only the second period of oscillations is selected.

Implementation of the oscillatory discharge method is carried out by the use of additional equipment: high-voltage pulse generator (HVPG) and a special connecting device. 

Sphere of application:

Pulse TDR TDR-109 is used for control when installing or operating the following types of cable lines:

  • power cables;
  • aerial cable lines;
  • system cables communications;
  • signal and control cables;
  • computer networks;
  • television and radio cable lines;
  • to determine the length of the cable during its manufacture, storage and trade;


  • the possibility of applying the most modern methods of diagnosis and cable fault prelocation: TDR method, Arc-Reflection Method (ARM), the voltage wave(Decay), the method of the current wave(ICM);
  • 3 line inputs to connect to the three phase cables;
  • display waveforms on a color 5.7 ” TFT-LCD with a resolution of 640×480 pixels;
  • the ability to display all measurement channels in all combinations (6 waveforms);
  • non-volatile memory – at least 1000 waveforms, up to six of them for comparison;
  • subtraction mode to show only waveform differences;
  • maximum range – 128 km;
  • the possibility of sensing with an increased pulse amplitude (U2 = 86 V on open circuit ) to work on cables with high attenuation;
  • real time measuring;
  • two cursors measuring system;
  • possibility of a detailed review of any portion of the reflectogram – the function of multiple zoom;
  • asynchronous noise suppression;
  • intermittent fault mode detection  – the function “Capture”;
  • built-in velocity factor table up to 300 values;
  • External USB Flash drive to archive waveforms library and VOP library, as well as restore libraries to the device memory from USB flash;
  • splash proof and hermetically closing body with high mechanical strength (protection class IP67);

Technical specifications:

Measurement Modes
  • Time Domain Reflectometry (TDR);
  • Arc-Reflection Method (ARM) ;
  • Current method (ICM);
  • Decay;
Display Color TFT 5.7″ (640×480 pixels)
Range measuring distance (delay time) from 0 to 128000 m (0 to 1280 μs)
Sub-bands of distance (time delay) 0 – 62.5 m (0 – 0,625 μs), 0 – 125 m (0 – 1.25 μs), 0 – 250 m (0 – 2.5 μs), 0 – 500 m (0 -5 μs); 0 – 1000 m (0 – 10 μs), 0 – 2000 m (0 – 20 μs), 0 – 4000 m (0 – 40 μs), 0 – 8000 m (0 – 80 μs) 0 – 16000 m (0 – 160 μs), 0 – 32000 m (0 – 320 μs) 0 – 64000 m (0 – 640 μs) 0 – 128,000 m (0 – 1280 μs)
Distance instrumental error from 0.01% to 0.2% of subband (from 12.5 cm to 8 m at VOP = 60%)
The effective sampling rate 800 MHz
Range concerted resistance from 20 Ω to 600 Ω
Probe pulse duration from 10 ns to 100 μs
The amplitude of the probe pulse (at open circuit)
  • U1 – not less than 18 V;
  • U2 – not less than 86 V;
The sensitivity of the receiving path better than 1 mV
The dynamic range not less 80 dB
The setting range of the velocity factor from 1.000 to 3.000 (step 0.001)
Time delay adjustment range (Arc-Reflection method) from 0 to 50 ms (step 0.2 ms)
Synchronization (Arc-Reflection method)
  • measuring input
  • TRIG input
Amplitude synchronization (wave method) -60 to +60 V, step 2V
Continuous battery operating time at least 6 hours
Time of continuous operating time through the charger unlimited
Dimensions 70x246x124 mm
Operating temperature range from -20 °C to +40 °C
Weight with a battery not more than 2.5 kg



Delivery Contents

Cable Fault Locator TDR-109 1 item
AC Adapter 12 V 1 item
Connecting cable 75 Ohm, BNC.M – «Alligator clip» 1 item
Connecting cable 75 Ohm, 1 m, BNC.M-BNC.M  5 items
User Manual 1 item
CD-ROM with software 1 item
Accessories bag 1 item

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