TDR COUPLING FILTER FOR CABLE FAULT LOCATION PRE-LOCATION
PRINCIPLES OF OPERATION
High Voltage Coupling Unit
Pre-Locating distances to cable faults are not always as simple as connecting a TDR (Time domain Reflectometer) unit to the cable under test. When the fault resistance is higher than 120 ohms the fault can simply not be detected by any TDR. The AE101 and TDR combination was developed to fill the gap that exists above 120 ohms to well within the Megohm range. It will easily detect and display information which can be analyzed by anyone with TDR waveform analysis skills.
Principles of Operation
The AE101 is connected in series with any standard surge generator and faulty cable which provides the high voltage energy needed to temporarily break down high resistance cable faults. When flash-over occurs at the fault the AE101 will limit the current flowing and allow the arc to burn for a slightly longer period.
The AE101 allows the PCA101 to be coupled through suitable filters to the high voltage high energy pulse. Because burning arcs are always a low resistance, we can now use TDR techniques.
A single TDR pulse is superimposed on top of the HT pulse at the correct time. When the pulse arrives at the burning low resistance arc a short circuit is reflected to the TDR. The waveforms are then simply treated and analyzed as any other TDR waveform when a short circuit is detected.