Surge generator
A surge voltage generator is an electrical device for the periodic generation of high voltage pulses , which are used for testing and measuring purposes . Surge voltage generators with several megavolts are designed as Marx generators and are used in high-voltage laboratories for material testing, such as determining the dielectric strength and insulation properties . Smaller, mobile surge voltage generators with a test voltage of 3 kV to about 30 kV ( English "Thumper" ) also be installed in vehicles and are used for fault localization in underground High-voltage cables as part of repair work in power networks .
Localization of faults in underground cables
The exact location of the fault cannot simply be determined optically when buried, and laborious and expensive excavation work to find the fault location should be avoided, which is why a cable fault location is necessary.
The mobile surge voltage generator is connected from a vehicle at a suitable point such as a terminal box with the disconnected, defective line and earth . It charges a high-voltage capacitor at regular intervals of a few seconds and releases its energy in a short time. This briefly causes an electric arc at the faulty point in the cable , and the high voltage suddenly collapses.
This voltage drop propagates in the form of a wave along the line at a constant speed. By measuring the length of time and knowing the cable laying, the position of the fault can be roughly determined from the position of the feed over the running time; a spatial resolution of a few 10 m to 100 m is typical, depending on the distance from the fault and the available data the exact underground cable routing.
A more precise localization then takes place in the determined area by means of a floor microphone with which one can perceive the arc occurring at the fault location in the form of a bang. If two ground microphones at an appropriate distance and measuring devices with downstream signal processing are used to locate the location , the fault can be localized to within a few 10 cm. The excavation work can begin at the determined point in order to replace the defective cable section.
Web links
- Surge voltage generator for cable troubleshooting in the field
- Data sheet of a commercial surge voltage generator (pdf; 411 kB)