At first sight, there seems to be little reason for the use of a measuring instrument to localize breakdowns during works tests, given the high quality standards which apply in the manufacturing of state-of-the-art power cables with XLPE insulation. If, however, a breakdown nevertheless occurs, then it will very likely take place in the accessories of the test arrangement and in the junction sleeves or, in the case of long submarine cables, in the factory joints.
The cable manufacturer has a strong interest in performing the high voltage tests at his products with minimum outlay and in minimum time. If, however, breakdowns occur during a test, then he wishes to repair or replace the element concerned as quickly as possible.
This circumstance caused Prysmian Gron to use the newly developed device HiRES Locator from HIGHVOLT for breakdown localization in its factory routine tests.
Finding faults in real time
The high voltage tests are performed in shielded rooms (see photo) while the large cable drums at Prysmian are arranged outside the shielded room for logistic reasons. The electrical connection between the high voltage test system and the cable to be tested is provided by way of a special connection cable. The weak points in this test arrangement are the high voltage sealing ends and junction sleeves, notably due to the repeated use each time when a new cable drum is connected.
“In the past, we spent hours searching for the breakdown spot, and sometimes even additional measurements were necessary. Today we see on the monitor immediately which cable termination or junction sleeve is affected“, reports Abel Fustier, Test Bay Manager at Prysmian.
The tests themselves are not influenced by the online monitoring. No additional or specially trained personnel are required. Furthermore, the HiRES Locator requires very little space.
“It is very easy to retrofit existing systems with the HiRES Locator, “ assures HIGHVOLT engineer Tobias Miessler. “In the case of high voltage test systems from HIGHVOLT, the HiRES Locator can be integrated into the software architecture or control unit of the test system. It can, however, also easily be used in conjunction with third-party systems.”
The HiRES Locator and its applications
The HiRES Locator is a digital recorder developed by HIGHVOLT especially for the recording of breakdowns in plastic-insulated high voltage power cable systems. The signals which occur during the breakdown and spread as travelling waves in the cable are recorded and evaluated by way of time domain reflectometry (TDR).
Since the HiRES Locator is permanently connected to the cable system to be tested or monitored similarly to a black box and evaluates the original breakdown signals in case of a breakdown, neither additional voltage tests nor additional tests systems are required. This saves time and costs in localizing the fault location.
HIGHVOLT Prüftechnik Dresden GmbH
Tel.: + 49 3 51 84 25 – 700