Experience with an on-line monitoring system for 400 kV XLPE cables

Abstract

The use of high voltage cables is today recommended and sometimes mandatory in order to avoid environmental concerns of the public, especially when the power system is crossing areas of dense population. The reunion of the former GDR with the Federal Republic of Germany has stimulated the interest in this settlement especially for the city of Berlin, where the increase of energy demand requires the use of innovative solutions. The paper reports the activities that BEWAG, the electrical utility of Berlin, performs in order to investigate the feasibility of setting up an urban bulk power connection using 400 kV XLPE cables During a first accelerated voltage endurance test (at CESI in Miladtaly) on cables and accessories of six major European manufacturers several failures in joints and SF6 terminations were encountered [l]. testing period were additionally equipped with partial discharge sensors for an insulation monitoring system. Sensors of this type will in the future be integrated into the cable accessories to improve after laying quality control. It is thought that this partial discharge test will replace high voltage DC-tests which were found unsuitable for the 400 kV XLPE cable technology.

Discrimination between internal PD and other pulses using directional coupling sensors on HV cable systems

“…6 No. 6, December 1999 46.1 pF I1 819 2 0 or in dBR (5) Let us illustrate this. If the sensor would be able to divert the complete current IPD out of the cable into the measurement resistor, the voltage V , would be given by R F I~~, leading to a transfer impedance of 50 R or 34 dBR for a 50 R measurement system.…”

“…This can be done by using existing metallic structures within a cable joint [5] or by placing additional metallic foils in the joint or at the cables close to it. Usually the capacitive electrodes are placed above the semicon layers, but it is also possible to use the stress cones or the semicon layers around a joint as pick-up electrodes.…”

“…The second channel is attached to a probe, which is capturing the noise pulses, but as little as possible of the PD. On occurrence of a noise pulse at the gating channel, the primary channel is blocked for a short period of time [5,35]. The effectiveness of the method depends on the ability to establish a reliable gating signal and the total length of disturbed time periods.…”

“…Driven more by practical availability and experience on installed systems than derived from any PD threshold considerations, a sensitivity of <1 pC is seen as the acceptable goal. [5] and a 170 kV cable net in Switzerland [3,17]. In Japan, mainly capacitive sensors were used.…”

Research on Charge-Discharge Characteristics and Location of Cable Partial Discharge Detection System Based on Damped Oscillation Wave Voltage

“…Among them, the non-electrical method mainly includes infrared imaging method and ultraviolet imaging method, and the electrical method includes capacitance coupling method, electromagnetic coupling method, difference method, ultrahigh frequency method and so on [8,9]. These methods solve the problem of partial discharge evaluation of XLPE cable insulation in a certain state, but most of them have disadvantages about limited applicable conditions, low effectiveness and difficulty of field application [10].…”