method of determining an electrical isolierungszustandes on the method of electric network

摘要

The invention concerns a method for monitoring the electrical insulation status of a radial or ring-connected electric network and for detecting and locating a high-resistance ground fault. In the method, the zero-sequence voltage (U0' or U0M) with phase angle, the network line-to-neutral voltages (Uv) with phase angles, and the sum currents (I0i) of the sending ends with phase angles are measured. In the method, the absolute value of the zero-sequence voltage change vector ( DELTA U0) is monitored. If the absolute value of the zero-sequence voltage change vector ( DELTA U0) exceeds a predetermined threshold value, the line-to-neutral voltages (Uv) are compared to the zero-sequence voltage change vector ( DELTA U0) in the context of a change in the state of the network. According to an advantageous embodiment, the phase is interpreted as being faulted whose line-to-neutral voltage is ahead of the zero-sequence voltage change vector DELTA U0 by approximately 90 DEG . The fault resistance can be computed from the variables obtained independently for each sending end supplied by the electric station. IMAGE