Patent ID: 8271213

Claim:
A system for online monitoring partial discharge, which is connected in parallel with a busbar between a generator and an electric network, comprising: a near-end circuit on a generator side, which includes a near-end capacitive coupling sensor connected to the busbar and a near-end impedor connected in series with the near-end capacitive coupling sensor; a far-end circuit on an electric network side, which includes a far-end capacitive coupling sensor connected to the busbar and a far-end impedor connected in series with the far-end capacitive coupling sensor; and a detection device, which has a near-end input terminal connected to a connection point between the near-end capacitive coupling sensor and the near-end impedor through a near-end cable, a far-end input terminal connected to a connection point between the far-end capacitive coupling sensor and the far-end impedor through a far-end cable, and a processing unit, wherein a length L of the busbar between the two capacitive coupling sensors, a length L 1 of the near-end cable, and a length L 2 of the far-end cable satisfy L V b + L 1 V c = L 2 V c , in which V b is a transmission speed of a signal in the busbar and V c is a transmission speed of a signal in the cables, and the processing unit selects one pulse from each of a near-end signal input from the near-end input terminal and a far-end signal input from the far-end input terminal as a first comparison pulse and a second comparison pulse, and discriminates a partial discharge signal according to a comparison between a preset time delay threshold Δt 0 and a time delay between the first comparison pulse and the second comparison pulse; wherein the processing unit selects a pulse having the largest amplitude in the near-end signal as the first comparison pulse, if the first comparison pulse is a first pulse of the near-end signal, the processing unit selects a first pulse of the far-end signal as the second comparison pulse, if the first comparison pulse is a second pulse of the near-end signal, the processing unit selects a second pulse of the far-end signal as the second comparison pulse, otherwise, the processing unit selects a pulse having the largest amplitude in the far-end signal as the second comparison pulse.