With the development of power market construction, in order to ensure the effective competition of the power market and the stable operation of the system, under the competitive electricity market mode, it has become an urgent problem to improve the power sales market supervision system. Firstly, the characteristics of the electricity sales market under the competitive electricity market mode is analyzed. Secondly, problems in the surveillance of the electricity sales market are pointed out. Finally, the countermeasures and suggestions for the surveillance of the electricity sales market under the competitive electricity market mode are put forward.
Abstract. On-load tap-changer (OLTC) is an important part in power transformer, which is used to change the transformation ratio by switching contact form one winding tap to another without interrupting the load. It is necessary to make sure the effective running of OLTC. Thus, a fault recognition method for OLTC based on improved BP neural network is proposed in this paper, according to the working characteristicsof OLTC. The feature of this improved neural network is that the learning rate is variable. Experimental results on 2000 test samples from offline AC test device have showed the effectiveness of the proposed fault recognition method.
DC faults are critical events in a flexible high-voltage dc (HVDC) grid. Thus, ensuring that the power system returns to normal operation rapidly and reliably after fault isolation is very important. This requires a HVDC breaker. In overhead line systems under temporary faults, reclosing is often required. However, once the dc circuit breaker (DCCB) is reclosed directly, the large second overcurrent may occur which could damage the power electronic devices. To avoid this problem, a current-commutation DC circuit breaker with adaptive reclosing capability is proposed. Compared with the traditional auto-reclosing strategy, the second damage under permanent fault condition can be avoided by the proposed DCCB, which can identify the fault property. Compared with the hybrid DCCB, the power electronic breaking branch composed of lots of IGBTs is replaced by the current-commutation branch, which is employed to interrupt bi-directional dc fault current. Moreover, bypassing branch is configured to reduce the energy dissipation of arrester and shorten the fault isolation time effectively. Finally, simulation cases in PSCAD /EMTDC verify the effectiveness and superiorities of the proposed DCCB.
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