The Non-unit Transient-based Protection and Its Settings for 35 kV Distribution Lines Based on the Line Boundary Characteristic of Electronic Voltage Transformer
As a large number of distributed generations are connected to the distribution networks,the performance of traditional three-stage current protection deteriorates seriously.The non-unit transient-based boundary protection is expected to be an effective scheme to improve the relay protection performance of active distribution networks due to its outstanding advantages,such as being independent of power supply property.However,the effectiveness of this approach relies heavily on the strong filtering effect achieved at the line boundary.Therefore,this paper presents that the electronic voltage transformer,the metal-oxide arrester,and the remaining apparatus's stray capacitance of the smart substation and smart switching station can be used together as the line boundary.The excellent high-frequency filtering characteristics of this arrangement can serve as a foundation for the design of non-unit transient-based boundary protection.Then,the protection criterion is constructed due to the difference in the energy of the high-frequency band of the inside-zone and outside-zone fault voltage traveling waves.Based on the reasonable coordination of the setting threshold and the action sequence,a non-unit transient-based two-stage protection is formed.Finally,the proposed protection scheme is performed based on the PSCAD platform to verify its effectiveness,sensitivity,and reliability,which can be coordinated with three-stage current protection to enhance the protection performance in the active distribution network.
distribution linesnon-unit transient-based protectionline boundaryelectronic voltage transformermetal-oxide arrestersmart substation