Abstract
Considering the generator voltage-class-reduction operation will affect the security and economics of the power systems, this paper proposed a method to analyze the feasibility of the voltage-class-reduction scheme. The paper includes two parts: one analyzes the short-circuit current changes in the scheme, and then the mathematical relationship between the short-circuit current changes in low-voltage side transformer bus and the generator parameters was established; the other part analyzes the economics of the scheme from the point of view of power loss in power line and transformer, and it tries to establish relationship between the power loss and the distance of the unit's outgoing line. From this paper, it can be concluded that the short-circuit current analysis model we proposed is more concise and has similar results compared with traditional simulation software. The paper also points out that there is an economic equilibrium point between economic benefits and the distance of the power line in the generator voltage-class-reduction operation, and within which the scheme is feasible and economical.
Highlights
China has been building large-capacity generator units, which aims to relieve the urban load in recent years
The power generated by these units is depressurized by 500 kV transformers and supplied to 220 kV substations, and it is conducive to maintaining transient stability of power systems and reducing the short-circuit current of the 220 kV system [1]
THE ANALYSIS MODEL OF SHORT-CIRCUIT CURRENT OF THE VOLTAGE-CLASS-REDUCTION SCHEME When large-capacity generator units are connected to 220 kV substation, the short-circuit current of the 220 kV bus will be changed from different aspects
Summary
China has been building large-capacity generator units, which aims to relieve the urban load in recent years. THE ANALYSIS MODEL OF SHORT-CIRCUIT CURRENT OF THE VOLTAGE-CLASS-REDUCTION SCHEME When large-capacity generator units are connected to 220 kV substation, the short-circuit current of the 220 kV bus will be changed from different aspects. Based on the BPA simulation of power grid in the Hunan province, the 3-phase short-circuit current changing of the 220 kV bus under the three kinds of voltage-class-reduction scheme were calculated. 2) TRANSFORMER LOSS The large-capacity generator voltage-class-reduction scheme will change the load rate of subordinate power grid of 500 kV transformers, the active loss of 500 kV transformers will be changed. 4 km ∼ 42 km is a reasonable length for the voltage-class-reduction scheme to operate in economically
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