Transformer neutral point fault voltage analyzing method

Abstract

The invention discloses a transformer neutral point fault voltage analyzing method. The method comprises the steps that sequence network analysis is carried out on a boundary condition with the single-phase-to-earth fault of a distributed photovoltaic power supply accessing a distribution network; a new fault boundary condition is acquired according to protection action, and accordingly the analytical equation of the main transformer neutral point voltage deviation after the protection action and influencing factors thereof are acquired; according to the output characteristics of the distributed photovoltaic power supply which is off-network in a short time, the relationship among the main transformer neutral point voltage, a local load and the output power of the photovoltaic power supply is acquired; the acquired typical daily output power curve of the distributed photovoltaic power supply is compared with the local load power demand curve; and accordingly the deviation level of the main transformer neutral point voltage after faults at different moments is acquired. The method is suitable for the configuration analysis of the main transformer gap protection in a new scenario with the distributed photovoltaic distribution network, is not limited by other operating conditions and line characteristic data, and has the advantages of simple operation and high practicality.

Description

technical field [0001] The invention relates to the technical field of power system analysis, in particular to an analysis method for transformer neutral point fault voltage. Background technique [0002] At present, the rapid development of distributed photovoltaics is conducive to alleviating the contradiction between energy and load demand in my country, but the access of distributed power sources such as photovoltaics has changed the structure of the distribution network, making the distribution network structure change from a single power source radial network to The complex topology structure of dual power sources or even multiple power sources has increasingly prominent impact on the fault characteristics of the power grid system and its relay protection. Due to geographical restrictions, many regions in my country vigorously develop distributed photovoltaics, which are connected to 110kV substations after 10kV collection. After an asymmetrical ground fault occurs in ...

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Problems solved by technology

However, when there is distributed photovoltaic access on the low-voltage side of the transformer, the continuous fault current provided by it may further increase the offset voltage of the neutral point of the main transformer, posing a threat to the insulation of the neutral point. The original transformer neutral point zero-sequence The related configuration of overvoltage protection and discharge gap will be affected

[0003] In the prior art, the research on the impact of distributed power sources on relay protection is mainly aimed at the impact of distribution network line protection. Distributed photovoltaic power source access will raise the voltage of the neutral point of the transformer and the configuration of gap protection, which troubles the field operation and needs to be further studied. Research, the existing technology fails to give the displacement degree of the neutral point voltage of the main transformer of the distribution network substation with distributed photovoltaic access and its quantitative relationship with the local load and distributed photovoltaic capacity

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