Distribution network line distance protection method after connection of large-scale distributed photovoltaic power supply

Abstract

The invention discloses a distribution network line distance protection method after the connection of a large-scale distributed photovoltaic power supply. The method comprises the following steps of:in view of the over-range protection misoperation at a distribution network photovoltaic downstream fault line system side, setting relatively short-delay three-stage directional circle characteristic distance protection at a line system side at the downstream of a photovoltaic power supply grid-connected point; in view of the incapability of cutting off a fault at a photovoltaic upstream fault line load side, setting relatively long-delay three-stage directional circle characteristic distance protection at a line load side at the upstream of the photovoltaic power supply grid-connected point; and enabling the two protection methods to cooperate with the current protection of a bus head end out line system side without the connection a the photovoltaic power supply. The distribution network line distance protection method is not affected by a photovoltaic output condition, solve the difficult setting calculation of the protection current threshold of the downstream line system side after the connection of the photovoltaic power to the distribution network power supply circuit, and incapability of cutting off the photovoltaic fault current of the photovoltaic connection point upstream load side, guarantees reliable removal of line faults, and improves the system operational safety and reliability of the photovoltaic connection distribution network.

Description

technical field [0001] The invention relates to the technical field of grid-connected new energy power generation, in particular to a method for protecting the line distance of a distribution network after a large-scale distributed photovoltaic power source is connected. Background technique [0002] Considering the low voltage ride-through control strategy, the fault current characteristics of the inverter photovoltaic power supply are quite different from those of the synchronous generator. The current limiting characteristics and continuous power transmission capacity of the inverter photovoltaic power supply under fault conditions make the power distribution of the decentralized access inverter photovoltaic power supply The current distribution and amplitude characteristics of the network line in the event of a fault change, and the protection of the radial distribution network configuration is mainly based on the multi-stage current protection of the line system side of ...

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to overcome the problems that the photovoltaic fault current on the upstream load side of the photovoltaic access point cannot be cut off after the low voltage ride-through control inverter type photovoltaic power supply is connected to the power grid, and the protection range is difficult to set due to the increase of the fault current at the protection installation on the system side , to provide a multi-stage double-end distance protection cooperation scheme for distribution network lines with large-scale distributed photovoltaic power sources connected to multiple downstream sending lines, so as to ensure the reasonable cooperation of the protection range and protection time limit of each protection equipment

[0006] Aiming at the problem of out-of-range misoperation of the system side protection of photovoltaic downstream fault lines in the distribution network, a relatively short-delay three-stage directional circular characteristic distance protection is set on the line system side downstream of the photovoltaic power grid-connected point; for photovoltaic upstream fault line load side cannot For the problem of cutting off the fault, set a relatively long-delay three-stage directional circular characteristic distance protection on the line load side upstream of the photovoltaic power grid connection point; send the above two protection methods and the bus head end without photovoltaic power access to the line system side Current protection cooperates together; the relatively short delay and relatively long delay are relative concepts corresponding to the protection of the system side and the load side

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