A Method for Assessing the Security of Loop-closing Operations in Medium-Voltage Distribution Networks

Abstract

Disclosed is a method for evaluating the security of a closed-loop operation of a medium-voltage distribution network. The method includes: on the basis of acquired topological structures and device parameters of a closed-loop network, and acquired real-time running data before loop closing of the closed-loop network, estimating a state of a high-voltage distribution network to obtain voltage amplitude values and phase angles of 10kV buses at head ends of closed-loop feeders; selecting a ratio of an active load of each load point on each of the closed-loop feeders to the active power at the head end of the feeder and a ratio of a reactive load of each load point on the closed-loop feeder to the reactive power at the head end of the feeder as input variables, and calculating, on the basis of historical load data of each load point, a multi-order semi-invariant of each of the input variables; calculating a certainty power flow and closed-loop currents; calculating multi-order semi-invariants of the closed-loop currents; obtaining the cumulative probability distribution of the closed-loop currents; and calculating the limit violation probability of each of the closed-loop currents, and determining that a closed-loop operation has security insofar as the multiple limit violation probabilities are all less than a pre-set threshold value.

Description

technical field [0001] The invention relates to the field of safe and stable operation of electric power systems, in particular to a method for evaluating the safety of loop closing operation of a medium-voltage distribution network. Background technique [0002] The medium-voltage distribution network adopts the power supply mode of closed-loop design and open-loop operation. Under normal circumstances, the contact switch is opened, and the distribution network operates in a radial structure; during equipment maintenance or accident handling, the load can be transferred without power failure through the loop closing operation of the contact switch. The loop-closing operation of the medium-voltage distribution network may generate a large loop-closing current in the loop-closing network, causing line current protection actions or overloading of some electrical equipment, resulting in a wider range of power outages. Therefore, operators need to evaluate its safety before clo...

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to provide a method for assessing the safety of the loop closing operation of the medium-voltage distribution network. Aiming at the problem that the voltage phase angle data of each bus in the distribution network cannot be obtained, a method for state estimation of the high-voltage distribution network is adopted To get the bus phase angle information

Aiming at the problem that the real-time load data of feeder load points required for loop closure current calculation cannot be obtained, the probability distribution characteristics of load values ​​at each load point are first analyzed based on historical load data, and then based on the probability power flow theory, the half-step variable method is used to obtain the loop closure The cumulative distribution curve of the current, and finally evaluate the safety of the loop-closing operation by calculating the probability of the loop-closing current exceeding the limit

Images