Low-voltage power grid safety monitoring method

Abstract

The invention relates to power grid safety, in particular to a low-voltage power grid safety monitoring method which includes the steps: acquiring three-phase transient current signals iA (t), iB (t) and iC (t) and three-phase transient voltage signals uA (t), uB (t) and uC (t) of a head end of a low-voltage power grid circuit; taking any two phases as a loop to form a high-order differential equation; calculating a coefficient of the high-order differential equation in the second step; solving an equivalent parameter by the aid of the relationship between the transient high-order differential equation coefficient and a stable equivalent parameter; extracting characteristics such as fundamental frequency components in the acquired three-phase transient current signals and three-phase transient voltage signals. The data sampling frequency of the current signals and the voltage signals is 10kHz, and a time window is a disturbed half cycle. The low-voltage power grid safety monitoring method can judge whether a power grid is safe or not according to the impedance of a neutral wire and practical degree of unbalance of a load.

Description

technical field [0001] The invention relates to the safety of a power grid, in particular to a method for monitoring the safety of a low-voltage power grid. Background technique [0002] As the last link of the entire power grid, the low-voltage power network is directly connected to users, and its security has received widespread attention. The national standard stipulates that in the case of three-phase power supply, it is necessary to ensure that the three-phase load is evenly distributed and the neutral line impedance is zero. However, in actual operation, the three-phase load is often unbalanced, and the existence of the neutral line impedance makes the virtual neutral point voltage on the load side shift, and at least one phase of the load terminal voltage rises, that is, the neutral point overvoltage occurs. For the user, it is easy to burn out the electrical appliance when it is running under the condition of overvoltage; secondly, the zero-sequence current generate...

AI Technical Summary

Problems solved by technology

However, it is also impossible to characterize the voltage drop on the load by only using current information, and when it is used for three-phase load unbalance monitoring, since the three-phase current is affected by the impedance of the neutral line, the impedance of the neutral line changes under the same load state , the resulting load imbalance changes accordingly, so the current information alone is not convincing enough

In addition, the inability to monitor the neutral line impedance and its changes is also a deficiency of existing methods

Images