The Monitoring Method of Invading Alternating Current in DC Power System

Abstract

The invention discloses a monitoring method for emerging of alternating currents in a direct-current power supply system. An internal timer of an MCU is used for carrying out sampling time interval controlling for AD collection; ground voltage digital quantities of a positive bus and a negative bus are collected continuously and regularly; when 2N points that can be 200 points within two adjacentalternating-current cycles are collected completely, ground direct-current voltages of the positive bus and the negative bus and ground alternating-current voltages of the positive bus and the negative bus are calculated; whether the system has an alternating-current emerging phenomenon and the polarity of the alternating-current emerging are determined, and according to positive and negative busground resistance calculation formula of balance bridge detection or unbalance bridge detection, ground resistance values of the positive and negative buses are calculated and corresponding warning signals are sent out; and according to a data changing situation of a branch leakage current sensor, an alternating current emerging branch and polarity are determined. According to the invention, sinceno special-purpose alternating-current amount separation collection circuit needs to be added and no filtering circuit for the frequency of 50 Hz needs to be added for the direct-current voltage, thedevice cost is lowered; and thus the device works normally under the condition of alternating current emerging, so that the applicability, reliability, and stability of the device are enhanced.

Description

technical field [0001] The invention belongs to the field of direct current power supply system monitoring, and in particular relates to a monitoring method for the intrusion of alternating current in a direct current power supply system. Background technique [0002] In the power system, the DC power system is the main control and protection circuit power supply, and is the key to ensure the safe and stable operation of the power system. Due to the large number of cable branches and wiring outlets, there are often faults that cause low-voltage AC to enter the DC circuit due to mis-connection, mis-wiring, insulation reduction or damage, etc. When the AC power enters the DC circuit, it will cause the DC power system to be grounded, and the insulation monitoring device will fail to operate normally; It is the main transformer non-electricity protection action, bus differential protection action, circuit breaker failure protection action and other accidents. In recent years, ...

AI Technical Summary

Problems solved by technology

The monitoring of AC intrusion by existing insulation monitoring devices is realized by adding various types of hardware measures such as AC signal separation, conditioning, and acquisition circuits, which increases the cost of the device

Moreover, when there is AC intrusion, although the AC voltage can be detected by the added AC detection circuit, due to hardware cost and device size limitations, it is impossible to separate the low-frequency 50HZ signal from the positive and negative bus DC voltage well, resulting in The detection error of the positive and negative busbars to ground voltage is large, and even jumps, so it is impossible to accurately calculate the positive and negative busbars to ground voltage through the busbar to ground voltage according to the traditional balanced bridge method and unbalanced bridge method, and it is impossible to further distinguish between the positive and negative busbars. Whether the metal directly enters or enters through a certain resistance value due to insulation reduction or damage

Therefore, the existing DC power system insulation monitoring device will fail to operate normally and lose other functions in addition to generating an AC intrusion alarm function after the system intrudes into the AC power system.

Images