Insulation resistance monitoring method based on sine wave alternating current injection

Abstract

The invention relates to an insulation resistance monitoring method based on sine wave alternating current injection. The method comprises the following steps of injecting a sine wave alternating current signal between a direct current positive electrode, a direct current negative electrode and the ground, sampling a ground current by using an RC blocking circuit, eliminating a direct current component of the ground current, and comparing and calculating the sampled sine alternating current signal and the injected sine alternating current signal so as to acquire the direct-current ground insulation resistance value. Compared with a traditional square wave injection insulation monitoring method, the method has the advantages that the influence on a ground capacitance can be ignored, the method is not influenced by the magnitude of a direct-current voltage and the change of the direct-current voltage, the monitoring speed is high, and the monitoring frequency is high. The method can be applied to online ground insulation resistance monitoring of various direct current systems and off-line insulation resistance monitoring without a direct current voltage.

Description

technical field [0001] The application belongs to the field of online insulation resistance monitoring, and specifically relates to an insulation resistance monitoring method based on sine wave AC injection. Background technique [0002] Today's DC insulation monitoring methods (such as: CN106053946A, CN103983857A, CN106405354A) mainly include the unbalanced bridge method and the small signal square wave AC injection method, and these two methods all possess the following deficiencies: 1. When there is a grounding capacitance in the DC system Under normal circumstances, both methods need to charge the capacitor first, and then perform sampling and calculation after it is fully charged. Since the bridge resistance is very large, the charging time will be very long, greatly extending the insulation monitoring cycle, and the real-time performance is not good. 2. Due to the limitation of A / D sampling resolution, for the unbalanced bridge method, the smaller the DC voltage, the w...

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Problems solved by technology

[0002] Today's DC insulation monitoring methods (such as: CN106053946A, CN103983857A, CN106405354A) mainly include the unbalanced bridge method and the small signal square wave AC injection method, and these two methods all possess the following deficiencies: 1. When there is a grounding capacitance in the DC system Under normal circumstances, both methods need to charge the capacitor first, and then perform sampling and calculation after it is fully charged. Since the bridge resistance is very large, the charging time will be very long, greatly extending the insulation monitoring cycle, and the real-time performance is not good.

2. Due to the limitation of A / D sampling resolution, for the unbalanced bridge method, the smaller the DC voltage, the worse the monitoring accuracy; for the square wave AC injection method, the larger the DC voltage, the worse the monitoring accuracy

3. When the ground capacitance and DC voltage change in a monitoring cycle, the monitoring accuracy becomes worse

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