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Method and device for measuring ground capacitance of DC system

A technology of ground capacitance and DC system, which is applied in the direction of measuring devices, measuring electrical variables, measuring resistance/reactance/impedance, etc., can solve problems such as grounding faults in DC systems, protection malfunctions, system safety hazards, etc., to avoid grounding faults , the effect of preventing impact

Active Publication Date: 2010-07-07
ELECTRIC POWER RES INST OF GUANGDONG POWER GRID
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  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

The most obvious shortcoming of this method is that it is necessary to connect the resistor R3 between the bus bar of the DC power system and the ground, so that an artificial ground fault occurs in the DC system, which brings potential safety hazards to the system, and the calculation results are also easily affected by artificial reading errors, resulting in Inaccurate measurements
[0017] Due to the limitations of these two measurement methods, they have not been widely used in the running substation DC power system. There is no accurate understanding of the size of the busbar-to-ground capacitance of the running DC power system, which leads to a point ground fault in the DC system. Occasionally cause protection malfunction

Method used

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  • Method and device for measuring ground capacitance of DC system
  • Method and device for measuring ground capacitance of DC system
  • Method and device for measuring ground capacitance of DC system

Examples

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Embodiment 1

[0033] figure 1 Shown is the schematic flow chart of Embodiment 1 of the method for measuring the ground capacitance of the DC system of the present invention:

[0034] Step 101: Inject the AC signal between the positive and negative bus bars of the DC system and the ground through capacitive coupling;

[0035] Step 102: measuring the voltage amplitude, current amplitude and phase difference of the voltage and current of the AC signal;

[0036] Step 103: Calculate the ground capacitance of the DC system according to formula (3), and calculate the ground insulation resistance of the DC system according to formula (4).

[0037] C + + C - = R 1 2 + X 1 2 2 * π * f ...

Embodiment 2

[0044] The difference between this embodiment and Embodiment 1 is that this embodiment adds the steps of signal isolation in Step 101 and Step 102 of Embodiment 1 respectively. In Step 101 of this embodiment, the AC signal is injected through the coupling capacitor after signal isolation. Between the bus bar and the ground, in step 102 of this embodiment, signal isolation processing is performed on the measured voltage amplitude, current amplitude, and voltage-current phase difference of the AC signal.

[0045] Other technical features in the second embodiment are the same as those in the first embodiment, and will not be repeated here.

Embodiment 3

[0047] The difference between this embodiment and Embodiment 2 is that this embodiment adds the steps of signal amplification in Step 101 and Step 102 of Embodiment 2 respectively. In Step 101 of this embodiment, the AC signal is isolated and amplified by the signal and passed through the coupling capacitor Injection between the bus bar and the ground, in step 102 of this embodiment, signal isolation and amplification processing is performed on the measured voltage amplitude, current amplitude, and voltage-current phase difference of the AC signal.

[0048] Other technical features in the third embodiment are the same as those in the second embodiment, and will not be repeated here.

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Abstract

The invention discloses a method and a device for measuring a ground capacitance of a DC system. An AC signal is injected between a bus and the ground in a capacitance coupling mode. The ground capacitance is calculated according to amplitudes and phase differences of a voltage and a current of the AC signal and a signal frequency. Compared with a capacitance bridge method which needs to carry out measurement under the condition that the DC system is powered off and a discharge method which needs to simulate the ground fault of the DC system to carry out measurement, the signal injection method can accurately measure the ground capacitance of the DC power system under the condition of not influencing the normal operation of the DC system and provides the effective means and method for the live line measurement of the ground capacitance of the operated DC system.

Description

technical field [0001] The invention relates to the technical field of DC power system detection, in particular to a method and device for measuring the capacitance of a DC system to ground. Background technique [0002] The ground capacitance of the DC system is mainly composed of the anti-interference capacitance, the switching power supply ground filter capacitance and the capacitance formed by the shielded cable core wire to the ground shielding layer. The larger the substation scale and the larger the area, the greater the ground capacitance. The charging and discharging of the DC power system's busbar capacitance to ground when it is grounded is one of the key factors that cause protection malfunctions caused by one-point grounding of the DC power system. The comprehensive and systematic measurement of the ground capacitance of the DC system of the existing power plant and substation can fully understand the relationship between the size of the ground capacitance and t...

Claims

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Application Information

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IPC IPC(8): G01R27/26
Inventor 赵兵徐玉凤
Owner ELECTRIC POWER RES INST OF GUANGDONG POWER GRID
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