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Method for monitoring same-time same-proportion decline of insulativities to earth on two poles of DC system

A DC system, ground insulation technology, applied in the direction of testing dielectric strength, etc., can solve problems such as malfunction of protection relay, violent fluctuation of bus voltage, and difficulty in monitoring faults such as faults that the insulation between two poles of DC system drops in the same proportion at the same time. Avoid false positives

Active Publication Date: 2015-02-04
BEIJING PEOPLES ELECTRIC PLANT
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Both have defects in monitoring the ground fault of the DC system: the "balanced bridge method" is difficult to monitor the fault that the two poles of the DC system are grounded and the insulation drops in the same proportion at the same time, and it is impossible to calculate the resistance value of the positive and negative poles of the busbar to the ground; the "unbalanced bridge method" The "bridge method" does not have the above-mentioned defects, but when the bridge circuit is switched, it will cause violent fluctuations in the bus voltage, and even cause the protection relay to malfunction in severe cases.

Method used

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  • Method for monitoring same-time same-proportion decline of insulativities to earth on two poles of DC system
  • Method for monitoring same-time same-proportion decline of insulativities to earth on two poles of DC system
  • Method for monitoring same-time same-proportion decline of insulativities to earth on two poles of DC system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0059] Real-time sampling and recording of the positive pole-to-ground voltage U of the DC system busbar + , analyze the sampling data, and determine whether the DC system has a fault in which the insulation between the two poles and the ground drops in the same proportion at the same time. The data analysis process is as figure 1 shown.

[0060] Let the time difference between two adjacent voltage samples be T 0 , then the relation (1) is satisfied:

[0061] T=T 0 *(2n+1) (1)

[0062] In the formula:

[0063] T: sampling time period

[0064] (2n+1)=T / T 0 , is the number of samples

[0065] The counting CNT of sampling bus positive pole to ground voltage starts from zero.

[0066] When CNT+ , and store the sampled values ​​in the array U p CNT bits of [2n+1]. CNT plus 1.

[0067] When CNT=2n+1, select the array U p The maximum U in [2n+1] pmax and minimum U pmin .

[0068] When CNT=2n+1, if the flag of unipolar insulation fault is not set, judge U pmax and U ...

Embodiment 2

[0106] Real-time sampling and recording of the ground voltage U of the negative pole of the DC system busbar - , analyze the sampling data, and determine whether the DC system has a fault in which the insulation between the two poles and the ground drops in the same proportion at the same time. The data analysis process is attached Figure 4 shown.

[0107] Let the time difference between two adjacent voltage samples be T 0 , then the relation (1) is satisfied:

[0108] T=T 0 *(2n+1) (1)

[0109] Sampling bus negative pole-to-ground voltage U - The count of CNT starts from zero.

[0110] When CNT- , and store the sampled values ​​in the array U n [2n+1] CNT bits. CNT plus one.

[0111] When CNT=2n+1, select the array U n The maximum U in [2n+1] nmax and minimum U nmin .

[0112] When CNT=2n+1, if the flag of unipolar insulation fault is not set, judge U nmax and U nmin Whether the following relationship is satisfied:

[0113] u nmax -U nmin =ΔU -r (15) ...

Embodiment 3

[0138] Real-time sampling and recording of the positive pole-to-ground voltage U of the DC system busbar + and negative ground voltage U - , analyze the sampling data, and judge whether the DC system has a fault in which the insulation between the two poles and the ground drops in the same proportion at the same time. The data analysis process is attached Figure 7 shown.

[0139] Let the time difference between two adjacent voltage samples be T 0 , then the relation (1) is satisfied:

[0140] T=T 0 *(2n+1) (1)

[0141] Sampling bus positive pole-to-ground voltage U + and the negative pole-to-ground voltage U - The count of CNT starts from zero.

[0142] When CNT+ and U - , calculate the absolute value difference U between the two abs :

[0143] u abs =|U + |-|U - | (23)

[0144] Will U abs stored in the array U a [2n+1] CNT bits. CNT plus one.

[0145] When CNT=2n+1, select the array U a The maximum U in [2n+1] amax and minimum U amin .

[0146] When CN...

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Abstract

The invention relates to a method for monitoring the same-time same-proportion decline of insulativities to earth on two poles of a DC system, which is characterized by judging whether the DC system has same-proportion decline in insulativities to earth on two poles and has the failure that time difference delta t exists between insulativity declines at the positive pole and at the negative pole by monitoring the variation in the voltage to earth at the positive pole or the negative pole of a bus or the variation in the difference between the absolute values of the voltages to earth at the positive pole or the negative pole of the bus. With the method, the switching of an unbalance bridge is not needed, no fluctuation in bus voltage can be caused, and a protective relay can be prevented from maloperations.

Description

technical field [0001] The invention relates to the insulation monitoring technology of a DC IT system. Background technique [0002] The DC systems of power plants and substations provide power for control, protection, signals and automatic devices. The safe, reliable and continuous operation of DC systems is of great significance to ensure normal power generation and power supply. In order to ensure the continuity and reliability of power supply, the DC system is generally designed as a floating ungrounded system, that is, an IT system. According to the design requirements of the DC system of electric power engineering, it is necessary to carry out insulation monitoring on the DC IT system. [0003] The existing insulation monitoring technology is mainly based on the bridge method, which can be divided into "balanced bridge method" and "unbalanced bridge method" according to the realization principle. Both have defects in monitoring the ground fault of the DC system: the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/12
Inventor 南寅王雪楠张景德
Owner BEIJING PEOPLES ELECTRIC PLANT
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