Direct current line fault recognition method based on polar line current gradient sum
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A technology of DC line fault and current gradient, applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve problems such as easy refusal to operate, and achieve the effect of concise criteria
Active Publication Date: 2016-03-16
KUNMING UNIV OF SCI & TECH
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In the case of remote high resistance, the protection is often prone to refusal
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Embodiment 1
[0022] Example 1: ±800KV direct current transmission line such as image 3 shown. The positive line is 10km away from the M terminal, a metallic ground fault occurs, and the sampling frequency is 10kHz.
[0023] (1) Calculate the gradient sum S(k) of the fault current according to steps (1)-(2) of the claims.
[0024] (2) S(k), S(k+1), S(k+2), S(k+3), S(k+4) are respectively 10.35, 14.81, 14.96, 16.96, 18.56, respectively. If it is greater than 1.5pu, it is judged as the line internal fault criterion.
Embodiment 2
[0025] Example 2: ±800KV direct current transmission line such as image 3 shown. The positive line is 750km away from the M terminal, a ground fault occurs, and the transition resistance is 100Ω.
[0026] (1) Calculate the gradient sum S(k) of the fault current according to steps (1)-(2) of the claims.
[0027] (2) S(k), S(k+1), S(k+2), S(k+3), and S(k+4) are respectively 13.100, 3.630, 4.29, 4.561, 4.613, respectively. If it is greater than 1.5pu, it is judged as the line internal fault criterion.
Embodiment 3
[0028] Embodiment 3: ±800KV direct current transmission line such as image 3 shown. The outlet of the rectifier side is faulty, and the transition resistance is 100Ω.
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Abstract
The invention relates to a direct current line fault recognition method based on the polar line current gradient sum, and belongs to the technical field of electric power system relay protection. After a high voltage direct current line has a metallic grounding fault, a latter current value of an adjacent sampling point measured by a measuring terminal is employed to subtract a former current value, and the ratio of the difference of the current values to a sampling interval is defined as the current gradient. The fixed length before the current sampling point is selected as the time window length, the sum of the current gradients of all the sampling intervals is calculated, and an obtained value is defined as the current gradient sum of the current sampling point. When the current gradient sum of five continuous sampling points of the measuring terminal is greater than a setting value, it is determined that inner faults of the line occur; and when the current gradient sum of the five continuous sampling points is smaller than the setting value, it is determined that external faults of the line occur. It is indicated that the method is reliable and the precision is high for fault type discrimination via a lot of simulation.
Description
technical field [0001] The invention relates to a DC line fault identification method based on the polar line current gradient sum, and belongs to the technical field of electric power system relay protection. Background technique [0002] Due to its unique advantages, DC transmission has been more and more widely used in power transmission. The distance of DC transmission lines is long, and the environment across regions is complex, and the probability of failure is high. For DC line faults, the fault process and its dynamic characteristics are closely related to the DC control function, so the impact of the DC control system on the DC line protection, especially the backup protection cannot be ignored. The line protection currently used in engineering is mainly based on the traveling wave protection with the core of the electrical change rate as the main protection. In the case of high resistance at the remote end, this protection is often prone to refusal to operate. T...
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