A Method to Solve the Influence of Sampling Frequency Deviation on Directional Components of Current Protection
A sampling frequency and current protection technology, applied to electrical components, emergency protection circuit devices, etc., can solve problems such as protection reverse fault malfunction, protection forward fault refusal to operate, and adverse effect of the directional judgment of the protection device. To achieve the effect of improving accuracy and reliability
Active Publication Date: 2019-01-18
NANJING GUODIAN NANZI POWER GRID AUTOMATION CO LTD
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Problems solved by technology
When calculating the phase comparison between the historical data and the fault time data, if the inherent deviation caused by the deviation of the sampling frequency between the two phase angles is not compensated, it will have an adverse effect on the result of the directionality judgment of the protection device, which may It may cause the failure to operate in the positive direction of the protection, and may also cause the failure to operate in the reverse direction of the protection.
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[0040] In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.
[0041] The application principle of the present invention will be described in detail below in conjunction with the accompanying drawings.
[0042] The sampling frequency of the existing microcomputer relay protection device is controlled by the crystal oscillator of the CPU of the device. First, the frequency generated by the crystal oscillator itself has errors, which cannot be 100% accurate. This type of error can be considered as an inherent deviation; secondly, due to the crystal oscillator The temperature characteristics of the component, the frequency generated by the component will deviate with the change of tempera...
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The invention discloses a method for avoiding the influence of sampling frequency deviation on a current protection directional element. The method comprises the steps of calculating and storing phaseangle deviation caused by the sampling frequency deviation in real time according to voltage waveforms when a power grid system normally runs; using memory voltage and current fault current to conduct phase comparison calculation when the power grid system breaks down, and then the compensating phase angle difference between the memory voltage and the fault current in combination with the cycle from voltage dropping to fault current occurring and the obtained phase angle deviation. According to the method for avoiding the influence of the sampling frequency deviation on the current protectiondirectional element, the influence of the phase angle deviation caused by the sampling frequency deviation on the calculation result can be reliably avoided, the accuracy of judging the direction ofthe directional element is improved, and the reliability of overcurrent protection is improved.
Description
technical field [0001] The invention belongs to the technical field of power system automation, and in particular relates to a method for solving the influence of sampling frequency deviation on a current protection directional element. Background technique [0002] In the low-voltage power grid of the power system, in order to improve the reliability of power supply, the important substations in the system are often powered by double-sided power supply or ring grid power supply. In this type of power grid, due to the need to ensure the selectivity of relay protection actions , generally implemented using directional elements. Therefore, in low-voltage line protection, directional elements have been widely used in current protection. The commonly used directional element mainly introduces non-fault phase voltage and fault phase current for phase comparison calculation, and when a three-phase fault occurs or the voltage value is lower than the calculation threshold, it is ne...
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IPC IPC(8): H02H7/26
Inventor 王闰羿康丰李玉平张玮陈栋杨青松刘庆海
Owner NANJING GUODIAN NANZI POWER GRID AUTOMATION CO LTD