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Method for computing sequence components under frequency changing situation

A technology of frequency change and calculation method, applied in the field of electric power system, can solve the problems of sudden drop in output power of generator set, and the calculation of sequence component is no longer applicable.

Active Publication Date: 2013-11-27
NR ELECTRIC CO LTD +1
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Problems solved by technology

However, in some new applications, such as the variable frequency start-up process of pumped storage units and gas turbine units, or the sudden drop in the output power of the generator set caused by a system decommissioning accident, the generator set is still in three-phase symmetrical operation, but its frequency will change rapidly Or operate at low frequency, the previous sequence component calculation based on the rated frequency is no longer applicable

Method used

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  • Method for computing sequence components under frequency changing situation
  • Method for computing sequence components under frequency changing situation
  • Method for computing sequence components under frequency changing situation

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Embodiment Construction

[0054] The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0055] The present invention provides a calculation method of the sequence component under the condition of frequency change, combining figure 1 shown, including the following steps:

[0056] (1) The relay protection device or safety automatic device measures the secondary side electrical quantity of the voltage or current transformer of the protected object, and obtains the current frequency of the electrical quantity.

[0057] One of the commonly used algorithms for frequency measurement is the linear fitting zero-crossing algorithm, which is described in detail in the document "Transformer and Medium and Low Voltage Network Digital Protection", which can be referred to image 3 shown. The linear fitting zero-crossing algorithm requires a complete electrical quantity period T e It takes a long time to calculate the correct frequency me...

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Abstract

The invention discloses a method for computing sequence components under the frequency changing situation. The method comprises the following steps of (1) sampling the electric quantity on the secondary side of a voltage or current transformer of a protected object through a relay protection device or an automatic safety device, and using the inter-phase short-window frequency measurement algorithm to obtain the current frequency of the electric quantity, and (2) computing the positive-sequence component, the negative-sequence component and the zero-sequence component of the electric quantity according to the current frequency, obtained in the step (1), of the electric quantity. According to the computing method, the computing accuracy of the sequences during frequency changing can be improved.

Description

technical field [0001] The invention belongs to the field of power systems, and in particular relates to a method for calculating sequence components under the condition of frequency variation, and relates to a relay protection device and a safety automatic device applying the method. Background technique [0002] The power system operates based on the rated frequency (50Hz or 60Hz). Article 3.1 of "GB / T15945-2008 Power Quality Power System Frequency Deviation" stipulates: "The frequency deviation limit under normal operating conditions of the power system is ±0.2Hz. When the system When the capacity is small, the deviation limit can be relaxed to ±0.5Hz.". Sequence component calculation is one of the basic algorithms in the power system application field. Because the power system frequency changes very little, the previous sequence component calculations are based on the system rated frequency. When the frequency deviates from the rated value or changes, the sequence compon...

Claims

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Application Information

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IPC IPC(8): H02J3/00G06F19/00
Inventor 王光陈俊张琦雪严伟李华忠
Owner NR ELECTRIC CO LTD
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