Current differential protection method automatically adaptive to variable frequency motor
A variable frequency motor and differential protection technology, which is applied in the direction of automatic disconnection emergency protection devices, emergency protection circuit devices, electrical components, etc., can solve problems such as inability to adapt to variable frequency motors, and achieve the effect of improving protection capabilities
Active Publication Date: 2012-10-03
NORTH UNITED POWER CO LTD +2
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However, traditional differential protection cannot adapt to variable frequency motors, so it is very meaningful to research and develop differential protection suitable for variable frequency motors
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[0014] The present invention will be described in further detail below in conjunction with accompanying drawing and example.
[0015] Such as figure 1 Shown is a schematic diagram of the variable frequency motor current differential protection powered by the frequency converter. The differential protection method of the variable frequency motor disclosed in the present invention, the differential protection method performs differential current and braking current according to the three-phase current collected by the current transformer CT1 at the machine end of the variable frequency motor and the three-phase current of the neutral point current transformer CT2 calculation, and then form a phase-separated current differential protection. When it is determined that the motor is faulty, the differential protection device sends a trip command to the circuit breaker to cut off the power supply. Refer to the attached figure 1 , since the present invention is a phase-separated curr...
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The invention discloses a current differential protection method suitable for a variable frequency motor. Through HHT (Hilbert-Huang Transform), the amplitude and phase information of each frequency component of non-stable signals is acquired, the frequency component with the maximum energy (maximum amplitude) is selected as a main frequency of the signals, the actual running condition of the variable frequency motor is considered, the main frequency component is the main component of the signals and other frequency components can be regarded as harmonic components. The main frequency components subjected to HHT of three-phase current at the head and tail ends of the variable frequency motor are taken to calculate phasor differential to form the HHT-based differential protection principle. The current differential protection method can automatically adapt to the running conditions of the variable frequency motor under different frequencies, and avoids the problem that the traditional power frequency differential protection method cannot protect the variable frequency motor.
Description
technical field [0001] The invention belongs to the technical field of relay protection and automation of electric power systems, and in particular relates to a differential protection method of a variable frequency motor. Background technique [0002] Frequency conversion motors powered by frequency converters have a relatively wide frequency range. Frequency conversion power supply has a great impact on the relay protection of high-voltage motors, especially the current differential protection that is the main protection of large-capacity high-voltage motors. Because the conventional differential protection device is based on the power frequency of 50Hz, it cannot correctly protect the high-voltage variable frequency motor with wide range speed regulation. At present, certain temporary measures have been taken on site for motors equipped with frequency converters during frequency conversion operation: when running in frequency conversion mode, in order to avoid malfunction...
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IPC IPC(8): H02H7/08H02H3/26
Inventor 吴景龙石维柱郭锡玖张涛姚斌聂娟红刘全屠黎明
Owner NORTH UNITED POWER CO LTD