Looking for breakthrough ideas for innovation challenges? Try Patsnap Eureka!

A Differential Protection Method Suitable for Variable Frequency Motor

A variable frequency motor and differential protection technology, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as heat generation, motor harmonics, and equipment long-term operation effects, and achieve suppression of DC components and harmonic components, and anti-interference capabilities Strong, fast and reliable protective effect

Active Publication Date: 2019-01-18
NANJING GUODIAN NANZI POWER GRID AUTOMATION CO LTD
View PDF4 Cites 0 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The frequency converter brings harmonics and heat to the motor, which has a certain impact on the long-term operation of the equipment
The traditional motor differential protection is designed based on the power frequency. After the inverter is installed, the current frequency is not 50Hz, and the differential protection has to be withdrawn during the frequency conversion operation. At this time, the protection of the motor only depends on the protection function of the inverter.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • A Differential Protection Method Suitable for Variable Frequency Motor
  • A Differential Protection Method Suitable for Variable Frequency Motor
  • A Differential Protection Method Suitable for Variable Frequency Motor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment Construction

[0029] In order to ensure that the operation of the high-voltage motor will not be affected when the frequency converter fails, the frequency conversion transformation basically adopts the structure of frequency converter processing frequency bypass. figure 1 As shown, the high-voltage frequency conversion system mainly includes three parts: a phase-shifting transformer, a frequency converter, and a bypass cabinet. The phase-shifting transformer plays the role of system isolation. For the switching of frequency conversion / power frequency operation mode. When the motor is running at power frequency, the bypass switch GD3 is closed, and GD1 and GD2 are disconnected; when the motor is running at variable frequency, the bypass switch GD3 is disconnected, and GD1 and GD2 are closed. Considering the power frequency operation of the motor, the cable from the incoming line switch to the motor machine end can be protected by the original motor comprehensive protection device, and the c...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

PUM

No PUM Login to View More

Abstract

The invention discloses a differential protection method applicable to a variable-frequency motor. Phasor differential protection based on frequency tracking is combined with sampling value differential protection, whether a tripping outlet acts or not is determined through the combination result of the phasor differential protection and the sampling value differential protection. Sampling points are arranged at the generator terminal and neutral points of the variable-frequency motor respectively, the momentary values of currents on two sides are collected, the operation frequency of the motor is detected in a current tracking frequency manner, the sampling frequency is adjusted in real time, the sampling number of each cyclic wave is maintained to be unchanged, then the current phasors on two sides are calculated by using half-wave fourier algorithm, corresponding differential current and brake current are solved, distinguishing is carried out according to certain action characteristics, and meanwhile the sampling value differential motion without being influenced by frequency change is added, so that errors caused by a difference stream generated by the phasor differential protection during frequency discontinuity are avoided, and the anti-jamming capability of differential protection is improved.

Description

technical field [0001] The invention relates to how to realize the differential protection action logic of a frequency conversion motor in a high-voltage frequency conversion system, and belongs to the field of relay protection of electric power systems. Background technique [0002] With the gradual implementation of policies such as separation of power plants from power grids and grid bidding, it is imperative for power plants to reduce power consumption. Variable frequency motors are widely used in fan and pump loads in power plants because of their excellent speed regulation, starting and braking performance. The high-voltage frequency conversion technical transformation of the auxiliary equipment of the power plant can realize the soft start of the motor, reduce the starting current of the motor, and reduce the impact and mechanical wear on the insulation layer of the motor stator winding. At the same time, the traditional mechanical throttling adjustment method is not...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

Application Information

Patent Timeline
no application Login to View More
Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/08
CPCH02H7/08
Inventor 杨青松李玉平张玮康丰刘庆海
Owner NANJING GUODIAN NANZI POWER GRID AUTOMATION CO LTD
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Patsnap Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Patsnap Eureka Blog
Learn More
PatSnap group products