Agritech products HS code classification

List of Contents of this article:

• 1 ,Agritech products HS code classification How about He Yangzan's power system analysis
• 2, What is a three-phase short circuit?
• 3, [Ask for advice] What courses do you need to learn first to learn power system analysis?

How about He Yangzan's power system analysis

Personally, I think these two books are not bad. You can have a look. Their introduction and expenses. Power System Analysis, published by China Power Publishing House on February 2, 2010, the authors are Li Meilan and Lu Wenpeng.This book is a textbook recommended by the Department of Vocational Education and Adult Education of the Ministry of Education.

There are two main options for power system textbooks. One is He Yangzan's. This version is sorted in a mess, but some parts are more streamlined. One is from China Electric Power Publishing House. This version is very comfortable and detailed, and the content is relatively more complicated.

The fault analysis part of He Yangzan's textbook is very complete, and the complex fault analysis is well written. Other textbooks are not as good as it. However, there is no power system status estimation, static safety analysis and other contents, so it should be read by Zhu Junwei and Xia Daozhi's books later.

Usually there are only 2 sets. One set is the steady-state analysis of the power system of the power publishing house. The transient analysis, the third edition of Chen Yan's transient forgets what it is called.. One set is the first and second books of Huake He Yangzan's power system analysis..

What is a three-phase short circuit?

Three-phase short circuit is also known as three-phase short circuit. It is a short circuit that the three phases A, B and C are directly connected without load.

Three-phase short circuit refers to the short circuit of two or more lines in three-phase four lines. The main types include three-phase short circuit, two-phase short circuit, single-phase short circuit and two-phase grounded short circuit.

Three-phase short circuit: three-phase A, B and C are connected together. Two-phase disconnection: A, B or B, C or C, A are two-phase disconnected, and only C, or A or B are charged. Two-phase electricity: only A, B or B, C or C and A have electricity. Three-phase electricity: A, B and C three-phase normally charged. Single-phase grounding: A or B or C one-phase grounding.

In a three-phase system, possible short circuits are: three-phase short circuit, two-phase short circuit, two-phase short circuit grounding and single-phase grounding short circuit. Three-phase short circuit is also known as symmetrical short circuit, and the system is still in a symmetrical state as during normal operation. Other types of short circuits are not symmetrical short circuits.

[Ask for advice] What courses do you need to learn first to learn power system analysis?

Of course, it is naturally better to have some understanding of other professional basic courses, such as Power System Equipment, Relay Protection, Automatic Control Principle, Advanced Language Programming (Current Computing Needs), etc. As long as you have studied circuit and electrical engineering, it is relatively easy to understand the analysis of the power system with a little effort.

The basics of power system analysis in the postgraduate entrance examination are related to undergraduate courses such as circuit principle, electrical engineering, electromagnetic field, engineering mathematics and automatic control theory.

In the analysis of the power system, it is relatively simple to calculate various parameters at the beginning, followed by current calculation, voltage adjustment, frequency adjustment, calculation of various short circuit situations, etc. These are relatively important. Just remember the formula and do some exercises. The most difficult part is related to the motor, which is generally not involved in the exam, except for the postgraduate entrance examination.

I think we should not only learn, but also learn the circuit well. Especially the content of resistive network analysis! The idea of "equivalent" should be applied skillfully. Learn the circuit well, and then learn the electrical division, so that it is much easier to learn the content of fault analysis and calculation.