Calculation method of zero sequence, positive sequence and negative sequence current?

Calculation method of zero sequence, positive sequence and negative sequence current?

(1) Finding the zero sequence component: add the three vectors together to find the sum. That is, phase a does not move, and the origin of phase B moves to the top of phase a (arrow). Note that phase B only moves, but cannot rotate. In the same way, translate the origin of phase C to the top of phase B. at this time, make the vector from the origin of phase a to the top of phase C (arrow to arrow in some cases). This vector is three-phase

The difference between zero sequence, negative sequence and positive sequence
My friend said: generally, positive sequence voltage exists all the time, while negative sequence voltage appears in asymmetric short circuit and zero sequence voltage appears in single-phase short circuit, Because I think single-phase short circuit is also considered as asymmetric short circuit. How to distinguish? Also, the setting value of bell sequence protection for a switch is 0.6a10 seconds. Can it be understood that the three-phase phase difference will act after more than 0.6a10 seconds? What is the meaning of positive sequence 2.0a2 seconds?

First of all, when the three-phase AC system is in balance, there is no negative sequence and zero sequence, only positive sequence
When the three-phase current is unbalanced, if it is three-phase three wire, there is only negative sequence and no zero sequence current (because the sum of three-phase currents is equal to zero). Only when the sum of three-phase currents is not equal to zero, there is zero sequence current
Both negative sequence current and zero sequence current are different from unbalanced current. Generally speaking, unbalanced current refers to the difference of three-phase current
It is very simple to measure zero sequence current, only clamp ABC three-phase wire with clamp ammeter (excluding zero sequence!) reading is zero sequence current
You may not understand what I say. You can read the book about the sequence components of unbalanced circuits

Is "dripping wears away stone" a physical action or a chemical action?

All of them
There is physical dissolution friction
Erosion of chemical carbonic acid

Alum water purification is a physical or chemical action, why?
rt.
Isn't there a chemical reaction during hydrolysis?

Alum is potassium aluminum sulfate 24h2o (k2so4.al2 (SO4) 3.24h2o) or potassium aluminum sulfate dodecahydrate (Kal (SO4) 2.12h2o). There are two processes in alum water purification: 1. Aluminum ion in alum is hydrolyzed to form aluminum hydroxide colloid with adsorption; Al3 + + 3H2O Al (OH) 3 (colloid) +