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лапидус

а.а

трансформация

токов

напряжений

серия

роликов

вопрос

грозного

00:00:01

hello, dear colleagues, we

00:00:03

continue the topic of transformation of currents and

00:00:06

voltages in transformers under

00:00:08

various short circuits and with

00:00:11

various circuits and groups of connections of

00:00:13

transformer windings, in order to

00:00:17

understand this lecture, I recommend that you

00:00:20

watch the previous two lectures, the

00:00:22

first is the circuits and the second is the groups of

00:00:25

connections of transformer windings,

00:00:28

briefly

00:00:29

there We were talking about the following circuits, different

00:00:33

circuits are needed, different circuits are important, a

00:00:36

star is needed, a triangle is needed, in

00:00:39

some cases a zigzag is needed and as

00:00:42

part of the same transformer,

00:00:44

sometimes this is more accurate, often it

00:00:47

happens that two different

00:00:49

circuits are needed, so all sorts of non-zero

00:00:52

groups arise, for example, group 11, well Next

00:00:56

we pose the following question: how, in the event of a

00:00:58

short circuit on one side,

00:01:00

will the currents and voltages behave on the

00:01:04

other side of the transformer? The structure of

00:01:07

this lecture will be like this. First, we will

00:01:10

look at the diagram of group 11, that is, it is a

00:01:13

gas triangle with a zero,

00:01:15

then a star star with a zero, that is,

00:01:19

group 0 at the same time, we will

00:01:22

conduct our reasoning, so to speak, on two floors, the first

00:01:26

floor is very simple,

00:01:27

there will be very simple reasoning without

00:01:30

involving any special concepts

00:01:32

from electrical engineering,

00:01:34

but although therefore we will inevitably

00:01:37

come to a semantic dead end,

00:01:39

well, more precisely, for the simplest circuits

00:01:42

and the simplest cases of a short

00:01:44

circuit,

00:01:45

everything will be fine and smoothly, at some

00:01:47

point nothing will work out for us, and then

00:01:50

for these difficult cases we will have to

00:01:52

involve, well, like

00:01:54

a walk along the second floor, that is, along the

00:01:57

floor of sequences, we will introduce the

00:02:00

concepts of a direct reverse zero

00:02:02

sequence, but more precisely it has not been introduced

00:02:04

Let's remember what it is and unfortunately in

00:02:07

some cases there is no way without them,

00:02:09

so please tune in for a long,

00:02:12

hard but very interesting

00:02:16

job, we will analyze a lot of

00:02:20

different vector diagrams for these

00:02:24

circuits and first of all we will look at how

00:02:26

Tokyo

00:02:27

short circuit currents behave on different

00:02:30

sides Well, at the end of the lecture we will look at

00:02:33

the transformation of voltages, and I want to say right away

00:02:36

that the power in transformers is

00:02:39

not transformed in any way, the power is

00:02:42

lost a little there, but this is a completely

00:02:44

different conversation, that is, there is no such

00:02:46

thing as transformation of power, well,

00:02:48

or transformation of resistance, there are

00:02:52

two basic concepts: transformation of currents

00:02:54

and transformation of voltage, and so we

00:02:58

begin to look at the diagram of a triangle

00:03:00

star with zero 11 group, I will remind you that

00:03:03

the triangle is needed in order, firstly, to

00:03:06

smooth out non-sinusoidalities in order to

00:03:08

provide a beautiful sinusoid, and

00:03:11

secondly, to balance the voltage

00:03:14

when the load is uneven across the phases on the

00:03:17

side 0 4 kilovolts, for example 0 4 but in

00:03:22

connection with this, such a

00:03:23

traditional group 11 appeared, we will start with it,

00:03:27

so we will consider a single-phase short

00:03:30

circuit on the low voltage side,

00:03:32

let’s say a phase, but in front of us is such a

00:03:35

transformer, it has a lower country

00:03:37

star with a zero above a country triangle

00:03:39

for example 6 or 10 kilovolts and for example 0

00:03:43

4 kilovolts we are considering a single-phase

00:03:46

short circuit, and we understand

00:03:48

that here the current of

00:03:52

this very single-phase case is circling along this circuit;

00:03:55

there are no currents in other phases; well, since

00:03:58

it takes place here, this is a current, then in theory

00:04:01

it should somehow transform to the

00:04:03

higher side but let's think about how,

00:04:06

but probably we just need to take and

00:04:09

draw an arrow like this, that is, in

00:04:13

this way we make such an important

00:04:16

thesis

00:04:17

that if there is current here, then a

00:04:22

roller should appear here in the same phase, I have this phase of the

00:04:24

transformer itself, not its conclusions,

00:04:27

but here the insides of a transformer, so to speak,

00:04:29

in fact, what I am

00:04:33

pronouncing now is not always like that, well, more

00:04:36

precisely, look at this picture,

00:04:40

if there is a current below, then there is a current at the top,

00:04:43

if there is no current at the bottom, then there is no current and

00:04:46

at the top,

00:04:47

such beauty does not always take place,

00:04:50

but only in in those cases where there is no

00:04:54

imbalance of magnetic fluxes, I

00:04:57

mean transformers with a connection diagram of a

00:05:00

triangle star with a zero, that is, there

00:05:03

is a triangle diagram and can be

00:05:05

closed to the zero

00:05:08

sequence,

00:05:09

as follows from the previous lecture, the

00:05:13

connection diagram of the windings of transformers

00:05:15

if we have one of the windings connected

00:05:17

star

00:05:18

without an output neutral, then in this

00:05:21

case zero-sequence currents cannot exist in it,

00:05:23

and this is

00:05:26

such a special case when we have unbalanced

00:05:28

zero-sequence flows,

00:05:30

but for this case it

00:05:32

will be a little different, that is, if

00:05:35

there is no current on one side, then on the other

00:05:37

side a current may appear, however to

00:05:41

begin with, we looked at such circuits and

00:05:43

here everything is fine with the flows, they

00:05:45

are balanced, so the rule here is very

00:05:48

simple: there is a current at the bottom there is a current at the top it

00:05:51

is transformed there is

00:05:52

no current at the bottom there is no current up it and so

00:05:56

we look, we now have two

00:05:59

in-phase vectors, I called this vector a

00:06:02

a I don’t want to name this one yet

00:06:05

because it is inside the

00:06:07

transformer and I need to know what

00:06:09

is outside the one that will flow along

00:06:11

these lines,

00:06:13

for this we use the following logic,

00:06:16

look, when this current

00:06:19

ticks to this point, it should, in theory, be

00:06:22

developed to curl part should flow here and

00:06:24

part of it should flow here into the line, but in this phase there is

00:06:29

no current transformer phase because

00:06:33

it is not here

00:06:35

and therefore nothing can flow here,

00:06:37

roughly speaking, this is the path for the current, it

00:06:41

has a very high resistance, the current

00:06:43

will not flow there, it just cannot be here

00:06:46

and that means there cannot be a branch

00:06:48

from here and therefore the current will flow upward without

00:06:51

distorting, that is, for example, 1 ampere flows in

00:06:54

and 1 ampere flows out, so starting from

00:06:57

this moment I understand that it turns out that

00:06:59

this yellow arrow

00:07:01

is really the current vector in the phase and I don’t

00:07:04

mean

00:07:05

the line and so from this moment it is

00:07:07

called so let's move on and what in

00:07:13

this phase b

00:07:14

well, look at this node, from this

00:07:18

node we have a current flowing out, you can see

00:07:21

this yellow current flowing out and nothing

00:07:25

flows here, nothing flows out for the

00:07:28

simple reason that here only no, well,

00:07:30

based on this, we must admit that 1

00:07:33

from this node something flowed out, then exactly the same amount

00:07:35

should flow here, but only

00:07:38

in the opposite direction, and we see that yes,

00:07:41

indeed, a current flows along this line,

00:07:43

we call it the current in phase b,

00:07:47

well So far we have built this

00:07:50

diagram, as for position currents,

00:07:54

it is not here from the phenomenon,

00:07:56

why, because

00:08:00

nothing can flow out or flow from this node

00:08:02

on this side and nothing on this

00:08:04

side, there are no currents here, so there is

00:08:06

no current in this line this is precisely why

00:08:10

when a single-phase short

00:08:12

circuit occurs on the 0-4 kilovolt side, on the

00:08:16

6 or 10 kilovolt side the currents

00:08:20

behave as if there were a

00:08:22

two-phase short circuit here, this can be seen

00:08:26

from this vector diagram, and it’s

00:08:29

interesting that if this current is

00:08:31

single but one hundred percent of the

00:08:34

transformer rating, for example,

00:08:37

then these 2 currents will be

00:08:40

slightly less than Janis divided by the root

00:08:42

of 3,

00:08:43

but maybe I was in vain when I said about the

00:08:46

transformer rating, I mean that if we

00:08:48

make the transformer reduced, that

00:08:51

is, we assume that it has a

00:08:52

transformation coefficient of unity, then in relation

00:08:56

to this unit current here there will be

00:08:58

58 percent and here 58 but of course

00:09:01

all this still needs to be clicked on the

00:09:03

transformation ratio but we are interested in

00:09:06

relative units let me explain

00:09:08

why this is so but for this we need to

00:09:11

remember what the rated current

00:09:12

of the transformer is the rated current of

00:09:14

the transformer this current of course,

00:09:17

this one, but that is, I don’t mean

00:09:19

this one, not inside

00:09:21

the phases, but this one, which is precisely why the

00:09:24

current can be calculated from this linear voltage, the

00:09:28

total power of the transformer, but if there is

00:09:31

no intrigue here, because

00:09:34

here only in the line of Ryan currents in the phase, then

00:09:36

here there is a difference, that is, I already said

00:09:40

and gave such an example that if

00:09:42

10 amperes flow here, but here,

00:09:44

accordingly, 10 here is 10, then here it

00:09:46

will be the root of three times more, that

00:09:48

is, 17 in other words, normal,

00:09:51

normal, this current should be the

00:09:53

root of three times more than this current,

00:09:56

but specifically in this mode it doesn’t

00:09:59

work out that way, we have already said that this current

00:10:01

flows unhindered without

00:10:03

paying attention to this node, that is, it does

00:10:05

not change, but in the nominal mode it

00:10:08

should change, it should increase by the

00:10:10

root of 3, which is why

00:10:11

here we divide this unit by the

00:10:14

root of 3,

00:10:15

in other words, for one we take

00:10:18

this linear current, which normally

00:10:21

should be the root of 3 greater than

00:10:24

this phase current,

00:10:25

but since they coincide here, we

00:10:28

divide by the root of 3,

00:10:30

but why this one the current in normal

00:10:33

mode should be the root of three times

00:10:35

greater than each phase current, this can be seen from

00:10:38

this diagram

00:10:39

here in normal mode I will repeat the

00:10:41

criticism the result of the phase and the current of phase c follows,

00:10:45

so I take and minus the spokes I don’t get

00:10:48

this vector

00:10:49

which is the root of three since, in theory,

00:10:51

it should be greater than this phase

00:10:54

vector, and since we take this vector

00:10:57

as a unit, then this current against the background of this

00:11:00

unit is the root of three times less than what

00:11:03

is displayed in this formula, that is, 58

00:11:05

percent of this current.

00:11:08

Now let’s consider a two-phase short

00:11:10

circuit to on the low voltage side,

00:11:12

for example, between phases b and c,

00:11:17

well, we know that in this case the currents

00:11:20

circulate in this way, that they are in

00:11:22

antiphase and that we don’t have any ground

00:11:26

here yet, we will then consider a two-phase

00:11:28

short circuit to earth

00:11:30

and begin reasoning like these currents

00:11:32

are transformed from the top, but so far everything is

00:11:35

very simple: this current is here and this one is here, and

00:11:38

here there was a zero and that means there

00:11:41

will be 0 here too,

00:11:42

so while I’m drawing these

00:11:45

2 currents at the top and I’m at a loss as to how I should

00:11:49

name them, but now we’ll figure out what

00:11:52

that's it, let's go, so

00:11:57

green current flows into this node and nothing can flow out

00:12:00

because it's just not here

00:12:02

because it wasn't here either, and that means

00:12:06

this green current will flow further and

00:12:08

this is really the current in phase B, we

00:12:11

call it that, so I put a letter here but here’s

00:12:15

what I’ll have, for example here or

00:12:17

here, while this is in question, I got

00:12:20

some kind of current, but that’s where it

00:12:22

will go next, well, let’s look, it will reach

00:12:26

this point and it can’t branch here,

00:12:29

or vice versa,

00:12:31

nothing can be a forerunner from here because

00:12:33

that there is no current here and therefore

00:12:35

this current will flow without changing

00:12:39

here, that is, in other words, this

00:12:41

red arrow will turn

00:12:43

into this yellow one, you see, I drew it earlier

00:12:46

but was not sure what to call it in the opera, I

00:12:48

understand that it is in the opposite direction,

00:12:49

look red down and yellow then

00:12:52

up and this is essentially the

00:12:55

current in the line and so what is here

00:12:58

but some current flows into this node and

00:13:02

1 and 2 flow out, that is,

00:13:05

two identical currents flow out, well, that means

00:13:09

this current should be double

00:13:11

in this case it will be divided into

00:13:14

two equal in magnitude and

00:13:17

directional currents, so we see the

00:13:21

following picture: the current in phase c, I

00:13:24

mean here the phenomenon

00:13:26

is twice as large as each current in phase a and

00:13:29

in base b, and note how interesting it is that

00:13:33

here we have a special phase and it is different

00:13:35

from all the others, and here already at the top there is a

00:13:38

special phase c. Please note that to

00:13:43

reason from this picture, from the

00:13:45

previous ones, we did not need any

00:13:48

sequences, direct, inverse 0,

00:13:50

we can reason without them, so now as

00:13:55

for the length,

00:13:56

but as I already said, this vector is twice as

00:13:59

long as this, therefore here is a two, here is a

00:14:01

one, and from the previous reasoning we

00:14:04

must also divide by the root of 3,

00:14:06

but here it is clear that these are unit vectors

00:14:09

and the most difficult case is a two-phase

00:14:15

short circuit to ground on the

00:14:17

low voltage side, for

00:14:19

example, phases b and c, a

00:14:21

very important point is that this is a goat

00:14:24

on let's figure out the ground

00:14:27

when there was no ground, these two currents

00:14:31

were out of phase and in total they gave

00:14:33

0, but now it’s completely wrong now these

00:14:37

two currents are not out of phase, they are

00:14:40

somehow directed like this

00:14:41

if initially we had such a

00:14:43

symmetrical star

00:14:45

a b c then now the current is in the phase and also these

00:14:51

two vectors b and c add up to the current

00:14:55

that flows into the ground and closes in

00:14:57

this way, and this

00:14:59

total current is simply the geometry

00:15:02

of this construction is the same as the current in the

00:15:06

phase I, well, or would be if the short

00:15:10

circuit was 3

00:15:11

phase but only in the opposite direction, that

00:15:13

is, what I mean is that this vector is equal to

00:15:15

this vector, but this vector no longer

00:15:18

exists, it disappeared only in the phase and no,

00:15:21

well, and therefore it must be said that

00:15:24

together with a two-phase short circuit

00:15:27

to the ground, exactly the same flows as

00:15:31

these 2 phase currents, but only at a

00:15:34

different angle,

00:15:36

well, according to tradition,

00:15:40

we display the red arrow here, the

00:15:41

green one here, we don’t display anything

00:15:43

here, and for now we draw these 2 two

00:15:46

arrows and we are thinking about what to call them,

00:15:50

this one like this, it flows further because

00:15:53

nothing can branch from here, that

00:15:55

is, no matter how it flows, it won’t say upward and

00:15:59

this is the current in the line b, this current is

00:16:05

essentially this one, well, because this

00:16:09

this red arrow must come from somewhere

00:16:10

from here and it can’t be taken from

00:16:13

zero here and zero here

00:16:15

so it must stop from here and

00:16:17

therefore this vector is red,

00:16:21

I turn that side because

00:16:23

red is up and yellow is down and calling

00:16:26

it current in lines, what about this

00:16:32

current here, let's look here

00:16:35

the red one came here the green current went away that is,

00:16:38

we must take their difference the difference

00:16:42

between the red current on this side and the

00:16:45

green current on this side it is

00:16:47

directed in that direction here it is here I

00:16:50

draw like that in that direction side,

00:16:55

well, now as for the length of the notes,

00:16:58

I’m a little out of scale here,

00:16:59

but nevertheless, everything is signed correctly,

00:17:01

that is, if this is a current of 100 percent, well, that

00:17:04

is, this unit is a unit and this

00:17:06

unit is tannoy background, I this will also be

00:17:08

a unit if we have a transformer

00:17:10

given with it, the

00:17:12

transformation coefficient is also unity, but these 2 1

00:17:15

are divided by the root of 3, and where

00:17:16

does this root of 3 come from,

00:17:18

we have already discussed many times, now

00:17:21

let’s work the same thing, but in the

00:17:24

language of sequences, that is, direct

00:17:26

inverse and zero sequences,

00:17:28

what is this for, but if Frankly,

00:17:31

for the previous tasks there is

00:17:34

no particular need for this, but on the other hand, this

00:17:38

method is also useful because, firstly,

00:17:41

the tasks may be more complex and we

00:17:43

will encounter them,

00:17:44

and secondly, most importantly, this method

00:17:47

sometimes gives a more

00:17:49

technologically advanced conveyor belt.

00:17:53

here is a simple way of working with

00:17:58

vectors because what was happening now

00:18:00

over the last 5 10 minutes, well,

00:18:04

perhaps not everyone understood it, I

00:18:06

reasoned in a haphazard way, that is, I

00:18:09

said that let’s take this

00:18:12

current, this is the current, why in this

00:18:15

order it may not be it was very clear

00:18:17

and when a person starts from scratch and is

00:18:21

afraid of this task, he does not understand

00:18:25

where to start, but if you

00:18:28

have worked out sequences, then

00:18:30

everything is very typed and

00:18:34

unified, that is, we take a

00:18:36

specific sequence and rotate it

00:18:39

in a certain direction by a certain

00:18:40

amount degrees, we take another

00:18:42

sequence, the third, and then

00:18:45

we just take it all and add the vector to

00:18:47

so maybe you will find it more useful

00:18:50

this, as I call it, the second floor

00:18:53

of knowledge is already more complex

00:18:56

technologically called

00:18:58

sequences, well then you need to

00:19:00

delve into the sequences,

00:19:03

in fact, it would be better if you

00:19:05

watched the lecture on our channel on the method of

00:19:08

symmetrical components,

00:19:09

well, more precisely, there are as many as 2 persons, well, at least

00:19:12

listen to the first one, but if you don’t have

00:19:16

time, then very briefly,

00:19:18

any asymmetrical triple of victors,

00:19:21

for example, currents, can be decomposed into 3

00:19:25

symmetrical triples,

00:19:26

direct inverse and zero

00:19:29

sequences, direct

00:19:31

sequence a b c inverse and

00:19:33

vice versa,

00:19:34

action b, that is, spin in the opposite

00:19:36

direction and 0 are three vectors that are

00:19:40

in-phase and not shifted relative to

00:19:41

each other in books they usually draw this

00:19:45

star, this one is sort of co-directional, which is what

00:19:48

they have from the vector, but they stick out like this and the

00:19:50

zero sequence is also

00:19:52

directed like this I really don’t like this

00:19:53

because it makes students

00:19:56

think that supposedly these three

00:19:58

triples are always vertical from Krasilnikov,

00:20:00

in fact, with this

00:20:03

drawing I emphasize that this is not

00:20:05

so, but more precisely, it all depends on the mode in

00:20:08

some modes to phase a of the direct line along

00:20:10

zAO inversely and phase a 0 they are all

00:20:13

lined up vertically but in

00:20:15

most modes this is not the case and therefore I

00:20:17

emphasize that the direct and reverse can

00:20:20

be shifted by an arbitrary angle, the

00:20:23

direct vector and the reverse vector a

00:20:27

can have different lengths for example this one is

00:20:30

longer this one is smaller or vice versa the

00:20:32

same with zero

00:20:33

sequence vectors they are not obliged

00:20:35

to follow the phase or length of some other

00:20:38

sequence so I drew it like

00:20:40

this arbitrarily if we have a

00:20:43

symmetrical mode that is only

00:20:45

three-phase or generally normal then

00:20:47

we have a direct sequence and

00:20:50

only direct

00:20:51

for any asymmetry, the reverse is also added,

00:20:53

that is, direct is

00:20:55

reverse, as soon as we have a

00:20:58

short circuit involving the ground or

00:21:02

uneven loading occurs by

00:21:04

single-phase

00:21:05

consumers, then in this case, in addition to the

00:21:09

direct and reverse sequence, a

00:21:10

0 also appears and

00:21:14

so it turns out in the case 11 groups, the

00:21:17

direct sequence

00:21:19

turns 30 degrees clockwise, of

00:21:22

course, if we go from the side of the

00:21:24

star to the triangle, why is this so we

00:21:28

already discussed in the second lecture of this

00:21:31

series, this lecture is called groups of

00:21:33

connections, well, let me briefly remind you that here

00:21:36

we have a vector phase and a vector here in

00:21:42

this line in phase a are formed as a

00:21:45

yellow

00:21:46

minus red arrow, look yellow

00:21:48

minus red we get

00:21:51

such a vector according to the triangle rule, yes

00:21:52

indeed it is

00:21:54

rotated 30 degrees clockwise relative to this vector,

00:21:57

this is simply a consequence of the

00:21:59

concept of group 11, but here is the reverse

00:22:03

sequence in in the case of the same 11th

00:22:05

group, in the case there from a star to a

00:22:07

triangle, it rotates by the same 30

00:22:09

degrees, but already counterclockwise,

00:22:11

once again the direct sequence is

00:22:14

clockwise, the reverse is counterclockwise,

00:22:16

let's understand why, look in the

00:22:19

previous case for the direct

00:22:21

sequence we had vectors

00:22:25

for the reverse sequence we have

00:22:28

victor on the contrary short circuit.

00:22:31

and that’s why we have such a

00:22:34

situation, let’s see, and so this vector

00:22:37

is formed as a yellow minus red

00:22:40

arrow, please look at the yellow minus

00:22:43

red arrow here, that is, in relation to

00:22:47

this vector on our side, this

00:22:51

vector, look in relation to this

00:22:54

vector, this vector is unfolding

00:22:57

30 degrees counterclockwise, I

00:22:59

repeat once again, this is typical for

00:23:02

group 11 when we move from a star to a

00:23:05

triangle, as for the zero

00:23:08

sequence, it does not

00:23:11

turn anywhere and, moreover,

00:23:13

it often does not transform at all, well, no,

00:23:16

we’ll get there, I’ll tell you in more detail, so a

00:23:19

single-phase short circuit on the

00:23:21

low voltage side in phase and here

00:23:24

three sequences are drawn, direct

00:23:28

reverse and 0, on this side on the

00:23:32

low voltage side, why are they

00:23:35

exactly like that, that is, why, for example,

00:23:37

vector a is in phase and and here, for

00:23:40

example, here the arrow here here, and for

00:23:44

some reason not long the same way, and

00:23:47

here in this lecture I will not explain

00:23:49

this is a separate, difficult and long

00:23:53

conversation about this you can read in

00:23:57

Ulyanov’s textbook, which is called

00:24:01

electromagnetic transient processes,

00:24:03

if necessary, write in the comments, I will

00:24:07

definitely record a lecture on this topic, but

00:24:10

it is quite extensive and complex therefore

00:24:13

within the framework of this lecture, I propose to

00:24:16

proceed from the fact that supposedly we already

00:24:19

know this and this does not raise questions in our minds, this is

00:24:24

the convention we will have, of course, this is a drawback of the

00:24:27

method of symmetrical components, that is,

00:24:29

in order to use it confidently,

00:24:31

you need to know that when in a single-phase case,

00:24:34

we have exactly the same picture along the direct

00:24:37

reverse 0, and with two-phase it is different

00:24:39

with two-phase on the ground on 3 or

00:24:42

three-phase 4, well, let’s say we opened

00:24:45

a reference book or a book by this same

00:24:47

Ulyanov and found there such a

00:24:51

standard trio of victors, well,

00:24:54

if starting from this premise,

00:24:57

then everything becomes very simple,

00:24:59

look, this three, moving

00:25:03

from a star to a triangle,

00:25:04

turns 30 degrees

00:25:06

clockwise until look here, I

00:25:09

just take it and doctors turn it 30 degrees, and

00:25:11

this three turns in the opposite direction by 30

00:25:13

degrees and as for this three,

00:25:16

it generally disappears, or rather, these

00:25:19

zero-sequence currents, as you

00:25:21

already know, they are of course

00:25:23

transformed here into these phases, but

00:25:26

since they are in-phase and since for

00:25:29

in-phase currents

00:25:30

one minus 1 will be zero, then they are out of

00:25:33

bounds here they don’t come out of this triangle,

00:25:35

they just circle around it,

00:25:37

in this sense they don’t

00:25:39

transform into a line here,

00:25:41

look, but the phase of the transformer they

00:25:44

transform, but these currents

00:25:47

that we will depict here,

00:25:51

these currents interest us from the point of view of

00:25:53

this line and therefore we must

00:25:55

say so the zero-

00:25:57

sequence currents here here are

00:25:59

not transformed into a line, so here

00:26:02

this three is present in the lower side on this side,

00:26:05

it is absent on the upper side,

00:26:07

now we take it and on each

00:26:11

side, as if we collect it, we glue together from

00:26:14

all the yellow arrows all the green

00:26:16

arrows from all the red arrows our

00:26:19

rectors already different currents, well, that is,

00:26:22

once again, these are such

00:26:23

sequences, these are some

00:26:25

abstract fictitious currents that

00:26:27

actually do not exist in the phase, but

00:26:29

from them you can concoct full

00:26:31

real currents that you can measure on the

00:26:34

intermeter, and so if I add up all the

00:26:36

yellow arrows, then they will triple for me

00:26:39

because they are all in phase,

00:26:41

I got this vector, if I add up

00:26:44

all the red ones, look, look at this plus it

00:26:48

will give me an arrow down and this is up and they

00:26:52

will balance each other,

00:26:53

well, as I already said, the swan cancer and the pike

00:26:56

will be zero, so there is no red arrow here

00:26:59

and the green ones will be the same thing, but

00:27:02

actually this is understandable because it

00:27:04

rotates only in phase and on this side

00:27:07

2 red arrows balance each other,

00:27:09

two yellow ones, then the total

00:27:13

current is up, two green ones are the total current down,

00:27:17

in fact, if you

00:27:18

add some arrows like this, they

00:27:21

will turn into such an elongated vector,

00:27:26

colleagues, we got the same picture

00:27:28

that we got before based on very

00:27:30

simple reasoning, but now these

00:27:32

reasoning are carried out at a completely different

00:27:35

level, two-phase goats on the

00:27:39

low voltage side in the Bates slots,

00:27:43

again,

00:27:48

I took this pair of symmetrical components from

00:27:53

Ulyanov’s textbook, but that is, we don’t

00:27:56

think now why this is so, we

00:27:58

just need to know there

00:27:59

is no zero sequence here

00:28:02

because there is no ground here, and if we

00:28:06

know this, then everything is very simple, then

00:28:09

we turn this three

00:28:11

clockwise by 30, this three

00:28:14

counterclockwise by 30 and we just take and

00:28:16

add from these yellow

00:28:20

arrows we form 0 from the

00:28:24

green ones such a deal is formed according to

00:28:27

this principle one then the other

00:28:29

and this is the amount we get red

00:28:33

arrows give such an arrow we see that

00:28:35

you got the same thing as in the

00:28:38

previous reasoning

00:28:41

only I may have turned these currents upside down,

00:28:46

they seemed to me to be vertical now

00:28:47

and not horizontal, there is no special meaning to this,

00:28:49

I just arbitrarily

00:28:51

directed them upward, don’t look for some

00:28:53

deep meaning in this, this is correct and this is correct, it’s

00:28:55

just more traditional,

00:28:58

and here are two red ones arrows c gave

00:29:02

us a double arrow, two green here

00:29:07

and two yellow here, that is, these

00:29:11

currents are half as much, each of them is two

00:29:14

less than the current position, this is completely

00:29:17

consistent with what we received on the

00:29:19

first floor of the reasoning two-phase

00:29:23

casino ground on the low

00:29:25

voltage side phase c

00:29:28

what does it mean here, again, and a reference book

00:29:32

from a textbook from memory, that is, when there

00:29:36

and this seems to have been mastered, here

00:29:40

we have such three triplets of these vectors,

00:29:44

permissibly we know all this and note that

00:29:46

here it is important to know not only the relative

00:29:49

position of these vectors, that for example

00:29:51

this top this one is down, but they also give

00:29:54

us the length, I don’t have it and it’s clear and there’s no

00:29:57

error that this arrow is bigger,

00:29:59

this is smaller, they really are in this

00:30:01

ratio, so let’s say and we know all this

00:30:04

further, then easily we rotate this

00:30:07

three clockwise

00:30:08

this one counterclockwise 30 degrees, well,

00:30:11

we just discard this one, I already explained

00:30:13

that these zero-

00:30:16

sequence currents are of course

00:30:18

transformed here from here no, now

00:30:22

we collect the full phase currents and so

00:30:25

red arrow + red + red if

00:30:28

you carefully attach

00:30:30

this vector here and for example, let’s do this into

00:30:33

the drawing like this and down from it this

00:30:36

red arrow like this downwards then you will have

00:30:38

this long vector, don’t

00:30:41

let us draw here, the same thing will happen with

00:30:43

vector v,

00:30:44

well, for example, for variety, I’ll

00:30:47

attach this ray to this vector and

00:30:49

here so and down to it, get this green

00:30:52

vector and in total I got

00:30:54

this vector and I’ll move it parallel

00:30:56

here

00:30:58

as for the higher side, the two red

00:31:02

vectors are not just in phase, so

00:31:04

they will give a larger total vector here the

00:31:09

green line seems to go lower and it’s

00:31:11

longer

00:31:12

and here less is shorter and therefore the

00:31:16

lower direction will win, so this arrow will go here,

00:31:18

we will go up symmetrically here,

00:31:22

friends, and this is what we have now looked at the

00:31:24

transformation of short circuit currents

00:31:26

for group 11, that is, a triangle star

00:31:30

with a zero, if we have group 0, well, for example, a

00:31:34

star star with a zero

00:31:37

the justification for such a group is as follows:

00:31:40

if on the low voltage side we have an

00:31:42

ideally three-phase load, for example,

00:31:45

three-phase asynchronous electric motors

00:31:48

with a squirrel-cage, then why not

00:31:51

the circuit becomes simpler, there is

00:31:54

no shift, the alley

00:31:57

protection is simplified, judging because here the 0 group

00:32:00

would seem from the point of view of transformation of

00:32:03

currents and voltages and this circuit is very

00:32:05

easy, obvious, in fact, it is not

00:32:07

complicated, and because in this circuit, in the

00:32:10

presence of ground, that is, in the presence of

00:32:13

zero-sequence currents, we have

00:32:17

magnetic fluxes that are not balanced, we are

00:32:19

now faced with this complexity and so a

00:32:22

single-phase short circuit on the

00:32:24

low voltage side, well for example, phase,

00:32:27

but let’s say here we have

00:32:30

this current spinning as before, and then,

00:32:33

as before, we reason that if there

00:32:35

is a current here, then it should

00:32:37

transform here and we will remove it like

00:32:40

this and draw friends, now

00:32:43

look at our contradiction there

00:32:46

is no current here and it seems like this is wrong, yes,

00:32:50

but it seems like it shouldn’t

00:32:53

be here either, no, and therefore it supposedly

00:32:56

shouldn’t be here, so look, we have

00:32:58

a contradiction, we have a

00:32:59

certain current flowing out of this point,

00:33:02

they are flowing in, nothing like that can be

00:33:04

here here there is no contradiction

00:33:07

because it spins in a circle and here

00:33:10

it simply flows out, so the case of

00:33:13

such an unbalanced transformer

00:33:16

cannot be reasoned as follows:

00:33:18

if there is no current here, that is, there is no current,

00:33:20

if there is no current here, this is

00:33:23

not true due to the fact that the flows 0

00:33:25

sequence is unbalanced, this

00:33:29

reasoning is unacceptable and therefore you are

00:33:32

reasoning differently here, namely,

00:33:35

in order for this

00:33:38

unit current to flow here and here, there must be

00:33:41

some currents that will provide the

00:33:44

sum of this current, firstly and secondly,

00:33:46

they judging because these two phases are

00:33:52

equivalent, that they are under the same

00:33:54

conditions, these two should only be the

00:33:56

same, and from here we come to the

00:33:58

following picture: this current is twice

00:34:02

as large as each of these, the sum is 0, as it

00:34:06

should be according to Kirchhoff’s first law, and

00:34:08

look at the consequences of

00:34:11

imbalance magnetic fluxes in

00:34:13

such a transformer

00:34:14

there is no current here somehow the

00:34:17

window appears why but because

00:34:19

here the zero sequence current is completely lost

00:34:23

we saw this later

00:34:25

and in order to see this

00:34:26

we talk about the same situation in the

00:34:29

language of sequence now this

00:34:31

language is now very important and without it it won’t

00:34:34

work out in any way because my

00:34:38

guess is that here is an arrow down

00:34:40

and here is an arrow down, but to be honest, this

00:34:43

is written on the water with a pitchfork, what if

00:34:45

green is here, red is here and they

00:34:48

will form for me some kind of vector equal to the

00:34:51

current, but that’s why everything is here

00:34:54

questionable, let's now understand in a

00:34:56

more strict language sequences

00:34:58

and so you already know this picture, you

00:35:01

know that with a single-phase goat we have

00:35:04

three such triplets formed,

00:35:06

but in addition you know that if you have 0

00:35:08

group of connections of

00:35:10

transformer windings, then there is no shift here

00:35:12

then there is this three, it just

00:35:14

transgresses to the world from here and this three here

00:35:16

without any shift, I have already explained a lot,

00:35:19

they can in the first lecture of this

00:35:21

series that just like that, this

00:35:24

phase current does not shift here and

00:35:26

for example, the phase voltage here does not

00:35:28

shift in this simplicity, but these

00:35:31

three vectors

00:35:33

completely disappear, which means completely, but

00:35:36

this means that in the diagram of the triangle they

00:35:38

disappeared, but

00:35:40

not so completely, that is, they appeared

00:35:42

at some point in the triangle itself

00:35:45

but did not go beyond its limits, but here

00:35:47

they disappear without any trace at all trace

00:35:49

because if there were ponies here, then this

00:35:52

would lead to a violation of

00:35:54

Kirchhoff's first law, we stick 3 in-phase ones here,

00:35:57

but nothing follows, nothing like that

00:35:58

happens, so they just disappear,

00:36:03

now let's collect from them complete

00:36:05

Tokyo 3 yellow arrows will give us an

00:36:08

arrow like this here is a

00:36:11

swan crayfish and pike 0 and green

00:36:16

arrows are the same 0 so there

00:36:17

will be only one current left here, well, actually I

00:36:20

came out just repeating this is already superfluous,

00:36:23

but here there will be relatively new

00:36:26

material, which means these two arrows

00:36:28

will give this and green + green will not

00:36:34

give the same amount vertically down and

00:36:37

red red in the same way the sum will be given

00:36:40

vertically down, and the

00:36:42

vertical arrows will be half

00:36:45

as large as these, this is easy to establish

00:36:47

based on trigonometry, so now

00:36:52

why are there 066 here, the thing is that there

00:36:54

was a unit,

00:36:58

that is, current 1 flowed here,

00:37:02

but all this unit is here

00:37:04

unable to transform, why

00:37:06

because this 0 sequence breaks off from it,

00:37:10

yes, look,

00:37:12

it was one two three,

00:37:15

but it became only two, where did the third go, but

00:37:18

in the form of a zero sequence it

00:37:20

left, so one turned into two

00:37:23

thirds, or sixty-seven percent,

00:37:25

but 66 and wrote a little incorrectly

00:37:29

67 if we round and it turns out that if

00:37:35

we divide this figure it will be exactly the

00:37:36

same 033, if we did

00:37:39

n’t know this method, we wouldn’t have

00:37:42

guessed that here it is 066

00:37:44

here 033 and that these two currents are

00:37:46

in reality, it’s late and are not directed

00:37:49

at angles like that,

00:37:50

so consideration of this situation

00:37:53

on the second floor, but here the

00:37:57

following pretentious short circuit on the

00:38:00

low voltage side is very important, for example,

00:38:02

the phases are afraid,

00:38:04

look at this picture, you are well familiar with it

00:38:10

since there is no ground here and there are no

00:38:13

zero currents there are no sequences here

00:38:15

with these dances with a tambourine

00:38:17

about the fact that 0 the sequence

00:38:19

is lost and some miracles

00:38:21

happen there there are no miracles here this

00:38:24

here this

00:38:25

here then everything is very simple this is the

00:38:28

simplest situation a two-phase short

00:38:30

circuit on our side leads to the

00:38:33

fact that the currents on the higher side flow as

00:38:35

if there was also a two-phase

00:38:38

short circuit here and in the same phases

00:38:41

now it’s the same in the language

00:38:43

of the sequence, but friend we lied a little

00:38:45

and there’s no way

00:38:46

we did something wrong, I’ve already shown this picture to you

00:38:49

here there is no zero

00:38:53

sequence in principle because

00:38:55

there is no earth transformer with a star circuit

00:38:58

with a star star with 0 group these vectors do not

00:39:02

unfold so I

00:39:04

just copied this picture up and I

00:39:06

copied this one up only Perry called it in

00:39:08

capital letters we

00:39:09

glue together the full phase currents carefully

00:39:13

just look I’ll be silent

00:39:14

and you look at everything that is, the yellow

00:39:21

victor disappeared from us and the red ones here

00:39:23

turned into a horizontal line,

00:39:26

and the green one here also turns into a horizontal

00:39:28

line, everything is simple and clearly

00:39:32

complicated; a

00:39:35

two-phase casino earth appears on the

00:39:37

low voltage side, let’s say in phases bc the

00:39:39

notorious 0

00:39:43

sequence appears, so this is what we have

00:39:46

already looked at

00:39:49

if we just take it and act

00:39:52

as if it’s obvious, then we’ll take the simple

00:39:56

path, but this arrow goes here, then we’ll

00:39:59

come to some kind of contradiction, but

00:40:01

look,

00:40:03

we have these 2 currents, they’re not in

00:40:06

phase; moreover, there’s an angle between them that’s

00:40:08

not 180 degrees it’s 120 degrees,

00:40:11

their sum is not equal to 0, it’s well, and therefore

00:40:15

it feels like the sum of these two currents is

00:40:17

also not equal to zero,

00:40:18

that is, it’s something like that, but it also

00:40:22

can’t be that nothing flowed into this node

00:40:24

in this phase, but what kind of flow did you have? I

00:40:27

hope I’ll show you the amount, that’s about the

00:40:30

amount, it can’t be that way, and therefore

00:40:34

some kind of current simply has to tick here, and

00:40:36

we come again, well,

00:40:38

to this seemingly apparent

00:40:41

violation of common sense; in fact, there are

00:40:43

no violations, but it seems so out of

00:40:45

habit that here 0 current appeared here another

00:40:47

time, but again these are all the

00:40:51

consequences of the fact that in this

00:40:54

transformer there are unbalanced

00:40:56

zero-sequence magnetic fluxes

00:40:58

and it is because of this that such a

00:41:02

seemingly unfair situation appears here, that

00:41:05

is, the real thing then there really

00:41:06

is, but who knows which one knows

00:41:10

which ones here any what if here it’s not 120

00:41:12

degrees here for example 120 and here it’s

00:41:15

120 here suddenly here it’s not like this maybe

00:41:20

this vector here is not a single one and

00:41:24

this one is also unclear what and here’s this

00:41:27

picture or more precisely this scenario

00:41:29

this is a vivid example of the fact that without

00:41:32

consistency, but you definitely can’t

00:41:33

figure it out in the previous paintings, well, at the very

00:41:36

least, with some

00:41:38

primitive handicraft considerations

00:41:40

you can do something, but here it’s no longer

00:41:43

possible, and that’s why here we resort to these

00:41:47

sequences and so here we go

00:41:49

you already know this situation, we have already

00:41:51

looked at this three does not

00:41:56

unfold in any way, this also does not unfold in any way 0 group does

00:41:59

not unfold, this disappears,

00:42:01

we put together a sum from these triplets, and

00:42:05

since here the picture turns out to be

00:42:07

large, I removed the diagram so that everything that is

00:42:10

happening here on the screen can be seen, so

00:42:13

let’s begin, let’s say yellow

00:42:16

phase vectors a up + down + down look

00:42:21

double vector up and 2 single

00:42:24

down, well it’s clear what the sum will be 0

00:42:27

now a more complex situation green

00:42:30

vector a phase b here here it is to it you

00:42:35

attach the reverse sequence

00:42:36

here it is and to it we attach 0 here Well,

00:42:42

it’s clear that here we will have the full current,

00:42:44

we do the same with phase c

00:42:46

here at the top with phase and not as simple

00:42:52

as here it just disappeared and

00:42:54

here it is, look at the double

00:42:56

vector up and

00:42:57

once down and it turns out this is a

00:43:01

half length, as it were the

00:43:03

red arrow here and to it you

00:43:07

attach the red one here, we do the same with the

00:43:10

green ones and here we

00:43:12

will have the currents being undermined,

00:43:14

so I’ll now scroll back to the

00:43:18

next slide here, these are the

00:43:22

arrows, they have already been cleared, so to speak, from the

00:43:24

direct reverse zero

00:43:26

sequence, these are the phase currents I

00:43:28

I’ll look through it several times so that you pay

00:43:31

attention to the difference between the bottom and the

00:43:34

top picture,

00:43:36

please look at the bottom picture, that is,

00:43:39

here the angle between the phases is

00:43:42

120 degrees and the lengths are single, but in the

00:43:46

top picture this angle is no longer 120,

00:43:50

well, for example, this one here is

00:43:53

approximately 100 degrees and from 100 in

00:43:56

total 360 360 -100 -100 that is minus

00:44:00

200 well and here it turns out 160 that is

00:44:03

far from 120 and their length is not unit

00:44:06

why not unit let me scroll

00:44:09

back yes because this vector is not here here it is

00:44:12

zero

00:44:14

sequence,

00:44:15

if there was one, then the total length would be like this,

00:44:18

but it is not there at all, the bin is smaller, that is,

00:44:21

if it is one hundred percent, this is the

00:44:23

length like here

00:44:26

from here to here, one hundred percent, then this

00:44:28

will be less, that is, 88 percent,

00:44:31

where does the number exactly 88 come from,

00:44:35

but like this you can’t tell it on your fingers, you

00:44:37

just need to take millimeters q and

00:44:38

build it, you’ll see that if you have

00:44:41

ten centimeters here, you’ll have 8 and 8 here,

00:44:44

but where does 033 come from, this

00:44:48

can be explained, the fact is that against the background of this

00:44:51

length, this length is 66

00:44:56

percent why exactly this way I

00:44:58

explained it and therefore this length,

00:45:04

which is half as long, look, we

00:45:07

subtract the half vector from the large vector,

00:45:10

it becomes half the size, it

00:45:12

becomes 066

00:45:13

in half, that is, 033, well, the next topic

00:45:17

is the transformation of stresses with

00:45:20

asymmetrical goats,

00:45:21

here we are already moving on to another side, that

00:45:24

is, we take a short circuit on

00:45:26

your side and, as it were, run it

00:45:29

by transforming the voltage through one

00:45:32

transformer for interest there, for someone

00:45:35

else's transformer,

00:45:37

this example was made for a very

00:45:40

specific circuit, but if you

00:45:43

understand this example, then for

00:45:46

any other circuit you build a

00:45:48

voltage transformation and so the circuit

00:45:51

is such that there is a distribution device here

00:45:53

110 kilovolts from it doesn’t matter it can be

00:45:55

more there 220 and higher kilovolts here

00:45:57

there is a transformer from the

00:45:59

connection diagram star-solya-triangle

00:46:01

it has group 11 there is a discord device

00:46:05

for example 10 kilovolts but distribution goes further away from it

00:46:07

transformers, for

00:46:10

example, with a star-star-

00:46:13

zero or triangle circuit, they fell asleep for you or a

00:46:16

star zigzag with salt, so the formulation of the

00:46:19

question is that here at the top there was a

00:46:22

single-phase short circuit of the phase and

00:46:25

the question is how the voltage will behave,

00:46:27

both phase and linear at a voltage of

00:46:30

0 4 kilovolts,

00:46:32

answering this question can be

00:46:34

predict

00:46:35

voltage dips

00:46:38

at a nominal value of 0 - 4 kilovolts, well, for example,

00:46:41

you can predict the following, which

00:46:45

magnetic starters will no longer be

00:46:47

included, and are more likely to be switched on for

00:46:50

different or linear voltages, well, we are talking

00:46:53

about magnetic starters through which the

00:46:55

stator windings of asynchronous ones are powered, but let’s

00:46:59

say electric motors with a

00:47:01

squirrel-cage,

00:47:02

so let’s first consider a transformer

00:47:05

here is this distribution circuit with a star

00:47:07

star with a zero, we arrange a

00:47:11

short circuit mentally to a

00:47:12

voltage of 110 kilovolts, here we had a

00:47:16

normal mode, it turned into this

00:47:18

in the normal mode, a triple is such a

00:47:21

traditional triple of phase voltages, but there

00:47:24

is also a corresponding linear one for a

00:47:27

single-phase short circuit to a phase and the

00:47:30

voltage at becomes equal to zero and the

00:47:33

voltage at the butt becomes antiphase

00:47:36

and equal to each other, if we have a short

00:47:40

circuit

00:47:41

not at this point directly at the

00:47:44

device, but somewhat remote or

00:47:46

through some transition resistance,

00:47:48

then this vector u is no longer

00:47:52

equal to zero, it is slightly -it grows a little, but

00:47:55

these two vectors u

00:47:57

are moving a little, well, that is, this is such an

00:47:59

extreme situation, this is some kind of average, well, let’s

00:48:02

see how in normal mode, in an extreme

00:48:05

situation, in an average situation, the

00:48:07

voltage is transformed to the lower

00:48:08

side, and so first we need to

00:48:11

go through this this this boundary star

00:48:14

triangle reasoning for the following here

00:48:18

we have late and voltages well and

00:48:20

accordingly linear we know that

00:48:25

the phase voltage of phase a turns

00:48:29

into this voltage that is the voltage

00:48:32

between the phase and look at the price phase that is in

00:48:37

other words the voltage is 0 and here is 0 a

00:48:41

turns into voltage c&c

00:48:47

that is, I build parallel to this

00:48:49

vector this vector and similarly

00:48:52

parallel to this I build this and

00:48:54

parallel to this this for example this

00:48:57

voltage of the center phase will be formed here

00:49:00

that is the voltage between this point and

00:49:03

this point that is between b and c

00:49:07

how we built this

00:49:09

triangle, then we reach this

00:49:13

star, we have a linear

00:49:16

voltage here, for example, here y a b here

00:49:18

y dc here and y a c here and based on

00:49:24

this triangle of linear voltages

00:49:26

we formed a star of phase voltages,

00:49:30

but really here I am I expanded

00:49:33

the matter a little in that this triangle of

00:49:34

linear voltages, in theory, should

00:49:37

coincide with this, but I deliberately

00:49:41

turned it around, why, well, because we

00:49:43

are interested in the transformation in the

00:49:45

transformers themselves, that is, what happened

00:49:48

at this stage and then separately that

00:49:51

at this stage we are not very I'm interested in the

00:49:54

mutual orientation of these vectors in

00:49:56

relation to these nobody, we just

00:50:00

draw a triangle here like this,

00:50:01

inverted like this, then both this

00:50:04

star and this star will be inverted,

00:50:06

it's a little ugly, non-standard,

00:50:09

so to speak, so I decided to do it this way

00:50:13

if you don't like it, you just

00:50:15

you will have to rotate these two pictures

00:50:17

back by 30 degrees, their

00:50:20

mutual orientation will not change in any way,

00:50:22

you just complicate this view a little,

00:50:26

but there will be a more correct

00:50:28

orientation between these vectors, so

00:50:31

we have a single-phase short

00:50:33

circuit,

00:50:34

but here we have phase

00:50:37

voltage o 0b late voltage u 0 c

00:50:42

and phase voltage he ult she disappeared,

00:50:46

respectively, we are left with linear

00:50:49

voltage at abe here it is linear

00:50:53

voltage at stock here it is and linear

00:50:56

voltage at bc

00:50:58

that is, the phase voltage of the mind which is

00:51:01

equal to zero

00:51:02

turned into voltage father i already

00:51:05

explained why the father, that is, 0 phase

00:51:11

voltage 0b turned into ab.

00:51:16

late voltage u 0 c turned into

00:51:20

b.c.

00:51:21

we check c this is between b and c, so

00:51:28

these two vectors are aligned exactly

00:51:31

the same as these, but

00:51:34

if we have a

00:51:36

phase voltage y that is slightly non-zero,

00:51:39

then it has transformed accordingly,

00:51:41

you have a slightly non-zero linear

00:51:43

voltage, fathers, so such a triangle has appeared here

00:51:47

now for For convenience,

00:51:50

we unfold these two pictures a little

00:51:52

at this angle and see the following: in

00:51:57

relation to this neutral,

00:51:59

we have already formed a neutral here,

00:52:01

so we can operate with this

00:52:03

concept, so in relation to this neutral

00:52:06

we have these two points, that is, two

00:52:08

phase voltages u 0 a and a 0 c and y 0b

00:52:15

well, the linear voltages are as they were

00:52:17

and remain, so they are just what it is, in a

00:52:20

triangle circuit it is not customary to talk about

00:52:22

different voltages, but here this is already important

00:52:25

and further since our circuit is a 0 group

00:52:28

they are simply transformed down without

00:52:31

any reversal and here, similarly,

00:52:35

to these points a and c

00:52:37

from the neutral I ran two such beams and

00:52:40

they went here without distortion and here is the conclusion

00:52:44

from this picture that in case of a

00:52:46

single-phase short circuit on the

00:52:49

high voltage side behind this particular

00:52:52

transformer we have

00:52:54

such a situation will arise in our father’s line voltage

00:52:57

will become equal to zero and the phase

00:53:01

voltage will be more or less normal,

00:53:03

or in any case, the voltage lines will

00:53:06

greatly decrease between the points and the

00:53:09

phase voltage will be not that

00:53:12

they are all nominal,

00:53:14

but in any case they are clearly not zero in

00:53:17

other words, there is a high probability that there

00:53:20

will be no need for magnetic starters

00:53:22

connected specifically to linear and not to

00:53:25

phase voltage, and if we have a

00:53:30

triangle SV asleep on,

00:53:32

well, then I won’t repeat similar reasoning,

00:53:36

I understand that you are tired,

00:53:39

similar reasoning will show us the

00:53:41

opposite picture, look here at the

00:53:44

phase voltage u 0 and he has an alba,

00:53:47

but 0 c doesn’t have it, it’s gone, we do

00:53:50

n’t have

00:53:51

phase voltage llc, well, more precisely, it can

00:53:55

appear in such an

00:53:57

intermediate situation, but it’s very

00:53:58

small old line voltage here is

00:54:01

quite large, both here and here,

00:54:04

for example, this is what a ts

00:54:08

well, here it’s so half-hearted, here

00:54:10

it’s so half-hearted, this already says the

00:54:12

opposite, that in such a situation there is a high

00:54:15

probability that those

00:54:17

magnetic starters that are switched on to

00:54:21

phase voltage will no longer be needed, and if you switch on to

00:54:25

linear voltage, then most

00:54:28

likely they will most likely remain

00:54:30

unplugged and finally star zigzag with

00:54:35

zero is group 11 and again we have

00:54:40

already worked through all this, I mean

00:54:42

this is the normal mode this was our

00:54:44

first lecture these are the situations

00:54:48

we didn’t have, but nevertheless they are

00:54:50

completely analogous to the connection triangle

00:54:54

with zero because and here and there we have

00:54:56

group 11, this triangle just unfolds a little,

00:54:59

and here the conclusions are the

00:55:01

same as in the previous triangle diagram,

00:55:04

which is more likely

00:55:06

in case of single-phase short circuits at

00:55:09

high voltage, we have

00:55:12

magnetic starters 0 4 kilovolts

00:55:14

that are turned on phase voltage and

00:55:17

less likely to

00:55:19

linear voltage colleagues, but that’s all

00:55:23

I wanted to tell you about the transformation of

00:55:25

currents and voltages during short

00:55:28

circuits, in fact, the topic may

00:55:33

imply the position you are looking at, if you

00:55:36

need something, I will write down this material, what

00:55:40

may be needed, well, perhaps you

00:55:42

I will be interested in what we have with the transformation of

00:55:46

short circuit currents in the case of a

00:55:48

zigzag about the voltage, I said about the ducts,

00:55:51

no, it may be necessary to

00:55:55

give more expanded ideas on

00:56:00

these things, which is why, for example, with

00:56:02

two-phase short circuits, this is

00:56:04

exactly the picture that develops; I stayed for all

00:56:07

these textbooks and this question didn’t

00:56:11

cover much, but in general this lecture gives

00:56:16

an idea of the transformation of currents and

00:56:18

voltages,

00:56:19

if you listened carefully to this lecture,

00:56:22

then you can take from scratch any circuit of

00:56:25

any type of short circuit, both from

00:56:27

above and from below, based on simple

00:56:30

reasoning, try to form

00:56:33

only distributions and it won’t work,

00:56:36

or if you have doubts, then

00:56:39

you need to involve such concepts as direct

00:56:41

reverse and 0 sequence, but for now this is the

00:56:45

end of the lecture, thanks for your

00:56:47

attention

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