JPS5843892B2 - Parent-child instrument transformer with tertiary winding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parent-child instrument transformer with a tertiary winding.

A grounded instrument transformer in which one end of the primary winding is grounded is generally provided with a tertiary winding in order to detect zero-sequence voltage that occurs in a system fault or the like.

Figure 1 shows an example of the configuration of a conventional parent-child instrument transformer with a tertiary winding, in which a tertiary winding is wound around a parent-child instrument transformer whose secondary winding consists of a sub-winding and a sub-winding. It is.

In the figure, 1 is the primary winding, and U and 0 are its terminal symbols.

Reference numerals 2 and 3 denote secondary windings, which are wound around a common iron core 5 together with the secondary winding 1, with one winding 2 serving as a secondary winding and the other winding 3 serving as a child winding.

U. −θ1. u2-θ2 are terminal symbols of the secondary winding 2 and the child winding 3, respectively.

4 is a tertiary winding, which is similarly wound around the iron core 5, and a and b are its terminal symbols.

6 conceptually shows the passage path of the main magnetic flux when the next winding 2 is short-circuited between the terminals ul+θ1.

- The secondary winding 1 and the tertiary winding 4 are wound so that the centers of their respective axial lengths substantially coincide, and the axial lengths of the secondary winding 2 and the child winding 3 are respectively the same as that of the tertiary winding 4. 1/2 of axial length
wrapped within.

In a parent-child instrument transformer with a tertiary winding having such a configuration,
If the secondary winding 2 is short-circuited, for example between the terminals ul and θ1, the main magnetic flux 6 passes through the path shown in the figure, so most of it interlinks with the child winding 3, but the tertiary winding 4 is only a part of it. This means that there will only be a chain reaction.

That is, if the total number of turns of the tertiary winding 4 is N3, and the number of turns that effectively interlinks with the main magnetic flux 6 is N3', the tertiary winding induced voltage V, which is positive when the secondary winding 2 is short-circuited, is: 3-N3×V3N, and it has been experimentally confirmed that (3) is 40 to 60 better than V3N.

Note that V3N is the rated tertiary voltage.

Figure 2 shows an example of how to connect the secondary winding of a parent-child voltage transformer with a tertiary winding configured as shown in Figure 1. The same numbers as in Figure 1 represent the same names, and 7 is for system protection. Relay (protection Ry
) to the next winding 2, and 8 is a voltage differential relay (differential R
y) between the secondary winding 2 and the child winding 3.

In the figure, when the next winding 2 is short-circuited between terminals u1 and θ1, the terminal voltage of the next winding 2 becomes almost zero, but the terminal voltage of the child winding 3 is almost the rated voltage, so the protection By making the operating time of Ry7 slower than the operating time of differential Ry8, the protection Ry7 will not operate in the event of a fault unrelated to the grid, such as a short circuit between the terminals of a potential transformer, and the power supply will be reduced. There will be no supply disruption.

In this case, the terminal voltage ■3 of the tertiary winding 4 is as described above.
= (0,4 to 0.6)V3N.

Figure 3 is a wiring diagram when three parent-child instrument transformers with tertiary windings configured as shown in Figure 1 are connected to a three-phase system, and the same numbers as in Figures 1 and 2 have the same names. In addition, 9 is a relay connected between the open triangular connection terminals a+f of the tertiary winding to detect the zero-phase voltage.

Note that the connection instruments for the secondary windings 2 and 3 are not shown.

In the same figure, when a balanced three-phase voltage is applied to the primary winding terminals U, V, and W, and there is no failure in either the new winding 2 or the child winding 3,
The voltage generated between the open triangular connection terminal af becomes almost zero.

However, if the new winding 2 of one of the three instrument transformers is short-circuited between terminals U1 and θ4, the induced voltage in the tertiary windings a and b wound on the same core 5 will be as described above. niV
3-(0,4~0.6) V3N, the voltage Vaf generated between the open triangular connection terminals a and f is Vaf
=Va'f =VaN V3-V3N (0,4~0
．． 6) V3N=(0,6~0.4)V3N, and generally V3N=110/3V, so Vaf=22~1
It becomes 5■.

This voltage value will exceed the minimum setting value of the relay 9, typically 10 cm.

On the other hand, even if the child winding 3 is short-circuited between the terminals U2 and θ2, the voltage Vaf generated between the open triangular connection terminals a and f will exceed the minimum setting value of the relay 9 for exactly the same reason.

Therefore, in the conventional configuration, in order to prevent malfunction of the relay 9,
Even if either the new winding 2 or the child winding 3 is short-circuited, the operation of the relay 9 must be suppressed, and the protection circuit has a complicated configuration and low reliability in terms of protection.

The object of the present invention is to obtain a parent-child instrument transformer with a tertiary winding that corrects such drawbacks.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, where the same parts as in FIG. 1 are given the same numbers, a primary winding 1, a new winding 2, a child winding 3, and a tertiary winding 14 are wound 7)) on one leg of the iron core 5.

In this case, the tertiary winding 14 is wound so that its axial length is approximately equal to the axial length of the new winding 2, and the centers of their respective axial lengths are approximately aligned.

In this configuration, if the new winding 2 is short-circuited between the terminals U and -01, the main magnetic flux will pass through path 6 as shown in Figure 1, so it will almost be chained to the new winding 2 and the tertiary winding 4. The voltage induced in the tertiary winding 4 is almost zero, but the child winding 3 is connected to the terminal u2-θ.
If there is a short circuit between the two, the main magnetic flux passes through the path shown in FIG. 4, so that approximately the rated voltage is induced in the tertiary winding 4.

In other words, when three parent-child instrument transformers with tertiary windings with such a configuration are combined, when the new winding 2 is short-circuited, a zero-phase voltage is generated between the open triangular connection terminals a and f, but at the child winding terminal If a short circuit occurs between them, almost no zero-sequence voltage will be generated.

Therefore, it is only necessary to suppress the operation of the relay 9 when the new winding 2 is short-circuited, and it is not necessary to suppress the relay 9 when the sub-winding 3 is short-circuited. A parent-child type instrument transformer with a high tertiary winding can be obtained.

FIG. 5 shows another embodiment of the present invention, in which the same numbers as in FIG. 1 represent the same names.

In this embodiment, the tertiary winding 14 is wound so that its axial length is approximately equal to the axial length of the child winding 3, and the centers of their respective axial lengths are approximately aligned.

In this configuration, as is clear from the previous explanation, when the secondary winding 3 is short-circuited, a zero-sequence voltage is generated between the open triangular connection terminals a and f, but when the new winding 2 is short-circuited, a zero-sequence voltage is generated. I will not do it.

Therefore, it is only necessary to suppress the operation of the relay 9 when the child winding 3 is short-circuited, and as in the case of FIG. It will be done.

FIG. 6 shows still another embodiment of the present invention, in which the same numbers as in FIG. 1 represent the same names.

In this embodiment, the tertiary winding 14 includes a primary winding 1, a new winding 2,
The child winding 3 is wound around the opposite leg of the core leg around which the child winding 3 is wound.

In this configuration, as is clear from the explanation of FIGS. 4 and 5, even if either the new winding 2 or the child winding 3 is short-circuited,
Since the main magnetic flux passes through the iron core legs around which the tertiary winding 14 is wound,
Almost the rated voltage will be induced between the tertiary winding terminals a and b.

That is, even if a short circuit occurs between the terminals of either the new winding 2 or the child winding 3, approximately the rated voltage will be induced in the tertiary winding 14.

Therefore, when three parent-child instrument transformers with tertiary windings with such a configuration are combined, even if either the new winding 2 or the child winding 3 is shorted between the terminals, there will be little difference between the open triangular connection terminals a and f. Since no zero-sequence voltage is induced, there is no need to suppress the relay 9, and a voltage transformer with a tertiary winding that is much simpler and more reliable than the conventional configuration can be obtained.

As explained above, in the parent-child type voltage transformer with tertiary winding according to the present invention, when three units are used in combination, a zero-sequence voltage is generated between the open triangular connection terminals when the parent and child windings are short-circuited. Since the number of cases can be reduced or eliminated, the configuration of the protection circuit is much simpler than that of conventional parent-child voltage transformers with tertiary windings, and the reliability of system protection is significantly improved.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional parent-child instrument transformer with a tertiary winding, Figure 2 is the wiring diagram of Figure 1, and Figure 3 1 is a parent-child instrument transformer with a secondary winding. is a connection diagram when applied to a three-phase system, FIG. 4 is a configuration diagram showing an embodiment of a parent-child instrument transformer with a tertiary winding according to the present invention, and FIGS. It is a block diagram which shows another Example. 1...-Next winding, 2...New winding, 3.
...Child winding, 4.14...Secondary winding, 5
...Iron core, 6,10...Main magnetic flux path, 7
, 8.9... Protective relay.

Claims (1)

[Claims] 1. m consisting of an iron core, a secondary winding, a secondary winding, and a child winding:
In a parent-child type instrument transformer with a tertiary winding wound with a secondary winding and a tertiary winding, the center of the axial length of the tertiary winding is approximately equal to the center of the axial length of the secondary winding. A parent-child instrument transformer with a tertiary winding, characterized in that the coils are matched. 2. In a parent-child type instrument transformer with a tertiary winding, in which a negative winding, a secondary winding consisting of a sub winding, and a sub winding, and a tertiary winding are wound around an iron core, the tertiary winding is A parent-child type instrument transformer with a tertiary winding, characterized in that the center of the axial length is substantially coincident with the center of the axial length of the child winding. 3. In a parent-child type instrument transformer with a tertiary winding, in which a negative winding, a secondary winding, and a tertiary winding consisting of a secondary winding and a child winding are wound around an iron core, the tertiary winding is A parent-child type instrument transformer with a tertiary winding, characterized in that the secondary winding and the secondary winding are wound on a core leg other than the core leg on which the secondary winding is wound.