JPS5845167B2 - Parent-child instrument transformer - Google Patents

Description

Detailed Description of the Invention The present invention provides a connection lead wire between a new winding terminal of a parent-child voltage transformer and a system protection relay terminal, in which a short circuit occurs between the coarse winding terminals due to dielectric breakdown or the like. The present invention relates to a parent-child type instrument transformer whose purpose is to prevent malfunction of the system protection relay due to residual voltage in the child winding.

FIG. 1 is an operational explanatory diagram schematically showing a parent-child type instrument transformer.

In the figure, 1 is a high-voltage winding, and 2 and 3 are low-voltage windings, each of which is wound around a common core 4. One of the low-voltage windings, 2, is used as a coarse winding, and the other winding 3 is used as a sub-winding. There is.

Further, 5 is a system protection relay (protection Ry) connected to the coarse winding 2, and 6 is a voltage differential relay (differential) (y) connected between the coarse winding 2 and the child winding 3. .

In the parent-child instrument transformer shown in Fig. 1, the high voltage winding 1
With a voltage applied between U and V of the coarse winding 2
When the circuit FF' is short-circuited, the terminal voltage of the coarse winding 2 becomes almost zero.

At this time, if a residual voltage is generated in the child winding 3 and the operating time of the protection Ry5 is made slower than the operating time of the differential Ry5, failures not related to the system, such as lead wires, can be prevented. The protection RY5 does not operate, and there is no problem in power supply.

FIG. 2 shows the conventional configuration of a parent-child type voltage transformer used for such purposes, and the same numbers as in FIG. 1 represent the same names.

7 to 9 conceptually show the magnetic flux when the rough winding 2 is short-circuited between terminals u and V. From the viewpoint of characteristics, the parent winding, child winding, and high-voltage winding were arranged so that the centers of their axial lengths were approximately the same, so the child winding terminal voltage when the parent winding was short-circuited or The new winding terminal voltage was only about 60% of the rated value.

This is because, as shown by numbers 7, 8, and 9 in FIG. 2, more of the magnetic flux when the parent or child windings are short-circuited does not interlink with the child or coarse windings.

By the way, from the application of differential Ry - L, the residual voltage of the child or coarse winding when the parent or child winding is short-circuited is 80 to 80% of the rated value.
Although it is desirable to select 120%, the conventional configuration has the drawback of not satisfying this value as described above.

The present invention has been made to improve these drawbacks.
FIG. 3 shows one embodiment of the present invention, and the same numbers as in FIGS. 1 and 2 represent the same names.

In the figure, the parent winding 2 and the child winding 3 are arranged so that the centers of their axial lengths do not coincide with each other.

With this configuration, when the parent winding 2 is short-circuited, the magnetic flux interlinking with the parent winding 2 becomes approximately O, so the magnetic flux generated by the canned winding 1 is shown in the figure with the number ? , 8, and 9, most of it interlinks with the child winding 3.

Therefore, even when the parent winding 2 is short-circuited, the residual voltage of the child winding 3 can be selected to be 90 to 100% of the rated value.
This has also been confirmed experimentally, i.e. protection R
It is possible to sufficiently satisfy the residual voltage of 80 to 120% required by application-L of y, and it is possible to operate the differential Ry sufficiently, thereby increasing the reliability of system protection.

The above explanation is about the residual voltage in the child winding 3 when the main winding 2 is short-circuited, but the same thing applies to the residual voltage in the main winding 2 when the child winding 3 is short-circuited. I can say that.

Furthermore, if the parent and child windings are configured to have the same shape and are arranged in positions symmetrical to the center of the axial length of the high voltage winding 1, the parent winding 2 and the child winding 3 There is also the advantage that the residual voltage is almost the same even if either of them is short-circuited, making it desirable to apply protection Ry.

In addition, in the embodiment shown in FIG. 2, the average winding diameters of the parent winding 2 and the child winding 3 are shown to be approximately the same, but if necessary, the average winding diameters of the respective windings may be made different. It is possible.

As explained above, in the parent-child type voltage transformer according to the present invention, when the lead wires of the parent or child windings are short-circuited, the residual type E+ll of the child or parent winding can be selected to an appropriate value. It has the advantage of being able to use commonly used inexpensive and economical voltage differential relays as is.13 Furthermore, by suppressing short-circuit current, damage to equipment due to short-circuit accidents is reduced and equipment reliability is increased. There are also advantages.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the operation of a parent-child type voltage transformer, Fig. 2 is a configuration diagram showing a conventional parent-child type voltage transformer, and Figure 3 is an example of a parent-child type 31 voltage transformer according to the present invention. FIG. 1... Elevated -) winding, 2, 3... Main winding and child winding, 4... Iron core, 5...
System protection relay, 6...Voltage differential relay, 7,
8.9...Magnetic flux.

Claims (1)

[Scope of Claims] 1. A parent-child instrument transformer in which a high-voltage winding and a low-voltage winding consisting of a coarse winding and a child winding are wound around an iron core, in which at least at least the coarse winding and the child winding are wound. 1. A parent-child instrument transformer, characterized in that one of the two is arranged so that the center of its axial length does not coincide with the center of the axial length of the high voltage winding. 2. The parent and child according to claim 1, characterized in that the center of the axial length of each of the coarse winding and the child winding is arranged symmetrically with respect to the center of the axial length of the high voltage winding. type instrument transformer.