JPH0620347B2 - Protective relay device for transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention also relates to a protective relay device for a transformer for protecting a transformer in which windings of Δ connection are mixed.

(Prior Art) Conventionally, for example, A circuit configuration as shown in FIG. 3 is known in the case of protecting a two-winding transformer in which the secondary winding is Δ-connected by a ratio differential relay. In this circuit, the transformer 11 Due to, there is a phase difference of 30 ° between the transformer primary currents pa, pb, pc and the secondary currents sa, sb, sc. Therefore, if these currents are input to the ratio differential relays 14a to 14c via the current transformers 12a to 12c and 13a to 13c provided for each phase of the primary side and the secondary side of the transformer 11, they are transformed. Even if there is no mismatch due to the ratio and the current change ratio, the differential currents Δa to Δc due to the phase difference flow as shown in FIG.
14a to 14c may malfunction.

Therefore, in the prior art, as shown in FIG. 5, the secondary side circuit of the current transformers 12a to 12c on the primary side of the transformer 11 is connected in the same manner as the secondary side of the transformer 11 by the Δ connection, and the current transformers 12a to 12c are connected. 12c secondary side current pa ′,
pb ′, pc ′ and secondary current of transformer 11 sa, sb, s
c, in other words, the secondary side currents sa ′, s of the current transformers 13a to 13c
The phase difference between b'and sc'is eliminated. At the same time, by setting the secondary side circuit of the current transformers 12a to 12c in a Δ connection, the magnitude of the current can be reduced. Because of the doubling, each of these secondary circuits has a current ratio The matching auxiliary current transformers 15a to 15c are connected to correct the magnitude of the current so that the differential current flowing through the ratio differential relays 14a to 14c is set to zero.

(Problems to be solved by the invention) However, according to this, the current transformer on the primary side of the transformer 11
12a to 12c are dedicated to the ratio differential relays 14a to 14c, so the phase current on the primary side of the transformer 11 If you want to connect other relays or meters that are used by inputting, enter another current transformer or use current transformers 12a to 12c.
The secondary cable of (1) was pulled into the building, other relays, etc. were connected, and then Δ wiring was used to connect the matching auxiliary current transformers 15a to 15c.

Therefore, when the current transformers are separately provided, the burden of facility costs becomes large, and when the current transformers 12a to 12c are also used as other relays, the work of connecting many cables is complicated. There was a problem. Further, in any case, since the matching auxiliary current transformers 15a to 15c are used in order to eliminate the difference current, there is also a drawback that the cost becomes high in this respect as well.

The present invention has been proposed to solve the above problems, and its purpose is The secondary side circuit of the current transformer on the connection side does not depend on the method such as Δ connection, but the calculation function of the microcomputer allows the secondary side circuit And the current ratio is corrected to reduce the differential current flowing to the ratio differential relay to zero, and the auxiliary current transformer for matching and a separate current transformer are not required to improve the economical efficiency and the cable connection work is complicated. It is to provide a protective relay device for transformer that eliminates the above.

(Means for Solving Problems) In order to achieve the above-mentioned object, the present invention has a primary side A transformer whose secondary side is Δ-connected is provided on each of the primary side and the secondary side. In the protective relay device for a transformer, which is protected by a ratio differential relay between the secondary side circuits of the current transformer, one of the transformers
A first calculating means for obtaining a vector difference between secondary side phase currents of the current transformer provided on the secondary side, and a second calculating means for multiplying each phase current vector obtained by the first calculating means by 1 / √3 Calculating means for calculating each phase current calculated by the second calculating means and each secondary side phase current of the current transformer provided on the secondary side of the transformer. Current and outflow current are the features.

(Operation) In the present invention, the secondary side circuit of the current transformer is obtained by determining the vector difference of the secondary side current of the primary side current transformer of the transformer for each phase by the first computing means. Is a condition equivalent to the one connected with △. Thereafter, the second computing means sets each phase current vector, which is the computation result of the first computing means, to 1
/ √3 times and correct the current ratio to make the phase and magnitude equal to the secondary current of the secondary current transformer.

Then, each phase current, which is the calculation result of the second calculation means, is set as the inflow current of the ratio differential relay, and the secondary side current transformer of the transformer is changed to 2.
Let each secondary phase current be the outflow current.

(Example) An example of the present invention will be described below with reference to the drawings. In FIG. 1, 1 indicates that the primary side is the same as above. The transformer is a two-winding transformer in which the secondary side is Δ-connected, and the current transformers 2a, 2b, 2c are provided in each phase of the primary side, and the current transformers 3a, 3b are provided in each phase of the secondary side. , 3c are connected respectively.

Therefore, in the present invention, the secondary current transformers 2a, 2b, 2c of the transformer 1 are
The secondary side currents pa ', pb', pc 'of the And the current ratio is corrected,
Secondary side currents sa ', sb' of secondary side current transformers 3a, 3b, 3c,
It makes the phase and magnitude equal to sc '. In this embodiment, each current transformer 2a, 2b, 2c, 3a, 3
Ratio differential relays 5a, 5 connected between the secondary circuits of b, 3c
Since the functions b and 5c can also be realized by the software of the microcomputer 4, these are also shown as components of the microcomputer 4 for convenience.

That is, in the microcomputer 4, the current transformer
After taking in the secondary currents pa ', pb', pc 'of 2a, 2b, 2c and performing A / D conversion, The block 6 performs the following calculation.

The vector diagram of each of these currents is as shown in FIG. 2, and pa *, pb *, pc * are pa ′, pb ′, pc ′.
The phase is delayed by 30 °, and the size is This is equivalent to connecting the secondary side circuits of the current transformers 2a, 2b, 2c by Δ as in the conventional case. Then, the following calculation is performed to correct the current change ratio.

The equation (1) is calculated by the first calculating means, and the equation (2) is calculated by the second calculating means.
These arithmetic means are realized by the hardware and software of the microcomputer.

Then, the calculation result of the equation (2) is the ratio differential relays 5a, 5
b, 5c, and the secondary side currents of the secondary side current transformers 3a, 3b, 3c of the transformer 1 are also ratio differential relays 5.
The outflow currents of a, 5b, and 5c are respectively taken in.

As can be seen from Fig. 2, the phases of "pa", pb ", and pc" thus obtained are delayed by 30 ° with respect to pa ', pb', and pc ', respectively, while the magnitudes are equal. ", Pb" and pc "are secondary currents sa 'and s of the current transformers 3a, 3b and 3c provided on the secondary side of the transformer 1.
Both b ′ and sc ′ have the same phase and magnitude. Therefore, no differential current flows through the ratio differential relays 5a, 5b, 5c, and the ratio differential relays 5a, 5b are in a state where no accident such as winding short circuit or ground fault occurs in the protection section including the transformer 1. There is no risk that the 5c will malfunction.

It should be noted that this embodiment applies the present invention to a two-winding transformer. Of course, it can be applied to a three-winding transformer, etc.

(Effect of the Invention) As described in detail above, according to the present invention, the primary side of the transformer to be protected. Of the secondary side current of the current transformer installed in And the correction of the current change ratio is realized by the first and second means such as a microcomputer, the same as the conventional one. It is not necessary to connect the secondary side circuit of the current transformer on the side by Δ to make this current transformer dedicated to the ratio differential relay. Therefore, on the secondary side of this current transformer, the phase current of the transformer primary side It is possible to connect other relays and meters that are used by inputting, and it is possible to significantly increase the economic efficiency by eliminating the need for adding a new current transformer.

Further, since the number of secondary side cables of the current transformer is also small, it is possible to reduce labor without the trouble of pulling and connecting a large number of cables into the building as in the conventional case.

Further, since the matching auxiliary current transformer for correcting the current flow ratio is not required, the cost can be further reduced.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention.
FIG. 1 is a configuration diagram of a differential protection circuit, FIG. 2 is a vector diagram of each current shown in FIG. 1, FIG. 3 is a configuration diagram of a conventional differential protection circuit, and FIG. FIG. 5 is a vector diagram of each current shown in FIG. 3, and FIG. 5 is a configuration diagram of a differential protection circuit showing another conventional example. 1 …… Transformer, 2a ～ 2c, 3a ～ 3c …… Current transformer 4 …… Microcomputer 5a ～ 5c …… Ratio differential relay 6 …… Conversion block

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 54-76949 (JP, A) JP 58-186330 (JP, A) JP 61-26425 (JP, A) JP 59- 41114 (JP, A)

Claims (1)

[Claims] 1. The primary side A transformer whose secondary side is Δ-connected is provided on each of the primary side and the secondary side. In the protective relay device for a transformer, which protects by a ratio differential relay between the secondary side circuits of the current transformer, a vector of phase currents on the secondary side of the current transformer provided on the primary side of the transformer. And a second calculation means for multiplying each phase current vector calculated by the first calculation means by 1 / √3, and each phase current calculated by the second calculation means. A protective relay device for a transformer, wherein each of the secondary side phase currents of the current transformer provided on the secondary side of the transformer is set as an inflow current and an outflow current of a ratio differential relay, respectively.