JPH07231559A - Inner fault detector for voltage regulator - Google Patents

Abstract

PURPOSE:To detect inner fault highly accurately without lowering the detection sensitivity even when the transformation ratio (turn ratio) of a transformer is altered through tap change when the inner fault of a transformer with taps is detected using a ratio differential relay. CONSTITUTION:The constant N for matching the primary and secondary currents of a transformer providing an input to a ratio differential relay 2 has been fixed conventionally to the intermediate value of the switching width of a current transformation ratio. In the inventive detector, the matching constant N is switched automatically to a value suitable to the transformation ratio upon switching F the transformation ratio n1-nm through switching taps, for example, thus matching the transformation ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal failure detecting device for a voltage regulator, and more particularly to an internal failure detecting device for a voltage regulator which adjusts a voltage by changing a transformation ratio between a primary side and a secondary side.

[0002]

2. Description of the Related Art In a load voltage regulator, such as a load tap change transformer, a power transformer with a tap, or an induction voltage regulator, which adjusts the voltage by changing the transformation ratio between the primary side and the secondary side, BACKGROUND ART It has been practiced to detect a primary side current and a secondary side current and detect an internal fault from the difference current. In this case, generally, the primary current and the secondary current are matched by the change ratio (transformation ratio) of the center tap. Thus, the lowest or highest tap maximizes the current transformer secondary current imbalance. Therefore, the ratio characteristic of the ratio differential relay is set so as not to operate with this maximum imbalance.

FIG. 2 is a conventional explanatory view using a ratio differential relay. 1 is a protected transformer, and CT ₁ and CT ₂ are current transformers provided on the primary side and secondary side of the transformer 1, respectively. The device 2 is a ratio differential relay and is composed of current detecting elements A, B, and C. The secondary sides of both current transformers CT ₁ and CT ₂ are connected to current detection elements A and C and B and C, respectively, and the currents flowing through both current detection elements A and B are taken into current detection element C, and the difference current Detect I _d .

In the figure, X is the primary current of the current transformer CT ₁ received on the primary side of the transformer 1, and Y is the primary current of the current transformer CT ₂ provided on the secondary side of the transformer 1. Is shown.

In the ratio differential relay 2, the calculation shown in FIG. 3 is performed to determine whether the relay is operating or not.

In FIG. 3, I ₁ and I ₂ are currents on the secondary side of the current transformers CT ₁ and CT ₂ , respectively, and either one of these currents, in this example, the current on the I ₂ side is changed in step S _1. I ₂ (Y / XN) is calculated for ratio matching, and a matching current I ₂ ′ is obtained. It should be noted that N is a matching coefficient, which is generally a current ratio (transformation ratio) of the tap center value of the transformer 1.

Next, in step S ₂ , the difference between the currents I ₁ and I ₂ ′, I _X, is obtained, and in step S ₃ , the ratio is discriminated and compared with a preset setting ratio, setting ratio ≦ (I _X / I _X /
In the case of I ₂ ′), the ratio differential relay 2 operates and the current transformer CT ₁
Detect faults inside the transformer, including faults between CT and CT ₂ .

[0008]

As described above, in the load voltage regulator by switching the taps or the like, when the taps are switched, the transformation ratio (transformation ratio) of the transformer winding is changed. Matching is performed with a transformation ratio, and the matching coefficient N is fixed. Therefore, the unbalance is maximum at the lowest or highest tap, so the ratio ratio of a ratio differential relay must not operate at this maximum unbalance current, which makes the ratio differential relay extremely sensitive to operation. It was low. Further, increasing this sensitivity may cause malfunction.

In view of the above points, it is an object of the present invention to provide an internal failure detection device of this kind that operates with high sensitivity even when the transformation ratio is switched, without lowering the sensitivity.

[0010]

In the present invention, the means for solving the above-mentioned problems is one of the protected voltage adjusting devices.
The currents on the secondary side and the secondary side are detected, one of the detected currents is matched with a matching constant based on the transformation ratio of the voltage regulator, the difference between the matched current and the other detected current is obtained, and the difference is calculated. In a failure detection device equipped with a ratio differential relay that operates when the ratio between the current and the detected current becomes equal to or greater than a set ratio, the matching constant is changed to a change ratio of the voltage adjustment device. Sometimes, in conjunction with this, the constant is changed to a constant that matches the transformation ratio, and even if the transformation ratio changes, an error in the matching constant does not occur.

[0011]

The matching coefficients n ₁ , n ₂ ... N _m are set in accordance with the transformation ratio of the protected voltage adjusting device to match the changed transformation ratio, and the transformation ratio of the protected voltage adjusting device is switched. Then, a matching coefficient that matches the transformation ratio is automatically selected, and this is used as a matching constant.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. Figure 1 is a flow diagram of one embodiment of the present invention, although the step S ₁ to S ₃ are the same as the conventional example, the N value of the matching constant, in accordance with the transformation ratio to be switched by the tap switching (transformation ratio) It is designed to be switched.

That is, since the tap value and the transformation ratio (transformation ratio) of the transformer 1 are determined for each tap, the transformation ratio for each tap is set in advance and the current tap from the transformer 1 is set. The value is fetched, which tap value is discriminated, and the matching constant N is determined based on the transformation ratio matching the tap. For example, if the tap value is 1, the transformation ratio is n
₁ , the transformation ratio when the tap value is 2 is n ₂ , and the transformation ratio when the tap value is m is n _m , the matching constant N in step S ₁
change.

Specifically, as shown in FIG. 1, the tap switching signal T _P of the transformer 1 is input, the current tap value is discriminated in step S _O , and the discriminated matching constant signal is output in step S _O. Input ₁ and change the matching constant N in step S ₁ . For example, when the tap value is _2, the matching constant N at the current transformation ratio n ₂ is obtained.

As described above, when the taps of the transformer are switched, the matching constant is changed in association with the tap switching, so that the primary current and the secondary current are always properly matched, and the taps are switched. The imbalance no longer occurs.

The voltage adjusting device switched by the tap has been described above, but the same applies to the induction voltage adjusting device.

[0017]

As described above, according to the present invention, since the matching constant is automatically switched in association with the change of the transformation ratio of the transformer, the matching constant always becomes a constant that matches the transformation ratio, and the minimum or Even the highest tap will not carry an unbalanced current. Therefore, since the sensitivity of the ratio differential relay can be increased, the internal failure of the protected voltage adjusting device can be detected with high sensitivity and precision.

[Brief description of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention.

FIG. 2 is a basic circuit diagram for detecting an internal failure of a transformer.

FIG. 3 is a flowchart of a conventional example of detecting an internal failure of a transformer.

[Explanation of symbols]

1 ... Transformer 2 ... Ratio differential relay CT ₁ ... Transformer primary side current transformer CT ₂ ... Transformer secondary side current transformer I ₁ ... Current transformer CT ₁ secondary current I ₂ ... primary current Y ... primary current N ... constants for matching current transformer CT ₂ of the current transformer CT ₂ of the secondary current X ... current transformer CT ₁

Claims (1)

[Claims] 1. A current on the primary side and a secondary side of a protected voltage adjusting device is detected, and one of these detected currents is matched with a matching constant according to a transformation ratio of the voltage adjusting device, and this matched current In the failure detection device including a ratio differential relay that operates when the difference between the other detected current and the difference current and the detected current becomes a set ratio or higher, An internal failure detection device for a voltage regulator, wherein the constant is changed to a constant that matches the transformation ratio when the transformation ratio of the regulator is switched.