JPH09260167A - Transformer for capacitor-type instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor-type instrument which can prevent a voltage vibration produced at the time of restoration after secondary short circuiting during test of resonance with iron. SOLUTION: An inhibitor 7 of resonance with iron comprising of a series circuit of a saturatable reactor 8 and a resistor 9 is parallelly connected to the secondary side of a transformer 4. A series circuit of a filter capacitor 21 and an adjustment reactor 22 is serially connected to the saturatable reactor 8. The saturatable reactor 8 is not saturated for a voltage of 1.2 times or less the rated voltage. The capacitance of a filter capacitor 21, the inductance of the adjustment reactor 22 and the inductance of the saturatable reactor 8 in non saturated state are set so that a parallel circuit of a series circuit of the filter capacitor 21 and the adjustment reactor 22 and a saturatable reactor 8 in non saturated state may satisfy the resonance condition at a rated frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor type transformer for a meter, which is connected to a bus bar or a line of a substation or the like to supply a voltage to a meter or a relay.

[0002]

2. Description of the Related Art A transformer for a capacitor type instrument (hereinafter referred to as CVT)
Also called. ) Is provided with a main capacitor, a voltage dividing capacitor connected in series to the main capacitor, and a transformer in which the voltage across the voltage dividing capacitor is input to the primary side. A voltage of a bus bar or a line is applied to both ends of a series circuit of.

FIG. 2 shows an example of a conventional CVT circuit configuration. In FIG. 2, 1 is a power supply, 2 is a main capacitor connected to a bus or line whose one end is connected to the power supply 1, and 3
Is a voltage dividing capacitor connected in series with the main capacitor by connecting one end to the other end of the main capacitor 2,
The other end of the voltage dividing capacitor 3 is grounded. One end of the primary coil of the transformer 4 is connected to the non-grounded terminal of the voltage dividing capacitor, and the other end of the primary coil is connected to the grounded terminal of the voltage dividing capacitor through the resonance reactor 5.
A ball gap 6 is connected to both ends of the reactor 5, and a ferroresonance suppressing device 7 is connected to both ends of the secondary coil of the transformer 4. The iron resonance suppression device 7 is composed of a series circuit of a saturable reactor 8 and a resistor 9.

In the CVT shown in FIG. 2, the transformer 4
The resonance reactor 5, the ball gap 6, the saturable reactor 8 and the resistor 9 are housed in a common tank (not shown) filled with insulating oil, and the main capacitor 2 and the voltage dividing capacitor 3 are provided above the tank. And are supported.

[0005] In the capacitor type voltage transformer, when an electric shock such as a priming of the primary voltage, a short circuit on the secondary side, or a recovery is given, the capacitance of the voltage dividing capacitor and the nonlinear reactance of the transformer are reduced. Due to this, resonance of subharmonic (ferro-resonance) such as 1/3 harmonic or 1/5 harmonic of the power supply frequency may occur. CVT shown in FIG.
In order to improve the nonlinearity of the iron core by designing the rated magnetic flux density Bm of the iron core of the transformer to be ⅕ of the saturation magnetic flux density, the iron resonance suppressing device 7 is provided on the secondary side of the transformer.
To suppress the occurrence of ferroresonance.

The iron resonance suppression device 7 saturates the saturable reactor 8 when the condition in which the transformer is saturated by electric shock and the resonance of subharmonic is attempted to be satisfied, and the saturable reactor 8 is saturated with respect to the secondary coil of the transformer. Parallel shunts are formed, and current is passed through the shunts to consume energy in the resistor 9 and suppress the occurrence of subharmonic resonance.

The CVT is subjected to the ferroresonance test specified by the IEC-186 standard. In this ferroresonance test, a test voltage obtained by multiplying the rated voltage by a specified voltage coefficient (usually 1.5 times the rated voltage) is applied to both ends of a voltage dividing circuit consisting of a main capacitor and a voltage dividing capacitor. Therefore, it is specified that there is no voltage fluctuation that lasts for 2 seconds or more when the secondary short circuit recovery is performed 10 times.

In the CVT shown in FIG. 2, although the iron resonance suppressing device 7 can suppress the iron resonance phenomenon that generates a high voltage, in the iron resonance test, when the secondary side of the transformer is restored from a short circuit. It is difficult to suppress the fluctuation of a relatively low voltage (when the secondary side of the transformer is opened) (a voltage that is 1.2 times or less the normal rated voltage) that occurs, and the voltage fluctuates for 2 seconds or more when the secondary short circuit recovers. In some cases, it was not possible to satisfy the IEC standard that does not occur.

FIG. 3 shows a circuit configuration of another conventional CVT. In this CVT, a filter composed of a parallel circuit of a filter capacitor 10 and a filter reactor 11 and a series circuit of a resistor 12 is shown. The circuit is connected in parallel to the ferroresonance suppressor 7. The other points are the same as the CVT shown in FIG.

In the CVT shown in FIG. 3, the transformer 4
The resonance reactor 5, the ball gap 6, the saturable reactor 8, the resistor 9, the filter capacitor 10, the filter reactor 11 and the resistor 12 are housed in a common tank (not shown), and above the tank. The main capacitor 2 and the voltage dividing capacitor 3 are supported.

In the CVT of FIG. 3, the filter capacitor 10 and the filter reactor 11 are set to satisfy the parallel resonance condition with respect to the rated frequency, and the capacitor 10 and the reactor 11 and the resistor 12 are rated frequency. Constitutes a bandpass filter for passing.

As shown in FIG. 3, when a filter circuit is connected in parallel to the ferroresonant suppressor 7, fluctuations of the low voltage that occur when the secondary short circuit of the transformer recovers is suppressed and voltage fluctuations are reduced. be able to.

[0013]

As described above, in the CVT shown in FIG. 2, it is difficult to suppress the voltage fluctuation that occurs when the secondary short circuit of the transformer is restored.

On the other hand, in the CVT shown in FIG. 3, it is possible to reduce the fluctuation of the voltage generated at the time of recovery from the secondary short circuit of the transformer, but this CVT requires the resistor 12 in the filter circuit. It was unavoidable that the number of parts increased and the cost increased.

Further, in the CVT shown in FIG. 3, since the number of parts to be housed together with the transformer in the tank housing the transformer is large, not only the tank becomes large, but also the transformer and the iron resonance suppressing device. There is a problem in that the wiring for connecting between the filter circuit and the filter circuit is complicated and the workability of assembly is poor.

An object of the present invention is to provide a transformer for a capacitor type instrument, which is capable of suppressing fluctuation of the voltage which occurs at the time of recovery from secondary short circuit of the transformer by using fewer components than the conventional CVT. Especially.

[0017]

SUMMARY OF THE INVENTION The present invention is directed to a main capacitor, a voltage dividing capacitor connected in series with the main capacitor, and a transformer in which the voltage across the voltage dividing capacitor is input to the primary side. And a ferro-resonance suppressing device having a saturable reactor and a resistor connected in series to the saturable reactor and connected in parallel to the secondary coil of the transformer It is related to transformers for electric power.

In the present invention, the series circuit of the filter capacitor and the adjusting reactor is connected in parallel to both ends of the saturable reactor, and the saturable reactor has a secondary voltage of the transformer 1.2 times the rated voltage. It is configured not to saturate when the value is less than the value. When the saturable reactor is not saturated, the capacitance of the filter capacitor is set so that the parallel circuit of the series circuit of the filter capacitor and adjustment reactor and the saturable reactor satisfies the parallel resonance condition at the rated frequency. And the inductance of the adjusting reactor and the inductance of the saturable reactor when it is not saturated.

In the above CVT, when a ferroresonance phenomenon in which a high voltage is generated is about to occur due to an electric shock such as a secondary short circuit of a transformer, the saturable reactor is saturated, and the saturable reactor and the resistance are combined. A series circuit with the transformer forms a shunt in parallel with the secondary coil of the transformer, and a current is passed through the shunt so that energy is consumed by the resistor and the ferroresonance phenomenon is suppressed.

Further, when a low voltage fluctuation occurs at the time of recovery from the secondary short circuit of the transformer in the ferroresonance test, the saturable reactor does not saturate and the filter capacitor and the adjustment reactor are operated against the rated frequency. The resonance condition of the parallel circuit of the series circuit and the saturable reactor is satisfied. At this time, the parallel resonant circuit consisting of the series circuit of the adjusting reactor and the filter capacitor and the saturable reactor exhibits infinite impedance with respect to the rated frequency component, so the rated frequency component appearing on the secondary side of the transformer remains unchanged. It is output to the output terminal side. On the other hand, the subharmonic component appearing on the secondary side of the transformer is absorbed by the saturable reactor and the resistor that have low impedance with respect to the subharmonic component.

In the present invention, since the adjusting reactor is provided in series with the filter capacitor, the inductance of the saturable reactor required to satisfy the parallel resonance condition with respect to the rated frequency can be reduced, so that the rated voltage can be reduced. The inductance of the saturable reactor is set to be small enough to absorb most of the subharmonic components of low-voltage oscillation that is 1.2 times or less of the Can be suppressed.

In the present invention, as shown in FIG. 3, a conventional C having a filter circuit connected to the secondary side of the transformer.
Unlike the VT, it is not necessary to connect the resistor separately from the resistor of the ferroresonant suppressor, so that the number of parts can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a power supply, 2 is a main capacitor, and one end of the main capacitor 2 is connected to a bus line or line connected to the power supply 1. A voltage dividing capacitor 3 is connected in series to the main capacitor 2 by connecting one end to the other end of the main capacitor 2. The other end of the voltage dividing capacitor 3 is grounded. Reference numeral 4 is a transformer having a primary coil 4a and a secondary coil 4b, and one end of the primary coil 4a of this transformer is connected to a non-grounded side terminal of the voltage dividing capacitor 3. The other end of the primary coil of the transformer 4 is connected to the ground side terminal of the voltage dividing capacitor 3 through the resonance reactor 5, and the ball gap 6 is connected in parallel to both ends of the reactor 5. A ferro-resonance suppressing device 7 including a saturable reactor 8 and a resistor 9 connected in series to the saturable reactor 7 is provided at both ends of the secondary coil of the transformer 4.
Is connected. Output terminals t1 and t2 are drawn out from both ends of the secondary coil of the transformer.

The above construction is similar to that of the conventional CVT shown in FIG. 2, but in the present invention, the saturable reactor 8 is used.
At both ends of the filter condenser 21 and the adjustment reactor 2
Connect a series circuit with 2 in parallel. Then, when the secondary voltage of the transformer is equal to or less than 1.2 times the rated voltage, the saturable reactor 8 is prevented from being saturated, and when the saturable reactor is not saturated, adjustment is made with the filter capacitor 21. When the series circuit with the reactor 22 and the parallel circuit with the saturable reactor 8 satisfy the parallel resonance condition with respect to the rated frequency, when the capacitance of the filter capacitor 21, the inductance of the adjusting reactor 22 and the saturable reactor 8 are not saturated. And the inductance of are set.

The capacitance of the filter capacitor 21 is C1, the unsaturated inductance of the saturable reactor 8 is L1, and the inductance of the adjusting reactor 22 is L2.
, And the angular frequency of the power source 1 is ω, the parallel resonance condition is given by the following equation.

Ω (L1 + L2) = 1 / ωC1 (1) In the CVT shown in FIG. 1, the transformer 4, the resonance reactor 5, the ball gap 6, the saturable reactor 8, the resistor 9, the filter capacitor 21, and The adjusting reactor 22 and the adjusting reactor 22 are housed in a common tank (not shown) filled with insulating oil, and the main capacitor 2 and the voltage dividing capacitor 3 are supported above the tank.

When the ferroresonance test is performed on the CVT shown in FIG. 1 by the method specified in IEC, a test voltage (usually a rated primary voltage) is applied across the series circuit of the main capacitor 2 and the voltage dividing capacitor 3. Voltage of 1.5 times the voltage) is applied and the secondary side of transformer 4 is short-circuited and restored (secondary side is open)
Repeat 10 times.

When the secondary side of the transformer 4 is short-circuited, the terminal voltage of the voltage dividing capacitor 3 rises and a high voltage exceeding 1.2 times the rated voltage is generated on the secondary side of the transformer. Is about to occur. At this time, the saturable reactor 8 is saturated, and the series circuit of the saturable reactor 8 and the resistor 9 forms a shunt in parallel with the secondary coil of the transformer, and the secondary coil of the transformer is connected. Since a current flows through this shunt and energy is consumed by the resistor 9, the occurrence of a ferroresonance phenomenon that causes a high voltage is suppressed.

When the secondary short circuit of the transformer 4 is restored, the terminal voltage of the voltage dividing capacitor 3 fluctuates due to the discharge of the electric charge stored in the voltage dividing capacitor 3, and the voltage is 1.2 times or less than the rated voltage. Although voltage oscillation is about to occur, the saturable reactor 8 does not saturate at this time and the filter capacitor 21
The parallel circuit of the saturable reactor 8 and the series circuit of the adjustment reactor 22 and the saturable reactor 8 satisfies the parallel resonance condition with respect to the rated frequency, and the parallel resonance circuit exhibits an almost infinite impedance with respect to the rated frequency. The voltage of the frequency component is directly output from the output terminals t1 and t2.

On the other hand, 1/3 or 1 of the rated frequency
Since the parallel circuit does not resonate with respect to a subharmonic component such as / 5, the subharmonic component is a series circuit of the saturable reactor 8 and the resistor 9 that exhibits low impedance with respect to the subharmonic component. Absorbed by. In order to sufficiently absorb the subharmonic component, it is necessary to sufficiently reduce the unsaturated inductance of the saturable reactor 8. However, in the present invention, since the adjustment reactor 22 is provided, Since the unsaturated inductance value of the saturable reactor required to satisfy the parallel resonance condition can be made sufficiently small, most of the subharmonic components are absorbed and the secondary short circuit of the transformer is restored. The voltage fluctuation can be reduced, and the condition of the iron resonance test defined in the IEC standard can be satisfied.

Further, with the above configuration, the CV of FIG.
Since the resistor 12 required in T is not required, the number of parts can be reduced and the tank for accommodating the transformer together with the ferroresonant suppressor and the like can be prevented from becoming large.

Further, with the above structure, the wiring on the secondary side of the transformer can be simplified and the assembling workability can be improved, and the number of parts can be reduced, and the cost can be reduced. Can be achieved.

In the example shown in FIG. 1, the resonance reactor 5 is connected to the primary side of the transformer 4, but when the resonance reactor is connected to the secondary side of the transformer, or the resonance reactor is not provided. The present invention can also be applied in such cases.

In the example shown in FIG. 1, only the discharge gap 6 is connected in parallel at both ends of the resonance reactor 5, but when the discharge gap and the series circuit of the resistor are connected in parallel at both ends of the resonance reactor 5. There is also.

[0035]

As described above, according to the present invention, the series circuit of the filter capacitor and the adjusting reactor is connected in parallel to the saturable reactor of the iron resonance suppressing device, and the filter capacitor and the adjusting reactor are connected in series. Since the constant is set so that the parallel circuit of the circuit and the saturable reactor resonates up to 1.2 times the rated voltage with respect to the rated frequency, the fluctuation of the voltage when the secondary short circuit of the transformer recovers is suppressed. Therefore, there is an advantage that the voltage fluctuation can be reduced.

Further, according to the present invention, the number of parts can be reduced as compared with the conventional CVT in which the filter circuit is connected to the secondary side of the transformer, so that the transformer is combined with the ferroresonant suppressor and the like. It is possible to prevent the size of the storage tank from increasing.

Further, according to the present invention, the wiring on the secondary side of the transformer can be simplified and the assembling workability can be improved,
Combined with the fact that the number of parts can be reduced, the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration example of a transformer for a capacitor type meter according to the present invention.

FIG. 2 is a circuit diagram showing a circuit configuration of a conventional capacitor type transformer for a meter.

FIG. 3 is a circuit diagram showing a circuit configuration of another conventional capacitor type transformer for a meter.

[Explanation of symbols]

 2 Main capacitor 3 Voltage dividing capacitor 4 Transformer 7 Ferro-resonance suppressor 8 Saturable reactor 9 Resistor 21 Filter capacitor 22 Adjusting reactor

Claims (1)

[Claims] 1. A main capacitor, a voltage dividing capacitor connected in series to the main capacitor, a transformer in which the voltage across the voltage dividing capacitor is input to the primary side, a saturable reactor and the A transformer for a capacitor type instrument, comprising: a ferroresonance suppressor connected in parallel to a secondary coil of the transformer, the resistor having a resistor connected in series to a saturation reactor; A series circuit of a capacitor and an adjusting reactor is connected in parallel to both ends of the saturable reactor, and the saturable reactor is not saturated when the secondary voltage of the transformer is 1.2 times the rated voltage or less. In the state where the saturable reactor is not saturated, the parallel circuit of the series circuit of the filter capacitor and the adjusting reactor and the saturable reactor is a rated frequency. In contrast, the capacitance of the filter capacitor, the inductance of the adjusting reactor, and the unsaturated inductance of the saturable reactor are set so as to satisfy the parallel resonance condition.