JPH07184317A - Ratio differential protective relay - Google Patents

Abstract

PURPOSE:To block erroneous output from a ratio differential protective relay by making a decision that a fault has not occurred but an exciting surge current has entered when an input current contains the second harmonic by a predetermined amount or more. CONSTITUTION:The differential current DELTAI between the primary and secondary currents of a transformer is detected by a differential current detecting element 8 and when it is higher than a set data, a differential current operation decision element 11 delivers an output. When the ratio 2f/1f between the basic wave (1f) detected by a basic wave detecting element 10 and the second harmonic (2f) detected by a second harmonic detecting element 9 exceeds a predetermined value, a signal is delivered to a 2f operation memory 15. The memory 15 stores the signal until the outputs from both elements 12, 11 are turned OFF. When the element 11 is operating and no operation is stored in the memory 15, an output decision element 14 delivers an operation signal for a ratio differential protective relay.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ratio differential relay device used for detecting an internal short circuit accident of a transformer in a power system.

[0002]

2. Description of the Related Art Conventionally, a ratio differential protection relay device as shown in FIG. 4 has been used as a device for protecting a circuit by detecting an internal short circuit accident of a transformer in a power system.

In this ratio differential protection relay device, an instrument current transformer 2 and a circuit breaker 3 are provided on the primary side of the transformer 1, and an instrument current transformer 4 and a circuit breaker 5 are provided on the secondary side. , The current outputs of the current transformers 2 and 4 on both sides are connected to the ratio differential relay 6, and the current I flowing to the current transformers 2 and 4 due to an internal short circuit of the transformer 1 or the like. ₁ and I ₂
When the difference current value and the difference current ratio between them become equal to or more than the set values, the ratio differential relay 6 operates to break the circuit breakers 3 and 5 to protect the circuit.

FIG. 5 is a block diagram of a conventional ratio differential protection relay device. As shown in the figure, the primary and secondary currents I ₁ and I ₂ of the transformer 1 are input to the ratio differential protection relay device 6 via the instrument current transformers 2 and 4. . The input currents I ₁ and I ₂ are converted into digital values by the analog / digital conversion element 7, sampled at regular intervals, and the difference current detection element 8, the fundamental wave detection element 10 and the first harmonic detection element 9 are sampled.
Sent to each of the.

In the differential current detecting element 8, the input currents I ₁ and I ₂
The ratio value of the absolute value of the difference current and the current value of is calculated.

The fundamental wave detecting element 10 and the second harmonic detecting element 9 are digitally filtered to obtain the current values 1f and 2f of the respective frequency components.

The calculation processing of the difference current detection element 8, the fundamental wave detection element 10, and the second harmonic detection element 9 is executed at regular intervals, and the result (calculated value) is the difference current operation determination element 11,
It is sent to each of the 2f motion determining elements 12.

The differential current operation determination element 11 compares the preset data from the preset set value storage element 13 with the differential current data and the ratio data from the differential current detection element 8 to calculate the difference current value and the ratio value. When both are larger than the respective set values, the operation output is sent to the output determination element 14. Two
In the f operation determination element 12, the ratio of the current value of each frequency component included in each of the input currents I ₁ and I ₂ detected by the fundamental wave detection element 10 and the second harmonic detection element 9 is calculated, The content ratio of the second harmonic to the fundamental wave is calculated and
When the harmonic content exceeds a preset constant value (2
f / 1f ≧ K) The operation output is sent to the output determination element 14.

The output determination element 14 is configured to execute output with the ratio differential protection relay device when there is an operation output from the differential current operation determination element 11 and no operation output from the 2f operation determination element 12. ing.

That is, when the second harmonic component contained in the input current exceeds a certain value, the circuit breaker 3 on the power source side is turned on by applying an action to suppress the output, and the power source is applied to the transformer 1. At that time, even if the inrush current flows only on the power source side of the transformer due to the iron core saturation of the transformer 1 and the difference current detecting element operates, the ratio difference due to the second harmonic component included in the inrush current is large. The purpose is to prevent malfunction of the dynamic protection relay device.

[0011]

By the way, the above-described transformer inrush current and the fundamental wave and the second harmonic contained in this current are attenuated with the passage of time, but they are attenuated while maintaining a constant content rate. Instead, the content rate of the second harmonic generally decreases with the passage of time. Therefore, if the content rate of the second harmonic is quickly attenuated below the detection value before the differential current value falls below the operation setting value, there is a danger that the suppression of the operation output of the ratio differential protection relay will not be able to act and malfunction will occur. There are also actual examples of malfunctions.

Next, the problem of the conventional circuit will be described with reference to the attenuation chart of the transformer inrush current of FIG.

In FIG. 6, (a) is a decay chart of the exciting inrush current flowing when the power source is applied to the transformer, and shows that the current decays as shown by the broken line with the passage of time t.

(B) is an attenuation chart of the difference current between the input currents I ₁ and I ₂ calculated by the exciting inrush current flowing when the power source is applied to the transformer, which is shown in the same time series as (a). The inrush current is one of the voltage application side of the transformer (I ₁
Or I ₂ ), so that all of them have a difference current (ΔI)
Becomes

Further, a large current of 8 to 10 times the rated current of the transformer flows as the exciting inrush current.

[0016] On the other hand, the differential current ([Delta] I) operation setting value is usually about 30% general transformer rated current, the transformer between difference current ([Delta] I) element operation from the time of voltage application to t _a in It shows that you do.

(C) shows an attenuation chart of the content rate of the second harmonic (2f) with respect to the fundamental wave (1f) contained in the transformer inrush current, which is expressed in the same time series as (a). There is. Further, it is shown that this 2f content rate becomes less than or equal to the detected value of the 2f content rate t _B after the inrush current flows when a voltage is applied to the transformer.

As described in the block diagram, the ratio differential protection relay device is configured to output when the differential current (ΔI) element is operating and the second harmonic (2f) detecting element is not operating. However, according to such a configuration, FIG.
If such is 2f content detected as shown by (c) to return faster t _a time duration only operation output -t _b shown in (d) is performed.

As described above, there is a risk that the transformer malfunctions in a normal state in which a voltage is applied to the transformer and all the equipment in operation is stopped.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a ratio differential protection relay device capable of detecting at a high speed without causing a malfunction due to an exciting inrush current when a transformer is turned on. It is in.

[0021]

DISCLOSURE OF THE INVENTION The ratio actuated protective relay device of the present invention obtains a differential current between a primary input current and a secondary input current of a transformer and detects that the differential current is equal to or greater than a set value. Difference current detecting means for determining the value of the fundamental wave component included in the primary input current and the secondary input current, and the value of the second harmonic component included in the primary input current and the secondary input current The second harmonic detecting means for obtaining and the ratio of the second harmonic to the fundamental wave is obtained from the detection values of these detecting means,
By storing the output from the second harmonic operation determination means that produces an output when this ratio is equal to or greater than a predetermined set value and the second harmonic operation determination means, the operation signal of the differential current detection means disappears. Second harmonic operation storage means for releasing this storage, and output determination means for determining a no-accident state when the second harmonic operation storage means is in the stored state during operation of the differential current detection means are provided. And Further, the ratio operation protection relay device according to claim 2 sequentially stores the difference current between the primary input current and the secondary input current of the transformer, which is obtained in a predetermined period, and sequentially stores the difference current in advance. The differential current increase detection means is provided as a second harmonic operation storage means by performing a comparison operation between the current value and the current difference current value to determine that the differential current value has increased and producing an output. It is characterized in that the memory is also canceled by the output of. Further, the ratio operation protection relay device according to claim 3 obtains a difference current between the primary input current and the secondary input current of the transformer, and detects a difference current which is equal to or more than a set value. Means and
A fundamental wave detecting means for obtaining a value of a fundamental wave component contained in the primary input current and the secondary input current, and a second harmonic detection for obtaining a value of a second harmonic wave component contained in the primary input current and the secondary input current Means, the ratio of the second harmonic to the fundamental wave is obtained from the detection values of these detecting means, and the second harmonic operation determining means that produces an output when the ratio is equal to or greater than a preset value, and the second harmonic OFF-delay means for delaying the return of the operation signal from the operation-judging means by a predetermined time, and output-judging means for judging the no-accident state when the OFF-delay means is in delay when the difference current detecting means is operating. When,
Is provided.

[0022]

In the ratio actuation protection relay device of the present invention, the differential current between the primary input current and the secondary input current of the transformer is calculated, and it is detected that the differential current is equal to or greater than the set value, and the primary input current is detected. And the value of the fundamental wave component contained in the secondary input current, the value of the second harmonic component contained in the primary input current and the secondary input current, and the second harmonic relative to the fundamental wave from these detected values. The ratio of the waves is calculated, and when the ratio is equal to or more than a predetermined set value, an output is generated, the output from the second harmonic operation determination means is stored, and the operation signal of the differential current detection means disappears. If the memory is released and the second harmonic operation memory means is in the memory state when the difference current detecting means is operating, it is determined that there is no accident. Further, in the ratio operation protection relay device according to claim 2, the difference current between the primary input current and the secondary input current of the transformer, which is obtained in a predetermined cycle, is sequentially stored, and the previously obtained differential difference is stored. A comparison calculation between the current value and the current difference current value is performed, it is determined that the difference current value has increased, an output is generated, and storage is also performed by the output of the difference current increase detection means as the second harmonic operation storage means. To release. Further, in the ratio operation protection relay device according to claim 3, the differential current between the primary input current and the secondary input current of the transformer is obtained, and it is detected that the differential current is equal to or more than a set value, and the primary current is detected. The value of the fundamental wave component contained in the input current and the secondary input current is obtained, and the value of the second harmonic component contained in the primary input current and the secondary input current is obtained. The ratio of the two harmonics is obtained, and when the ratio is equal to or more than a predetermined set value, an output is generated, and the return of the operation signal from the second harmonic operation determination means is delayed by a predetermined time to detect the difference current. When the off-delay means is being delayed during operation of the means, it is determined that there is no accident.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the ratio actuation protection relay device of the present invention will be described. In FIG. 1, reference numeral 8 denotes a differential current and a differential current ratio between the primary input current and the secondary input current of the transformer,
Difference current detecting means for detecting that the difference current and the high current ratio are both set values or more, 10 is a fundamental wave detecting means for obtaining a value of a fundamental wave component contained in the primary input current and the secondary input current, 9 Is the second harmonic detecting means for obtaining the value of the second harmonic component contained in the primary input current and the secondary input current, and 12 is obtained by the fundamental wave detecting means 10 and the second harmonic detecting means 9, respectively. Second harmonic operation determining means for obtaining the ratio of the second harmonic to the fundamental wave from the value and detecting that the ratio is equal to or greater than a preset value, and 15 for the second harmonic operation determining means 12. Second harmonic operation storage means for storing the output and resetting this storage when the operation signals of both the differential current detection means 9 and the second harmonic operation determination means 12 disappear.
Reference numeral 14 is an output determination means for outputting an operation signal when the difference current detection means 8 is operating and the operation of the second harmonic operation storage means 15 is extinguished, and FIG. 2 is described in claim 2. Fig. 16 shows the configuration diagram of the ratio operation protection relay device, 16 stores the differential current between the primary input current and the secondary input current of the transformer, and the previous differential current value obtained previously and the current differential current obtained this time The difference current increase detecting means for judging the increase of the difference current value by performing the value comparison operation, and 15a indicates that the operation signal of the second harmonic operation judging means 12 has disappeared and the difference current detecting means 11 has When the operation signal is output, or the difference current increase detection means 16
Is a second harmonic operation memory release function that releases the operation memory when is operated. FIG. 3 is a block diagram of the ratio actuation protection relay device according to the third aspect of the present invention, in which the second harmonic operation detection 17 delays the return of the operation signal from the second harmonic operation determination means by a predetermined time. It is an off-delay means.

That is, in the present embodiment, the difference current between the primary and secondary input currents of the transformer and the ratio thereof are obtained, and the difference current detecting means 8 which operates when both the difference current and the difference current ratio become equal to or more than the set values. , A fundamental wave detecting means 10 for obtaining the value of the fundamental wave component included in the primary and secondary input currents, a second harmonic wave detecting means 9 for obtaining the value of the second harmonic wave component, and these fundamental wave detecting means 10 and the second. A second harmonic operation determining means that operates when the content rate of the second harmonic with respect to the fundamental wave is obtained from the value obtained by the harmonic detection means 9 and the content rate of the second harmonic becomes a certain value or more. The second harmonic operation storing means 15 for storing the operation of the second harmonic operation determining means 12 until the difference current detecting means 8 is restored, and the second current operation storing means 15 for operating the second harmonic operation When the storage means 15 is restored (when not operating), the ratio differential protection relay According to the embodiment of the present invention, the differential current between the primary and secondary input currents of the transformer is calculated, and this value is stored and calculated last time. The difference current increase detection means 16 for detecting that the difference current obtained this time has increased with respect to the difference current, and the difference current detection means restores the operation memory of the second harmonic operation storage means 15 or The difference current increase detecting means is configured to continue until it operates. In the embodiment of claim 3, instead of the second harmonic operation storing means 15, a second harmonic operation output off-delay means 17 is provided. It is characterized in that the recovery of the operation output from the second harmonic detection means 9 is delayed by a predetermined time.

With the above-mentioned configuration, it is detected that the transformer inrush current contains the second harmonic of a certain value or more, and the second harmonic detection signal is stored and stored. When the difference current value becomes equal to or less than the operation difference current set value, the second harmonic detection signal is released from the memory, and if there is this memory, the operation of the ratio differential protection relay device is blocked.

With this configuration, even if the difference current value of the transformer exciting inrush current and the attenuation characteristic of the second harmonic content rate are different and the second harmonic content rate is earlier than the detected value, the ratio is obtained. It is possible to prevent malfunction of the differential protection relay device.

According to the second aspect of the present invention, it is detected that the transformer inrush current contains the second harmonic wave having a constant value or more, the detected signal is stored, and the sampling is performed at regular intervals. The difference current value is stored, the previous difference current value is compared with the current difference current value, and when the difference current detection value of the current value increases by a certain value or more with respect to the previous value, the second harmonic detection storage is canceled. To do. Further, similarly to the first aspect, the second harmonic detection memory is also canceled when the differential current value becomes equal to or less than the operating differential current set value.

According to this structure, in the case of a normal exciting inrush current, in the same manner as in the above-mentioned claim 1, when the second harmonic content rate is earlier than the detected value, the ratio differential protection relay is used. If the malfunction of the device can be prevented, a new accident occurs while the operation output is blocked, the difference current increases, and the content rate of the second harmonic is below the detected value, the second harmonic detection memory is promptly released. Since it is canceled, it becomes possible to respond to an accident immediately after applying a voltage to the transformer.

Further, in the third aspect of the present invention, it is detected that the transformer exciting inrush current contains the second harmonic of a certain value or more, and the detection signal is delayed by a certain time. Let Further, it is configured to prevent the output of the operation output of the ratio differential protection relay device even if the differential current is detected by the detection signal. With such a configuration, even if the second harmonic content rate detection is restored before the differential current detection operation is restored in the normal transformer excitation inrush current attenuation transient, the ratio differential protection relay device is protected by the restoration delay time. It is possible to prevent malfunction.

FIG. 1 is a block diagram of a ratio differential protection relay device 18 according to one embodiment of the present invention, which is applied in place of the ratio differential protection relay device 6 in the power system shown in FIG. The description of the system is the same as the description of FIG. 4 of the prior art.

Further, the conventional ratio differential protection relay device 6 of FIG.
The elements denoted by the same reference numerals have the same function in the same manner.

The ratio differential protection relay device 18 of FIG. 1 is connected to the secondary side of the transformer current transformers 2 and 4 on the primary side and the secondary side of the transformer 1 of FIG. 4 and its secondary current I ₁ , I ₂ is incorporated into the ratio differential protection relay 18.

Each of the input currents I ₁ and I ₂ is converted into a digital value by the analog / digital conversion element 7, sampled at regular intervals, and the difference current (ΔI) detection element 8, the fundamental wave (1f) detection element 10, Second harmonic (2f) detection element 9
The sampling data is read in each of.

The difference current (ΔI) detecting element 8 obtains the absolute value of the difference current between the input currents I ₁ and I ₂ and the difference current ratio at every constant sampling period, and the data of the calculation result is the difference current (ΔI) operation. It is read by the judgment element 11.

The fundamental wave (1f) detecting element 10 and the second harmonic (2f) detecting element 9 are digitally filtered at constant sampling intervals to obtain the current values 1f and 2f of the respective frequency components. Calculation result is 2
f It is read by the motion determination element 12.

In the difference current (ΔI) operation determination element 11, the set value storage element 13 preset for each constant sampling period is used.
And the difference current (ΔI) data from the differential current (ΔI) detection element 8 are compared to calculate the difference current (Δ) value and the difference current ratio value. When both are larger than the respective set values, the difference current (Δ
I) Send the operation output to the output determination element 14 and the 2f operation storage element 15.

In the 2f operation determination element 12, the fundamental wave (1f) detection element 10 and the second harmonic (2
f) Read the data of the respective frequency components contained in each of the input currents I ₁ and I ₂ obtained by the detection element 9, and calculate the content rate of the second harmonic (2f) with respect to the fundamental wave (1f). When the calculation result 2f / 1f exceeds a preset value K (2f / 1f ≧ K), the 2f detection operation output is sent to the 2f operation storage element 15.

In the 2f operation storage element 15, the judgment results of the difference current (ΔI) operation judgment element 11 and the 2f operation judgment element 12 are read in every constant sampling period, and the operation output of the 2f operation judgment element 12 is stored. . Further, this memory is erased when both the operation output of the 2f operation determination element 12 and the difference current (ΔI) operation determination element 11 are turned off. The stored data is sent to the output determination element 14.

The output determination element 14 reads the operation output of the difference current (ΔI) operation determination element 11 and the 2f operation storage element 15 at regular intervals, and the difference current (ΔI) operation determination element 11 is operating to perform the 2f operation. When there is no operation memory of the memory element 15, the operation signal of the ratio differential protection relay device is output.

That is, when the second harmonic is included in the input current more than a certain value, it is not an accident, but it is determined that it is an exciting inrush current that normally flows when a voltage is applied to the transformer, and the ratio differential protection is performed. It prevents the output of the operation signal of the relay device, and the content ratio of the second harmonic becomes earlier than the detection value earlier in the state of exceeding the operation value of the differential current in the decay transient of the exciting inrush current. Also, by continuing the 2f operation storage, it becomes possible to prevent an erroneous output from the ratio differential protection relay device, and it is possible to improve the stabilization of the power supply of the power system.

FIG. 2 is a block diagram of a ratio differential protection relay device 19 according to another embodiment of the present invention, which is applied in place of the ratio differential protection relay device 6 in the power system shown in FIG.
The description of the power system is the same as the description of FIG. 4 of the related art.

Further, the conventional ratio differential protection relay device 6 of FIG.
The elements denoted by the same reference numerals have the same function in the same manner.

The ratio differential protection relay device 19 of FIG. 2 is connected to the secondary side of the transformer current transformers 2 and 4 on the primary side and the secondary side of the transformer 1 of FIG. 4, and its secondary current I ₁ , I ₂ have been incorporated into the ratio differential protection relay 19.

Each of the input currents I ₁ and I ₂ is converted into a digital value by the analog / digital conversion element 7, sampled at regular intervals, and the difference current (ΔI) detection element 8, the fundamental wave (1f) detection element 10, Second harmonic (2f) detection element 9
Sampling data is read by each of the differential current (ΔI) rapid increase detection elements 16.

In the difference current (ΔI) detecting element 8, the absolute value of the difference current between the input currents I ₁ and I ₂ and the difference current ratio are obtained in every constant sampling period, and the data of the calculation result is the difference current (ΔI) operation. It is read by the judgment element 11.

The fundamental wave (1f) detecting element 10 and the second harmonic (2f) detecting element 9 are digitally filtered at constant sampling intervals to obtain current values 1f and 2f of the respective frequency components. Calculation result is 2
f It is read by the motion determination element 12.

In the difference current (ΔI) operation determination element 11, the set value storage element 13 preset for each constant sampling period is used.
And the difference current (ΔI) data from the differential current (ΔI) detecting element 8 and the difference current ratio data are compared to calculate both the difference current (Δ) value and the difference current ratio value. Are both larger than the respective set values, the difference current (ΔI) operation output is output as the output determination element 14 and the 2f operation storage element.
Send to 15.

In the 2f motion determining element 12, the fundamental wave (1f) detecting element 10 and the second harmonic (2
f) Read the data of the respective frequency components contained in each of the input currents I ₁ and I ₂ obtained by the detection element 9, and calculate the content rate of the second harmonic (2f) with respect to the fundamental wave (1f). When the calculation result 2f / 1f exceeds a preset value K (2f / 1f ≧ K), the 2f detection operation output is sent to the 2f operation storage element 15.

The difference current (ΔI) sudden increase detection element 16 obtains the absolute value of the difference current between the input currents I ₁ and I ₂ at every constant sampling period, stores this data in a single memory, and stores it as the previously calculated data. When the difference current (ΔI) value obtained this time is larger than the previously obtained difference current (ΔI) value by a predetermined value by comparing with the calculated data this time, the difference current (ΔI) suddenly increases. The detection output is sent to the 2f operation storage element 15.

In the 2f operation storage element 15, the difference current (ΔI) operation determination element 11 and the 2f operation storage element 15 are arranged at regular sampling intervals.
The motion determination element 12 further reads the determination results of the ΔI sudden increase detection element 16, and stores the motion output of the 2f motion determination element 12. Also, this memory is erased when the operation output of the 2f operation determination element 12 is off and both the operation outputs of the difference current (ΔI) operation determination element 11 and the difference current (ΔI) sudden increase detection element 16 are off. . Note that this stored data is output determination element 14
Sent to.

The output determination element 14 reads the operation output of the difference current (ΔI) operation determination element 11 and the 2f operation storage element 15 at regular intervals, and the difference current (ΔI) operation determination element 11 operates to perform the 2f operation. When there is no operation memory of the memory element 15, the operation signal of the ratio differential protection relay device is output.

That is, when the second harmonic is included in the input current at a certain value or more, it is determined that it is not the accident but the exciting inrush current that normally flows when the voltage is applied to the transformer, and the ratio differential protection relay is determined. The output signal of the electric device is blocked, and even if the content ratio of the second harmonic becomes earlier than the detection value earlier in the state of exceeding the differential current operating value in the decay transient of the exciting inrush current. By continuing the 2f operation memory, it is possible to prevent the erroneous output from the ratio differential protection relay device, and it is possible to improve the stabilization of the power supply of the power system and to apply a voltage to the transformer. If a short-circuit accident occurs immediately after that, it is possible to immediately release the 2f operation memory and obtain the operation signal of the ratio differential protection relay device, and it is possible to provide a relay device with higher reliability. Becomes

FIG. 3 is a block diagram of a ratio differential protection relay device 20 according to another embodiment of the present invention, which is applied in place of the ratio differential protection relay device 6 in the power system shown in FIG.
The description of the power system is the same as the description of FIG. 4 of the related art.

Further, the conventional ratio differential protection relay device 6 of FIG.
The elements denoted by the same reference numerals have the same function in the same manner.

The ratio differential protection relay device 20 of FIG. 3 is connected to the secondary side of the transformer current transformers 2 and 4 on the primary side and secondary side of the transformer 1 of FIG. 4, and its secondary current I ₁ , I ₂ have been incorporated into the ratio differential protection relay.

Each of the input currents I ₁ and I ₂ is converted into a digital value by the analog / digital conversion element 7, sampled at a constant cycle, and the difference current (ΔI) detection element 8, the fundamental wave (1f) detection element 10, Second harmonic (2f) detection element 9
The sampling data is read in each of.

The difference current (ΔI) detecting element 8 obtains the absolute value of the difference current between the input currents I ₁ and I ₂ and the difference current ratio at every constant sampling period, and the data of the calculation result is the difference current (ΔI) operation. It is read by the judgment element 11.

The fundamental wave (1f) detecting element 10 and the second harmonic (2f) detecting element 9 are digitally filtered at constant sampling intervals to obtain current values 1f and 2f of their respective frequency components. Calculation result is 2
f It is read by the motion determination element 12.

In the difference current (ΔI) operation determination element 11, the set value storage element 13 set in advance every constant sampling period.
And the difference current (ΔI) data from the differential current (ΔI) detecting element 8 and the difference current ratio data are compared to calculate both the difference current (Δ) value and the difference current ratio value. When both are larger than the respective set values, the difference current (ΔI) operation output is sent to the output determination element 14.

In the 2f motion determining element 12, the fundamental wave (1f) detecting element 10 and the second harmonic (2
f) Read the data of the respective frequency components contained in each of the input currents I ₁ and I ₂ obtained by the detection element 9, and calculate the content rate of the second harmonic (2f) with respect to the fundamental wave (1f). When the calculation result 2f / 1f exceeds a preset value K (2f / 1f ≧ K), the 2f detection operation output is sent to the 2f off-delay processing element 17.

The 2f off-delay processing element 17 monitors the operation output of the 2f operation determination element 12 at regular intervals to detect 2f
When the operation determination element 12 is operating, the operation output of the 2f off-delay processing element 17 is sent to the output determination element 14.

Further, the operation output of the 2f operation determination element 12 is ON.
When it changes from OFF to OFF, the output of the 2f off-delay processing element 17 which has been sent to the output determination element 14 is turned off after a predetermined time delay.

The output judgment element 14 reads the operation output of the difference current (ΔI) operation judgment element 11 and the 2f operation storage element 15 at regular intervals, and the difference current (ΔI) operation judgment element 11 is operating and 2f off. Only when the operation output of the delay processing element 17 is off, the operation signal of the ratio differential protection relay device is output.

In FIG. 6, 61 is a differential current element operation range, 62 is an operation set value, 63 is a 2f content rate detection range, 64 is a detection set value, and 65 is an output.

[0065]

According to the present invention, when the second harmonic is included in the input current at a certain value or more, it is determined that it is not the accident but the exciting inrush current that normally flows when the voltage is applied to the transformer. The output of the operating signal of the ratio differential protection relay device is blocked, and the content ratio of the second harmonic is detected earlier in the state where the differential current operating value is exceeded in the decay transient of the exciting inrush current. Even if it is less than the value, delaying the return of the 2f operation signal for a predetermined time can prevent erroneous output from the ratio differential protection relay device, thus improving the stabilization of the power supply of the power system. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a ratio differential protection relay device of the present invention.

FIG. 2 is a block diagram showing another embodiment of the ratio differential protection relay device of the present invention.

FIG. 3 is a block diagram showing another embodiment of the ratio differential protection relay device of the present invention.

FIG. 4 is a power system configuration diagram to which a conventional power system and the ratio differential protection relay device of the present invention are applied.

5 is a block diagram of the conventional ratio differential protection relay device of FIG. 4;

6A and 6B are a chart diagram for explaining the operation of the conventional ratio differential protection relay device of FIG. 5 and a decay chart diagram of a transformer excitation inrush current.

[Explanation of symbols]

 7 ... Analog / digital conversion element 8 ... Differential current (ΔI) detection element 9 ... Second harmonic detection element 10 ... Fundamental wave detection element 11 ... Differential current (ΔI) operation determination element 12 ... Second harmonic operation determination element 13 Operating value storage element 14 Output determination element 15 Second harmonic operation storage element 16 Differential current (ΔI) rapid increase detection element 17 2f Off-delay processing element

Claims (3)

[Claims] 1. A differential current detecting means for obtaining a differential current between a primary input current and a secondary input current of a transformer and detecting that the differential current is equal to or more than a set value, and the primary input current and the secondary input current. Fundamental wave detecting means for obtaining the value of the fundamental wave component contained in the input current, second harmonic detecting means for obtaining the value of the second harmonic wave component contained in the primary input current and the secondary input current, and these detecting means From the detected value of the means, the ratio of the second harmonic to the fundamental wave is obtained, and when the ratio is equal to or more than a predetermined set value, the second harmonic operation determining means that produces an output, and the second harmonic operation determining means The second harmonic operation storage means for storing the output of the differential current detection means and canceling the storage when the operation signal of the differential current detection means disappears; and the second harmonic operation storage means for operating the difference current detection means. If the memory status Ratio operating protective relay device formed by including an output determining unit, the for. 2. A differential current between a primary input current and a secondary input current of a transformer, which is obtained in a predetermined synchronization, is sequentially stored, and a comparison calculation between a previously obtained differential current value and a current differential current value is performed. And a difference current increase detection means for generating an output by determining that the difference current value has increased, and as a second harmonic operation storage means, the storage is also canceled by the output of the difference current increase detection means. A ratio actuated protective relay device according to claim 1, characterized in that there is. 3. A difference current detecting means for obtaining a difference current between a primary input current and a secondary input current of a transformer and detecting that the difference current is a set value or more, and the primary input current and the secondary input current. Fundamental wave detecting means for obtaining the value of the fundamental wave component contained in the input current, second harmonic detecting means for obtaining the value of the second harmonic wave component contained in the primary input current and the secondary input current, and these detecting means From the detected value of the means, the ratio of the second harmonic to the fundamental wave is obtained, and when the ratio is equal to or more than a predetermined set value, the second harmonic operation determining means that produces an output, and the second harmonic operation determining means When the off-delay means and the difference current detection means are operated by delaying the return of the operation signal of a predetermined time, the off-delay means, when the delay is in progress, an output determination means for determining an accident-free state,
A ratio actuation protection relay device comprising.