JPH0884430A - Ratio differential protection relay - Google Patents

Abstract

(57) [Summary] [Object] The present invention detects a second harmonic of a current of a transformer for each of a positive component and a negative component, so that the second harmonic which is apparently lowered due to cancellation of both positive and negative components. Is reliably detected to prevent false cutoff and improve reliability. [Structure] A fundamental wave detecting means (13) detects a fundamental wave component included in the primary and secondary currents, and a second harmonic positive component detecting means (21) detects a positive component of the second harmonic. , Second
The harmonic negative component detecting means (22) detects the negative component of the second harmonic, and the component comparison detecting means (23) compares the positive component and the negative component of the second harmonic in magnitude to determine the larger component. And the content calculating means (24) detects the second component of the fundamental wave component based on the fundamental component and the component of the larger second harmonic component.
Calculating the content rate of harmonics, blocking prevention means (24, 25)
Is a ratio differential protection relay device that compares the calculated content rate with a reference content rate and prevents the breaking operation of each circuit breaker when the content rate exceeds the reference content rate.

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, and particularly to a primary side current and a secondary side current which are unbalanced. Also relates to a ratio differential protection relay device capable of preventing erroneous disconnection and improving reliability when the content rate of one of the positive and negative components of the second harmonic is high, because it is an exciting inrush current.

[0002]

2. Description of the Related Art Conventionally, in the detection of an internal short-circuit accident of a transformer in a power system, a ratio difference for judging the presence or absence of an internal short-circuit accident based on the difference current between the primary side current and the secondary side current of the transformer. Dynamic protection relays are widely used.

Such a ratio differential protection relay device obtains a difference current value and a current ratio between the primary side current and the secondary side current of the transformer, and calculates the difference current value and the current ratio. When the ratio is higher than the standard value, the internal short-circuit accident of the transformer is detected and the breaker is shut off.

However, this kind of ratio differential protection relay device determines that an accident occurs when the difference and ratio between the primary side current and the secondary side current are high, and therefore when a voltage is applied to a normal transformer. There is a problem that the exciting inrush current flowing is detected and the accident is erroneously determined to occur and the breaker is cut off.

Therefore, recently, based on the characteristic that the exciting inrush current contains a large amount of the second harmonic component, even if the primary side current and the secondary side current are unbalanced, the content rate of the second harmonic is high. The present inventor has considered a ratio differential protection relay device that prevents erroneous disconnection when it is high when it is an exciting inrush current (Japanese Patent Application No. 5-325543).

FIG. 2 is a block diagram of an electric power system to which such a ratio differential protection relay device is applied. In this ratio differential protection relay device, the first instrument current transformer 1 and the first circuit breaker 2 are arranged on the primary side of the transformer 3, and similarly, the second instrument current transformer 4 is arranged. And the second circuit breaker 5 is arranged on the secondary side of the transformer 3. The first instrument current transformer 1 detects the primary side current of the transformer 3 and sends the primary input current I ₁ to the ratio differential relay 6, and the second instrument current transformer 4 is the transformer. The secondary input current I ₂ is detected by detecting the secondary side current of 3 and the differential relay 6
Send to.

The ratio differential relay 6 calculates a difference current value ΔI (= | I ₁ −I ₂ |) of both currents I ₁ and I ₂ based on the primary input current I ₁ and the secondary input current I _2. , Current ratio ΔIp
(= I ₁ / I ₂ ) is detected, and when the difference current value ΔI and the current ratio ΔIp exceed the set values, the first and second circuit breakers 2 and 5 are cut off to protect the circuit. There is.

FIG. 3 is a block diagram showing the structure of the ratio differential protection relay 6. In the ratio differential protection relay 6, the primary input current I ₁ and the secondary input current I ₂ are provided from the first and second instrument current transformers 1 and 4. These primary input current I ₁ and secondary input current I ₂ are A /
It is input to the differential current detection unit 12, the fundamental wave detection unit 13, and the second harmonic detection unit 14 via the D converter 11.

The differential current detector 12 calculates a differential current value ΔI (= │I) based on the primary input current I ₁ and the secondary input current I _2.
1- I ₂ |) and the current ratio ΔIp (= I ₁ / I ₂ ) are detected, and these ΔI and current ratio ΔIp are sent to the ΔI operation determination unit 15.

The ΔI operation determination unit 15 executes a comparison calculation based on the ΔI and the current ratio ΔIp and the reference difference current value ΔIs and the reference current ratio ΔIsp preset in the set value storage unit 16. As a result of this comparison operation, when each detected value exceeds the reference value, that is, ΔI> ΔIs
And when ΔIp> ΔIsp, the imbalance detection signal is sent to the output determination unit 17.

On the other hand, the fundamental wave detector 13 digitally filters the primary input current I ₁ and the secondary input current I ₂ ,
The primary input current I ₁ of the fundamental wave component I ₁ of a frequency (1f), to detect a secondary input current I ₂ of the fundamental wave component I ₂ (1f), these fundamental component I ₁ (1f), I ₂ (1f) is changed to the 2f motion determination unit 18
Send to.

Similarly, the second harmonic detector 14 digitally filters the primary input current I ₁ and the secondary input current I ₂ to obtain a second harmonic component I ₁ (2f) of the primary input current I ₁ . ,
The second harmonic component I ₂ (2f) of the secondary input current I ₂ is detected, and these second harmonic components I ₁ (2f) and I ₂ (2f) are sent to the 2f operation determination unit 18. As the second harmonic component, originally, as shown in FIG. 4, a damping vibration waveform having both positive and negative components is shown, but here, as shown in FIG. 5, the sum of the positive component and the negative component is shown. Absolute value is detected.

The 2f operation judging section 18 is arranged to detect each input current I ₁ ,
Content of the second harmonic relative to the fundamental wave for each I ₂ (I ₁ (2f)
/ I ₁ (1f) and I ₂ (2f) / I ₂ (1f)), and when the content rate of these second harmonics exceeds a predetermined standard content rate k,
The cutoff prevention signal is sent to the output determination unit 17.

When the output judging section 17 receives only the unbalanced detection signal, the output judging section 17 issues a disconnection command to disconnect the first and second circuit breakers 2 and 5 on the assumption that an internal short-circuit accident has occurred in the transformer 3. When it outputs to the circuit breakers 2 and 5, and receives the unbalance detection signal and the interruption prevention signal, it does not output the interruption command to continue the operation of the transformer 3 because the normal inrush current flows to the transformer 3. .

That is, even when the difference between the primary input current I ₁ and the secondary input current I ₂ is large and an imbalance is detected, the connection state of the circuit is high when the content rate of the second harmonic is high. Holding

As a result, when the first circuit breaker 2 on the power source side is turned on and a voltage is applied to the transformer 3, an exciting inrush current flows only on the power source side of the transformer 3 due to iron core saturation of the transformer 3. Even if an imbalance between the primary input current I ₁ and the secondary input current I ₂ is detected, the second harmonic component included in the magnetizing inrush current is determined to be an imbalance in normal operation and the circuit breaker is detected. It blocks a few false cutoffs.

[0017]

However, in the above-mentioned ratio differential protection relay device, each of the circuit breakers 2 and 5 is cut off when it is determined that the content ratio of the second harmonic is low.
There is a possibility that the circuit breakers 2 and 5 will be accidentally cut off in the following cases.

For example, even when it is determined that the content ratio of the second harmonic is low, when the positive component and the negative component of the second harmonic are close to each other as shown in FIG. Both components may be canceled by taking the absolute value of the sum of the components. For this reason, there is a possibility that the content rate of the second harmonic is apparently low, although it actually contains a large amount of the second harmonic.

The present invention has been made in consideration of the above-mentioned circumstances, and by detecting the second harmonic of the current of the transformer for each of the positive component and the negative component, the positive and negative components are canceled out, and the apparent lowering is achieved. An object of the present invention is to provide a ratio differential protection relay device that can reliably detect the second harmonic and thus prevent erroneous cutoff and improve reliability.

[0020]

According to a first aspect of the invention, a circuit breaker is arranged on each of a primary side and a secondary side of a transformer,
The operating state of the transformer is determined based on the difference current between the primary-side current and the secondary-side current in the transformer, and when both the currents are unbalanced, it is not possible to operate the circuit breakers. In a ratio differential protection relay device that generates a balance detection signal, a fundamental wave detection unit that detects a fundamental wave component included in the primary side current and the secondary side current, and the primary side current and the secondary side current Second harmonic positive component detecting means for detecting a positive component of the included second harmonic component, and second harmonic for detecting a negative component of the second harmonic component included in the primary side current and the secondary side current. Negative component detecting means, a positive component of the second harmonic component detected by the second harmonic positive component detecting means, and a negative component of the second harmonic component detected by the second harmonic negative component detecting means And the component comparison and detection means for comparing the Based on the fundamental wave component detected by the fundamental wave detecting means and the larger component of the second harmonic wave detected by the component comparing and detecting means, the content rate of the second harmonic wave in the fundamental wave component is determined. The content rate calculating means for calculating is compared with the content rate calculated by the content rate calculating means and the reference content rate, and when the content rate exceeds the reference content rate, even if the imbalance detection signal is generated. A ratio differential protection relay device comprising: a blocking prevention unit that blocks the breaking operation of each of the circuit breakers so as to continue the operation of the transformer.

The cut-off prevention means includes an operation determination section which generates a cut-off prevention signal when the content rate exceeds the reference content rate, and the operation determination section which generates a cut-off prevention signal when the operation determination section generates the cut-off prevention signal. It may be provided with an erroneous blocking prevention unit that opens the connection between the location where the balance detection signal is generated and each of the circuit breakers.

[0022]

Therefore, according to the invention corresponding to claim 1, by taking the above-mentioned means, the fundamental wave detecting means detects the fundamental wave component contained in the primary side current and the secondary side current.
The harmonic positive component detecting means detects the positive component of the second harmonic component included in the primary side current and the secondary side current, and the second harmonic negative component detecting means is included in the primary side current and the secondary side current. The component comparison and detection means detects the negative component of the second harmonic component,
The positive component of the second harmonic component detected by the second harmonic positive component detecting means and the second component detected by the second harmonic negative component detecting means
The negative component of the harmonic component is compared in magnitude to detect the larger component, and the content rate calculation means detects the fundamental wave component detected by the fundamental wave detection means and the second harmonic detected by the component comparison detection means. The content ratio of the second harmonic in the fundamental wave component is calculated based on the component of the larger wave, and the cut-off prevention unit calculates the content ratio calculated by the content ratio calculation unit and the reference content ratio. When comparing and the content rate exceeds the standard content rate,
Even if an unbalance detection signal is generated, the breaking operation of each circuit breaker is blocked so as to continue the operation of the transformer, so the second harmonic of the current of the transformer must be detected for each positive and negative component. As a result, it is possible to reliably detect the second harmonic wave, which is apparently lowered due to the cancellation of both the positive and negative components, thereby preventing erroneous interruption and improving reliability.

Further, in the above-mentioned cutoff prevention means, the operation judging section generates a cutoff preventing signal when the content rate exceeds the reference content rate, and the erroneous cutoff preventing section generates the cutoff prevention signal in this operation judging section. At this time, since the connection between the location where the unbalanced detection signal is generated and each circuit breaker is opened, the same operation as the operation corresponding to claim 1 can be achieved with a relatively simple configuration.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a ratio differential relay applied to a ratio differential relay device according to an embodiment of the present invention. The same parts as those in FIG. Are omitted and only different parts will be described here.

That is, the device of this embodiment detects the second harmonic of the primary input current I ₁ and the secondary input current I ₂ of the transformer 3 by dividing them into a positive component and a negative component, and detects the apparent appearance of the second harmonic. This is intended to prevent the above reduction and improve the reliability of the relay operation. Specifically, as compared with the device shown in FIG. 3, instead of the second harmonic wave detection unit 14 and the 2f operation determination unit 18, A 2f positive component detector 21 for detecting a positive component of the second harmonic, a second
2f Negative component detector 2 for detecting negative component of harmonic
2. A 2f comparison detection unit 23 for detecting a large component of both components, and a content rate of the second harmonic is obtained according to the detection result, and a cutoff prevention signal is sent to the output determination unit 17 based on the content rate. The 2f motion determining unit 24 is provided.

Here, the 2f positive component detecting section 21 uses the A / D
From the input currents I ₁ and I ₂ received from the converter 11, the positive components I ₁ (+ 2f) and I ₂ (+ 2f) of the second harmonic thereof are detected, and the detection results are sent to the 2f comparison / detection unit 23. To do.

The 2f negative component detecting section 22 includes an A / D converter 1
The negative components I ₁ (-2f) and I ₂ (-2f) of the second harmonic of the input currents I ₁ and I ₂ received from ₁ are detected, and the detection results are sent to the 2f comparison detection unit 23. It is a thing.

The 2f comparison / detection unit 23 includes the component detection units 2
Positive components I ₁ (+ 2f) and I ₂ (+ 2f) detected by 1 and 22
And the negative components I ₁ (-2f) and I ₂ (-2f), a large component of both positive and negative components is compared and detected for each input current I ₁ and I ₂ , and this comparison detection result is operated for 2f. It has a function of giving it to the judging section 24.

The 2f operation determination section 24 is a 2f comparison detection section 2.
Based on the comparison detection result of 3 and the fundamental wave component received from the fundamental wave detector 13, the second current is input for each of the input currents I ₁ and I ₂ .
It has a function of obtaining the content rate of higher harmonics and sending a cut-off prevention signal to the output determination section 17 based on this content rate.

The output determining section 17 is, as described above, the unbalance detection signal from the ΔI operation determining section 15 and the 2f operation determining section 2.
Among the cutoff prevention signals from 4, the function of outputting a cutoff command to each breaker 2 and 5 to perform a cutoff operation when receiving only the unbalanced detection signal, and the unbalanced detection signal Also, it has a function of ignoring the imbalance detection signal and not outputting the cutoff command when receiving the cutoff prevention signal.
The output determination unit 17 includes, for example, a non-inverted input terminal of an unbalanced detection signal received from the ΔI operation determination unit 15, an inverted input terminal of a cutoff prevention signal received from the 2f operation determination unit 24, and a cutoff command (not shown). An AND circuit (erroneous interruption prevention unit) having an output terminal for outputting a balance detection signal) to each of the circuit breakers 2 and 5 can be used.

Next, the operation of such a ratio differential protection relay device will be described. Now, the primary input current I ₁ and the secondary input current I ₂ are provided from the first and second instrument transformers 2 and 5. These primary input current I ₁ and secondary input current I
₂ is input to the differential current detection unit 12, the fundamental wave detection unit 13, the 2f positive component detection unit 21 and the 2f negative component detection unit 22 via the A / D converter 11 every constant sampling period.

As described above, the difference current detection unit 11 sends the difference current value ΔI and the current ratio ΔIp detected based on the input currents I ₁ and I ₂ to the ΔI operation determination unit 15. ΔI
The operation determination unit 15 calculates the ΔI and the current ratio ΔIp,
A comparison calculation is executed based on the reference difference current value ΔIs and the reference current ratio ΔIsp in the set value storage unit 16, and when each detected value exceeds the reference value as a result of the comparison calculation (Δ
When I> ΔIs and ΔIp> ΔIsp), the imbalance detection signal is sent to the output determination unit 17.

On the other hand, the fundamental wave detector 13 digitally filters the primary input current I ₁ and the secondary input current I ₂ ,
The primary input current I ₁ of the fundamental wave component I ₁ of a frequency (1f), to detect a secondary input current I ₂ of the fundamental wave component I ₂ (1f), these fundamental component I ₁ (1f), I ₂ (1f) is changed to the 2f motion determination unit 24
Send to.

Next, the 2f positive component detecting section 21 digitally filters the primary input current I ₁ and the secondary input current I ₂ to obtain a positive component I ₁ (+ 2f) of the second harmonic of the primary input current I ₁ . )
And the positive component I ₂ (+ 2f) of the second harmonic of the secondary input current I ₂ .
And the positive components I ₁ (+ 2f) and I ₂ (+ 2f) are sent to the 2f comparison and detection unit 23.

Similarly, the 2f negative component detector 22 digitally filters the primary input current I ₁ and the secondary input current I ₂ to obtain the negative component I ₁ (-2 (-2) of the second harmonic of the primary input current I ₁ .
and f), negative component of the second harmonic of the secondary input current I ₂ I ₂ (-2
f) and are detected, and these negative components I ₁ (-2f) and I ₂ (-2f) are detected.
Is sent to the 2f comparison detection unit 23.

The 2f comparison / detection unit 23 detects the positive component I ₁ (+ 2f).
, I ₂ (+ 2f) and the negative components I ₁ (-2f) and I ₂ (-2f), a large component of both positive and negative components is compared and detected for each input current I ₁ and I ₂ . The comparison detection result is given to the 2f operation determination unit 24.

For example, the positive component I ₁ (+2 of the primary input current I ₁
f) and the negative component I ₁ (-2f) are compared, and the positive component I ₁ (+ 2f)
Is larger, the positive component I ₁ (+ 2f) is given to the 2f motion determining unit 24. Similarly the secondary input current I ₂ of the positive component I ₂ (+
2f) and the negative component I ₂ (-2f) are compared, and the positive component I ₂ (+ 2f)
Is larger, the positive component I ₂ (+ 2f) is given to the 2f motion determining unit 24.

The 2f operation determination unit 24 is a 2f comparison detection unit 2.
Based on the comparison detection result of 3 and the fundamental wave component received from the fundamental wave detection unit 13, the content ratio of the second harmonic with respect to the fundamental wave component is obtained for each of the input currents I ₁ and I ₂ , and based on this content ratio The cutoff prevention signal is sent to the output determination unit 17.

For example, as described above, when the positive component of both the positive and negative components of the second harmonic is larger, the 2f operation determination unit 24 causes the content ratio of the second harmonic positive component in the primary input current I ₁ ( I ₁ (+ 2f) / I ₁ (1f)) is obtained, and when this content exceeds the standard content k (I ₁ (+ 2f) / I ₁ (1f)>
k), the cutoff prevention signal is sent to the output determination unit 17.

Similarly, the content ratio (I ₂ (+ 2f) / I ₂ (1f)) of the second harmonic positive component in the secondary input current I ₂ is obtained,
When this content exceeds the standard content k (I ₂ (+ 2f) /
I ₂ (1f)> k), and sends a cutoff prevention signal to the output determination unit 17.

Similarly to the above, the output judging section 17 receives the first and second circuit breakers 2, 5 when it receives only the unbalanced detection signal.
A shutoff command is output to each of the circuit breakers 2 and 5 to shut off, and when the unbalance detection signal and the shutoff prevention signal are received, the shutoff command is not output to continue the operation of the transformer 3.

That is, even when the unbalanced detection signal is generated, the primary input current I ₁ or the secondary input current I ₂ contains the positive component or the negative component of the second harmonic in excess of the reference content rate. At this time, it is determined that it is not the internal short circuit accident of the transformer 3 but the exciting inrush current flowing when the voltage of the transformer 3 is applied,
The connection state is maintained to prevent erroneous disconnection of the circuit breakers 2 and 5.

As described above, according to this embodiment, the fundamental wave detecting section 13 determines the fundamental wave components I ₁ (1f) and I ₂ (1f) contained in the primary input current I ₁ and the secondary input current I _2. Detected, 2f
The positive component detector 21 detects the positive components I ₁ (+ 2f), I of the second harmonic component contained in the primary input current I ₁ and the secondary input current I _2.
2 (+ 2f) is detected, and the 2f negative component detection unit 22 causes the negative components I ₁ (-2f) and I ₂ (-of the second harmonic component included in the primary input current I ₁ and the secondary input current I ₂ to be detected. 2f) is detected, and the 2f comparison / detection unit 23 compares the positive component and the negative component of the second harmonic in magnitude to detect the larger component I ₁ (+ 2f) and I ₂ (+ 2f). Two
Based on the fundamental wave component detected by the fundamental wave detection unit 13 and the larger component of the second harmonic detected by the 2f comparison detection unit 23, the f operation determination unit 24 determines the first component of the fundamental wave component. Calculate the content rate of two harmonics (I ₁ (+ 2f) / I ₁ (1f) and I ₂ (+ 2f) / I ₂ (1f)) and compare this content rate with the standard content rate k. When the content rate exceeds the reference content rate, a cutoff prevention signal is transmitted, and the output determination section 17 receives the cutoff prevention signal even if it receives the unbalance detection signal, so that the operation of the transformer 3 is continued. Each circuit breaker 2, 5
The second harmonic of the transformer current is detected for each of the positive and negative components to reliably detect the second harmonic that is apparently low due to the cancellation of both the positive and negative components. Therefore, false cutoff can be prevented and reliability can be improved.

Further, the output judging section 17 is constituted by an AND circuit which opens the connection between the location where the unbalance detection signal is generated and each circuit breaker in accordance with the input of the cutoff prevention signal, thereby making it relatively simple. It can be configured. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0045]

As described above, according to the invention corresponding to claim 1, the fundamental wave detecting means detects the fundamental wave component contained in the primary side current and the secondary side current, and the second harmonic positive component. The detecting means detects a positive component of the second harmonic component contained in the primary side current and the secondary side current, and the second harmonic negative component detecting means detects the second harmonic component contained in the primary side current and the secondary side current. The negative component of the component is detected, and the component comparison and detection means detects the positive component of the second harmonic component detected by the second harmonic positive component detection means and the second harmonic detected by the second harmonic negative component detection means. The negative component of the wave component is compared in magnitude to detect the larger component, and the content rate calculating means detects the fundamental wave component detected by the fundamental wave detecting means and the second harmonic wave detected by the component comparing and detecting means. Based on the larger component of
The content rate of harmonics is calculated, and the cutoff prevention means compares the content rate calculated by this content rate calculation means with the reference content rate, and when the content rate exceeds the reference content rate, an imbalance detection signal is generated. Even so, since the breaking operation of each breaker is blocked so as to continue the operation of the transformer, by detecting the second harmonic of the current of the transformer for each of the positive and negative components, both positive and negative components are detected. It is possible to provide the ratio differential protection relay device that can reliably detect the second harmonic wave that is apparently lowered due to the cancellation, thereby preventing erroneous cutoff and improving reliability.

In the cut-off prevention means, the operation judging section generates a cut-off preventing signal when the content rate exceeds the reference content rate, and the erroneous cut-off preventing section generates a cut-off prevention signal in the operation judging section. At this time, the connection between the location where the unbalance detection signal is generated and each circuit breaker is opened, so that the effect of claim 1 can be achieved with a relatively simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a ratio differential relay applied to a ratio differential relay device according to an embodiment of the present invention;

FIG. 2 is a configuration diagram of a power system to which a conventional ratio differential protection relay device is applied,

FIG. 3 is a block diagram showing a configuration of a conventional ratio differential protection relay.

FIG. 4 is a waveform diagram for explaining a conventional operation.

FIG. 5 is a waveform diagram for explaining a conventional operation.

FIG. 6 is a waveform diagram for explaining a conventional operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st instrument current transformer, 2 ... 1st circuit breaker, 3 ... transformer, 4 ... 2nd instrument current transformer, 5 ... 2nd circuit breaker, 6 ...
Ratio differential relay, 11 ... A / D converter, 12 ... Differential current detection unit, 13 ... Fundamental wave detection unit, 15 ... ΔI operation determination unit, 1
6 ... Set value storage unit, 17 ... Output determination unit, 21 ... 2f positive component detection unit, 22 ... 2f negative component detection unit, 23 ... 2f comparison detection unit, 24 ... 2f operation determination unit, I ₁ ... Primary input current, I
₂ ... Secondary input current I ₂ .

Claims (2)

[Claims] 1. A circuit breaker is arranged on each of a primary side and a secondary side of a transformer, and an operating state of the transformer is determined based on a difference current between a primary side current and a secondary side current in the transformer. ,
A ratio differential protection relay device that generates an unbalanced detection signal for interrupting each of the circuit breakers when the both currents are unbalanced, in which a basic current included in the primary current and the secondary current is included. A fundamental wave detecting means for detecting a wave component; a second harmonic positive component detecting means for detecting a positive component of a second harmonic component included in the primary side current and the secondary side current; Second harmonic negative component detecting means for detecting a negative component of the second harmonic component contained in the secondary side current; and a positive component of the second harmonic component detected by the second harmonic positive component detecting means, and Component comparison and detection means for comparing the magnitude of the negative component of the second harmonic component detected by the second harmonic negative component detection means and detecting the larger component, and the fundamental detected by the fundamental wave detection means. The wave component and the first detected by the component comparison and detection means. A content rate calculating means for calculating the content rate of the second harmonic in the fundamental wave component based on the higher harmonic content component, and the content rate calculated by the content rate calculating means and the reference content rate. And when the content rate exceeds the reference content rate, a shutoff preventing means for shutting off the shutoff operation of each of the circuit breakers so as to continue the operation of the transformer even if the unbalance detection signal is generated. A ratio differential protection relay device characterized by comprising: 2. The ratio differential protection relay device according to claim 1, wherein the cut-off prevention unit includes an operation determination unit that generates a cut-off prevention signal when the content rate exceeds the reference content rate. A ratio differential, comprising: an erroneous cutoff prevention unit that opens a connection between the location where the imbalance detection signal is generated and each of the circuit breakers when a cutoff prevention signal is generated in the operation determination unit. Protective relay device.