JP3269220B2 - Transformer protection relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer protection relay device for protecting a transformer using a ratio differential relay or the like.

[0002]

2. Description of the Related Art A conventional transformer protection relay is shown in FIG.
It was configured as follows. In FIG. 4, 1, 2, and 3 are 3
This is a ratio differential relay element provided for each phase, and operates according to the ratio of the difference current 1d to the suppression current Ir. Output signals of these ratio differential relay elements 1, 2, 3 are supplied to non-inverting input terminals of AND circuits 4, 5, 6 with inverting input terminals, respectively. Reference numerals 7, 8, and 9 denote second harmonic lock elements provided for each of the three phases. The second harmonic lock elements operate according to the ratio between the fundamental current and the second harmonic current contained in the difference current 1d. The output signals of the second harmonic lock elements 7, 8, 9 are supplied to the inverting input terminals of the AND circuits 4, 5, 6. The outputs of the AND circuits 4, 5, and 6 become, via the OR circuit 10, a trip signal of a circuit breaker (not shown) inserted in an electric circuit connecting the transformer and the electric power system. The characters in parentheses in the figure indicate the three phases.

In the apparatus configured as shown in FIG. 4, a difference current 1d is a difference current between a current flowing into a transformer and a current flowing out, and is almost always zero. Also, the suppression current Ir generally uses the sum of the slurs of the terminals of the transformer.
The ratio differential relay elements 1, 2, and 3 operate when Id / Ir becomes equal to or more than a predetermined value as in the operation characteristic of FIG. The second harmonic locking element 7, 8, 9 5 second harmonic Namibun current included in the example differential current Id as the operating characteristics of (b) the If ₂ basic Namibun current the If ₁ ratio the If ₂ / if ₁ is operated when it becomes 0.13 or more.

[0004] In the event of a fault inside the transformer, the differential current Id increases and the ratio differential relay element of the corresponding phase operates, so that the ratio inverting input terminal of the AND circuit of the corresponding phase becomes high level. On the other hand, at this time, all If ₂ / If ₁ does not become 0.13 or more, so that the second harmonic lock element (7, 8, 9) becomes inoperative and the AND circuit (4, 5, 6) The inverting input terminal goes low. Therefore, the AND circuit (4,
The AND condition of (5, 6) is satisfied, and the circuit breaker is tripped without trip lock.

[0005] Although the time the transformer is turned through magnetizing inrush current as the differential current Id, because it contains many second harmonic Namibun current the If ₂ in this inrush current, If ₂ / If _1>
The condition 0.13 is satisfied. Therefore, the second harmonic lock elements (7, 8, 9) operate to operate the AND circuit 4,
The conditions of 5 and 6 are not satisfied, and the trip output is locked. If the ratio differential relay elements 1, 2, and 3 operate before the trip lock is activated, a miss signal is output, so that the operating time of the ratio differential relay elements 1, 2, and 3 is delayed. Time coordination is performed so that no mistrip signal is output.

[0006]

(1) The If _{2 component} included in the exciting inrush current varies depending on various factors such as remanence, the closing phase, the structure of the iron core, and so on. the operating conditions of the wave locking element _{(7,8,9) (If 2 / If} 1> 0.13) does not necessarily satisfy. In particular, recently, the content of the second harmonic component current If ₂ has been reduced, and in the external phase lock method shown in FIG. 4, the excitation inrush current must be maintained unless the operating condition is about If ₂ / If ₁ > 0.1. In some cases, unnecessary trip output is output.

However, as described above, if the value of If ₂ / If ₁ detection of the second harmonic lock element (7, 8, 9) is set low, the ratio differential relay element (1, 2, 3) )) If ₂ included transiently during an accident inside the transformer, which is the protection area
The risk increases that the operation of the ratio differential relay element is temporarily locked. For this reason, there is a problem that the operation time of the ratio differential relay element is delayed, and the time for removing the accident is prolonged.

(2) The method of FIG. 4 locks the output of the ratio differential relay element when If ₂ / If ₁ exceeds a predetermined value. Therefore, the method of FIG. It is necessary to take time coordination that the ratio differential relay element operates slower than the two-harmonic lock element.

[0009] However magnetizing inrush current varies by various factors, even in the case close to the set value If ₂ / If ₁ is less ₂ minutes If becoming increasingly slow operation time of the second harmonic locking element Therefore, it is necessary to further delay the operation time of the ratio differential relay element, and the accident elimination time becomes longer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a transformer protection relay having a high protection without a delay in the time for removing an accident.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a transformer for protection.
The ratio of the difference current between the current flowing into and out of the vessel and the suppression current is a predetermined value.
A differential relay element that operates when the above
Connected to the transformer by the operation output of the differential relay element
Transformer protection relay that trips and protects an interrupted circuit breaker
In the device, For each of the three phases to which the transformer to be protected is connected
Are provided, and the ratio between the difference current and the suppression current is equal to or greater than a predetermined value.
And the differential relay element that operates when
Fundamental wave componentWherein the sum of the square values of each of the three phases and the difference
The second harmonic component of the current, the square value of each of the three phases
Ratio with sumIs less than or equal to a predetermined value, and 3 of the fundamental wave component
It operates when the total value of the phases is equal to or greater than the set current value.
A three-phase overcurrent relay element with a two-harmonic suppression function;
The operation output of the three-phase overcurrent relay element with harmonic suppression function,
The logical product of the three-phase ratio and the operation output of the differential relay
And AND circuits to be sought.
The AND condition of at least one of the AND circuits is satisfied.
Tripping the circuit breaker when standing up
are doing.

[0012]

(1) In the first aspect of the present invention, the difference between the currents flowing into and out of the transformer to be protected is almost zero in normal times, so that the ratio differential relay element does not operate.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

In the event of a fault inside the transformer, the ratio between the difference current and the suppression current exceeds a predetermined value, and the ratio differential relay element provided in the fault phase operates. At this time, the sum of the square values of each of the three phases of the fundamental wave component included in the difference current becomes large.
The three-phase overcurrent relay element with the harmonic suppression function operates, and the AND condition of the AND circuit in the fault phase is satisfied. For this reason, the circuit breaker is tripped and the accident section is quickly separated.

Even if the second harmonic component in one of the phases transiently increases during a transformer internal accident, the fundamental component is large, so the sum of the square values of the three phases of the second harmonic component is large. And basic waves
The ratio of the three-minute phase to the sum of the square values of each phase is equal to or less than a predetermined value.
Therefore, the three-phase overcurrent relay element with the second harmonic suppression function operates reliably, and the trip of the circuit breaker is not locked by the transient second harmonic component.

Also, when a transformer having an internal fault is turned on, the fundamental wave component in the difference current of the fault phase becomes large, so that the ratio differential relay element and the three-phase overcurrent relay with the second harmonic suppression function are provided. The electric element operates, the AND condition of the AND circuit in the accident phase is satisfied, and the circuit breaker is tripped. In this case, since the fundamental wave component of the input of the fault phase becomes larger than when the square is not squared, the lock of the ratio differential relay is released earlier, and the fault elimination time is shortened.

When the transformer is turned on, an exciting rush current flows as a difference current. The second harmonic component in the excitation inrush current is small in one phase but large in the other phase due to the relationship between the residual magnetism and the input phase. Therefore, the sum of the square values of the three phases is considerably large. growing. Therefore, the three-phase overcurrent relay element with the second harmonic suppression function does not operate, and the AND condition of each AND circuit is not satisfied. Therefore, even when the second harmonic component is small in one phase as described above, no unnecessary trip output is generated for the inrush current.

Since the trip output is output according to the AND condition of the ratio differential relay element and the three-phase overcurrent relay element with the second harmonic suppression function, there is no need for time coordination between the two elements, and the accident elimination time is reduced. Be shortened.

In a general digital relay adopting a product type arithmetic method, since the square value of each of the three-phase inputs can be directly obtained, the three-phase overcurrent relay element with the second harmonic suppression function is provided. Is significantly shortened. As a result, the operation time of the protection relay is shortened.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.
explain. First, reference examples related to the present invention will be described.
You. In FIG. 1, the same parts as those in FIG. FIG. 1 differs from FIG. 4 in that a three-phase overcurrent relay element 17 with a second harmonic suppression function is provided, and the operation output of the relay element 17 and the ratio differential relay elements 1, 2, 3 The AND of the operation output and the AND circuit 14, 1
5 and 16, the outputs of the AND circuits 14, 15, and 16 are input to the OR circuit 10, and the output of the OR circuit 10 is used as the circuit breaker trip output. Ratio differential relay element 1,
The operation characteristics of 2 and 3 are the same as those in FIG.

The three-phase overcurrent relay element 17 with the second harmonic suppression function operates when the following conditional expression is satisfied.

[0027]

(Equation 1)

[0028]

(Equation 2)

FIG. 2 shows the characteristics of the three-phase overcurrent relay element 17 with the second harmonic suppression function when α in the equation (1) is set to 0.15.

In the device configured as described above, when an exciting rush current flows when the transformer is turned on, even if the second harmonic component If _{2 of} one phase is small due to the relationship between the residual magnetism and the turning-on phase, The other phases contain a lot of If ₂ components accordingly. For this reason, if the average value of the three phases is obtained as in the above equation (1), ΣIf ₂ / ほ ぼ If ₁ becomes substantially high on average, and the three-phase overcurrent relay element 17 with the second harmonic suppression function operates. do not do. Thereby, the AND circuits 14, 15, 16
Are not satisfied and no trip output is issued. As described above, even if the value of α in the equation (1) is not extremely reduced, the excitation inrush current can be reduced by ΔIf ₂ / ΔIf ₁ ≦ α.
Does not hold and no unnecessary trip output is issued.

[0031] during transformer internal fault, as well as the fault phase the provided ratios differential relay elements (1,2,3) is operated, increases the fundamental wave component the If ₁ in differential current Σ
If ₂ / ΣIf ₁ ≦ α holds, and the second harmonic suppression function 3
The phase overcurrent relay element 17 operates. Therefore, an AND condition of the AND circuit (14, 15, 16) on the accident phase side is satisfied, and a trip output is issued.

Further, when a transformer having an internal fault is turned on, If ₁ of the fault phase increases and ΔIf ₂ / ΔIf ₁ ≦ α.
Holds, and a trip output is issued in the same manner as described above.

In the apparatus shown in FIG. 1, the ratio differential relay elements 1, 2, 2
Since the trip output is output due to the AND condition of the operation of the three-phase overcurrent relay element 17 with the third and second harmonic suppression functions 17, the operation time of the ratio differential relay element is set to the second time in consideration of the transient time. It is not necessary to set the operation time longer than the operation time of the three-phase overcurrent relay element with the harmonic suppression function. As a result, it is possible to shorten the time for removing accidents overall.

Next, an embodiment of the present invention will be described. When trying to realize the three-phase overcurrent element 17 with the second harmonic suppression function of FIG. 1 by a digital relay, the arithmetic processing time of the CPU becomes slightly longer, and the operation time as the protection relay cannot be shortened. is there.

The method of calculating the amplitude value of a digital relay can be broadly classified into an addition type and a product type. In the case of the addition type, the digital value is increased because the number of sampling points increases, the calculation time becomes longer, and the accuracy is poor. The product type is widely used as a relay.

However, in the case of the product type, since the square value of the AC input directly appears, it takes a considerable processing time to obtain the AC input by taking the square root of the square value. Therefore, in this embodiment, the three-phase overcurrent element 17 with the second harmonic suppression function of FIG.
Are set as shown in FIG. 3, and the operation is performed when the conditional expressions of the above-mentioned expression (2) and the following expression (3) are satisfied.

[0037]

(Equation 3)

If both sides of the above equation (3) are squared, the following equation is obtained.

[0039]

(Equation 4)

In a general digital relay adopting the product type operation method, since the square value of each phase input in the expression (4) can be directly obtained, the operation time of the entire expression (4) is very short. Can be shortened. Thereby, the operation time as the protection relay can be shortened.

In the device configured as described above, when an exciting rush current flows when the transformer is turned on, even if the second harmonic component If _{2 of} one phase is small due to the relationship between the residual magnetism and the turning-on phase, The other phases contain a lot of If ₂ components accordingly. Therefore, if the square root of the sum of the squares of the three phases is calculated as in the above equation (3), If ₂ / If ₁ becomes a considerably high value, and the three-phase overcurrent relay with the second harmonic suppression function is performed. Element 17 does not work. As a result, the AND circuit 14,
Each of the AND conditions 15 and 16 is not satisfied, and no trip output is issued. As described above, even if the value of α in the equation (3) is not extremely reduced, the equation (3) does not hold for the inrush current, and no unnecessary trip output is output.

Further during transformer internal fault, as well as the ratio differential relay element provided on the fault phase (1, 2, 3) is operated, increases the fundamental wave component the If ₁ in differential current ( 3) is satisfied, and the three-phase overcurrent relay element 17 with the second harmonic suppression function operates. Therefore, an AND condition of the AND circuit (14, 15, 16) on the accident phase side is satisfied, and a trip output is issued.

Further, when a transformer having an internal fault is turned on, If _{1 in} the fault phase increases, and the equation (3) is satisfied.
A trip output is issued in the same manner as described above.

[0044]

According to the present invention as described above,
The trip output is obtained by ANDing the operation output of the three-phase overcurrent relay element with the second harmonic suppression function that operates when the conditions of the equations (2) and (4) are satisfied and the operation output of the ratio differential relay element. , The following excellent effects can be obtained.

(1) Even if the suppression rate due to the second harmonic component is not extremely increased, unnecessary output due to the inrush current is not generated, so that the operation set value of the three-phase overcurrent relay element with the second harmonic suppression function is provided. α can be set large. Therefore or locked by transient second harmonic Namibun current the If ₂ during transformer internal fault, will not be delayed trip output ratio differential relay element. For this reason, the accident elimination time is shortened.

(2) Since the trip output is output by AND of the ratio differential relay element and the three-phase overcurrent relay element with the second harmonic suppression function, there is no need to coordinate the time between the two relay elements. , Accident elimination time can be shortened.

(3) Despite the effects described in the above items (1) and (2), trip lock does not occur when a transformer having an internal accident is turned on.

(4) The calculation processing time of the CPU can be shortened, the operation time of the protection relay can be shortened, and the failure elimination time can be shortened. Conversely, if the operation time is the same, the number of relay elements that can be processed by the same CPU can be increased, and the economic effect is large.

Further, according to the present invention , since each phase input is squared, the following effects can be obtained.

(1) In the transformer inrush current, if the second harmonic component is extremely small in one phase and the second harmonic component is large in another phase, the large phase component does not square. Since the influence is larger than in the case, the lock at the time of the inrush of the excitation becomes more reliable.

(2) When a transformer having an internal failure is already turned on, the fundamental component of the failed phase increases, and the sum of the fundamental components increases as compared with the case where the square is not squared. Are released sooner, and the fault elimination time is shortened. (3) Each phase using digital relay of product type operation
Since the square value of the input can be obtained directly, the calculation time
Is greatly reduced, which allows it to act as a protection relay.
The work time can be shortened.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a reference example related to the present invention.

FIG. 2 is an operation characteristic diagram of a three-phase overcurrent relay element with a second harmonic suppression function to which a reference example related to the present invention is applied.

FIG. 3 is an operation characteristic diagram of a three-phase overcurrent relay element with a second harmonic suppression function to which the present invention is applied.

FIG. 4 is a circuit diagram showing an example of a conventional transformer protection relay device.

5A and 5B show operation characteristics of each element in FIG. 4; FIG. 5A is an operation characteristic diagram of a ratio differential relay element; FIG. 5B is an operation characteristic diagram of a second harmonic lock element;

[Explanation of symbols]

 1, 2, 3 ... ratio differential relay element 7, 8, 9 ... second harmonic lock element 10 ... OR circuit 14, 15, 16 ... AND circuit 17 ... three-phase overcurrent relay with second harmonic suppression function Electric element

Claims (1)

(57) [Claims] 1. A ratio differential relay element that operates when a ratio of a difference current between a current flowing into and flowing out of a protection target transformer and a suppression current is equal to or greater than a predetermined value, and an operation of the ratio differential relay element. In a transformer protection relay device that trips and protects a circuit breaker connected to the transformer according to an output, a protection target transformer is provided for each of three phases to be connected,
A ratio differential relay element that operates when a ratio between the difference current and the suppression current is equal to or more than a predetermined value; and a fundamental wave component in the difference current, the square value of each of three phases.
And the second harmonic component in the difference current,
A three-phase with a second harmonic suppression function that operates when the ratio of the sum of the squares of each phase to the sum is equal to or less than a predetermined value and the sum of the three phases of the fundamental wave component is equal to or more than a set current value. AND for obtaining the logical product of the overcurrent relay element, the operation output of the three-phase overcurrent relay element with the second harmonic suppression function, and the operation output of the ratio differential relay element for each of the three phases. And a circuit for tripping the circuit breaker when an AND condition of at least one of the AND circuits among the AND circuits is satisfied.