JPH0654439A - Digital type transformer protection relay device - Google Patents

Abstract

PURPOSE:To make it possible to detect internal faults with high sensitivity and high speed by permitting the saturation of analog/digital conversion means in setting only for external faults where the maximum input current occurs among the external faults of transformers. CONSTITUTION:An input current transformer 1023 has an ordinary load current within A/D full scale at least at the system secondary current, but the system secondary current during an external fault on tertiary side is set to a conversion ratio exceeding the A/D full scale. Instantaneous data of differential current are obtained from digital data D1, D2 and D3, but the instantaneous data of the differential current is set to '0' when D3 is larger than a predetermined value. Because of this, an internal fault of a transformer 100 can be judged at a high speed by using the differential current. Also, an external fault on the secondary side of the transformer 100 can correctly be judged, and erroneous operation can be prevented even for the external fault on the tertiary side. That is, the dynamic range of current input is made small so that the internal fault can be detected with a high sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power system protection relay device, and more particularly to a digital type transformer protection relay device for protecting a transformer by a current differential relay system.

[0002]

2. Description of the Related Art A current differential relay system is generally used as a relay system for protecting a transformer. The basics of protection in this transformer protection are: (1) Detecting internal accidents with high sensitivity. (2) Do not malfunction during an external accident. There are two points. In order to achieve (1), it is necessary to keep the dynamic range of the current input small, but to achieve (2), conversely, the current that is faithful to the maximum current that flows when an external accident occurs. Since the input is taken in, it is necessary to expand the dynamic range of the current input. As one of the solutions to this protection requirement in the prior art, there is, for example, Japanese Patent Publication No. 53-29819. Less than,
This will be explained. FIG. 8 is a configuration example of a current differential relay device for a three-terminal transmission line disclosed in Japanese Patent Publication No. 53-29819. In the figure, 1 is a conversion device, 2 is a transmission device, and 3
And 4 are receivers, 5 are synthesizers, 6 is a differential detector,
7,8,9,13,14,15,18,19 are level detectors, 10,
16 and 20 are OR circuits, 11 and 17 are phase detectors, and 12 is an inhibit circuit. The illustrated device is provided at each terminal of a three terminal transmission line. Next, the reaction will be described. An alternating current I at the installed terminal of the device of FIG. 8 is applied to the converter 1 and produces an output alternating current quantity e ₃ . The relation between the current I and the instantaneous value of the electric quantity e ₃ is as shown in FIG. 9, and the magnitude of I is small and the saturation value I _S is small.
The electrical quantity e ₃ When there between -I _S is proportional to I, becomes more negative than Seimatawa -I _S than I _S, e ₃ does not change becomes saturated eS or -Es. The electric quantity e ₃ is applied to the transmitter 2, the synthesizer 5, and the level detector 7, and the transmitter 2 transmits the signal f _T corresponding to the instantaneous value of e ₃ to another terminal. As this signal, various signals such as a frequency corresponding to the instantaneous value of e ₃ and a digital code can be used. The receiving devices 3 and 4 receive the signals f _R1 and f _R2 from the similar transmitting devices at the other two terminals and generate the electric quantities e ₅ and e ₆ corresponding to the received signals f _R1 and f _R2 . Here, e ₅ and e ₆ are equal to the output of the converter 1 of the other terminal devices.

The electric quantities e ₃ , e ₅ and e ₆ are applied to the synthesizer 5 to produce an output electric quantity e ₇ . Where e ₇ is e ₃ ,
It is equal to the sum of e ₅ and e ₆ , and there is a relationship of e ₇ = e ₃ + e ₅ + e ₆ . The electric quantity e ₇ is applied to the differential detector 6, and e ₇
When the crest value of the signal becomes higher than the predetermined value, the differential detector 6 operates after the time delay φ and a continuous output is generated. Also, the electric quantities e ₃ , e ₅
And e ₆ are added to the level detectors 7, 13, 8, 14, 9, 15 respectively. Each of the level detectors 7 to 9 produces an output during a period in which the instantaneous value of the input electric quantity is in the positive direction from the positive planned value e _L , and the level detectors 13 to 15 respectively output the negative value of the instantaneous value of the input electric quantity. Outputs for a certain period in the negative direction from -e _L. If any of the outputs of the level detectors 7 to 9 occurs, the OR circuit 10
To the OR circuit 16 when any of the level detectors 13 to 15 produces an output. Further, the electric quantity e ₇ is added to the level detectors 18 and 19. The level detector 18 is e
_An output is produced when the instantaneous value of ₇ is negative, and the level detector 19 outputs e
Output is generated when the instantaneous value of ₇ is positive. Phase detector 11, 17
The output of the level detector 18 and the OR circuit 10 or the output of the level detector 19 and the OR circuit 16 are both constant time θ (for example, 60
°) If it continues to occur, it operates and produces output, and the output disappears after a certain period of time (for example, 360 °) elapses after this operating condition disappears. If an output is generated in either one of the phase detectors 11 and 17, an output is generated in the OR circuit 20. Inhibit circuit 12
Produces an output on the differential detector 6 and an output on the OR circuit 20 when there is no output, tripping the breaker. As described above, between the predetermined values e _L and −e _L of the level detectors 7 to 9 and 13 to 15 and the saturation values e _S and −e _S of the output electric quantity e ₃ of the conversion device 1 shown in FIG. , There is a relationship of | e _S |> | e _L |
Further, the values I _L and -I _L of the current I, which make the value of the electricity amount e _{3 be} e _L or -e _L , are set to values slightly larger than the maximum outflow current at the time of an internal accident such as unbalanced operation. Further, the time delay φ of the differential detector 6 is set to be slightly longer than the constant time θ of the phase detectors 11 and 17.

Next, the response of FIG. 8 will be described. Now current I _1A of the terminals, I _1B, smaller one I _1C is, when the instantaneous value of the current is always between I _L and -I _L in FIG. 9, the electric quantity e ₃ of each terminal, e ₅ and e ₆ are always e
It is between _L and -e _L , and neither of the level detectors 7-9 and 13-15 produces an output. Therefore, the OR circuits 10 and 16 have no output, the phase detectors 11 and 17 do not operate and produce no output, and the OR circuit 20 does not produce any output. If an output is generated in the differential detector 6 in this state, an output is output to the inhibit circuit 12 to cut off. If there is no accident inside the protection section, the sum of I _1A , I _1B , and I _1C is zero, and the converter 1 at each terminal does not saturate, so the output e ₃ of the converter 1 at each terminal 1A, 1B, 1C. Also becomes zero. Since the electric quantities e ₅ and e ₆ are equal to the electric quantities e ₃ of the other two terminals, the electric quantities e ₃
The sum of ₃ , e ₅ , and e ₆ becomes zero, and the output electric quantity e ₇ of the synthesizer 5 also becomes zero. If e ₇ is zero, the differential detector 6 does not operate to produce an output, and the cutoff is not performed.
If there is an accident inside the protection zone, the current I _{1A at} each terminal,
The sum of I _1B and I _1C is not equal to the fault current. Therefore, each terminal is the sum of the electric quantities e ₃ , e ₅ , e ₆ , that is, the electric quantity e
₇ also becomes a value corresponding to the fault point current, the differential detector 6 operates to generate an output, an output is obtained in the inhibit circuit 12, and the breaker is tripped.

Next, the case where the currents I _1A , I _1B and I _1C are large and the converter 1 is saturated will be described. In FIG. 10, the current I _1A and I _1B are small, and the converter 1 is not saturated at the terminals 1A and 1B, and the current I _1C is large at the terminal 1C, and the converter 1 is provided at the terminal 1A in the event of an external accident. It is a response of the device. In the figure, currents I _1A and I _1B are equal and I _1A , I _1B ,
The sum of I _1C is zero, and each current has a sinusoidal waveform. The electric quantities e ₃ , e ₅ and e ₆ are drawn on the same scale of the currents I _1A , I _1B and I _1C , respectively, and the electric quantities e ₃ and e where saturation does not occur.
₅ is shown in the same figure as the currents I _1A and I _1B , respectively. Since electric quantity e ₆ is the conversion device 1 of the terminal 1C saturated, not the same figure as the current I _1C, the saturation value e _S as shown, the waveform is saturated by -e _S. Due to this saturation, the electric quantity e ₇ does not become zero in spite of an external accident and becomes considerably large during the saturation period of the waveform of e ₆ . Therefore differential detector 6 operates, the period in which the instantaneous value of the period e ₇ waveform e ₇ is the saturation of e ₆ waveform has occurred in the positive wave is saturated negative, negative wave is positive . Since the instantaneous value of e ₆ is more positive than e _L during the period in which the e ₆ waveform is positive and slightly longer than the saturation period, the level detector 9 produces an output and the OR circuit 10 produces an output during this period.
Further, during the period e ₇ in which the waveform of e ₆ is positive and saturated, the waveform is negative, so that an output is generated at the level detector 18 during this period. Since both the OR circuit 10 and the level detector 18 have outputs, the phase detector 11 operates after the time θ and produces an output. Also, for a period slightly longer than the period in which the e ₆ waveform is negative and saturated, e ₆ is −
Since it is more negative than e _L , an output is generated in the level detector 15 and the OR circuit 16 during this period. In addition, since the e ₇ waveform is positive while the e ₆ waveform is negative and saturated, an output is generated to the level detector 19 during this period. Since both the detector 19 and the OR circuit 16 have outputs, the phase detector 17 operates after the time θ and produces an output.

Since the above-mentioned response is repeated every cycle of the current waveform, the outputs of the phase detectors 11 and 17 are continuous outputs due to the recovery time. As a result, a continuous output is obtained in the OR circuit 20, no output is provided to the inhibit circuit 12 regardless of the operation of the differential detector 6, and no interruption is performed. The operation of the differential detector 6 requires a time delay φ, and since φ is longer than θ, an output is generated in the detector 6 before the output of the OR circuit 20 is generated and is not tripped by the inhibit circuit 12. According to the above conventional technique, a converter having an appropriate saturation characteristic is used to obtain an electric quantity corresponding to each terminal current, and a differential relay that operates when the sum of the electric quantities (differential electric quantity) is under a predetermined condition, Due to the emphasizing operation of the phase comparator that responds to the phase relationship between the quantity of electricity corresponding to the terminal current and the quantity of differential electricity that meet the specified conditions, the converter is saturated and the quantity of differential electricity is changed in the event of an external accident. A relay device that can identify the inside and outside of the accident even if it occurs is obtained.

[0007]

However, in the conventional configuration, the operation of the differential detector 6 has a time delay φ. This time delay will always occur whether or not the converter is saturated. Therefore, since the trip time is always delayed by the time φ, there is a drawback that it becomes an obstacle when high-speed trip is required. The present invention has been made to solve the above problems, and in a device for protecting a transformer by a current differential relay system, an internal accident can be detected with high sensitivity and at high speed, and external It is an object of the present invention to provide a digital transformer protection relay device that can prevent malfunctions in the event of an accident.

[0008]

According to a first aspect of the present invention, there is provided a digital transformer protection relay device, which is an analog / digital converter only for the maximum input current at the time of an external accident in which the maximum input current occurs in the external accident of the transformer. The input conversion means set to saturate the conversion means, the detection means for detecting and outputting that the magnitude of the input current has reached the saturation value of the analog / digital conversion means, and at least the output of the detection means. As a condition, the control means controls the motion determination to the non-motion side. According to a second aspect of the present invention, there is provided a determination unit that determines and outputs that the polarity of the input current detected by the detection unit and the polarity of the differential current are opposite polarities. I tried to add it.

According to the first aspect of the present invention, the input transformer connected to each power source receives at least the maximum input power when the secondary current in the secondary side of the transformer is the maximum input power. At this time, the conversion ratio is such that A / D conversion can be performed correctly.
For the input transformer connected to the load, make sure that the load current at all times is within the full scale of A / D conversion, or that the secondary current of the system at the time of an external accident on the tertiary side becomes A / D full scale or more. It is set to a different conversion ratio. Therefore, the load terminal output is different from the relay input only when there is a tertiary external accident, and is equal to each relay input in other cases. If they are different, the differential output is set to "0", and in other cases, the operation determination is performed using the converted electric quantities and the differential outputs. According to a second aspect of the present invention, like the first aspect, first, a differential component is detected from each digital data, and when this is a predetermined value or more,
With respect to all of those having the predetermined value or more, whether there is one having a polarity opposite to that of the differential output obtained first is examined to make an internal / external determination.

[0009]

Embodiments will be described below with reference to the drawings. Figure 1
1 is a configuration diagram of an embodiment of a digital transformer protection relay device according to the present invention, which is applied to a three-winding transformer. In Fig. 1, 100 is a transformer, the primary and secondary sides of which are connected to the power source and the tertiary side of which is connected to the load. Transformer 10
The primary, secondary, and tertiary winding currents I ₁ , I ₂ , and I _{3 of 0} are the system secondary current i ₁ by the current transformers CT ₁ , CT ₂ and CT _{3, respectively.}
Converted to ₁ , i ₂ , i ₃ . System secondary current i ₁ ,
i ₂ and i ₃ are input to the digital protective relay 101 ,
The input transformers 1021, 1022 and 1023 respectively convert the electric quantities e ₁ , e ₂ and e ₃ of a predetermined magnitude by a method described later. The electric quantities e ₁ , e ₂ , e ₃ are input to the A / D conversion circuit 103 . This A / D conversion circuit 103 has a sample hold S
/ H, a multiplexer MUX, and an analog / digital conversion unit A / D, but since this configuration is publicly known, detailed description will be omitted. The A / D conversion circuit 103 uses e ₁ , e ₂ ,
e _{3 It} is converted into a digital value in a time series, and is converted into digital data D ₁ , D ₂ , D _{3 by} a digital operation unit (hereinafter referred to as MP
(U) 104. The MPU 104 inputs the digital data D ₁ , D ₂ and D ₃ and judges the presence or absence of an accident in the transformer 100 from the arithmetic processing described later based on these data, and when it judges that there is an accident, it outputs the trip output. Output.

Next, the operation will be described. Input transformer 10
21 is the system secondary current e ₁ at the secondary side external accident of the transformer 100
_{Is a} maximum input current i _1max , a conversion ratio is set so that the system secondary current i ₁ is converted into an electric quantity e ₁ so that A / D can be properly analog / digital converted at least when i _{1max is} input. . That is, i _1max is set within the full scale of A / D. In exactly the same manner, the input transformer 1022 is set to a conversion ratio such that the secondary current i _2max at the time of a primary side external _fault of the transformer 100 is within the full scale of A / D. In the input transformer 1023, at least the constant load current i _3L in the system secondary current i ₃ is within the A / D full scale. System secondary current i _{3max in} case of external accident on the tertiary side
Is set to a conversion ratio such that the full scale of A / D is obtained. By setting the conversion ratios of the input transformers 1021, 1022, and 1023 as described above, the digital data D ₃ is not equal to the magnitude of the relay input i ₃ only in the case of an external accident on the tertiary side, but in other states the digital data D ₃ is not. D _1, D _2, D ₃ both equal to relay input _{i 1, i 2, i 3} .

Next, the arithmetic processing of the MPU 104 will be described with reference to FIG. FIG. 2 is an example of a flowchart of the arithmetic processing of the MPU 104. In FIG. 2, in process f ₁ , the process of reading digital data D ₁ , D ₂ , D ₃ is performed, and process f ₂
Then, from this data D ₁ , D ₂ , D ₃ , D _d = D ₁ + D ₂ + D ₃ ………………………………………… (1) Instantaneous value data D _d is obtained.
In the process f ₃ , the absolute value of the digital data D ₃ and the predetermined value L
_Performs comparison processing with ₀ . At current f ₃ , D ₃ is L
When it is determined that the _{value is} greater than ₀ , the next process is f ₄ .
On the other hand, when it is determined that D ₃ is equal to or smaller than L ₀ , the next process is process f ₅ . In the process f ₄ , the instantaneous value data D _d of the differential current is set to the value “0”. Next, in the process f ₅ , the data D ₁ , D ₂ , D ₃ and D _d
Is used to make a motion determination. Although this operation determination method is publicly known and its detailed description is omitted, for example, | ΣD _d | -K ₁ || ΣD ₁ | + | ΣD ₂ | + | ΣD ₃ || ≧ K ₀ (2) K ₁ , K ₀ : a constant. Σ: Amplitude value calculation. The motion determination is performed by the following motion formula. In the calculation related to the equation (2), it is assumed that the current transformer ratio matching is performed by the input transformers 1021, 1022, 1023. The response in the embodiment of the present invention described above with reference to FIGS. 1 and 2 will be described below. The response of the present invention is a response in the arithmetic processing in the MPU 104,
Although it is a response to discrete digital data, an analog waveform will be used for the sake of simplicity.

FIG. 3 shows the amount of electricity e in the system when the system is healthy.
Waveforms of ₁ , e ₂ , e ₃ with primary side inflow, secondary and 3
The outflow shows the next side. The input transformer 1023 performs a conversion for a constant load-like flow input so that the A / D output is not saturated. Therefore, the level of the electric quantity e ₃ is lower than the output level L _0p of the input transformer 1023 corresponding to the predetermined value L ₀ in the process f ₃ of FIG. On the other hand, since the electric quantities e ₁ and e ₂ are not saturated, e ₁ ,
Differential current e _d calculated from e ₂ and e ₃ (ΣD in equation (2)
₍ corresponding to _d ) is “0”. This differential current e _d is calculated as ΣD _d shown in equation (2) in the operation determination. This ΣD _d is ideally zero, but it does not become zero due to the error of the current transformer and the error such as mismatch of the current ratio. Therefore, K ₀ shown in the equation (2), that is, the detection Give sensitivity, Σ
If D _d does not exceed a certain value, it is determined to be inoperative. It can be said that the lower the detection sensitivity K _{0, the} better the protection performance. By the way, in the digital protective relay device shown in FIG. 1, in consideration of K ₀ , it is necessary to further consider the quantization error in A / D. That is, it is possible to convert the system currents I ₁ , I ₂ , and I _{3 up} to a large current region in A / D. That is, if the full scale is large, an error occurs in the determination of the size due to a quantization error when a small current is input (for example, load flow). In particular, this problem is remarkable for the tertiary current I ₃ for the following reason.

In the case of an external accident in the primary or secondary of the transformer 100, only the passing current from the secondary or primary side power source flows respectively, whereas in the external accident in the tertiary, the current from both power sources is Will pass through. Therefore, in general, the CT ratio of the current transformer CT ₃ is set to be larger than that of CT ₁ and CT ₂ , but nevertheless, i ₁ and i ₂ at the time of a primary or secondary external accident of the transformer 100 are still set. Comparing the magnitude of i and i ₃ at the time of the _third external accident, the latter is several to ten times that of the former. Therefore, if i _3max is full scale,
The quantization error for i ₃ is extremely large for i ₁ and i ₂ , and the detection sensitivity K ₀ must be increased. In the present invention, as described above, since i _3L is set to be within the A / D full scale, I ₃ ie i ₃ and e ₃
Even if is small, quantization and error can be reduced, and e
The calculation of _d (ΣD _d ), that is, the detection sensitivity K ₀ can be lowered.

FIG. 4 shows an internal fault condition of the transformer 100.
At the time of an internal accident, e ₁ and e ₂ will flow in, and e ₃ will not flow because there is no power source behind it. Therefore, in the process of FIG. 2, the determination in the process f ₃ is | D ₃ | ≦ L ₀ , and when the configuration is such that there is no saturation with respect to e ₃ , the determination is exactly the same and the differential current e _d , that is, ΣD It can be determined at high speed using _d . Even when the full scale in A / D conversion is a value indicated by L _1p and L _2p with respect to e ₁ and e ₂ , the differential current e _d is as indicated by the broken line, but this is a hindrance to the operation determination. There is no.

FIG. 5 shows a secondary side external accident of the transformer 100. At this time, e ₁ flows in, e ₂ flows out, and e ₃ does not flow as in FIG. Therefore, at the time of this external accident, as in the case of FIG. 4, the determination of | D ₃ | ≦ L ₀ is made for the current f ₃ in FIG. 5, which is the same as when there is no saturation for e ₃ . The differential current e _d is zero, that is, ΣD _d is zero, and the external accident can be correctly determined.

FIG. 6 shows an external accident on the tertiary side of the transformer 100. At this time, e ₁ and e ₂ are inflow, and e ₃ is outflow.
As described above, the magnitude of the electric quantity e ₃ is equal to or larger than the full scale L _0p of A / D conversion. Therefore, the differential current e _d , that is, ΣD _d should not be generated, but e ₃ is A
/ D during the time that exceeds the level l _0p corresponding to the full scale l ₀ transformation t ₂ ~t ₃ and t ₇ ~t _8, differential current e _d corresponding to a size exceeding the full scale l _0p broken line Occurs like. However, e ₃ exceeds the level L _0p corresponding to the determination level L ₀ in the process f ₃ in FIG. 2 between times t _{1 to} t ₄ and t _{6 to} t ₉ , and the differential current D during this time. _As described in FIG. 2, the calculation of _d becomes zero by executing the process f ₄ . Therefore, it is possible to prevent malfunction even in the case of a tertiary external accident. It should be noted that the relay operation related to the internal accident with leakage is possible as in the conventional case. That is, even if there is an outflow in I ₂ or I ₃ , the outflow current is equivalent to the load current, and for a current of this magnitude, the A / D does not full scale over as described above. Therefore, it is clear that the motion determination can be executed by the equation (2) exactly as in the conventional case. As described above, according to this embodiment, the dynamic range of the current input is made small, so that the detection sensitivity can be made high and the internal accident can be detected with high sensitivity. Further, the difference current at the time of an external accident, which occurs with the reduction of the dynamic range of the current input, can be judged as an external accident by monitoring the input level, so that it can be controlled to zero in operation judgment. . Therefore, it is possible to prevent malfunction in the event of an external accident. Further, since it is possible to prevent malfunction in the event of an external accident, there is no need for delay in motion determination, and trip output can be output at high speed.

According to the above embodiment, the current inputs i ₁ ,
The case where it is known in advance which one of i ₂ and i ₃ is the tertiary input of the transformer has been shown as an example, but generally, any input may be connected to the tertiary. There is. In that case, it may be modified as follows. First, the input transformer 10
The current ratio matching at 21, 1022, and 1023 is performed by a known tap selection method. The current ratio matching can be freely selected by tap selection. In addition, the conversion ratio of the input transformers 1021, 1022, and 1023 is A / D for the system secondary currents i ₁ and i ₂ in any of the primary, secondary, and tertiary external faults of the transformer. Set so that full scale is not exceeded. Then M
In the arithmetic processing of the PU 104, the flow of FIG. 2 may be changed to the processing of FIG. However, the same processing symbol indicates the same processing. In FIG. 7, in process f _3A , digital data D
_{All 1} , ₁ , D ₂ , and D ₃ are compared with a predetermined value L ₀ . Then, as a result, when all are less than or equal to the predetermined value L ₀ , the process f ₅ is executed next. On the other hand, either one
If one exceeds the predetermined value L ₀ , then the process f ₆ is executed. In the process f ₆ , the digital data D ₁ ,
Of all D ₂ and D ₃ , the digital data D _d obtained in the process f ₂ for all the digital data which has become the predetermined value L ₀ or more in the process f _3A.
The polarity of and is determined. Then, if there is a reverse polarity, the process f ₄ is executed next, and if not, the process f ₅ is executed next. The other processes are the same as those in FIG. 2 and their explanations are omitted.

The response of the other embodiment shown in FIGS. 1 and 7 will be described below. As mentioned above, e ₁ ,
It has been set that e ₂ and e ₃ exceed the full scale of A / D conversion only when there is an external accident in the third transformer and when there is an internal accident in the transformer. Therefore, considering the first case, as shown in FIG. 6, it is only the terminal of the tertiary side input of the transformer 100 that exceeds the full scale l _0p ,
At this time, l _d and l ₃ have opposite polarities, that is, D _d and D ₃ have opposite polarities. On the other hand, considering the latter case, as shown in FIG. 4, both the secondary side input and the tertiary side input of the transformer 100 may exceed the full scale. However, in that case, the differential current e _d and the primary current have the same polarity. Therefore, in the process f ₆ in FIG. 7, it is an external accident when it is determined that the polarity is opposite, and when it is the same polarity, it is an internal accident, and the same action as the process in FIG. 2 is obtained. As explained above, in the configuration of FIG.
By selecting the conversion ratio of 1,1022,1023 so that the A / D does not full scale over in the event of any external accident of the transformer, and making the processing of MPU104 the processing of FIG. In addition to the effect of the configuration shown, it is possible to provide a device in which the connection of the relay input can be arbitrarily selected.

In addition to the above, various modified configurations are possible and will be listed and described below. (1) In the above description, the case of protecting a three-winding transformer was described, but it is clear that the same can be applied to a two-winding transformer. For example, considering the application of the arithmetic processing of FIG. 7, it is only necessary to consider the number of relay inputs as two. (2) In the processing of FIGS. 2 and 7, the method of controlling D _d to zero in the processing f ₄ has been described, but the present invention is not limited to this, and various modifications can be made as follows. Always controlled to a predetermined value close to zero regardless D _d to the magnitude of D _{d. Let} D _d be D _d ′ = D _d / K (K: a constant larger than 1)
And Instead of controlling D _d , the differential current amplitude calculation result Σ
Control D _{d in the same way} as zero or. Instead of controlling D _d , the left side of equation (2), that is, the calculated value of (motion amount-suppression amount) is controlled to zero or a value close to zero. (3) In the above description, the method of controlling the value in the operation determination formula such as the differential current when it is determined to be an external accident has been described, but the output may be simply locked. (4) In the above configuration, the current transformer ratio matching is performed by the input transformer, but the present invention is not limited to this, and the MPU may perform arithmetic processing. In that case, in the processes of FIGS. 2 and 7, a process of multiplying the digital data D ₁ , D ₂ and D ₃ by the current ratio matching coefficient is inserted between the processes f ₁ and f ₂ . Needless to say, the processing f ₂ and the processing f ₅ are performed in consideration of the current-changing ratio matching coefficient. (5) In the above description, the configuration in which the dynamic range of the current input is set by the input transformer is used, but the present invention is not limited to this. For example, a known amplifier circuit may be used as the input transformer having the configuration shown in FIG.
It is obvious that the circuit may be inserted between 1021, 1022, 1023 and the S / H, and the circuit having the amplifying function may be located anywhere between the input transformer and the A / D.

[0020]

As described above, according to the present invention, in the device for protecting the transformer by the current differential relay system,
The effects listed below are produced. (1) Since the dynamic range of the current input is made small, the detection sensitivity can be made high, the internal accident can be made highly sensitive, and (2) the difference current due to the reduction of the dynamic range of the current input can be reduced. Although it occurs, it is controlled by the external accident detection means so that it does not malfunction even with the differential current, (3)
By the method of preventing an external accident by the method of (2), it is possible to provide a digital transformer protection relay device capable of performing the same operation determination as in the past and having no operation delay.

[Brief description of drawings]

FIG. 1 shows an embodiment of the configuration of a digital transformer protection relay device according to the present invention.

FIG. 2 is a flowchart of a calculation process of the MPU in FIG.

[Fig. 3] Electricity e ₁ in the system when the system is in a healthy state,
Waveforms of e ₂ and e ₃ .

FIG. 4 is a waveform diagram at the time of an internal accident of a transformer.

FIG. 5 is a waveform diagram at the time of a secondary side external accident of the transformer.

FIG. 6 is a waveform diagram at the time of an external accident on the tertiary side of the transformer.

FIG. 7 is a flowchart of another embodiment of the MPU arithmetic processing according to the present invention.

FIG. 8 shows a configuration example according to a conventional technique.

FIG. 9 is a diagram showing a relationship between inputs and outputs from a system.

FIG. 10 is a diagram illustrating a state where an input current is highly saturated.

[Description of symbols] 101 Digital protective relay 1021, 1022, 1023 Input transformer 103 A / D converter circuit 104 Digital operation unit

Claims (2)

[Claims] 1. A digital transformer protection relay device for protecting a transformer by using a current differential relay system, wherein the maximum input current at the time of an external accident in which the maximum input current occurs among the external accidents of the transformer. Input conversion means set so that the analog / digital conversion means saturates, and detection means for detecting and outputting that the magnitude of the input current has reached near the saturation value of the analog / digital conversion means. A digital transformer protection relay device, comprising at least control means for controlling an operation determination to a non-operation side on the condition of an output of the detection means. 2. A determination means for determining that the polarity of the input current detected by the detection means and the polarity of the differential current are opposite polarities and outputting the determination result, wherein the output of the determination means is a condition of the control means. The digital relay protection relay device according to claim 1, wherein the digital relay protection relay device is added.