JPH0862272A - Ratio differential relay and improper connection-detector of current transformer - Google Patents

Abstract

PURPOSE: To detect improper connection of CT accurately even in the case, wherein there is a differential current owing to the limit (error) of adjustment and the differential current cannot be distinguished as to whether the different current is caused by improper connection of the CT or by the differential current. CONSTITUTION: A phase changing means 31 sequentially changes the phase between I1 and I2 from an input converter 42 by 0 deg.-360 deg. by pushing a phase- changing test switch 30. The differential current value of I1 -I2 (=I3 ) corresponding to the change is operated with an operating means 32. The phase, where the differential current value of I1 -I2 (=I3 ) becomes the minimum value or the maximum value, is detected by a phase detecting means 33. A phase judging means 34 judges an improper connection when the detected phase is a specified value (for example, when the phase of the maximum value of the differential current value of I1 -I2 is 0 deg., the polarity is wrong), and the warning is generated in an output means 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer erroneous connection detection device for checking whether or not a current transformer connection is correct, and a ratio differential relay incorporating the erroneous connection detection device.

[0002]

2. Description of the Related Art As a digital type protective relay, the Electric Cooperative Research Vol. 41, No. 4, "Digital Relay", Showa 6
Published by the Japan Electric Cooperative Research Group in January 1st. The basic configuration is shown in FIG. In the figure, 11 is a current transformer (hereinafter referred to as CT), 12 is a filter circuit for removing harmonic components contained in the output of CT 11 and extracting the fundamental frequency (50 Hz or 60 Hz) of the power system, and 13 is at the sampling time. A sample and hold circuit that holds the output value of the filter circuit 12, 14 is a multiplexer circuit that multiplexes the output from the sample and hold circuit 13, and 15
Is an analog-to-digital converter that quantizes the output of the multiplexer circuit 14 and converts it into time data of a digital amount.

Reference numeral 16 denotes a microprocessor, a random access memory, a read-on memory, etc., and an arithmetic processing section for arithmetically processing the time data from the A / D converter 15 to generate a control signal, and 17 an arithmetic processing section 16 The output interface circuit for converting the control signal of the logic level which is the output of the control signal into the control signal of the level capable of driving the relay, 18 is the exciting coil driven by the control signal from the output interface circuit 17, and 19 is the exciting coil 18. It is a contact that is opened and closed.

Further, as an analog type ratio differential relay which outputs an output by comparing and judging a differential current value and a suppression current value,
"Protective relay technology" Author Susumu Kobayashi, Issued the 1st edition of the 1st printing on October 15, 1972, 9 Transformer protection, 9-1 Power transformer protection. The basic configuration is shown in FIG.

In the figure, 40 is a ratio differential relay, 41
Is a protected object such as a transformer, 42 is an input converter that adjusts the current (I ₁ ) on the primary side and the current (I ₂ ) on the secondary side to be equal to each other across the object 41 to be protected, and 43 is Means for generating a differential current of I ₁ -I ₂ , 44 is a means for generating a suppressing current of I ₁ + I ₂ , 45 is a judging means for judging an abnormality of the protection target 41 by comparing the differential current and the suppressing current, Reference numeral 49 is an output means for outputting an abnormality signal at the time of abnormality determination. 46, 4
Reference numerals 7 and 48 denote A-phase, B-phase, and C-phase operation determination means for performing operation determination on each of the A-phase, B-phase, and C-phase to detect an abnormality.

The digital type ratio differential relay 20 shown in FIG. 20 is a combination of the FIG. 18 digital type protection relay and the FIG. 19 ratio differential relay cited in the above-mentioned conventional technique. Here, in order to explain the operation, the filter 1 shown in FIG.
2, sample and hold circuit 13, multiplexer circuit 1
4, analog-digital converter 15, exciting coil 1
8 and the contact 19 are included in the digital type ratio differential relay 20, but omitted.

In FIG. 20, reference numeral 20 is a digital type ratio differential relay, and 16 is an arithmetic processing section, which is an A-phase operation determining means 24 and a B-phase operation determining means 2 for making a digital operation determination.
5, the C-phase operation determination means 26 is included, and these are collectively processed. This is the A-phase operation determination means 46 and the B-phase operation determination means 4 for determining the operation in analog of FIG.
7 corresponds to the C-phase operation determination means 48.

Reference numeral 21 is a means for calculating a differential current value of I ₁ -I ₂ , 22 is a means for calculating a suppressing current value of I ₁ + I ₂ , 23
Is a judging means for judging the abnormality of the protection target 41 by comparing the differential current and the suppressing current, and 21, 22 and 23 are each executed by calculating by a microprocessor. It corresponds to 43, 44, 45 of the form ratio differential relay.

As a description of the operating principle, the case of a single phase will be described. FIG. 21 shows the operation of the ratio differential relay in the steady state. The input converter 42 is
When the magnitudes of I ₁ and I ₂ are changed by the above, it is a converter for making the current values fetched in the A-phase operation determination means 24 equal in magnitude, and already adjusted in FIGS. 21 to 23. And

This ratio differential relay has a CT11 on the primary side.
And the CT11 on the secondary side are protected, and this protection section is referred to as a protection section 51 of the ratio differential relay. The ratio differential relay outputs the operation output only when a failure such as a ground fault or a short circuit occurs in the protection section 51, and does not operate in the sections other than the protection section 51.

[0011] In Figure 21, from I ₁ ≒ I _2, differential current value means 21 for calculating the differential current value of I ₁ -I ₂ is I ₁ -I ₂ ≒
0. Even if an accident occurs outside the protection section 51 of the ratio differential relay as shown in FIG. 22, the primary side CT11
Since the ratio of I ₁ and I ₂ flowing in the secondary side CT11 is the same as in the steady state, the differential current value becomes I ₁ −I ₂ ≈0 and the operation does not occur. When an accident occurs in the protection section 51 of the ratio differential relay as shown in FIG. 23, the magnitudes of I ₁ and I ₂ change, and I ₁ −I ₂ ≠ 0. This makes the ratio differential relay
It operates when an accident occurs only in the protection section 51.

[0012]

Since the conventional ratio differential relay is configured as described above, the input converter 42 shown in FIG. 21 is adjusted so that I ₁ and I _{2 have} the same size. However, even if adjustment is made, there will be a difference in magnitude between I ₁ and I ₂ . Therefore, the differential current value of the means 21 for calculating the differential current value of I ₁ -I _{2 in} FIG. 20 is not I ₁ -I ₂ ≠ 0 even in the steady state, and the value of I ₁ -I ₂ = I ₃ is output. Come on.

Here, in FIG. 21, if the polarity (phase connection) of the CT11 on the primary side or the secondary side is wrong, for example, I ₂ becomes −I ₂ , and I ₁ − (− I ₂ ) = K. Comes out. Here, since both the differential current value K due to CT polarity (phase connection) error and the differential current value I _{3 due to} adjustment error have a certain amount of magnitude, even if the CT polarity (phase connection) is wrong, There was a problem that the CT polarity (phase connection) error could not be found in the steady state.

The present invention has been made in order to solve the above-mentioned problems, and provides an erroneous connection detection device for a current transformer which can detect CT polarity and erroneous phase connection, and this erroneous connection detection device. The purpose is to obtain a ratio differential relay with.

[0015]

An erroneous connection detection device for a current transformer according to the present invention detects the amount of electricity from two current transformers that are the objects of erroneous connection detection among the current transformers provided in an AC line. As input, phase changing means for changing the phase between the two electric quantities, arithmetic means for calculating the electric quantity of the difference between the two electric quantities corresponding to the change in the phase, the value of the changed phase angle and this phase angle Display means is provided for displaying the calculation result of the corresponding electric quantity of the difference.

Further, among the current transformers provided in the AC line,
Inputting the electric quantities from the two current transformers that are the targets of erroneous connection detection, phase changing means for changing the phase between the electric quantities, and calculating the electric quantity of the difference between the electric quantities corresponding to the change in the phase. And a phase detecting means for detecting at least one of the phases in which the electric quantity of the difference is minimum and maximum.

Further, among the current transformers provided in the AC line,
Inputting the electric quantities from the two current transformers that are the targets of erroneous connection detection, phase changing means for changing the phase between the electric quantities, and calculating the electric quantity of the difference between the electric quantities corresponding to the change in the phase. Calculating means, phase detecting means for detecting at least one of the phases in which the difference electric quantity is minimum and maximum, and it is determined whether or not the connection of the current transformer is normal according to the detection result. It is provided with a phase determination means.

Further, the phase determining means determines that the polarity of either one of the current transformers is reverse connection if the phase where the difference electric quantity is maximum is 0 ° or the phase where it is minimum is 180 °. It is a means to do.

Further, when the electric line is a three-phase AC line, the phase determining means sets the phase at which the difference has a maximum amount of electricity of + 60 ° or -60 °, or the minimum phase of +12.
If the angle is 0 ° or -120 °, it is used as a means for determining the incorrect connection of the current transformers of different phases.

Further, when the electric line is a three-phase AC line, the phase determining means determines that the phase at which the amount of difference is maximum is +120.
° or -120 °, or the minimum phase is +6
If it is 0 ° or −60 °, it is a means for judging that the current transformers of different phases are erroneously connected and the polarity of either one of the current transformers is erroneous.

Further, the phase changing means is a means for changing the phase by 0 ° to 360 ° in steps of a predetermined phase angle.

The ratio differential relay of the present invention has a built-in erroneous connection detection device for a current transformer.

[0023]

The erroneous connection detection device for a current transformer according to the present invention uses the electric quantities from two current transformers, which are the objects of erroneous connection detection, among the current transformers provided in the AC line as inputs. The phase between the quantities is changed by the phase changing means, the electric quantity of the difference between the two electric quantities corresponding to the change of the phase is calculated by the calculating means, and the changed phase angle value and the difference corresponding to this phase angle are calculated. The calculation result of the electric quantity of is displayed on the display means.

Among the current transformers provided in the AC line,
The electric quantities from the two current transformers, which are the objects of erroneous connection detection, are input, the phase between the electric quantities is changed by the phase changing means, and the electric quantity of the difference between the electric quantities corresponding to the phase change is calculated. The phase detecting means detects at least one of the phases where the difference is calculated by the calculating means and the difference electric quantity is minimum and maximum.

Among the current transformers provided in the AC line,
The electric quantities from the two current transformers, which are the objects of erroneous connection detection, are input, the phase between the electric quantities is changed by the phase changing means, and the electric quantity of the difference between the electric quantities corresponding to the phase change is calculated. The phase detection means detects at least one of the phases where the difference electric quantity is minimum and maximum calculated by the calculation means, and the phase of the current transformer is checked according to the detection result. Determined by the determination means.

Further, the phase determining means determines that the polarity of either one of the current transformers is reverse connection if the phase where the difference electric quantity is maximum is 0 ° or the phase where it is minimum is 180 °. To do.

Further, when the electric line is a three-phase AC line, the phase determining means uses + 60 ° or −60 ° for the phase where the difference is maximum, or +12 for the minimum phase.
If it is 0 ° or −120 °, it is determined that the current transformers of different phases are erroneously connected.

Further, when the electric line is a three-phase AC line, the phase determining means determines that the phase at which the amount of difference is maximum is +120.
° or -120 °, or the minimum phase is +6
If it is 0 ° or −60 °, it is determined that the current transformers of different phases are erroneously connected, and the polarity of either one of the current transformers is erroneous.

Further, the phase changing means changes the phase change by 0 ° to 360 ° in steps of a predetermined phase angle.

The ratio differential relay of the present invention has a built-in wrong connection detection device for a current transformer.

[0031]

【Example】

Example 1. First, the operating principle of detecting polarity and phase connection due to CT misconnection will be described. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 to 9 are vector diagrams for explaining the principle.

In FIG. 1, reference numerals 30 to 35 constitute an erroneous connection detecting device for detecting erroneous connection of the current transformer. Three
Reference numeral 0 denotes a phase change test switch, which sends a signal for changing the phase of I ₁ and I ₂ by a predetermined angle between 0 ° and 360 ° each time the test switch is pressed. Reference numeral 31 is a phase change means, which changes the phase of I ₁ and I ₂ by a predetermined angle in response to the signal from the phase change test switch 30. Numeral 32 is an arithmetic means for calculating a differential current value of I ₁ -I ₂ . Reference numeral 33 is a phase detecting means for detecting the phase at which the differential current value of I ₁ -I ₂ is maximum or minimum.

The phase changing means 3 receives the currents I ₁ and I ₂ from the input converter 42 according to the command from the phase changing test switch 30.
1 changes the phase between I ₁ and I ₂ at a predetermined interval. To change this phase, the analog waveforms of I ₁ and I ₂ are sampled and digitized, and the digitized I
The phase can be changed by extracting two waveform values with a time difference corresponding to the phase so as to obtain a desired phase from the waveforms of ₁ and I ₂ .

The calculating means 3 calculates the difference between the extracted I ₁ and I _2.
2 is calculated to obtain the differential current value of I ₁ -I ₂ . The phase detecting means 33 detects the phase (angle) at which the differential current value of I ₁ -I ₂ becomes maximum. The phase determination unit 34 determines that the phase in which the detected differential current value is maximum is the phase in which the incorrect connection occurs, which is the incorrect connection. In response to this determination, the output means 35 sends out a signal of incorrect connection to the outside. As described above, the incorrect connection of the current transformer can be detected.

The operation described above will be explained using vectors. FIG. 2 shows that when the polarity of CT11 in FIG. 1 is correctly connected, a differential current of I ₁ -I ₂ (= I ₃ ) is generated. Here, as shown in FIG.
By pressing the phase change test switch 30 shown in FIG. 1, the phase is sequentially changed from 0 ° to 360 °. In this figure, I ₂ is fixed, I ₁ is changed, and the vector I shown by the dotted line is changed.
A differential current value of ₁₋ I ₂ (= I ₃ ) is obtained.

The locus of the differential current value of I ₁ -I ₂ (= I ₃ ) is shown in FIG. That is, the phase 0 ° I ₃ minimum phase 180 ° I ₃ is maximized. If the polarity is wrong, the phase of I ₁ or I ₂ has changed by 180 °, so that I ₃ is 180 ° in FIG. 4 even if the phase is not changed by the phase change test switch 30. It will be maximum. If the phase of I ₁ is changed 180 degrees in this state,
It becomes a vector value at the position of 0 ° in the figure, and I ₁ −I ₂ (= I
It can be seen that the differential current value in ₃ ) is minimized and the polarity is incorrect. Therefore, if the differential current value of I ₁ -I ₂ (= I ₃ ) is maximized when the phase is changed by 0 ° or 360 °, it can be understood that the polarity is wrong.

Next, the case of three phases will be described. In Fig. 5, if the relay incorporates a three-phase alternating current with a phase shift of 120 ° between A phase, B phase, and C phase, CT
The polarity have matching, I ₁ and I ₂ is the A-phase with each other (B-phase with each other, C-phase with each other, either good but) When a,
The relationship of FIGS. 2 to 4 is maintained.

However, when the phases taken in by I ₁ and I ₂ are wrong, the phases of I ₁ and I ₂ are different by 120 ° as shown in FIG. 6, and the value of I ₁ -I ₂ becomes large. Here, by pressing the phase change test switch 30 in FIG. 1 the phase of I ₁ 0
When the phase is advanced from 360 ° (I ₁ -I _{2 in} FIG. 6 is 120 °) to 360 °, the vector locus of I ₁ -I ₂ as shown in FIG. 7 is obtained. That is, it becomes maximum at 60 ° and minimum at 240 °. In parentheses (300 °),
(120 °) is the angle when the phase is changed in the delay direction.

[0039] If it is this way, the polarity of the CT will match you make a mistake phase to incorporate to the relay in the I ₁ and I _2, I ₁ and I ₂
There is a phase difference of 120 ° between them. When the phase is changed ± 60 ° (60 ° with lead and lag) from this state,
If the differential current value of I ₁ -I ₂ (= I ₃ ) becomes the minimum on either the lead or the lag side, it can be determined that only the phase connection is wrong. Further, when the phase is changed by ± 120 ° (120 ° in advance or delay), if the differential current value of I ₁ -I ₂ (= I ₃ ) becomes the maximum in either advance or delay, Similarly, it can be determined that only the phase connection is wrong. In addition, when the phase is advanced, the maximum becomes 60 °, and 2
When it becomes the minimum at 40 °, or the phase is delayed 1
If the minimum is 20 ° and the maximum is 300 °, it can be determined that only the phase connection is wrong.

Next, consider a case where the phase taken into the relay is wrong between I ₁ and I _2, and the polarity of the wrongly taken phase is wrong. The relationship between the input phases of I ₁ and I ₂ is 180 ° due to incorrect polarity and 120 ° due to incorrect phase input.
Therefore, 300 °, that is, the phase difference between I ₁ and I ₂ is 60 ° as shown in FIG. When the phase is changed from 0 ° to 360 ° in this state, a vector locus of I ₁ -I ₂ as shown in FIG. 9 is obtained.

Phase is ± 120 ° (12 in lead and lag)
0 °) when changed, I or I
_If the differential current value of ₁₋ I ₂ (= I ₃ ) is maximum, it can be determined that the phase connection and the polarity are incorrect. Also,
When the phase is changed ± 60 ° (60 ° for lead and lag), I ₁ −I ₂ (= I ₃ ) for either lead or lag
If the differential current value of is the minimum, it can be determined that the phase connection and its polarity are also incorrect. Also, when the phase is advanced to become the minimum at 60 ° and becomes the maximum at 240 °, or when the phase is delayed to become the maximum at 120 ° and the minimum at 300 °, the phase connection and its polarity are the same. Can be judged to be wrong.

FIG. 10 is a diagram showing the maximum / minimum relationship of the differential current values when the phase is changed, and the determination result.

The above is the principle of operation of the present invention for detecting CT erroneous connection. Next, specific examples will be described. FIG. 11 is a diagram showing a main part of the CT erroneous connection detection device in the ratio differential relay. The arithmetic processing unit 16 of the ratio differential relay in FIG. 1, a protection target 41 such as a transformer, the CT 11, the input conversion. The device 42 and the like are omitted, and the I from the input converter 42 is omitted.
It is shown from the part where ₁ and I ₂ are introduced.

In the figure, reference numerals 30, 31, 32 and 35 are the same as those in FIG. 61 is a computing means 3
The means for detecting the phase when the differential current value becomes the maximum among the differential current values of I ₁ -I ₂ calculated in 2, and 62 is means for determining whether the phase detected in 61 is 0 °. .

In operation, each time the phase change test switch 30 is pressed, the phase is changed by the phase change means 31 and the value of I ₁ -I ₂ corresponding to the changed phase is calculated by the calculation means 3
2, the means 61 for detecting the phase having the maximum differential current value of I ₁ -I ₂ detects the phase at the maximum value, and the means 62 for judging whether the phase is 0 ° is detected. If the phase is 0 °, the output means 35 sends a signal to the outside. This signal may be displayed on a display device such as "current transformer polarity incorrect connection". An alarm sound or a voice output such as "The polarity of the current transformer is wrong" may be used.

The operation of detecting the erroneous connection is shown in the flowchart of FIG. Read currents I ₁ and I ₂ (S1), I ₁
And the phase between I ₂ are sequentially changed by 0 ° to 360 ° (S
2). The differential current value between I ₁ and I ₂ is calculated (S3) and repeated until the phase reaches 360 ° (S4). When it reaches 360 °, the phase at which the differential current value becomes the maximum value is detected (S
5), it is determined whether the detected phase is 0 ° (S6). If the determination result is YES, a signal of incorrect polarity connection is output (S
7) If NO, a signal of normal polarity connection is sent (S
8). It should be noted that if the polarity is normal, it is not necessary to send a signal, but sending a normal signal will help the person who checks.

As described above, it is possible to easily check the polarity error of the CT, which cannot be detected by the conventional ratio differential relay, and prevent the malfunction of the relay due to the incorrect connection of the CT. Further, in this case, since it is possible to determine that the contents of wrong connection of CT are “wrong polarity of CT”, there is an advantage that the work contents are very clear and the work efficiency is improved when the CT is replaced.

Example 2. Similar to the first embodiment, this embodiment detects a CT polarity error, and the configuration of the main part is shown in FIG. As shown in FIG. 13, means 71 for detecting the phase at which the differential current value of I ₁ -I ₂ is minimum and means 72 for determining whether the phase is 180 ° are provided, and further, I
Means 73 for storing the minimum value of the differential current value of _1- I ₂ is provided.

In operation, the phase at which the differential current value becomes the minimum value is obtained, and if the phase is 180 °, it is determined that the CT polarity is wrong. Here, the means 73 for storing the value determined as the minimum differential current value of I ₁ -I ₂ is provided is I
Because and storing the minimum value of ₁ -I ₂ differential current, I ₁ -I ₂ being detected during normal at I ₁ and I ₂ of the adjustment limit (error)
This is because the differential current value can also be stored, and there is an advantage that the I ₁ -I ₂ differential current value at the normal time can be known.

Example 3.3 A case will be described in which an erroneous connection between CTs of different phases is detected in a three-phase alternating current.
FIG. 14 is a diagram showing the configuration of the main part of the misconnection detecting device. FIG. 11 of the first embodiment except the means 74 for determining whether the phase is ± 60 °.
Is the same as. The phase where the differential current value of I ₁ -I ₂ (= I ₃ ) is maximum is detected, and if the phase is ± 60 (+ 60 ° or −60 °), it is determined that CTs of different phases are erroneously connected. judge.

Embodiment 4 FIG. Similar to the third embodiment, this embodiment is a case where an erroneous connection between CTs of different phases is detected, and the configuration of the main part is shown in FIG. FIG. 15 is provided with a means 75 for determining whether the phase is ± 120 °, and the other configurations are the same as those in FIG. 13 of the second embodiment. I ₁ -I ₂ (=
The phase of which the differential current value of I ₃ ) is minimum is detected, and if the phase is ± 120 (+ 120 ° or −120 °), it is determined that CTs of different phases are erroneously connected.

Example 5. In this embodiment, in a three-phase alternating current, the CTs of different phases are erroneously connected, and when either one of the CTs has the wrong polarity, the erroneous connection is detected. The configuration is shown. FIG. 16 shows means 75 for determining whether the phase is ± 120 °.
Others are the same as those in FIG. 14 of the third embodiment. I ₁ -I ₂ (=
I ₃ ). The phase having the maximum differential current value is detected, and if the phase is ± 120 (+ 120 ° or −120 °), the CTs of different phases are erroneously connected, and either one of them is detected. It is determined that the polarity of CT is wrong.

Example 6. Similar to the fifth embodiment, this embodiment also detects the wrong connection between CTs of different phases, and detects the wrong connection when the polarity of either one of the CTs is wrong. The configuration of the section is shown. FIG. 17 is provided with a means 74 for determining whether the phase is ± 60 °, and the other points are the same as those in FIG. 15 of the fourth embodiment. I ₁ -I ₂ (= I
₃ ) The phase that minimizes the differential current value is detected, and if the phase is ± 60 (+ 60 ° or -60 °), the CTs of different phases are erroneously connected and either one of the CTs is detected. It is judged that the polarity of is wrong.

Example 7. In the above embodiment, the configuration of the misconnection detection device has been described for various cases of misconnection.
The phase detecting means 33 in FIG. 1 is means for detecting both or one of the phases where the differential current value of I ₁ -I ₂ (= I ₃ ) is minimum and maximum, and the phase determining means is shown in FIG. As shown in the table, the relationship between the maximum / minimum of the differential current value when the phase is changed and the determination result are stored in a memory as a table, and the phase detected by the phase detecting means 33 and this table are stored. And a phase determining means for making a determination according to this comparison. Then, a display means may be provided to display the content of the determination result and output by voice. In this way, even if there are various causes of erroneous connection, the CT connection check can be performed at once, and all the checks can be facilitated in a short time.

Example 8. In this embodiment, the phase change test switch 30 does not change the phase each time the phase change test switch 30 is pressed, but the phase change test switch 30 only sends a start signal for starting the incorrect connection detection. The means 31 shifts the phase at a predetermined interval (eg 10
You may make it change 0 degree-360 degree automatically every (degree).

Example 9. In addition, the phase detection means 33 causes I ₁
When the phase at which the -I ₂ differential current value becomes the minimum or the maximum is detected, the phase is displayed or printed out using a display or a printer as a display means, and a person who checks the phase is shown in FIG. The connection state may be determined using the chart. Further, I ₁ -I ₂ (= I ₃ ) when the phase is changed by 0 ° to 360 ° by the calculating means 32.
The calculated result of the differential current value of I ₁ is displayed as shown in FIG. 4, FIG. 7, and FIG.
It is also possible to draw a locus of the differential current value of −I ₂ so that the person who checks it can judge.

Example 10. In the above embodiment, the example in which the CT wrong connection detecting device is incorporated in the ratio differential relay has been described, but the wrong connection detecting device may be configured as a single device without being incorporated in the ratio differential relay.

[0058]

As described above, according to the present invention, the phase between two electric quantities for checking the connection state is changed, and an error occurs due to the relationship between the difference between the two electric quantities and the phase. Since it is determined whether or not the connection is made, there is an effect that an erroneous connection can be easily detected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a ratio differential relay according to a first embodiment of the present invention.

FIG. 2 is a vector diagram of I ₁ -I ₂ differential currents generated when CT connections are correct.

FIG. 3 is a vector diagram when the phases of I ₁ and I ₂ are changed in FIG.

FIG. 4 is a diagram showing a vector locus of the differential current of FIG.

FIG. 5 is a diagram showing a phase relationship of three-phase alternating current.

FIG. 6 is a vector diagram showing a phase relationship when the phases of I ₁ and I ₂ are incorrect.

7 is a diagram showing a vector locus of the differential current in FIG.

FIG. 8 is a vector diagram showing a phase relationship between I ₁ and I _{2 and} a phase when one polarity is incorrect.

9 is a diagram showing a vector locus of the differential current in FIG.

FIG. 10 is a diagram showing a relationship between a differential current and a connection of CT according to a phase angle.

FIG. 11 is a configuration diagram of a main part of a comparative differential relay according to the first embodiment of the present invention.

FIG. 12 is a flowchart for checking the connection of the current transformer according to the first embodiment of the present invention.

FIG. 13 is a configuration diagram of a main part of a comparative differential relay showing a second embodiment of the present invention.

FIG. 14 is a configuration diagram of a main part of a comparative differential relay showing a third embodiment of the present invention.

FIG. 15 is a configuration diagram of a main part of a comparative differential relay showing a fourth embodiment of the present invention.

FIG. 16 is a configuration diagram of a main part of a comparative differential relay showing a fifth embodiment of the present invention.

FIG. 17 is a configuration diagram of essential parts of a comparative differential relay showing Embodiment 6 of the present invention.

FIG. 18 is a block diagram of a conventional digital relay.

FIG. 19 is a block diagram of a conventional analog type ratio differential relay.

FIG. 20 is a configuration diagram of a conventional digital ratio differential relay.

FIG. 21 is a diagram for explaining the operation of the ratio differential relay when the protection section is normal.

FIG. 22 is a diagram for explaining the operation of the ratio differential relay when an accident occurs outside the protection section.

FIG. 23 is a diagram for explaining the operation of the ratio differential relay at the time of an accident in the protection section.

[Explanation of symbols]

11 current transformer (CT), 12 filter circuit, 13 sample hold circuit, 14 multiplexer circuit, 15
Analog-digital converter, 16 arithmetic processing units, 1
7 Output interface circuit, 18 Excitation coil, 19
Contact, 20 digital type ratio differential relay, 21 I
_1- I ₂ differential current calculation means, 22 I ₁ + I ₂ suppression current value calculation means, 23 determination means, 24 A phase operation determination means, 25 B phase operation determination means, 26 C phase operation determination Means, 30 Phase change test switch, 31
Phase changing means, 32 computing means, 33 phase detecting means,
34 phase determination means, 35 output means, 40 ratio differential relay, 41 protection target, 42 input converter, 43 I
_1- I ₂ differential current generating means, 44 I ₁ + I ₂ suppressing current generating means, 45 determining means, 46 A
Phase operation determination means, 47 B phase operation determination means, 48 C phase operation determination means, 49 output means, 51 protection section, 61
Means for detecting the phase where the differential current value of I ₁ -I ₂ is maximum, 62 means for judging whether the phase is 0 °, 71 I ₁ -I ₂
Means for detecting the phase at which the differential current value of
Means for judging whether the phase is 180 °, means for storing the minimum value of the differential current of 73 I ₁ -I ₂ , 74 means for judging whether the phase is ± 60 °, 75 means for judging whether the phase is ± 120 °.

Claims (8)

[Claims] 1. A phase changing means for inputting an electric quantity from two current transformers, which are targets of erroneous connection detection, among the current transformers provided in the AC line, and changing a phase between the two electric quantities. A calculating means for calculating an electric quantity of a difference between both electric quantities corresponding to the change of the phase, a display means for displaying the value of the changed phase angle and the calculation result of the electric quantity of the difference corresponding to the phase angle. An erroneous connection detection device for a current transformer, which is provided. 2. A phase changing means for inputting an electric quantity from two current transformers to be detected as erroneous connections among the current transformers provided in the AC line and changing a phase between the electric quantities. Equipped with a calculating means for calculating an electric quantity of a difference between both electric quantities corresponding to the change in the phase, and a phase detecting means for detecting at least one of the phases in which the electric quantity of the difference is minimum and maximum. An erroneous connection detection device for current transformers. 3. A phase changing means for inputting an electric quantity from two current transformers to be detected as erroneous connections among the current transformers provided in the AC line and changing a phase between the two electric quantities. Calculation means for calculating the difference between the quantities of electricity corresponding to the change in the phase, phase detecting means for detecting at least one of the phases in which the difference in quantity is minimum and maximum, the detection result An erroneous connection detection device for a current transformer, comprising: phase determination means for determining whether or not the connection of the current transformer is normal. 4. The phase determining means according to claim 3, wherein the polarity of one of the current transformers is 0 if the phase at which the amount of difference has a maximum is 0 ° or the phase at which it has a minimum is 180 °. An erroneous connection detection device for a current transformer, characterized in that it is a means for determining that the connection is reverse. 5. The electric circuit according to claim 3, wherein the electric line is a three-phase AC line, the phase determining means has a maximum phase of + 60 ° or −60 °, or a minimum phase of +120. An erroneous connection detection device for a current transformer, characterized in that it is means for judging that the current transformers of different phases are erroneously connected if the angle is-° or -120 °. 6. The method according to claim 3, wherein when the electric line is a three-phase AC line, the phase determining means has a phase with a maximum difference of + 120 ° or −120 ° or a minimum phase of +60. Is 60 ° or -60 °, the current transformers of different phases are erroneously connected, and the polarity of either one of the current transformers is determined as erroneous connection. False connection detection device. 7. The phase changing means according to claim 1 or 2, wherein the phase changing means changes the phase from 0 ° to 3 in steps of a predetermined phase angle.
A connection inspection device for a current transformer, characterized in that it is changed by 60 °. 8. A ratio differential relay having a built-in erroneous connection detection device for a current transformer according to any one of claims 1 to 7.