JP5441625B2 - Busbar protection device - Google Patents

Description

  The present invention relates to a busbar protection device that protects a power system, and more particularly to a busbar protection device that protects a power system bus.

  Conventional bus bar protection devices take measures to prevent malfunctions due to error differential currents by measures against saturation of current transformers (hereinafter referred to as “CT”) in the accident phase.

  For example, Patent Document 1 below relates to a countermeasure against CT saturation of a busbar protection device. FIG. 3 of the document shows an embodiment of the invention, and FIG. 6 of the document shows an implementation of the conventional invention at that time. An example is shown. When the difference between the present invention and the prior art is clarified, in these conventional techniques, the suppression current of the accident phase is generated using the input current of the phase.

  Patent Document 2 below relates to a current differential bus protection device used for transformer protection. In the drawing of the document, only the interference method by the logic circuit regarding the operation of the own phase due to the content ratio of the second harmonic in the other phase exceeding a certain value is shown. Refers to the matching of the circuit breaker tripping suppression electrical quantity of the other phase by the field effect transistor that can pass through the analog quantity (this suppression quantity is specified in claims 1 and 2 as a high frequency component). It shows that the suppression amount (harmonic component) of the other phase is taken into the own phase as a countermeasure against malfunction due to the inrush current of the transformer.

JP-A-2-164225 Japanese Examined Patent Publication No. 61-11056

  However, the conventional busbar protection device takes measures against the error differential current in the accident phase, but does not take any special measures in the healthy phase with a small suppression current, such as a no-load transmission line In this case, the suppression current may become 0. In this case, if an error differential current occurs in the healthy phase due to induction by the accident current of the accident phase, there is a possibility that it may be mistaken for a simple internal accident. There was a point.

  The present invention has been made in view of the above, and is capable of maintaining a stable operation of a healthy phase even if an error differential current is generated in a healthy phase where no accident has occurred. The object is to obtain a device.

  In order to solve the above-described problems and achieve the object, the present invention provides a bus that protects the bus by inputting a phase current from an instrumental current transformer installed in each phase of a plurality of lines connected to the bus. In the protective device, the differential amount derivation circuit that takes the vector sum of the phase currents in each line, the suppression amount derivation circuit that takes the scalar sum of the phase currents, and the differential amount derivation circuit of the own phase A ratio difference in which a differential differential operation is performed using a differential current, a suppression current derived by the suppression amount derivation circuit for the own phase, and a suppression current derived by at least one suppression amount derivation circuit for the other phase And a dynamic operation circuit.

  According to this invention, since the predetermined value obtained by multiplying the suppression amount from the accident phase by a certain coefficient is introduced as the suppression amount of the healthy phase, an error differential current is generated in the healthy phase. In addition, there is an effect that the healthy phase can stably keep the malfunction.

FIG. 1 is a diagram illustrating an overall configuration centering on a busbar protection device according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining a situation in which an error differential current occurs in a phase where no accident has occurred. FIG. 3 is a configuration diagram of the busbar protection device according to the first exemplary embodiment of the present invention. FIG. 4 is a diagram showing ratio characteristics for explaining the operation of the busbar protection device 17 according to the first exemplary embodiment of the present invention. FIG. 5 is a configuration diagram of the busbar protection device according to the second exemplary embodiment of the present invention. FIG. 6 is a configuration diagram of the busbar protection device according to the third embodiment of the present invention. FIG. 7 is a configuration diagram of the busbar protection device according to the fourth exemplary embodiment of the present invention.

  Embodiments of a busbar protection device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an overall configuration centering on the busbar protection device 17 according to the first exemplary embodiment of the present invention. FIG. 1 shows buses 1a, 1b, and 1c of each phase of a three-phase bus that is a protection target of the bus bar protection device 17. Leaders (also referred to as “lines”) 2a, 2b, 2c, 3, and 4 from the buses 1a, 1b, and 1c include circuit breakers 5, 6, and 7 and CTs 8a, 8b, 8c, 9, and 10 And are installed. One end of the cables 11a, 11b, 11c, 12, and 13 is connected to each CT, and the other end of the cable 11a, the cable 12, and the cable 13 is an input converter group (not shown) installed in the busbar protection device 17a. Connected). The other end of the cable 11b is connected to the bus bar protection device 17b and the illustration is omitted, but the other end of the cable connected to the CT installed in the lead-out line from the bus 1b is connected. It is assumed that Similarly, the other end of the cable 11c is connected to the bus bar protection device 17c, and the other end of the cable connected to the CT installed in the lead-out line from the bus bar 1c is connected. .

  The bus bar protection device 17a mainly includes a line current calculation circuit (hereinafter simply referred to as “calculation circuit”) 14 for calculating each line current detected in each CT, and a current calculated by the calculation circuit 14. A suppression amount derivation circuit 15 that calculates a suppression current (suppression amount) and a differential amount derivation circuit 16 that derives a differential current (differential amount) based on the current calculated by the arithmetic circuit 14. Configured. In FIG. 1, the internal configuration of the bus bar protection devices 17 b and 17 c is basically the same as that of the bus bar protection device 17 a, and the illustration thereof is omitted. In the following description, the bus bar protection devices 17a, 17b, and 17c are simply referred to as a bus bar protection device 17 unless otherwise specified. Similarly, CT8a, 8b, and 8c are referred to as CT8, cables 11a, 11b, and 11c are referred to as cable 11, arithmetic circuits 14a, 14b, and 14c are referred to as arithmetic circuit 14, and suppression amount deriving circuits 15a, 15b, and 15c are referred to as CT11. The suppression amount deriving circuit 15 is referred to, and the differential amount deriving circuits 16 a, 16 b, and 16 c are referred to as the differential amount deriving circuit 16.

  First, an overall image of the busbar protection device 17 will be described. For example, the bus protection device 17a for the phase a determines whether or not an accident has occurred in the bus 1a to be protected, based on the current detected by the CTs 8a, 9 and 10 provided in the lead wires 2a, 3 and 4. judge. More specifically, the differential quantity derivation circuit 16 obtains the total vector sum based on the currents detected through all the lead lines 2a, 3 and 4. When no accident has occurred in the bus 1a, the differential amount is 0 according to Kirichoff's first law. When an accident has occurred in the bus 1a, the fault point current is the differential amount.

  If an accident has occurred outside the bus 1a, the differential amount may not always be zero due to CT error or CT saturation. Therefore, the suppression amount deriving circuit 15 calculates the scalar sum or maximum value of the currents from all the lead lines 2a, 3 and 4.

  As will be described in detail later, the bus protection device 17 according to the present embodiment compares the output of the suppression amount derivation circuit 15 and the output of the differential amount derivation circuit 16, and the differential amount exceeds a certain ratio. In this case, a predetermined relay operation command is output and the circuit breakers 5, 6, and 7 are energized to remove the accident. In the following description, the exchange of the suppression amount of each phase will be referred to. Here, in order to show that the busbar protection device 17 is provided independently for each phase, each phase is shown in the main part. Subscripts “a”, “b”, and “c” are added to clarify the phase division.

  FIG. 2 is a diagram for explaining a situation in which an error differential current occurs in a phase where no accident has occurred. FIG. 2A shows the excitation impedances 18a, 18b, and 18c of each CT8. Further, FIG. 2A shows a CT secondary current i and an induced voltage v induced by the induction of the current. Since the impedance of the input converter group 28 to which the CT cable (cable 11) is connected is extremely smaller than the CT excitation impedance 18, it is expressed as a line in FIG. FIG. 2B shows CT iron cores 19a and 19b, and further shows a magnetic flux 20a leaking from the iron core 19a due to CT saturation.

  Next, a situation in which an error differential current occurs in a phase in which no accident has occurred, which is the subject of the present application, will be described in detail. In FIG. 2A, since the cable 11 connected to the CT 8 is generally a multi-core cable, for example, when a large current i flows in the a phase of the CT 8a, an induced voltage is induced in the cable sheath or other phase core wire. The In the example of FIG. 2A, the induced voltage v is induced in the cable 11b connected to CT8b and the cable 11c connected to CT8c. In general, since the excitation impedance of CT8 is very large, the current caused by the induced voltage v is very small, and this is not a problem. However, when a CT8 having a poor performance (low excitation impedance) is applied, the induced voltage v A non-negligible current flows. That is, in the example of FIG. 2A, a current due to the induced voltage v flows through the cable 11b and the cable 11c.

  As another example, FIG. 2B shows a case where CT8a is saturated by a large current i. In the normal state where CT8a is not saturated, the magnetic flux 20a due to the current i shown in the figure is captured in the iron core 19a and does not reach the iron core 19b of CT8b. However, when CT8a is in a saturated state, no more magnetic flux can be captured in the iron core 19a of CT8a, and the magnetic flux 20a leaking from the iron core 19a reaches the iron core 19b. A secondary coil (not shown) of CT8b is wound around the iron core 19b. If this coil is wound non-uniformly, the circular integral of the magnetic flux along the coil does not become zero, and CT8b Current will also flow.

  In the case of FIG. 2B, the induced current amount is determined by the physical positional relationship between CT8a and CT8b and the non-uniform winding state of the secondary coil of CT8b on the induced side.

  FIG. 3 is a configuration diagram of the busbar protection device 17 according to the first exemplary embodiment of the present invention. Each bus protection device 17 shown in FIG. 3 includes a coefficient circuit (setting circuit) 21, an adder circuit 22, a ratio, in addition to the arithmetic circuit 14, the suppression amount derivation circuit 15, and the differential amount derivation circuit 16 described above. A differential operation circuit 23 and an output circuit 24 are included. The coefficient circuit 21 sets the suppression current derived by the suppression amount deriving circuit 15 for the other phase to a predetermined amount. For example, the coefficient circuit 21 sets a predetermined value obtained by multiplying the suppression current from the other phase by a certain coefficient. And output to an adder circuit 22 or selection circuits 26 and 28 described later. The addition circuit 22 adds the output from the coefficient circuit 21 and the output from the suppression amount derivation circuit 15 for the own phase, and the ratio differential operation circuit 23 adds the output from the differential quantity derivation circuit 16 to the addition. Ratio differential operation is performed by the output from the circuit 22. The output circuit 24 generates and outputs a trip signal for the circuit breaker based on the calculation result of the ratio differential calculation circuit 23.

  FIG. 4 is a diagram showing ratio characteristics for explaining the operation of the busbar protection device 17 according to the first exemplary embodiment of the present invention. FIG. 4A is a diagram showing a current distribution in the accident phase, and FIG. 4B and FIG. 4C are conventional techniques for comparison. FIG. 4 (b) is a diagram of the accident phase corresponding to FIG. 4 of Patent Document 1, and FIG. 4 (c) is a diagram in which the current flows in the accident-free phase as described in the paragraph “0019”. The movement on the characteristic diagram is shown. The letters “i1”, “i2”, etc. shown in the figure indicate the line current.

  The operation will be described below. First, the operation of the conventional busbar protection device will be described as follows. In FIG. 4A, for example, when an accident occurs in the line (leader line) 2, a current flows toward the accident point shown in FIG. When the current of the line 2 is i1, the current of the line 3 is i2, and the current of the line 4 is i3, this current is generally i1 + i2 + i3 = differential amount id = 0. At this time, for example, if the suppression amount ir = | i1 | + | i2 | + | i3 |, current exists on the horizontal axis of FIG. 4B, and the busbar protection device does not operate.

  As described in the above-mentioned Patent Document 1, CT saturation is likely to occur in the busbar protection device. For example, when CT8 shown in FIG. 4A is saturated, the differential amount id does not become zero. As shown in FIG. 4B, the arrows in the characteristic diagram are shown. For the accident phase, even if such a differential amount id occurs, measures are taken to keep the busbar protection device stably inoperative by various measures such as ratio characteristics.

  However, in the accident-free phase, i1 = i2 = i3 = 0, which is generally stable. However, when the error differential current ie flows as shown in FIG. 2, id = ir as shown in FIG. = Ie, and malfunction may occur depending on the operating characteristics. Specifically, the diagram shown on the left side of FIG. 4C shows a locus when id = ir = ie, and the ratio of the suppression current ie to the differential current ie is relatively high. It becomes small and it turns out that the locus | trajectory (point a) by differential current ie and suppression current ie has reached the operating region. On the other hand, the diagram shown on the right side of FIG. 4C shows the ratio characteristics of the bus bar protection device 17 according to the present embodiment. For example, when the suppression current derived from the suppression amount derivation circuit 15 for the own phase is the above-described suppression current ie, the bus protection device 17 according to the present embodiment is derived from the suppression amount derivation circuit 15 for the other phase. By adding the suppression current ir ′ obtained by multiplying the suppression current by a predetermined coefficient and the suppression current ie described above, the ratio of the suppression current (ir ′ + ie) to the differential current ie becomes relatively large. It is configured as follows. As a result, the locus (point b) due to the differential current ie and the suppression current (ir ′ + ie) is set in the non-operation area, and the busbar protection device can stably keep the nonoperation.

  Next, operation | movement of the bus-bar protection apparatus 17 concerning this Embodiment is demonstrated using FIG. For example, when the accident phase is a phase, in the bus protection device 17a related to the accident phase, each line current is calculated by the line current circuit 14a, and the suppression current is calculated by the suppression amount deriving circuit 15a. This suppression current is subjected to a ratio differential calculation together with the output of the differential quantity deriving circuit 16a, that is, the differential current, in the ratio differential calculation circuit 23a.

  On the other hand, the output of the suppression amount deriving circuit 15a is output to the busbar protection device 17b for the b phase, which is an accident-free phase, and the suppression current is set to an appropriate magnitude by the coefficient circuit 21b and is suppressed by the adding circuit 22b. It is added to the output of the derivation circuit 15b and applied to the ratio differential operation circuit 23b together with the output of the differential quantity derivation circuit 16b to perform ratio differential calculation. In the above description, an accident-free phase (own phase) is assumed to be b-phase, and the coefficient circuit 21b is configured to introduce a suppression amount from the suppression amount derivation circuit 15a of the accident phase (other phase). For example, the coefficient circuit 21b may be configured to introduce the suppression amount from the suppression amount derivation circuit 15c of the accident phase (other phase). Further, for example, when the accident-free phase (own phase) is set to phase a, the coefficient circuit 21a may be configured to introduce a suppression current from the suppression amount derivation circuit 15b or 15c of the accident phase (other phase). However, when the accident-free phase (own phase) is the c-phase, the coefficient circuit 21c may be configured to introduce the suppression current from the suppression amount derivation circuit 15a or 15b of the accident phase (other phase). Needless to say. The ratio differential operation in this case is the same as described above, and the description thereof is omitted below.

  As described above, the busbar protection device 17 according to the present embodiment introduces the predetermined value obtained by multiplying the suppression amount from the accident phase by a certain coefficient as the suppression amount of the accident-free phase. Therefore, even in a situation where an error differential current is generated in the phase without an accident due to induction from the accident phase or the like, it is possible to stably keep the malfunction. As a result, the unnecessary operation of the circuit breaker for the accident-free phase is suppressed, and it is possible to improve the long-term use and durability of the circuit breaker.

Embodiment 2. FIG.
In the first embodiment, the accident phase is described in phase a. However, since the accident phase is not fixedly fixed, in this second embodiment, the other two phases are applied to the phase without accident. The suppression amount from the suppression amount derivation circuit is introduced. In this way, universal measures against the accident phase are possible. The same parts as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts are described.

  FIG. 5 is a configuration diagram of the busbar protection device 17 according to the second exemplary embodiment of the present invention. The bus bar protection device 17 includes a coefficient circuit 25 that multiplies the output from the suppression amount derivation circuit 15 for other phases by a constant coefficient as a new component.

  Next, operation | movement of the bus-bar protection apparatus 17 concerning this Embodiment is demonstrated using FIG. For example, when the accident phase is a phase and c phase, each line current is calculated by each line current circuit 14a, 14c in the busbar protection devices 17a, 17c related to the accident phase. 1 suppression current is calculated, and the suppression amount deriving circuit 15c calculates the second suppression current. These suppression currents are subjected to a ratio differential calculation together with outputs of the differential quantity derivation circuits 16a and 16c, that is, a differential current, in the ratio differential calculation circuits 23a and 23c.

  On the other hand, the outputs of the suppression amount derivation circuits 15a and 15c are output to the bus protection device 17b for the b phase, which is an accident-free phase, and are appropriately sized by the coefficient circuits 21b and 25b. 15b and added to the differential differential operation circuit 23b together with the output of the differential quantity derivation circuit 16b to perform the differential differential operation.

  As described above, the busbar protection device 17 according to the present exemplary embodiment uses the predetermined value obtained by multiplying the suppression amount from the other two phases that are the accident phase by a certain coefficient as the suppression amount of the accident-free phase. Therefore, even in a situation where an error differential current is generated in a phase without an accident due to induction from the accident phase, etc., it is possible to keep the operation universally and stably.

Embodiment 3 FIG.
In the first and second embodiments, the accident phase is described in phase a or phase c, but as described in the paragraphs “0017”, “0018”, “0019”, “0020” above, The influence of the physical arrangement has a great influence on how other inductions affect other phases. At the time of installing the busbar protection device, such physical arrangement is often determined. Therefore, it is effective to provide a selection function in order to eliminate unnecessary suppression for other phases. Since the busbar protection device 17 according to the present embodiment has this selection function, the most efficient countermeasure against the accident phase is possible. Note that the same parts as those of the second embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts are described.

  FIG. 6 is a configuration diagram of the busbar protection device 17 according to the third exemplary embodiment of the present invention. The bus protection device 17b shown in FIG. 6 includes a selection circuit 26b that takes in the outputs from the coefficient circuits 21b and 25b, selects these outputs, and sends them to the adder circuit 22b.

  Next, the operation of the busbar protection device 17 according to this exemplary embodiment will be described with reference to FIG. First, in the bus protection devices 17a and 17c in the accident phase, each line current is calculated in each line current circuit 14a and 14c, and, for example, a first suppression current is calculated from the suppression amount deriving circuit 15a, and the suppression amount is derived. A second suppression current is calculated by the circuit 15c. These suppression currents are subjected to ratio differential calculation together with outputs of the differential quantity derivation circuits 16a and 16c, that is, differential currents, in the bus bar protection devices 17a and 17c in the accident phase.

  On the other hand, the output of the suppression amount deriving circuits 15a and 15c is output to the bus protection device 17b for the accident-free phase, and is set to an appropriate size by the coefficient circuits 21b and 25b, and either or both are selected by the selection circuit 26b. And sent to the adder circuit 22b. Further, the output from the selection circuit 26b is added to the output of the suppression amount deriving circuit 15b by the adding circuit 22b and applied to the ratio differential operation circuit 23b together with the output of the differential amount deriving circuit 16b to perform the ratio differential operation. Is called.

  As described above, the busbar protection device 17 according to the present embodiment is obtained by multiplying the suppression amount from the other two phases that are accident phases (outputs of the suppression amount deriving circuits 15a and 15c) by a certain coefficient. Since either or both of the predetermined values are selected and introduced as a suppression amount for the accident-free phase, even in situations where differential current occurs in the accident-free phase due to induction from the accident phase, etc. Efficient measures can be taken against the accident phase.

  Note that the selection circuit 26b can exhibit a greater effect by being settable. To explain this, for example, when the device arrangement is fixed, the affected phase sequence is often determined. In this case, if the selection circuit 26b is set in advance so as to select the leading phase or the lagging phase, a great effect can be shown rather than going through the setting work.

  When the device arrangement is fixed, the affected phase sequence and the amount received are often determined. In this case, the selection circuit 26b is not only set in advance so as to select the leading phase or the lagging phase, but can be operated more safely if the coefficients of the coefficient circuits 21b and 26b described above can be individually set. A greater effect can be shown.

Embodiment 4 FIG.
In the first to third embodiments, the case where the influence of an accident occurs is described without limiting FIG. 2 (a) and FIG. 2 (b), but is described in the above paragraphs “0017” and “0019”. As described above, CT saturation may occur as a case where guidance from the accident phase is likely to occur. In this case, if it is possible to select whether or not to introduce the suppression of the other phase by the output of the CT saturation detection function, unnecessary suppression for the other phase can be eliminated. In this way, the most efficient countermeasure against the accident phase is possible. Note that the same parts as those of the third embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts are described.

  FIG. 7 is a configuration diagram of the busbar protection device 17 according to the fourth exemplary embodiment of the present invention. The bus protection device 17a shown in FIG. 7 has a CT saturation detection circuit 27a, and the bus protection device 17c is configured to have a CT saturation detection circuit 27c in the same manner as the bus protection device 17a. The busbar protection device 17b includes a selection circuit 28b that selects the output from the coefficient circuits 21a and 25b based on the signal from the CT saturation detection circuit 27.

  Next, operation | movement of the bus-bar protection apparatus 17 concerning this Embodiment is demonstrated using FIG. First, in the bus bar protection devices 17a and 17c in the accident phase, each line current is calculated by each line current circuit 14a and 14c, and the suppression current is calculated by the suppression amount deriving circuits 15a and 15c. Subsequent movements are the same as those in the paragraph “0026”, and description thereof will be omitted.

  On the other hand, the outputs of the suppression amount deriving circuits 15a and 15c are output to the busbar protection device 17b for the accident-free phase, and are set to appropriate sizes by the coefficient circuits 21b and 25b, and either or both are selected by the selection circuit 28b. And sent to the adder circuit 22b. Further, the output from the selection circuit 28b is added to the output of the suppression amount deriving circuit 15b by the adding circuit 22b and applied to the ratio differential operation circuit 23b together with the output of the differential amount deriving circuit 16b to perform the ratio differential operation. Is called.

  As described above, the busbar protection device 17 according to the present embodiment is obtained by multiplying the suppression amount from the other two phases that are accident phases (outputs of the suppression amount deriving circuits 15a and 15c) by a certain coefficient. Either or both of the specified values are selected by the signal from the CT saturation generation phase and introduced as the amount of suppression for the accident-free phase. Even in such a situation, it is possible to keep the malfunction properly and stably.

  In the above description, the suppression amount of the phase in which CT saturation has occurred is introduced to the phase without accident by the signal from the phase in which CT saturation has occurred. In addition, when CT saturation generate | occur | produces, it is known that the suppression amount of the phase in which CT saturation generate | occur | produced will reduce. Therefore, when CT saturation occurs, more effective stabilization can be achieved by introducing the suppression amount of the phase in which CT saturation has not occurred into the accident-free phase. That is, when CT saturation occurs, the selection circuit 28b selects the suppression amount from the phase where CT saturation has not occurred based on the signal from the CT saturation detection circuit 27, and sends it to the addition circuit 22b.

  In the above description, as an application of the present invention, the case of a bus protection device with a countermeasure against CT saturation has been described as an example. However, other bus protection devices without a countermeasure against CT saturation (for example, in Embodiments 1 to 3) It can also be applied to the bus bar protection device shown).

  In the above-described Embodiments 2 to 4, when the accident-free phase (own phase) is the b-phase and the accident phase (other phase) is the a-phase or the c-phase, the coefficient circuits 21b and 25b The configuration example in which the suppression current from the derivation circuits 15a and 15c is introduced has been described. For example, when the accident-free phase (own phase) is a phase and the accident phase (other phase) is b-phase or c-phase The coefficient circuits 21a and 25a introduce the suppression current from the suppression amount deriving circuits 15b and 15c. Also, when the accident-free phase (own phase) is the c-phase and the accident phase (other phase) is the a-phase or b-phase, the coefficient circuits 21c and 25c introduce the suppression current from the suppression amount derivation circuits 15a and 15b. To do. In this case, the selection operation of the selection circuits 26a, 26c, 28a, 28c and the ratio differential calculation operation of the ratio differential calculation circuits 23a, 23c are the same as described above, and the description thereof will be omitted below.

  The busbar protection device 17 shown in the first to fourth embodiments is configured to include the coefficient circuits 21 and 25, but is not limited to this, for example, the suppression current itself from the accident phase. May be introduced into the ratio differential arithmetic circuit 23.

  As described above, the present invention can be applied to a bus protection device that protects a power system bus. In particular, even if an error differential current is generated in an accident-free healthy phase, the healthy phase is not stably operated. It is useful as an invention that can hold

1a, 1b, 1c Bus 2a, 2b, 2c, 3, 4 Leader 5, 6, 7 Breaker 8a, 8b, 8c, 9, 10 CT
11a, 11b, 11c, 12, 13 Cable 14, 14a, 14b, 14c Line current calculation circuit 15, 15a, 15b, 15c Suppression amount deriving circuit 16, 16a, 16b, 16c Differential amount deriving circuit 17, 17a, 17b, 17c Busbar protection device 18a, 18b, 18c Excitation impedance 19a, 19b Iron core 20a Magnetic flux 21a, 21b, 21c, 25a, 25b, 25c Coefficient circuit (setting circuit)
22a, 22b, 22c Adder circuit 23a, 23b, 23c Ratio differential operation circuit 24a, 24b, 24c Output circuit 26a, 26b, 26c, 28a, 28b, 28c Select circuit 27a, 27b, 27c CT saturation detection circuit 28 Input converter Group i CT secondary current i1, i2, i3 line current id differential amount ie error differential current ir suppression amount v induced voltage

Claims (11)

In the busbar protection device that protects the busbar by inputting a phase current from an instrumental current transformer installed in each phase of a plurality of lines connected to the busbar,
A differential amount derivation circuit for taking a vector sum of each phase current in each line;
A suppression amount derivation circuit for taking a scalar sum of the currents of the respective phases;
A differential current derived by the differential phase derivation circuit for the own phase, a suppression current derived by the suppression amount derivation circuit for the own phase, and a suppression current derived by at least one suppression amount derivation circuit for the other phase; , And a ratio differential arithmetic circuit that performs ratio differential arithmetic using
A bus bar protection device comprising: The ratio differential arithmetic circuit is:
The differential current derived by the self-phase differential amount derivation circuit, the suppression current derived by the self-phase suppression amount derivation circuit, and the suppression current derived by any of the other-phase suppression amount derivation circuits The bus bar protection device according to claim 1, wherein a ratio differential operation is performed using The ratio differential arithmetic circuit is:
The differential current derived by the self-phase differential amount deriving circuit, the suppression current derived by the self-phase suppression amount deriving circuit, and the first phase derived by the other two-phase suppression amount deriving circuit 3. The busbar protection device according to claim 1 or 2, wherein a ratio differential operation is performed using the suppression current and the second suppression current. A selection circuit that selects either or both of the first suppression current and the second suppression current;
The ratio differential arithmetic circuit is:
A ratio difference using the differential current derived by the differential phase derivation circuit of the self phase, the suppression current derived by the suppression amount derivation circuit of the self phase, and the suppression current selected by the selection circuit 4. The bus bar protection device according to claim 3 , wherein a dynamic calculation is performed. The selection circuit includes:
The bus bar protection device according to claim 4 , wherein an introduction ratio between the first suppression current and the second suppression current is settable. The selection circuit includes:
5. The busbar protection device according to claim 4, wherein a lead phase suppression current is selected from the first suppression current and the second suppression current. 6. The selection circuit includes:
5. The busbar protection device according to claim 4, wherein a delayed-phase suppression current is selected from the first suppression current and the second suppression current. 6. The selection circuit includes:
6. The busbar protection device according to claim 5 , wherein the introduction ratio is configured to be separately settable for a leading phase and a lagging phase. A current transformer saturation detection circuit for detecting the saturation of the current transformer and outputting a saturation detection signal;
The selection circuit includes:
Based on the saturation detection signal output from one of the current transformer saturation detection circuits for the other phase, select the suppression current derived by the other phase suppression amount derivation circuit where the current transformer saturation was detected. The busbar protection device according to any one of claims 4 to 8, wherein: A current transformer saturation detection circuit for detecting the saturation of the current transformer and outputting a saturation detection signal;
The selection circuit includes:
Based on the saturation detection signal output from one of the current transformer saturation detection circuits for the other phase, the suppression current derived by the suppression amount deriving circuit for the other phase where the current transformer saturation for the instrument is not detected is calculated. The busbar protection device according to any one of claims 4 to 8, wherein the busbar protection device is selected.   The busbar protection device according to claim 1, further comprising a settling circuit that sets a suppression current derived by the suppression amount deriving circuit for the other phase.

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