JP4810311B2 - Digital protective relay device - Google Patents

Description

  The present invention relates to a digital protection relay device that performs a protection operation by determining the presence or absence of an accident in a power system based on digital data obtained by sampling a current or voltage AC signal of the power system and performing analog / digital conversion.

  In general, digital protective relay devices are digital data obtained by inputting AC signals of currents and voltages of power systems with instrument transformers, sampling AC signals of input currents and voltages, and further performing analog / digital conversion. By performing a predetermined calculation based on this, it is determined whether or not there is an accident in the power system, and when it is determined that there is an accident, a protection operation is performed.

  Digital protective relays input power system current and voltage with high accuracy, detect power system failures in the protection section with high sensitivity, and perform protection operations. On the other hand, accidents occur in the protection section When it is not, it must not operate, and it is not allowed to operate due to disturbances.

For this reason, in the digital protective relay device, measures are taken to prevent malfunctions against disturbances such as lightning surges and switching surges. A lightning surge is a surge current caused by a lightning strike to a power system or the like that flows into the ground of a substation and is guided to a control cable to enter a digital protective relay device. In addition, an open / close surge due to the opening / closing of the circuit breaker or disconnector is also generated and enters the digital protective relay. Since these surges are higher in frequency than the system frequency, a digital protection relay device employs a technique such as attenuation by a filter. In addition, there is one that suppresses the influence of harmonic components included in the fault voltage and fault current of the system (see, for example, Patent Document 1).
JP 2002-262447 A

  However, a large current of up to several tens of kA flows due to a ground fault or a short-circuit accident in the power system, and a large magnetic field may be generated around it. There was no problem in the past about the effect of this magnetic field invading the digital protective relay device, but it may become a problem as the digital protective relay circuit becomes more accurate. . The magnitude of the magnetic field is proportional to the magnitude of the current and inversely proportional to the distance from the current.

  As shown in FIG. 32, when a large current if flows through the substation 11, the alternating magnetic field h is linked to the circuit loop inside the digital protective relay 12 installed in the substation 11, and the voltage or current induction amount That is, noise is generated.

  FIG. 33 is an explanatory view of a state in which an external magnetic field affects a conventional digital protective relay. It is assumed that the digital protective relay 12 is affected by the magnetic field h from the large current if of another power system 13A adjacent to the power system 13.

  The digital protection relay 12 inputs the electric quantity a1 input from the transformer 14 of the power system 13 via the auxiliary transformer 15. The output a2 of the auxiliary transformer 15 is an output smaller than the amount of electricity a1 input from the transformer 14. That is, the auxiliary transformer 15 converts the amount of electricity a1 input from the transformer 14 into a smaller auxiliary transformer output a2. The auxiliary transformer output a2 transmits the signal line PN, and the analog input amount a3 transmitted through the signal line PN is sampled by the analog / digital conversion circuit 16 and analog / digital converted to become digital electrical quantity data dig. The digital electric quantity dig, which is the output of the analog / digital conversion circuit 16, is input to the arithmetic processing unit 17, and a protective relay calculation is performed in the arithmetic processing unit 17 to determine the presence or absence of an accident in the power system.

  On the other hand, the digital protection relay 12 is affected by the magnetic field h from the large current if of another power system 13A adjacent to the power system 13. That is, the external magnetic field winding induction amount ex is generated by the change of the magnetic field h interlinked in the secondary winding of the auxiliary transformer 15 in the digital protective relay 12. Furthermore, an external magnetic field closed circuit induction amount ey is also generated due to a change in the magnetic field h interlinked with the closed circuit loop LP formed by the signal line PN.

  As a result, the analog input amount a3 input to the analog / digital conversion circuit 16 is obtained by adding the sum of the external magnetic field winding induction amount ex and the external magnetic field closed circuit induction amount ey in addition to the auxiliary transformer output a2. It will be a thing. The external magnetic field induction amount ex is proportional to the total area of the winding loop of the auxiliary transformer 15, that is, the winding area and the number of turns, and the external magnetic field closed circuit induction amount ey is proportional to the area of the closed circuit loop LP.

  Thus, the amount of electricity input to the analog / digital conversion circuit 16 of the digital protection relay 12 is generated only by the amount of electricity a1 input from the original power system 13 due to the amount of induction by the magnetic field from the outside of the digital protection relay 12. The amount of electricity changes, and the digital amount of electricity input to the arithmetic processing unit 17 also changes similarly. For this reason, the presence or absence of an accident in the power system 13 may not be correctly determined. Moreover, it is difficult to distinguish the waveform of the induction amount from the electric amount waveform of the power system that should be protected originally or the waveform of the induction amount from another power system, and the frequency matches the power system frequency such as 50 Hz or 60 Hz. Therefore, selection deletion by the filter cannot be expected, and it is difficult for the arithmetic processing unit 17 to correctly perform the determination calculation of the presence or absence of the system fault.

As a practical example in a substation, it is assumed that a large current having an effective value of 20 kA flows in the vicinity of 20 m of the digital protection relay 12. In that case, when the circuit loop LP on the printed circuit board of the digital protective relay 12 is about 100 cm ² and is perpendicular to the magnetic field, the external magnetic field closed circuit induction amount ey generated in the circuit loop is about 1 millivolt. is there. Since this is a value larger than the resolution of the high resolution analog / digital converter 16 used in the digital protection relay 12 in recent years, it affects the operation.

  There are various types of digital protection relay 12, and there is a digital protection relay 12 that operates by current differential as one that requires attention to the influence on the external magnetic field. FIG. 34 is an explanatory diagram of the operation principle of current differential protection, and FIG. 35 is an internal block diagram of a conventional current differential protection relay.

  As shown in FIG. 34, in the current differential protection, the sum of the currents of all the terminals flowing into the protection section is calculated, and it is determined that there is no accident when the sum of currents is 0, and that there is an accident when it is not 0. For example, when protecting a bus in a substation, an accident is determined using the currents i1 to in of all the lines Fa to Fn connected to the bus 18. Moreover, when protecting the transmission line which connects two substations, the accident is judged using the electric current in the substation of both ends. In this case, current data is communicated between substations. The currents ia, ib,..., In flowing from the plurality of lines Fa, Fb,... Fn connected to the bus 18 that is the protection section are small current values ia1, ib1 that can be input to the digital protection relay 12 by the current transformers 19a to 19n. ... convert to in1.

  As shown in FIG. 35, in the digital protection relay 12, the output currents ia1, ib1,... In1 from the current transformers 19a to 19n are converted into analog input circuits (secondary side of the auxiliary transformer 15) by the auxiliary transformers 15a to 15n. To the analog / digital converter 16), the current values are converted to smaller current values ia2, ib2,. In the analog input circuit, ia2, ib2,... In2 are sampled and converted into digital values diga, digb,.

  The differential operation unit (DIF) 20 in the operation processing unit 17 calculates the sum of diga, digb,..., Dign, and compares it with the set value iset stored in the storage unit (MEM) 21 or the like to protect. It is determined whether or not there is an accident in the bus 18 that is a section. If no accident has occurred in the protection zone PZ, the same amount of current flows into any of the protection zones, and the sum of ia, ib,... In is 0 because of Kirchhoff's law. On the other hand, if there is an accident in the protection zone PZ, that is, a ground fault or a short circuit accident, current flows to the ground, another phase of the transmission line, another line, etc. at the location of the accident. The sum of ib,... in does not become 0, but an accidental current that flows out. Therefore, the arithmetic processing unit 17 determines that there is no accident when the sum of the digital values diga, digb,..., Signn is smaller than a predetermined set value iset, and an accident when the sum is large (Pro). This method is called a current differential method, and since the current flowing out from the accident location is directly calculated, it is possible to detect even a small accident current, but its operation tends to be easily influenced by an external magnetic field.

  FIG. 36 is an explanatory diagram of the influence of an external magnetic field on a conventional current differential protection relay. When a magnetic field h is applied to the digital protection relay 12 from the outside, induction amounts exa, exb,... Exn are generated at each line input of the analog / digital conversion circuit 16. These induction amounts are sampled by the analog / digital conversion circuit 16 and subjected to analog / digital conversion, and are output as digital amounts diga, digb,. The differential calculation unit (DIF) 20 in the calculation processing unit 17 calculates the sum of diga, digb,..., Dign, and determines that there is an accident in the protection section PZ when the sum is larger than the set value iset. Resulting in. If there is an amount of electricity from the power system 13, it is superimposed on it. If there is no accident, the difference current should be zero. However, if there is an induction amount due to a magnetic field, a difference current is generated, so that it is determined that there is an accident. In particular, since the bus protection relay inputs the amount of electricity of a large number of lines and calculates the sum, the sum of the induction amounts of each line tends to be large, and it tends to be easy to determine whether there is an accident.

  An object of the present invention is to provide a digital protective relay device that can determine whether or not there is an accident in a power system with high sensitivity without being affected by disturbance.

The digital protection relay device according to the present invention performs a protection relay operation based on digital data obtained by inputting an analog electrical quantity from a power system to be protected, sampling the analog electrical quantity, and performing analog / digital conversion, thereby performing the power relay operation. Digital protection relay that determines the presence or absence of accidents, and cancels the induction amount generated in the auxiliary transformer or the internal circuit of the analog input unit that inputs the amount of electricity due to the external magnetic field due to the accident current of the unprotected power system A suppression unit that suppresses the influence of an external magnetic field, and the suppression unit includes an external magnetic field detection unit that detects the amount of induction generated in the analog input unit by detecting the magnitude of the external magnetic field, and the external magnetic field detection The digital data obtained by analog / digital conversion is corrected based on the induction amount obtained by Wherein the suppressing effect.

According to the present invention, the digital data obtained by analog / digital conversion is corrected based on the induction amount obtained by the external magnetic field detection unit, and the amount of electricity is reduced due to the external magnetic field due to the fault current of the unprotected power system. The influence of the external magnetic field is suppressed by canceling the induction amount generated in the auxiliary transformer or internal circuit of the input analog input unit, so that it is possible to determine whether there is an accident in the power system with high sensitivity without being affected by disturbance. .

(First embodiment)
FIG. 1 is a configuration diagram of a digital protection relay device according to the first embodiment of the present invention. In the first embodiment, as compared with the conventional example shown in FIG. 33, a magnetic shielding housing 22 for shielding a magnetic field is provided so as to cover the digital protection relay 12 as a suppressing unit for suppressing the influence of an external magnetic field. Is. The suppression unit suppresses an induction amount generated in an auxiliary transformer or an internal circuit of the analog input unit that inputs the electric quantity due to an external magnetic field due to an accident current of an unprotected power system.

  In FIG. 1, the digital protection relay device according to the first embodiment includes a digital protection relay 12 that protects the power system 13 and a magnetic shielding housing 22 that surrounds the digital protection relay 12. The digital protective relay 12 is protected from the magnetic field from an external magnetic field h caused by a large current if of another power system 13A around the digital protective relay 12. The magnetic shielding housing 22 surrounds the entire digital protective relay 12, but it is not always necessary to surround the entire digital protective relay 12, and it is also effective to focus on a portion that is easily affected by a magnetic field.

  FIG. 2 is a block diagram showing another example of the digital protective relay device according to the first embodiment of the present invention. FIG. 2 shows an example in which only the auxiliary transformer 15 is shielded. FIG. 3 is a block diagram showing another example of the digital protection relay device according to the first embodiment of the present invention. FIG. 3 shows an example in which the auxiliary transformer 15 and the signal line PN are shielded. FIG. 4 is a block diagram showing still another example of the digital protection relay device according to the first embodiment of the present invention. FIG. 4 shows an example in which the auxiliary transformer 15, the signal line PN, and the analog / digital conversion circuit 16 are shielded.

  The magnetic field due to a large current has a frequency of 50 Hz or 60 Hz, and various magnetic shielding methods are effective in shielding with a material having high permeability, that is, a magnetic material, and are excellent in terms of cost. As shown in FIG. 5, the structure of the magnetic shielding housing 22 surrounds the entire 360 ° circumference of the digital protective relay 12, which is a shielded object, without gaps when viewed from the direction perpendicular to the external magnetic field. is important.

  The effect | action with respect to an external magnetic field by the magnetic shielding housing | casing 22 in 1st Embodiment comprised in this way is demonstrated. As shown in FIG. 5, the magnetic flux that has entered the magnetic shielding housing 22 from the outside mainly passes through a shielding material having a high magnetic permeability and avoids a hollow portion in the magnetic shielding housing 22. For this reason, a magnetic field is weakened inside the magnetic shielding housing | casing 22 with the digital protection relay 12. FIG.

  The shielding material having a higher magnetic permeability can increase the refraction angle at the time of penetration, and can pass more magnetic flux with the same cross-sectional area, so that the magnetic flux can be prevented from entering the shielding. Therefore, the effect can be obtained even with a shielding material having a thinner magnetic permeability material. Examples of materials having high magnetic permeability and suitable for shielding include permalloy, silicon steel plate, and iron.

  Although it is desirable that the shielding structure surrounds the entire circumference of the shielding target without gaps, a gap δ is usually formed. When the gap δ is formed, as shown in FIG. 6A, the gap perpendicular to the direction of the magnetic flux blocks the path of the magnetic flux, the magnetic flux diffuses inside the shield, and the shielding effect is significantly reduced. . On the other hand, as shown in FIG. 6B, the gap in the parallel direction has little decrease in the shielding effect.

  FIG. 7 is a structural diagram of an example of the magnetic shielding housing in the first embodiment of the present invention. 7A is a top and bottom view, FIG. 7B is a front view, and FIG. 7C is a left and right side view. Inside the magnetic shielding housing 22, an analog input unit composed of the auxiliary transformer 15 and the analog / digital conversion circuit 16 and an arithmetic processing unit 17 are housed. In addition, the number of components in the magnetic shielding housing 22 in FIG. 7 and the order of arrangement are various, and are not particularly restricted.

  The magnetic shielding case 22 is made of a material having high magnetic permeability, such as iron, in order to shield an external magnetic field. Generally, cable connection from the outside is required inside the magnetic shielding housing 22 and it is actually difficult to completely shield all six surfaces, so at least the upper and lower surfaces 23 and the left and right side surfaces 24 are completely shielded. Thereby, the magnetic field from the vertical and horizontal directions can be shielded.

  The magnetic shielding housing 22 generally requires ventilation holes 25a and 25b in order to dissipate heat generated by the internal electronic circuit. However, the upper and lower surfaces 23 are provided with ventilation holes 25a that are long in the left-right direction. Is provided with a long ventilation hole 25b in the vertical direction. Thereby, the passage of the magnetic field bypassed in the shielding material from the top, bottom, left, and right directions is not blocked, and the heat dissipation effect can be enhanced without reducing the shielding effect. In this case, the shielding effect on the magnetic field in the front-rear direction is small, but the magnetic field is arranged by arranging the windings of the auxiliary transformer 15 and the internal substrate loop that are easily affected by the magnetic field so as not to point in the front-rear direction. Can be less affected.

  FIG. 8 is a structural diagram showing an example of a winding loop arrangement for a plurality of auxiliary transformers in the first embodiment of the present invention, and FIG. 9 is a winding for a plurality of auxiliary transformers in the first embodiment of the present invention. It is a structural diagram showing another example of a line loop arrangement.

  In general, a plurality of auxiliary transformers 15 which are collected in a single unit are often used. However, it is effective to enclose this unit with a magnetic shielding housing 22. When the unit is a rectangular parallelepiped, it is generally difficult to shield all six surfaces, and it is difficult to shield the front and back surfaces where the cables are pulled out. Therefore, the top, bottom, left and right surfaces are shielded. As shown in FIG. 8, the upward component hup of the external magnetic field h is shielded, but the longitudinal component hfb and the lateral component hlr cannot be shielded. In order to reduce the influence of the front-rear direction component hfb, the vertical direction of the winding loop of the auxiliary transformer 15 is set as the left-right direction of the unit as shown in FIG. In order to reduce the influence of the left-right direction component hlr, the vertical direction of the winding loop of the auxiliary transformer 15 is set as the up-down direction of the unit as shown in FIG. Thereby, the influence of the external magnetic field h can be reduced.

  FIG. 10 is a structural diagram showing an example of the winding arrangement for the individual auxiliary transformers in the first embodiment of the present invention. As shown in FIG. 10, it is also effective to store each auxiliary transformer 15 in a magnetic shielding housing 22 which is a small iron box. Although it is difficult to completely seal and shield, the auxiliary transformer 15 having the iron core 26 and the winding 27 is housed in the cylindrical magnetic shielding housing 22 to reduce the influence of the external magnetic field h. .

  Only the analog input unit can be provided separately. In that case, it is possible to reduce the size and to perform shielding in an optimum manner. As shown in FIG. 11, a separate unit containing an auxiliary transformer 15, an analog / digital conversion circuit 16, and a transmission circuit 29 for transmitting a digital quantity of electricity to the arithmetic processing unit 17 via a cable 28. Set as 30. FIG. 11 shows an example in which the unit 30 is housed in the magnetic shielding housing 22.

  Although the above description has shown a rectangular parallelepiped shape as the shape of the magnetic shielding casing 22, it can actually take various forms, and as shown in FIG. 12, a box shape, a cylindrical shape, a flat plate shape. It is good. FIG. 12A shows the shielded digital protective relay 22 covered with a rectangular parallelepiped magnetic shield housing 22, and FIG. 12B shows the shielded digital protective relay 22 with a cylindrical magnetic shield. FIG. 12C shows the case where the shielded body 31 is sandwiched between two flat magnetic shielding materials 32 and is covered with the casing 22. As shown in FIG. 12C, when it is difficult to shield the entire circumference when shielding, the shielding effect is reduced even if the entire circumference is not enclosed.

  FIG. 13 is an explanatory diagram showing an example of a form in which the entire shielded body is not covered with the magnetic shielding material according to the first embodiment of the present invention. In the following description, the description will be made without particular attention to the top, bottom, left, and right. FIG. 13 (a) shows a case where only one surface is shielded by a flat magnetic shielding material 31, FIG. 13 (b) shows a case where two adjacent surfaces are shielded, FIG. 13 (c) shows a case where two opposite surfaces are shielded, FIG. 13 (d) is a U-shaped shield that covers three surfaces, FIG. 13 (e) is a shield that closes three surfaces, FIG. 13 (f) is a shield that shields four surfaces except for two adjacent surfaces, and FIG. FIG. 13 (h) shows a screen that covers five surfaces except for two opposite surfaces, that is, a cylindrical shape, FIG. 13 (h) shows a screen that shields five surfaces, FIG. Reference numeral 13 (j) shows a case where the cylindrical magnetic shielding material 31 is shielded by only one side having no bottom surface.

  According to the first embodiment, the portion of the digital protective relay 22 that is easily affected by the external magnetic field is covered with the suppression unit, and the influence of the external magnetic field is suppressed. Therefore, malfunction due to the external magnetic field can be prevented.

(Second Embodiment)
FIG. 14 is a block diagram of a digital protection relay according to the second embodiment of the present invention. In the second embodiment, the area of the loop of the pattern on the printed circuit board on which the circuit board of the digital protective relay is formed is formed as a suppressing unit that suppresses the influence of the external magnetic field.

  In FIG. 14, the amount of electricity a1 input from the transformer 14 of the power system 13 is input to the auxiliary transformer 15 of the digital protection relay 12, and converted to a secondary amount of electricity a2 smaller than the amount of electricity a1. The secondary electricity quantity a2 output from the auxiliary transformer 15 is transmitted to the analog / digital converter 16 through a pair of signal lines PN. In this case, in the closed circuit loop LP formed by the signal line PN, the external magnetic field closed circuit induction amount ey due to the influence of the change of the external magnetic field h due to the large current if of the other power system 13A around the digital protection relay 12 Occurs.

  Therefore, the external magnetic field closed circuit induction amount ey and the secondary electric amount a2 generated by the influence of the change of the external magnetic field h become the electric amount a3 after passing through the signal line PN. That is, the sum of the secondary electricity quantity a2 and the external magnetic field closed circuit induction quantity ey is input to the analog / digital conversion circuit 16, and is sampled by the analog / digital conversion circuit 16 to perform analog / digital conversion. The arithmetic processing unit 17 performs a protection relay calculation based on the digital electric quantity input from the analog / digital conversion circuit 16 and determines the presence or absence of an accident in the power system.

  In the second embodiment, the external magnetic field closed circuit induction amount ey generated by the influence of the magnetic field h linked to the loop LP formed by the pair of positive and negative signal paths PN is reduced. FIG. 15 is an explanatory diagram of the action of an external magnetic field on the closed circuit loop LP in the second embodiment of the present invention. As shown in FIG. 15, the external magnetic field closed circuit induction amount ey of the closed circuit loop LP is generated along the loop, and its magnitude is proportional to the area of the loop, more strictly, the projected area of the magnetic field on the vertical plane. To do. The polarity of the external magnetic field closed circuit induction amount ey is generated in a certain direction with respect to the magnetic field. Therefore, as shown in FIG. 16, when the closed circuit loop is twisted and configured by several small loops, the induction polarities in the individual loops are different.

  Next, a method for reducing the external magnetic circuit induction amount ey for the magnetic field h will be described. FIG. 17 is a perspective view of an example in which the interval between patterns on the printed circuit board 33 of the digital protection relay according to the second embodiment of the present invention is narrowed. FIG. 17 shows a case where the loop area is reduced when the signal line PN is a pattern on a printed circuit board. Now, assuming that one pattern of the signal line PN is P1, and the other pattern is P2, the pattern P1 and the pattern P2 are arranged close to each other. Thereby, the loop area can be reduced and the external magnetic circuit induction amount ey can be reduced.

  FIG. 18 is a perspective view of another example in which the interval of the pattern on the printed circuit board is narrowed by the digital protective relay according to the second embodiment of the present invention. FIG. 18 shows a case where the loop area is reduced when the signal line PN is a pattern on the printed circuit board 33 and the number of layers of the printed circuit board 33 is two or more. Now, if one pattern is P1 and the other pattern is P2, the pattern P1 and the pattern P2 are arranged in different layers, and the pattern P2 has a large area, and the pattern P1 is placed on the pattern P2. Deploy. Thereby, the loop area with respect to the magnetic field can be reduced.

  FIG. 19 is a perspective view of another example in which the interval of the pattern on the printed circuit board is narrowed by the digital protective relay according to the second embodiment of the present invention. FIG. 19 shows a case where the loop area is reduced when the signal line PN is a pattern on the printed circuit board 33.

  If the pattern on the printed circuit board 33 is P1 and P2, and the number of layers of the printed circuit board is two or more, the patterns P1 and P2 are changed on the printed circuit board 33 by appropriately changing the layers through holes. The positions of the left and right positions of the patterns P1 and P2 are sequentially switched, and the area of the loop portion on the left side of the pattern P1 is SS1L, SS2L,..., And the area of the loop portion on the right side is SS1R and SS2R. ,..., The sum of SS □ L and SS □ R is set to a close value.

  If the induced electromotive force eL in the loop portion on the left side of the pattern P1 in the traveling direction and the induced electromotive force eR in the loop portion on the right side in the traveling direction of the pattern P1, the induced electromotive force eL and the induced electromotive force are assumed. The polarity is opposite to that of eR, and each has the same electromotive force. Therefore, the total induced electromotive force generated in the closed circuit loop formed by the signal line PN is the sum of eL and eR, and can be reduced.

  According to the second embodiment, since the area of the loop of the pattern on the printed circuit board forming the circuit board of the digital protection relay is formed small, the external magnetic field due to the accident current is induced by interlinking with the loop. The magnitude of the induced electromotive force can be reduced, and the analog / digital conversion circuit 16 correctly inputs and samples the electric quantity of the power system to be protected, performs analog / digital conversion, and outputs a correct digital value. It is possible to determine whether or not there is a power system accident.

(Third embodiment)
FIG. 20 is a configuration diagram of the auxiliary transformer 15 of the digital protection relay device according to the third embodiment of the present invention. In the third embodiment, the secondary winding of the auxiliary transformer 15 of the analog input unit is configured as two or more divided windings as a suppressing unit for suppressing the influence of the external magnetic field, and each divided winding is configured. The wire is attached to the opposite position on the iron core.

  In FIG. 20, the auxiliary transformer 15 includes an iron core 26, a primary winding W1, and secondary windings W2L and W2R divided into two. When the electric quantity a1 is input to the primary side winding W1, secondary outputs a2L and a2R are obtained in the secondary windings W2L and W2R, the directions thereof are as shown in FIG. 20, and the auxiliary transformer As the output a2 of 15, the sum of the secondary outputs a2L and a2R is output. The presence / absence and structure of the iron core 26 and the attachment position of the primary winding W1 are various, and are not limited to those shown in FIG.

  FIG. 21 is an explanatory diagram of the action of an external magnetic field on the auxiliary transformer 15 shown in FIG. The external magnetic field h generates an induction amount exL in the winding W2L and an induction amount exR in the winding W2R. The direction of the guidance amount is as shown in FIG. For this reason, when the induction amount exL and the induction amount exR are close to each other, the total winding induction amount ex appearing at the output of the auxiliary transformer 15 is small.

  Here, the windings W2L and W2R can actually be arranged in various ways. FIG. 22 is a configuration diagram of an auxiliary transformer as another example of the digital protection relay device according to the third embodiment of the present invention. As shown in FIG. 22, windings W2U, W2L, W2D, and W2R may be provided on each of the four sides of the iron core 26 to take measures against both the magnetic field hv from the vertical direction and the magnetic field hh from the horizontal direction. It is. Also in this case, the total winding induction amount ex appearing at the output of the auxiliary transformer 15 is small.

  FIG. 23 is a configuration diagram of another example of the auxiliary transformer of the digital protection relay device according to the third embodiment of the present invention. As shown in FIG. 23, it is possible to provide a winding W2 around the entire circumference of the iron core 26 to take measures against the magnetic field h from all directions. Also in this case, the total winding induction amount en appearing at the output of the auxiliary transformer 15 is small.

  According to the third embodiment, induction to the winding of the auxiliary transformer 15 by the external magnetic field h can be reduced, and the auxiliary transformer 15 sets the electric quantity of the system to be protected to the correct secondary side. By converting to an output value, the analog / digital conversion circuit 16 performs sampling, analog / digital conversion, and comparing with the set value in the arithmetic processing unit, it is possible to correctly determine whether there is a power system fault. Therefore, even when an accident current flows, the digital protective relay 12 can correctly determine whether or not there is an accident in the power system by reducing the influence of the external magnetic field h.

(Fourth embodiment)
FIG. 24 is a block diagram of a digital protection relay device according to the fourth embodiment of the present invention. In the fourth embodiment, the digital protection relay 12 is a current differential relay, and is one of a plurality of auxiliary transformers 15a to 15n inside the digital protection relay 12 as a suppression unit that suppresses the influence of an external magnetic field. It is set as the structure which rotated the installation direction of the part. It is assumed that the system to which the digital protection relay device according to the fourth embodiment is applied is the same as the system shown in FIG.

  24, auxiliary transformers 15a to 15n for converting the currents ia1, ib1,... In1 input to the digital protection relay 12 into different current values ia2, ib2,. The analog / digital conversion circuit 16 that samples in2 and performs analog / digital conversion to convert to digital values diga, digb,..., and digital, and the sum of the analog / digital converted digital values diga, digb,. Compared with the set value iset, a calculation processing unit comprising a differential calculation unit (DIF) 20 for determining the presence or absence of an accident in the bus 18 which is a protection section, and a storage unit (MEM) 21 for storing the set value 17.

  In the fourth embodiment, as shown in FIG. 24, a part of the plurality of auxiliary transformers 15 a to 15 n is arranged such that the installation direction of the winding faces the opposite direction. Alternatively, the direction of installation of the auxiliary transformers 15a to 15n itself is not changed, the wiring connecting the auxiliary transformers 15a to 15n and the analog / digital conversion circuit 16, and the input part of the digital protection relay 12 and the auxiliary transformer The wiring connecting between the devices 15a to 15n is reversed in the middle of the wiring path. In this case, the wiring is inverted, but the correspondence between the polarity of the signal at the input to the digital protection relay 12 and the polarity of the signal input to the analog / digital conversion circuit 16 does not invert the auxiliary transformers 15a to 15n. It is the same as the polarity of the case. What is necessary is that the magnetic flux generated in the windings of the auxiliary transformers 15a to 15n by the external magnetic field h is installed so that the direction of each line is reversed.

  In the fourth embodiment configured as described above, when no accident occurs in the bus 18 serving as the protection section, the sum of the currents ia, ib,... In flowing into the bus 18 serving as the protection section is 0. Become. On the other hand, when an accident, that is, a ground fault or a short-circuit accident occurs in the bus 18 that is the protection section, current is lost at the accident location, and the sum of ia, ib,. Will be equal. Accordingly, the arithmetic processing unit 17 calculates the sum of the digital values diga, digb,..., Gn in the differential operation unit (DIF) 20, and no accident occurs when the value is smaller than the predetermined set value iset, and an accident occurs when the value is larger. Judge that it is.

  FIG. 25 is an explanatory diagram of the influence of an external magnetic field on the digital protective relay device according to the fourth embodiment of the present invention. When the digital protective relay 12 is exposed to an external magnetic field h, as shown in FIG. 25, induction amounts exa and exb generated by the external magnetic field h and input to the analog / digital conversion circuit 16 for each line. , Exc... Exn, some of the polarities are opposite, so that they are canceled by the sum operation in the differential operation unit (DIF) 20. When half of the polarities are opposite, the calculation result for the induction amount is minimized.

  FIG. 26 is a configuration diagram of another example of the digital protection relay device according to the fourth embodiment of the present invention. As shown in FIG. 26, the auxiliary transformers 15a, 15b, and 15c of the digital protective relay 12 may be rotated and arranged by 120 °. In this case, the vector direction of the guidance amount guided to each line is as shown in FIG. 27, and the result of the sum operation for every three lines can be zero. When reversing 180 °, if the number of input lines is odd, the amount of guidance for one line remains, but by combining 120 degrees of reversal, the amount of guidance is completely canceled even when the number of input lines is odd. Can do.

  According to the fourth embodiment, a part of the plurality of auxiliary transformers 15a to 15n is rotated in the installation direction to cancel the induction amount caused by the external magnetic field h. It is possible to correctly determine whether an accident has occurred.

(Fifth embodiment)
FIG. 28 is a block diagram of a digital protection relay device according to the fifth embodiment of the present invention. The fifth embodiment includes an external magnetic field detection unit that detects the magnitude of the external magnetic field and obtains an induction amount generated in the analog input unit as a suppression unit that suppresses the influence of the external magnetic field. A correction is made to digital data obtained by analog / digital conversion based on the obtained induction amount.

  In FIG. 28, a winding 34 dedicated to external magnetic field detection as an external magnetic field detection unit is provided in the digital protective relay 12. The induction amount exref from the winding 34 dedicated to external magnetic field detection is sampled by the analog / digital conversion circuit 16 and converted into an external magnetic field induction amount detection value digr by analog / digital conversion. The differential operation unit (DIF) 20 multiplies the detected value digr of the external magnetic field induction amount by a predetermined correction coefficient c to obtain a predicted value of the induction amount of the auxiliary transformer of each line, and subtracts it to obtain an external value. Counteract the effects of magnetic fields. The external magnetic field detection dedicated winding 34 can also be realized by diverting the auxiliary transformer 15z of an empty line and leaving the primary winding unconnected.

FIG. 29 is a configuration diagram of another example of the digital protection relay device according to the fifth embodiment of the present invention. As shown in FIG. 29, a pattern loop 35 having an area on the order of several hundreds of cm ² may be provided on the printed circuit board as the external magnetic field detector. Then, the induction amount exref from the pattern loop 35 is sampled by the analog / digital conversion circuit 16 and converted into an external magnetic field induction amount detection value digr by analog / digital conversion. In this case, the influence of the external magnetic field can be canceled as in the case shown in FIG.

  FIG. 30 is a configuration diagram of another example of the digital protection relay device according to the fifth embodiment of the present invention. As shown in FIG. 30, in the arithmetic processing unit 17 of the digital protection relay 12, an external magnetic field induction amount setting storage unit 36 for storing the external magnetic field induction amount cancellation value eset is provided in advance, and a differential operation unit (DIF) 20 In the sum calculation at, the influence of the external magnetic field may be canceled by subtracting the external magnetic field induction amount cancellation value eset.

  FIG. 31 is a configuration diagram of still another example of the digital protection relay device according to the fifth embodiment of the present invention. As shown in FIG. 31, in the analog input section of the digital protection relay 12, the induction amount generated in the auxiliary transformer 15 is canceled by the induction amount generated by the pattern loop 37 intentionally formed by the signal line PN of the substrate pattern. Also good.

  According to the fifth embodiment, it is possible to correctly determine whether there is an accident in the power system even if there is an external magnetic field.

The block diagram of the digital protection relay apparatus concerning the 1st Embodiment of this invention. The block diagram which shows another example of the digital protection relay apparatus concerning the 1st Embodiment of this invention. The block diagram which shows another example of the digital protection relay apparatus concerning the 1st Embodiment of this invention. The block diagram which shows another another example of the digital protection relay apparatus concerning the 1st Embodiment of this invention. Explanatory drawing of the magnetic shielding with respect to the external magnetic field in the 1st Embodiment of this invention. Explanatory drawing of the shielding effect with respect to the external magnetic field by the presence or absence of the clearance gap in the 1st Embodiment of this invention. FIG. 3 is a structural diagram of an example of a magnetic shielding housing in the first embodiment of the invention. FIG. 3 is a structural diagram showing an example of a winding arrangement for a plurality of auxiliary transformers in the first embodiment of the present invention. FIG. 6 is a structural diagram showing another example of a winding arrangement for a plurality of auxiliary transformers in the first embodiment of the present invention. FIG. 3 is a structural diagram showing an example of a winding arrangement for an individual auxiliary transformer in the first embodiment of the present invention. The block diagram of the digital protection relay apparatus formed by accommodating the analog input part in the 1st Embodiment of this invention in the case of an installation type. Explanatory drawing of an example of the form of the magnetic shielding housing | casing in the 1st Embodiment of this invention. Explanatory drawing of an example of the form which does not cover the whole to-be-shielded body with the magnetic shielding housing | casing in the 1st Embodiment of this invention. The block diagram of the digital protection relay apparatus concerning the 2nd Embodiment of this invention. Explanatory drawing of the effect | action of the external magnetic field with respect to the closed circuit loop in the 2nd Embodiment of this invention. Explanatory drawing of an effect | action of an external magnetic field in case the closed circuit loop in the 2nd Embodiment of this invention is a twisted circuit loop. The perspective view of an example which narrows the space | interval of the pattern on a printed circuit board with the digital protection relay in the 2nd Embodiment of this invention. The perspective view of another example which narrows the space | interval of the pattern on a printed circuit board with the digital protection relay in the 2nd Embodiment of this invention. The perspective view of another example which narrows the space | interval of the pattern on a printed circuit board with the digital protection relay in the 2nd Embodiment of this invention. The block diagram of the auxiliary transformer of the digital protection relay apparatus concerning the 3rd Embodiment of this invention. Explanatory drawing of the effect | action of an external magnetic field with respect to the auxiliary transformer of the digital protection relay apparatus concerning the 3rd Embodiment of this invention. The block diagram of another example of the auxiliary transformer of the digital protection relay apparatus concerning the 3rd Embodiment of this invention. The block diagram of another another example of the auxiliary transformer of the digital protection relay apparatus concerning the 3rd Embodiment of this invention. The block diagram of the digital protection relay apparatus concerning the 4th Embodiment of this invention. Explanatory drawing of the influence of an external magnetic field with respect to the digital protection relay apparatus concerning the 4th Embodiment of this invention. The block diagram of another example of the digital protection relay apparatus concerning the 4th Embodiment of this invention. Explanatory drawing of the influence of an external magnetic field with respect to the digital protection relay apparatus shown in FIG. The block diagram of the digital protection relay apparatus concerning the 5th Embodiment of this invention. The block diagram of another example of the digital protection relay apparatus concerning the 5th Embodiment of this invention. The block diagram of another example of the digital protection relay apparatus concerning the 5th Embodiment of this invention. The block diagram of another another example of the digital protection relay apparatus concerning the 5th Embodiment of this invention. Explanatory drawing of the aspect which a magnetic field generate | occur | produces by the accident electric current of an electric power system. Explanatory drawing of the aspect in which an external magnetic field influences the conventional digital protection relay. Explanatory drawing of the operation principle of current differential protection. The internal block block diagram of the conventional current differential protection relay. Explanatory drawing of the influence of the external magnetic field with respect to the conventional current differential protection relay.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Substation, 12 ... Digital protection relay, 13 ... Electric power system, 14 ... Transformer, 15 ... Auxiliary transformer, 16 ... Analog / digital converter, 17 ... Arithmetic processing part, 18 ... Bus-bar, 19 ... Current transformer , 20 ... differential operation unit, 21 ... storage unit, 22 ... magnetic shielding housing, 23 ... upper and lower surfaces, 24 ... left and right side surfaces, 25 ... vent holes, 26 ... iron core, 27 ... windings, 28 ... cables, 29 ... Transmission circuit 30 ... unit 31 ... shielded body 32 ... magnetic shielding material 33 ... printed circuit board 34 ... external magnetic field detection winding 35 ... pattern loop 36 ... external magnetic field induction amount setting storage unit 37 ... Pattern loop

Claims (3)

A digital protective relay that inputs an analog amount of electricity from the power system to be protected, samples the analog amount of electricity, performs analog / digital conversion, and performs a protection relay operation to determine whether there is an accident in the power system When,
A suppression unit that suppresses the influence of the external magnetic field by canceling the induction amount generated in the auxiliary transformer of the analog input unit or the internal circuit due to the external magnetic field due to the fault current of the power system that is not protected The suppression unit includes an external magnetic field detection unit that detects the magnitude of an external magnetic field and obtains an induction amount generated in the analog input unit, and performs analog / digital conversion based on the induction amount obtained by the external magnetic field detection unit A digital protective relay device that corrects the digital data obtained in this way and cancels the amount of induction by the external magnetic field to suppress the influence of the external magnetic field . 2. The digital protection relay device according to claim 1, wherein the external magnetic field detection unit detects an auxiliary transformer output dedicated to external magnetic field detection of the digital protection relay and obtains an induction amount generated in the analog input unit. . 2. The digital protection relay according to claim 1, wherein the external magnetic field detection unit detects an induction amount of a loop-shaped signal line provided in the digital protection relay and obtains an induction amount generated in the analog input unit. Electrical equipment.

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