JP2005322603A - Protective circuit for power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective circuit for a power system with equipment cost saved as much as possible, and with trouble areas localized through restraint of the repercussion of short-circuit failure and grounding failures of equipment which are connected in branched manner to a power system. <P>SOLUTION: A serial circuit of a cutout 13 with a tripolar interlocking release function with an expulsion fuse 13a incorporated in free detachment, and a cylindrical cutout 14 with a current-limiting fuse 14a having an interruption function incorporated in free detachment is arranged the power source side of a reactor 12 branch connected to a distribution wire 11. Further, the rated current of the expulsion fuse 13a is set smaller than that of the current-limiting fuse 14a. By the protection coordination of the current-limiting fuse 14a and the expulsion fuse 13a, a given interruption capacity can be secured, to enable protection of the power system from the short-circuiting failures with respect to the reactor 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a protection circuit that protects a power system from, for example, a short circuit or a ground fault of an electrical device that is branched and connected to the power system.

Currently, the ungrounded system is mainly used for high-voltage distribution lines. When a ground fault occurs in such a high-voltage distribution system, a ground fault current and a zero-phase voltage are generated, and the ground fault current is equivalent to the ground charging current of the line. In addition, the ground fault current tends to increase due to the increase in the capacitance to the ground as the distribution line is underground and cabled in recent years. On the other hand, according to the provisions regarding electrical equipment, the second type grounding work for the pole transformer is obliged to prevent the danger of the low voltage customer when the high voltage distribution line and the low voltage distribution line are mixed in the same power pole. This type 2 grounding resistance value is determined by the magnitude of the high-voltage one-line ground fault current. When the ground fault current is large, a low grounding resistance value is required, and its construction is costly. For this reason, as shown in FIG. 5A, a reactor 101 may be provided as a measure for suppressing the ground fault current. In order to protect such an electric device such as the reactor 101, a switch 102 (high voltage load switch) is provided on the primary side (power supply side) of the reactor 101. In this case, an air switch or a gas switch is adopted as the switch 102. Further, as shown in FIG. 5B, when an electrical device such as the transformer 103 and the power supply side cable 104 are connected via the cable connector 105, a current limiting fuse 106 is incorporated in the cable connector 105. In addition, there is also known one in which short circuit protection of an electric device is achieved by the current limiting fuse 106 (for example, Patent Document 1). According to this configuration, since the circuit breaker can be omitted, it is possible to simplify the peripheral equipment of the electric equipment and reduce the equipment cost.
JP 2000-286021 A

  However, the conventional power system protection circuit has the following problems. That is, in the protection circuit shown in FIG. 5A, although the switch 102 is provided on the power source side of the reactor 101, the switch 102 cuts off the load current and has a short-circuit current cut-off function. Does not have. That is, for example, when an internal short circuit occurs in the reactor 101 for some reason, the conventional power distribution circuit cannot cut off the fault current (short circuit current). In order to protect the power distribution system from overcurrent caused by an internal short circuit of the reactor 101, for example, a current limiting fuse may be provided on each phase power supply side of the switch 102. However, in this case, when the one-phase current limiting fuse is blown, a phase failure state occurs, and the reactor L component does not act on the distribution line in a three-phase equilibrium state, which adversely affects the ground fault protection function. As a result, a substation circuit breaker (not shown) may trip in some cases. On the other hand, in the circuit described in Patent Document 1, although a current limiting fuse 106 is installed in each phase on the power supply side, a malfunction in a ground fault relay (ground fault relay) occurs due to an open phase condition (open phase fault). As a result, the circuit breaker 107 of the substation may trip.

  As a device having a predetermined breaking capacity and capable of opening three poles at the same time, there is a breaker. It is also conceivable to install the breaker on the power source side of an electric device such as a reactor or a transformer. However, in general, the circuit breaker is very expensive and is not realistic from the viewpoint of equipment cost. As described above, there is no appropriate protection device (protection circuit) that protects the power distribution system from short-circuit faults and ground faults of electric devices such as reactors and capacitors. For this reason, there was a possibility that the short circuit fault and the ground fault of the reactor would greatly spread. Therefore, it has been desired to localize a failure area caused by a short circuit of the reactor and a ground fault.

  The present invention has been made to solve the above-described problems, and its purpose is to save equipment costs as much as possible and to suppress the occurrence of short-circuit faults and ground faults in electrical equipment branched and connected to the power system. Thus, it is an object of the present invention to provide a power system protection circuit that can localize a failure area.

  According to the first aspect of the present invention, there is provided a primary cutout with a three-pole interlocking open function in which a discharge type fuse is detachably mounted on the power supply side of an electric device branched and connected to each phase of the power system, and a cutoff function. The gist of the invention is that a series circuit with a primary cutout different from the above, in which the current limiting fuse is detachably mounted, is arranged.

  The gist of the invention described in claim 2 is that the rated current of the discharge fuse is made smaller than the rated current of the current-limiting fuse in the protection circuit for the power system according to claim 1.

(Function)
According to the first aspect of the present invention, protection coordination is achieved by the discharge type fuse and the current limiting fuse. Specifically, protection coordination (short-circuit protection, ground fault protection, and phase loss prevention) can be achieved by making sure that inexpensive discharge fuses and current-limiting fuses with a shut-off function individually perform protection operations in their cut-off areas. can get. As a result, a predetermined breaking capacity can be ensured, and the power system can be protected against short-circuit faults and ground faults of electrical equipment. Therefore, it is possible to localize the failure area by suppressing the short circuit failure and the ground fault failure of the electrical equipment branched and connected to the power system.

  Moreover, short circuit protection and ground fault protection can be achieved at low cost by combining a primary cutout with a three-pole interlocking opening function and a primary cutout. In other words, for example, a circuit breaker equivalent to a circuit combining a primary cutout and a primary cutout with a three-pole interlocking open function is provided on the primary side (power supply side) of the electrical equipment, resulting in a large cost merit. . This is because, in general, a circuit breaker equivalent to the protection circuit according to the present invention is very expensive. Therefore, equipment costs can be saved as much as possible.

  According to the invention described in claim 2, in addition to the operation of the invention described in claim 1, the discharge type fuse blows faster than the current limiting fuse. By coordinating the discharge type fuse and the current limit fuse so that the discharge type fuse is always blown before the current limit fuse blows, only one phase or only two phases may be charged in electrical equipment. Absent. That is, when the current limiting fuse is operated, the discharge fuse of the primary cutout with the three-pole interlocking opening function is always blown, and the primary cutout with the three-pole interlocking opening function is opened at the same time. For this reason, it is prevented that a phase loss state occurs on the load side (electric device side).

  According to the present invention, the equipment cost can be saved as much as possible, and the failure area can be localized by suppressing the spread of short-circuit faults and ground faults of electrical equipment branch-connected to the power system.

  Hereinafter, an embodiment in which the present invention is embodied in a protection circuit that protects an electric power system from a short circuit failure of a reactor will be described with reference to FIGS. This reactor is used according to the system characteristics in order to compensate, for example, a one-line ground fault current.

<Overall configuration>
As shown in FIG. 1, a reactor 12 is connected to each phase (U phase, V phase, W phase) of the distribution line 11 via branch cables 11u, 11v, 11w. The neutral point of the reactor 12 is grounded. On the power source side (distribution line 11 side) of the reactor 12, a series circuit of a cutout 13 with a three-pole interlocking open function and a cylindrical cutout 14 is provided. The cutout 13 with the three-pole interlocking opening function is internally provided with a discharge fuse 13a, and the cylindrical cutout 14 is provided with a current limiting fuse 14a.

<Cylindrical cutout>
As shown in FIG. 3, the cylindrical cutout 14 is disposed on branch cables 11u and 11w connected to the U phase and W phase of the distribution line 11 on the primary side of the cutout 13 with the three-pole interlocking opening function. (See FIG. 1). The cylindrical cutout 14 includes a cylindrical main body insulator 21, and the main body insulator 21 is supported on a brace (not shown) of a utility pole via a mounting bracket. An upper contact 22 is disposed in the upper part of the main body insulator 21, and the upper contact 22 is connected to the power supply side of the branch cables 11 u and 11 w through an upper lead wire 23. A lower contact 24 is disposed in the lower part of the main body insulator 21, and the lower contact 24 is connected to the load side of the branch cables 11 u and 11 w through a lower lead wire 25. A current limiting fuse 14 a is mounted between the upper contact 22 and the lower contact 24 in the main body insulator 21 via an arc extinguishing tube 26. A sealing plug 28 is detachably or detachably attached to the lower end opening of the main body insulator 21.

  When a current exceeding a specified value (for example, a short-circuit current) flows through the distribution line 11, the load element of the cylindrical cutout 14 in the branch cables 11u and 11w is limited by fusing a fuse element (not shown) of the current limiting fuse 14a. The flow is interrupted. When replacing the current limiting fuse 14a, the sealing plug 28 is removed or opened, the used current limiting fuse is removed from the lower end opening of the main body insulator 21, and a new current limiting fuse 14a is installed at the lower end opening of the main body insulator 21. Insert from the part.

<Cutout with tripolar interlocking open function>
As shown in FIG. 1, the three-pole interlocking open function cutout 13 is attached to the primary side of the reactor 12 for the purpose of opening and closing the load current. The cutout 13 with the three-pole interlocking opening function is configured to open three poles at the same time when one of the three poles is blown by the discharge fuse 13a.

  As shown in FIG. 1, the cutout 13 with a three-pole interlocking opening function is provided on branch cables 11u, 11v, and 11w that are branched and connected to the U-phase, V-phase, and W-phase of the distribution line 11, respectively. The three box-shaped cutouts 13u, 13v, and 13w are provided. As shown in FIG. 3, each of the box-shaped cutouts 13 u, 13 v, and 13 w includes a box-shaped main body insulator 31 that is open on one side, and the opening of the main body insulator 31 is closed by a lid 33. . The lid 33 is supported by a lower portion of the main body insulator 31 through a pin 32 so as to be opened and closed, and an opening is formed in the lower portion of the lid 33.

  The main body insulator 31 is supported on the armature of the electric pole on the back surface thereof in an oblique manner via the mounting bracket 34. A support shaft 35 common to each phase is fixed to the mounting bracket 34, and a support lever 36 is fixed to the support shaft 35 at a predetermined interval (corresponding to the main body insulator 31 of each phase). A base end portion of a J-shaped interlocking lever 37 is rotatably supported at the distal end portion of each support lever 36. By engaging with a stopper 38 projecting from a part of the mounting bracket 34, the clockwise rotation range of the support lever 36 is restricted.

  An upper electrode 39 is provided in the upper part of the main body insulator 31, and the upper electrode 39 is connected to the power supply side of the branch cables 11 u, 11 v, 11 w (not shown in FIG. 4) via the connection terminal 40. . The upper electrode 39 is covered with an arc extinguishing cylinder 41. A lower electrode 42 is provided in the lower part of the main body insulator 31. The lower electrode 42 is connected to the load side of the branch cables 11u, 11v, 11w (not shown in FIG. 4) via a connection terminal 43, and an opening spring 44 is attached to the lower electrode 42.

  In the main body insulator 31, one end of an L-shaped actuating lever 45 is supported above the lower electrode 42 so as to be rotatable about a shaft 45 a, and the other end is also provided in the main body insulator 31 via a bent portion. It extends to the bottom. A locking pin 46 projects from the bent portion of the operating lever 45. A response lever 47 is supported at the lower portion of the main body lever 31 so as to be tiltable with the pin 32 as a fulcrum. One end portion of the responding lever 47 is an outer engaging portion 47 a extending outward from the main body lever 31, and the other end portion is also an inner engaging portion 47 b extending inward from the main body lever 31. Yes. The inner surface of the outer engaging portion 47 a of the response lever 47 can be engaged with the lower end portion of the interlocking lever 37. The inner engagement portion 47b can be engaged with the lower end portion of the operating lever 45 from the side.

  On the other hand, a discharge fuse 13a is attached to the inner surface of the lid 33. An upper contact blade 48 is fixed to the upper portion of the discharge fuse 13a so as to protrude inward, and a lower contact blade 49 is fixed to the lower portion so as to protrude inward. The upper contact blade 48 and the lower contact blade 49 are sandwiched between the upper electrode 39 and the lower electrode 42 so as to be able to contact and separate from each other. The lower contact blade 49 is in contact with the lower electrode 42 against the elastic force of the opening spring 44.

  A display cylinder 50 is attached to the lower part of the discharge fuse 13a, and the display cylinder 50 is always urged downward by the elastic force of a spring (not shown). The display tube 50 is configured to be ejected downward by the elastic force of the spring when a fuse element (not shown) is melted. An engagement protrusion 51 is formed on the upper side surface of the display tube 50.

  An opening lever 52 is supported at the base of the lower contact blade 49 so as to be rotatable about a shaft 52a. The opening lever 52 is always urged counterclockwise by a torsion coil spring (not shown) attached to the shaft 52a. A locking claw 53 is formed on the upper part of the opening lever 52, and a locking projection 54 is formed on the lower part. The locking claw 53 can be engaged with and disengaged from the locking pin 46 of the operating lever 45, and when the locking claw 53 engages with the locking pin 46, the lid 33 rotates clockwise (downward). Movement is regulated. The locking projection 54 is locked to the engagement projection 51 of the display tube 50, and thereby the rotation of the opening lever 52 in the counterclockwise direction is restricted.

<Operation of cutout with tripolar interlocking open function>
Therefore, when the fuse element of the discharge type fuse 13a is blown, the display cylinder 50 held at the upper position shown by the solid line in FIG. 4 is ejected downward against the elastic force of the spring by the tension of the fuse element. To do. Along with this, the engaging protrusion 51 of the display cylinder 50 is lowered, and the engagement with the locking protrusion 54 of the opening lever 52 is released. Then, the opening lever 52 rotates counterclockwise about the shaft 52a by the elastic force of the torsion coil spring. As the opening lever 52 rotates, the engagement between the locking claw 53 of the opening lever 52 and the locking pin 46 of the operating lever 45 is released. Then, the lid 33 is rotated clockwise about the pin 32 by its own weight and the elastic force of the opening spring 44. As a result, the upper contact blade 48 and the lower contact blade 49 are separated from the upper electrode 39 and the lower electrode 42, respectively, and the line is opened.

  When the lid 33 is opened to the open position indicated by a two-dot chain line in FIG. 4 (only the lower end 33 a of the lid 33 is shown in FIG. 4), the lower end 33 a of the lid 33 moves the lower end of the interlock lever 37. Push up. For this reason, the support lever 36 is rotated in the clockwise direction, and the support shaft 35 common to each box-shaped primary cutout is accordingly rotated in the clockwise direction.

  The box-shaped primary cutout of the other phase where the fuse element is not blown is opened in conjunction with the opening operation of the box-shaped primary cutout of the phase where the fuse element is blown. That is, as the support shaft 35 rotates in the clockwise direction, the support levers 36 corresponding to the other-phase box-shaped primary cutouts rotate in the same direction. Thereby, the interlocking lever 37 is pulled up, and the lower end portion 37 a of the interlocking lever 37 is engaged with the outer engaging portion 47 a of the responding lever 47. When the outer engagement portion 47a is pulled upward, the response lever 47 tilts clockwise about the pin 32. Along with this, the inner engagement portion 47b pushes the lower portion of the operating lever 45 to the right. Therefore, the operating lever 45 rotates counterclockwise and slightly upward about the shaft 45a. Then, the locking pin 46 is disengaged from the locking claw 53 of the opening lever 52, and the lid 33 is opened by the weight of the lid 33 and the elastic force of the opening spring 44.

  In this way, the three-pole interlocking open function cutout 13 can be opened in three poles at once. For this reason, unlike the case where each phase is opened, it is possible to prevent the load side (in this case, the reactor 12 side) from being in an open phase state. In addition, in this embodiment, the distribution line 11 comprises an electric power system, and the reactor 12 comprises an electric equipment. Further, the cutout 13 with a three-pole interlocking opening function constitutes a primary cutout with a three-pole interlocking opening function, and the cylindrical cutout 14 constitutes another primary cutout.

<Protection operation characteristics of discharge-type fuse and current-limiting fuse>
Next, the operating characteristics of the discharge fuse and the current limiting fuse will be described.
The rated currents of the discharge-type fuse 13a and the current-limiting fuse 14a are set so that the rated current of the discharge-type fuse 13a is smaller than the rated current of the current-limiting fuse 14a. In the present embodiment, due to the fusing characteristics of the fuse element, the discharge type fuse 13a is used for a rating of 1.3A (ampere), and the current limiting fuse 14a is used for 10A.

As shown in FIG. 2, the energy required for fusing the discharge fuse 13a (fusing energy I ² t) is smaller than the energy necessary for fusing the current limiting fuse 14a (fusing energy I ² t). When the short circuit failure occurs, the discharge fuse 13a is blown out (point A in FIG. 2) before the current limiting fuse 14a. Here, I indicates current and t indicates time. However, the discharge fuse 13a cannot interrupt the short-circuit current. This short-circuit current is blown out by the current limiting fuse 14a (point B1 in FIG. 2), and the current limiting is interrupted prior to the discharge fuse 13a (point B2 in FIG. 2). Incidentally, when only the current limiting fuse 14a is provided and the discharge type fuse 13a (the cutout 13 with the three-pole interlocking open function) is not provided, one phase current limiting fuse (for example, the limit of the U phase) among the respective phases. When the current fuse 14a) is blown, a single-phase operation state (open phase state) may occur, which may cause a substation to be erroneously recognized as a ground fault.

Here, conditions necessary for interrupting operation coordination between the discharge-type fuse 13a and the current-limiting fuse 14a with respect to the fault current, including the case of a short-circuit fault, will be described as follows.
“1. Operation coordination in the overcurrent region”
Fusing energy ^I 2 t fusing energy ^I 2 t <current limiting fuses 14a of release Fusing 13a
In the small current region, the discharge fuse 13a is blown (cut off) first.

"2. Coordination of operation when short circuit current is interrupted"
Fusing energy I ² t of the discharge-type fuse 13a <Operating energy I ² t of the current-limiting fuse 14a
When the current limiting fuse 14a is cut off due to a large current interruption, the discharge fuse 13a is always blown.

"3. Coordination with cutout 13 breaking capacity (thermal and mechanical strength) with tripolar interlocking open function"
Maximum passing energy I ² t at cutoff of cutout 13 with tripolar interlocking opening function> Operating energy I ² t of current limiting fuse 14a
When seeking cooperation in the overcurrent region as in the present application, the item “2.” is included in the item “1.”.

<Operation of Embodiment>
Next, the operation of the reactor protection circuit configured as described above will be described.
For example, when a short circuit failure of the reactor 12 occurs, the short circuit current generated by this failure is suppressed to a value equal to or less than the cutoff short circuit capacity of the cutout 13 with the three-pole interlocking open function by the current limiting fuse 14a in the cylindrical cutout 14. Thus, the discharge fuse 13a of a certain phase is blown out before the current limiting fuse 14a (see FIG. 2). When the discharge fuse 13a of a certain phase is blown, the latching claw 53 that holds the lid 33 in the closed position is pulled off in conjunction with the ejecting operation of the display tube 50 of the discharge fuse 13a. The body 33 opens. Then, the support shaft 35 common to the respective phases is rotated in conjunction with the opening operation of the lid 33, and the lid 33 of the other phase is thereby opened and opened. In this way, the primary side (power supply side) of the reactor 12 is collectively opened. As a result, it is possible to limit the failure section, avoid a single-phase operation state, and prevent malfunction of the ground fault relay.

In the present embodiment, the cut-off short-circuit capacity of the three-pole interlocking open function cutout 13 is 3000A, and the cut-out with the three-pole interlocking open function is always performed before the current limiting fuse 14a of the cylindrical cutout 14 is melted. Protection coordination of the current limiting fuse 14a and the discharge fuse 13a is achieved so that the 13 discharge fuses 13a are blown. By this protection coordination, the reactor 12 is not charged only in one phase or two phases. That is, a phase failure condition (phase failure) does not occur, and a malfunction of the ground fault relay (ground fault relay) and a trip of the substation circuit breaker are also prevented. Incidentally, in the protection circuit according to the present embodiment, a breaking capacity of about 12.5 kA (kiloamperes) can be obtained.

  Therefore, unlike the case where a breaker equivalent to the breaking capacity of this protection circuit is arranged on the primary side (power supply side) of the reactor 12, the reactor 12 branched and connected to the distribution line 11 while saving the equipment cost as much as possible. The power system (distribution system) is protected from short circuits and ground faults of electrical devices such as the above. This is because, generally, a circuit breaker having a breaking capacity equivalent to the protection circuit of the power system according to the present embodiment is very expensive. In addition, the short circuit failure and the ground fault failure of the electrical equipment such as the reactor 12 branched and connected to the distribution line 11 are suppressed, and the failure area is localized. Furthermore, since the series circuit of the cylindrical cutout 14 and the cutout 13 with the three-pole interlocking opening function is merely arranged on the primary side of the reactor 12, the cylindrical cutout 14 and the cutout 13 with the three-pole interlocking opening function are provided. The installation (post) is easy. All the devices of the cylindrical cutout 14 and the cutout 13 with the three-pole interlocking opening function are fixed to the armrest of the utility pole via the mounting bracket. Thus, the series circuit of the cylindrical cutout 14 and the cutout 13 with the three-pole interlocking open function functions as a realistic and appropriate protection circuit from both the viewpoints of the equipment cost and the power system protection function.

<Effect of embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) On the power source side of the reactor 12 branchedly connected to the distribution line 11, a cutout 13 with a three-pole interlocking open function in which a discharge fuse 13a is detachably mounted, and a current limiting fuse 14a having a cutoff function are attached and detached. A series circuit with a cylindrical cutout 14 that is embeddable is arranged. The cutout 13 with the three-pole interlocking opening function has a function of opening (opening) the three poles at the same time when one of the three poles is blown out. However, since the discharge-type fuse 13a cannot cut off the short-circuit current, the short-circuit current is cut off by the current-limiting fuse 14a. As described above, the protection current is coordinated by the current-limiting fuse 14a and the discharge-type fuse 13a, so that a predetermined breaking capacity (for example, 12.5 kA in the present embodiment) can be secured, and the reactor 12 is short-circuited. The power system can be protected against Further, it is possible to protect even in a region where the fault current is an overcurrent, such as a process of transition from a ground fault to a short circuit through protection coordination by the discharge fuse 13a and the current limiting fuse 14a.

  By the way, when only the current limiting fuse 14a is provided, there is a possibility that a phase failure will occur, and a ground fault may be erroneously detected, and the circuit breaker at the substation may trip. In the present embodiment, by providing the three-pole interlocking open function cutout 13 and releasing the three phases at once, an open phase state does not occur and an erroneous detection of a ground fault is prevented.

  (2) The rated current of the discharge fuse 13a is made smaller than the rated current of the current limiting fuse 14a. For this reason, the discharge fuse 13a is blown earlier than the current limiting fuse 14a. Since the discharge fuse 13a and the current limit fuse 14a are coordinated so that the discharge fuse 13a is always blown before the current limit fuse 14a is blown, the reactor 12 is charged only in one phase or only in two phases. Never become. That is, whenever the current limiting fuse 14a is operated, the discharge fuse 13a of the cutout 13 with the three-pole interlocking opening function is always blown, and the cutout 13 with the three-pole interlocking opening function is opened at the same time. For this reason, it can prevent becoming a phase loss state.

  (3) From the power source side, the cylindrical cutout 14 having the current limiting fuse 14a and the cutout 13 with the tripolar interlocking open function are arranged in this order. For this reason, it becomes possible to protect against a short-circuit failure that occurs between the cylindrical cut-out 14 and the cut-out 13 with the three-pole interlocking opening function, and it is possible to more effectively suppress the propagation to the distribution line 11 and to limit the failure area. Is achieved.

  (4) Further, by combining the cylindrical cutout 14 and the cutout 13 with the three-pole interlocking opening function, short circuit protection and phase loss prevention can be achieved at low cost. That is, as compared with the case where the circuit breaker equivalent to the circuit combining the cylindrical cutout 14 and the three-pole interlocking open function cutout 13 in the present embodiment is provided on the primary side (power supply side) of the reactor 12. The cost merit is great. For example, in the case of taking into account the pole material such as the cutout 13 with the three-pole interlocking opening function, the cylindrical cutout 14, and the arm (not shown), the conventional switch system (the switch is arranged on the power source side of the reactor) Less expensive).

  (5) When the discharge-type fuse 13a and the current-limiting fuse 14a are blown, the protection circuit can be easily maintained because the discharge-type fuse 13a and the current-limiting fuse 14a are simply replaced. Further, the three-pole interlocking open cutout 13 and the cylindrical cutout 14 are easy to mount.

  (6) Cutout 13 with a three-pole interlocking open function is composed of box-shaped cutouts 13u, 13v, 13w for each phase, and each of the box-shaped cutouts 13u, 13v, 13w is equipped with a discharge fuse 13a. I tried to do it. Further, the current limiting fuse 14 a is attached to the cylindrical cutout 14. For this reason, the replacement work of the discharge type fuse 13a and the current limiting fuse 14a becomes very simple.

<Another embodiment>
In addition, you may implement each said embodiment as follows.
In the present embodiment, on the primary side of the reactor 12, the cutout 13 with the three-pole interlocking opening function is arranged on the load side (reactor 12 side) and the cylindrical cutout 14 is arranged on the power supply side. The following may also be used. That is, the three-pole interlocking open function cutout 13 is arranged on the power supply side, and the cylindrical cutout 14 (current limiting fuse 14a) is arranged on the reactor 12 side. Even in this way, the reactor 12 can be protected.

-In this embodiment, although the case where the reactor 12 was branched and connected to the distribution line 11 was demonstrated, you may apply as a protection circuit of electric equipments, such as a capacitor | condenser and a transformer.
A cylindrical cutout may be replaced with a box cutout.

  As shown in FIG. 1, ZnO (zinc oxide) support insulators 61 u, 61 v, 61 w (that is, lightning arresters) may be provided between the cutout 13 with the three-pole interlocking opening function and the reactor 12. Each ZnO support insulator 61u, 61v, 61w is fixed to a case (not shown) of the reactor 12, for example. In this way, the pillars can be simplified and lightning damage measures can be achieved at a low cost.

<Other technical ideas>
Next, a technical idea that can be grasped from the above embodiment and another embodiment will be added below.
(B) The electric system protection circuit according to claim 1, wherein the electrical device is one of a reactor, a capacitor, and a transformer.

  (B) The power system protection circuit according to claim 1, 2, or (a), wherein the primary cutout and the primary cutout with a three-pole interlocking opening function are arranged in this order from the power source side.

The schematic block diagram of the protection circuit in this embodiment. FIG. 5 is an operation characteristic diagram of the discharge fuse and the current limiting fuse in the present embodiment. The front sectional view of the cylindrical cutout in this embodiment. The schematic block diagram of the cutout with a three-pole interlocking open function in this embodiment. (A), (b) is a schematic block diagram of the conventional protection circuit, respectively.

Explanation of symbols

11 ... Distribution lines constituting the power system, 12 ... Reactors constituting the electrical equipment,
13 ... Cutout with tripolar interlocking open function, 13a ... Emission fuse,
14 ... Cylindrical cut-out constituting the primary cut-out,
14a ... Current limiting fuse.

Claims (2)

On the power supply side of the electrical equipment branched and connected to each phase of the power system,
A primary cutout with a three-pole interlocking opening function, in which a discharge fuse is detachably mounted,
A power system protection circuit in which a series circuit with a primary cutout different from the above, in which a current limiting fuse having a breaking function is detachably mounted, is arranged. 2. The power system protection circuit according to claim 1, wherein the rated current of the discharge-type fuse is made smaller than the rated current of the current-limiting fuse.

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