JP5999989B2 - Overcurrent relay - Google Patents

Description

  The present invention relates to an overcurrent relay, and more specifically, an overcurrent having a configuration that secures an exciting current of a circuit breaker by commutating a secondary current of a current transformer by opening an internal contact when a circuit breaker trips. The present invention relates to a configuration for confirming the soundness of a relay.

  The current trip type overcurrent relay installed in the power distribution facility of a high voltage consumer can constitute an economical system because it does not require a power source for exciting the circuit breaker.

  In the current trip type overcurrent relay, when the secondary current of a current transformer (CT) provided in the distribution line becomes excessive, the b contact inside the relay through which the secondary current passes is Opened. When the b contact is opened, the secondary current is commutated to the exciting coil of the circuit breaker, so that the circuit breaker trips and the power path of the distribution line is interrupted.

  When a short circuit accident occurs in the distribution line, the secondary current of the current transformer also increases. Therefore, when the circuit breaker is tripped, a relatively large current needs to be interrupted by the b contact inside the relay, so that the b contact may be damaged. For this reason, when the relay operates (trips) due to the occurrence of an overcurrent, it is recommended to perform a test for confirming the soundness of the overcurrent relay.

  Japanese Laid-Open Patent Publication No. 59-123417 (Patent Document 1) describes a configuration in which a test terminal is provided in a current trip type overcurrent relay. Specifically, the overcurrent relay with a test terminal of Patent Document 1 is configured to perform an operation confirmation test by connecting a predetermined power source to the test terminal. As a result, the operation confirmation test can be executed easily and in a short time in the normal use state (overcurrent monitoring state) with the main current transformer connected.

JP 59-123417 A

  The overcurrent relay of Patent Document 1 generates a power supply for a control circuit by inputting an alternating current to a test terminal. Further, the trip output contact (b contact) can be opened by inputting a current at a level at which overcurrent detection is activated.

  The contact point b after cutting off a relatively large current increases the contact resistance (ideally almost zero) at the time of closing (on) due to contact wear and damage even if the switching operation is possible. Or contact resistance (ideally ∞) at the time of opening (off) may be reduced.

  Therefore, in order to sufficiently check the soundness, it is preferable to measure the contact resistance as well as whether or not the b contact can be opened and closed. However, the overcurrent relay of Patent Document 1 does not have a function of measuring contact resistance in a soundness confirmation test.

  Further, in a configuration in which a terminal block for contact resistance measurement is provided on the back surface of the b-contact and the user measures the resistance value with a resistance measuring device (tester), there is a concern that the convenience for the user is lowered. In particular, in order to confirm that the b contact is not welded, it is necessary to measure the contact resistance with the b contact excited. In this case, since a measurement by a tester is required after inputting a current for securing a power source for exciting the b contact, it takes time to perform a soundness confirmation test.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to contact the soundness of an internal contact (b contact) that operates when a circuit breaker is tripped by a simple test input. To provide an overcurrent relay configuration that can be verified based on resistance.

  In the overcurrent relay according to the present invention, when an overcurrent occurs in the distribution line, the overcurrent relay for generating a trip command for the circuit breaker inserted and connected to the distribution line includes the first and second A terminal, a third and a fourth terminal, a b-contact, a control circuit, a control power supply circuit, a test terminal, a test circuit, a detection unit, a measurement unit, and a display unit; The 1st and 2nd terminal is provided in order to electrically connect with the current transformer installed in the distribution line. The third and fourth terminals are provided for electrical connection with the exciting coil of the circuit breaker. The b contact is arranged such that one end is electrically connected to the first and third terminals and the other end is electrically connected to the second and fourth terminals. The control circuit controls the opening and closing of the b contact. The control power supply circuit generates an operation power supply for the control circuit from the currents input to the first and second terminals. The test terminal is provided for connecting a power supply external to the overcurrent relay in the test mode. In the test mode, the test circuit is configured to form a test current path including the test resistance element via the test terminal between the external power supply and the b contact. In the test mode, the detection means detects the voltage across the b-contact in the test current path. The measuring means measures the contact resistance of the b-contact based on the voltage detected by the detecting means in the test mode. The display unit displays information based on the measurement result of the contact resistance in the test mode.

It is a schematic circuit diagram for demonstrating operation | movement of a current trip type overcurrent relay. It is a circuit diagram for demonstrating the structure of the overcurrent relay shown as a comparative example. It is a circuit diagram for demonstrating the structure of the overcurrent relay by Embodiment 1 of this invention. FIG. 6 is a first circuit diagram for explaining a circuit state in a test mode of the overcurrent relay according to the first embodiment. FIG. 6 is a second circuit diagram for illustrating a circuit state in the test mode of the overcurrent relay according to the first embodiment. It is a conceptual diagram which shows the example of a setting of the direct current impedance of a trip coil. 3 is a flowchart illustrating a procedure of control processing in a test mode of the overcurrent relay according to the first embodiment. 6 is a flowchart illustrating a procedure of control processing in a test mode of an overcurrent relay according to a modification of the first embodiment. It is a figure explaining the example of a display of the measurement result of the contact resistance in the test mode of the overcurrent relay by the modification of Embodiment 1. FIG. FIG. 6 is a conceptual diagram showing a DC coil setting method for a trip coil in an overcurrent relay test mode according to a second embodiment. FIG. 10 is a conceptual diagram for explaining storage contents of a memory in an overcurrent relay according to a third embodiment. FIG. 6 is a circuit diagram for illustrating a configuration of an overcurrent relay according to a fourth embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 is a schematic circuit diagram for explaining the operation of a current trip type overcurrent relay.

  FIG. 1A shows a circuit state when the overcurrent relay is not operating, and FIG. 1B shows a circuit state when the overcurrent relay is operating (during a trip).

  With reference to Fig.1 (a), the overcurrent relay 100 is comprised so that the overcurrent of the distribution line 10 in which the circuit breaker 50 was provided may be detected. Input terminals 101 and 102 of the overcurrent relay 100 are connected to a main current transformer 30 provided in the distribution line 10. The secondary current I2 of the main current transformer 30 is input to the input terminals 101 and 102. The overcurrent relay 100 further has terminals 103 and 104 connected to the trip coil 60 for exciting the circuit breaker 50.

  The overcurrent relay 100 has an input converter 110 and a b contact 120 as an output contact. The b-contact 120 is closed in the non-excited state while being opened in the excited state. The input converter 110 outputs a voltage corresponding to the secondary current I2. That is, the secondary current I2, that is, the current Is of the distribution line 10 can be detected based on the output of the input converter 110.

  During normal times when no short circuit current has occurred due to an accident, the secondary current I2 is small, so the b-contact 120 is maintained in a non-excited state. At this time, the secondary current I2 of the main current transformer 30 passes through the input converter 110 and the b-contact 120 in a non-excited state (ie, a closed state). Therefore, no current flows through the path including the trip coil 60 via the terminals 103 and 104. For this reason, since the overcurrent relay 100 maintains the non-operation state in which the circuit breaker 50 is de-energized, the circuit breaker 50 is not tripped and remains closed.

  Referring to FIG. 1B, when a short circuit accident or the like occurs in the distribution line 10 and the current Is becomes excessive, a control circuit (not shown) excites the b contact 120 according to the increase in the secondary current I2. . As a result, the b-contact 120 is opened, so that the secondary current I2 is commutated to a path through the trip coil 60 via the terminals 103 and 104. As a result, the overcurrent relay 100 is activated and excites the circuit breaker 50, so that the circuit breaker 50 trips.

  As described above, when the overcurrent relay 100 of the current trip type is operated, the exciting current flowing through the trip coil 60 can be generated by the secondary current I2 of the main current transformer 30. For this reason, the power supply for an exciting current is unnecessary. Further, when the overcurrent relay 100 is in operation (when the circuit breaker 50 is tripped), the b-contact 120 blocks the secondary current I2 corresponding to the short-circuit current, so that damage such as welding may occur at the contact. is there.

  A schematic configuration of a general overcurrent relay 100 # will be described as a comparative example with reference to FIG. In addition, below, the structure of the overcurrent relay corresponding to one distribution line is demonstrated. In the three-phase AC system, since three distribution lines are provided for each line, the same overcurrent detection and circuit breaker operation control are performed for each of the distribution lines for at least two phases of the three phases. This configuration is required.

  The overcurrent relay 100 # shown in FIG. 2 is obtained by removing the configuration for the soundness confirmation test after the circuit breaker trip from the overcurrent relay according to the first embodiment of the present invention. That is, overcurrent relay 100 # corresponds to a functional part for overcurrent detection and circuit breaker operation control.

  Referring to FIG. 2, overcurrent relay 100 # includes input terminals 101 and 102, terminals 103 and 104, input converter 110, b contact 120, b contact excitation unit 125, and analog filter circuit 130. An arithmetic processing unit 150, a switch 160, a display unit 170, a transistor 180, a control power supply circuit 190, wirings 191 and 192, and a power supply line 195.

  The input terminals 101 and 102 are provided to connect to the main current transformer 30 provided in the distribution line 10 as shown in FIGS. Similarly, the terminals 103 and 104 are provided for connection to the trip coil 60 shown in FIGS. 1 (a) and 1 (b).

  An input converter 110 is provided in the wiring 191 electrically connected to the input terminal 101. Further, the wiring 191 is electrically connected to the b contact 120 and the terminal 103. The wiring 192 electrically connected to the input terminal 102 is electrically connected to the b contact 120 and the terminal 104. One end of the b contact 120 is electrically connected to the input terminal 101 and the terminal 103, and the other end is electrically connected to the input terminal 102 and the terminal 104. The b contact 120 is connected in parallel to the trip coil 60 with respect to the wirings 191 and 192.

  The input converter 110 is constituted by a transformer or the like, and generates an AC voltage corresponding to the secondary current I2. A high frequency component is removed from the output of the input converter 110 by the analog filter circuit 130 and is input to the arithmetic processing unit 150.

  The control power supply circuit 190 converts the output voltage of the input converter 110 into an operation power supply voltage of a circuit group inside the overcurrent relay, and outputs it to the power supply line 195. The operation power supply of the arithmetic processing unit 150 and the excitation current of the b contact 120 are supplied from the power supply line 195. The control power supply circuit 190 can be configured to include a general switching regulator.

  The arithmetic processing unit 150 generates an excitation command So for the b-contact 120 according to the secondary current I2. When the excitation command So is generated, the b contact 120 is opened (turned off) by supplying a current to the excitation unit 125 by the conduction of the transistor 180. On the other hand, when the excitation command So is not generated, the transistor 180 is turned off and no current is supplied to the excitation unit 125, so the b contact 120 is closed (turned on).

  The arithmetic processing unit 150 includes a multiplexer 152, an analog / digital conversion unit (A / D conversion unit) 154, a CPU (Central Processing Unit) 155, and a memory 156. The memory 156 includes a RAM (Random Access Memory) and / or a ROM (Read Only Memory).

  The multiplexer 152 selects one signal from the plurality of input signals and outputs the selected signal to the A / D conversion unit 154. The A / D converter 154 samples the output signal from the multiplexer 152 and outputs a digital signal. Based on the digital signal output from the A / D converter 154, the magnitude (amplitude, effective value, etc.) of the secondary current I2 can be detected.

  The CPU 155 executes arithmetic processing according to programs and data stored in advance in the memory 156. With this calculation process, an overcurrent is detected when the magnitude of the secondary current I2 exceeds a predetermined threshold, and an excitation command So is generated when the overcurrent is detected. On the other hand, the excitation command So is not generated when no overcurrent is detected (normal time).

  When the excitation command So is generated, the trip coil 60 is energized in response to the opening of the b contact 120 (see FIG. 1B), so that the circuit breaker 50 trips and interrupts the electric circuit of the distribution line 10. On the other hand, when the excitation command So is not generated, the trip coil 60 is not energized in accordance with the closing of the b contact 120 (see FIG. 1A), so the circuit breaker 50 does not trip. In this way, overcurrent detection and circuit breaker operation control are executed.

  As described above, overcurrent detection and circuit breaker operation control are required for each distribution line, but as shown by the dotted line in the figure, the secondary currents of other distribution lines are input to the same multiplexer 152. The hardware constituting the arithmetic processing unit 150 can be shared among a plurality of distribution lines. In this case, the function for the overcurrent detection in each of a some distribution line and the excitation command generation | occurrence | production of b contact can be performed by the arithmetic processing part 150 arrange | positioned at any one phase overcurrent relay.

  The switch 160 is provided for inputting an operation instruction from the user. A signal indicating an operation instruction input to the switch 160 is sent to the CPU 155. Then, the arithmetic processing unit 150 executes arithmetic processing according to the user instruction.

  The display unit 170 displays display data instructed from the CPU 155. For example, the display unit 170 is configured by a segment LED (Light Emitting Diode) display.

  FIG. 3 shows the configuration of overcurrent relay 100A according to the first embodiment of the present invention. In the overcurrent relay 100A, in addition to the configuration of the overcurrent relay 100 # shown in FIG. 2, a configuration for a test for confirming soundness after the circuit breaker trip operation is added.

  Referring to FIG. 3, overcurrent relay 100 </ b> A further includes a test circuit 200 and test terminals 201 and 202, compared to overcurrent relay 100 # shown in FIG. 2. The test terminals 201 and 202 are provided for connecting the external power source 290 of the overcurrent relay 100A in the test mode. The external power source 290 is a DC power source, and can be constituted by, for example, a dry battery pack.

  In the configuration of FIG. 3, the input terminals 101 and 102 correspond to “first and second terminals”, and the terminals 103 and 104 correspond to “third and fourth terminals”. The trip coil 60 corresponds to a “breaker exciting coil”.

  Test circuit 200 includes a test resistance element 210, wirings 220 and 230, a Zener diode 240, and a power supply unit 250. The resistance value R1 of the test resistance element 210 is known and stored in the memory 156 in advance.

  The wiring 220 is provided to electrically connect between the test terminal 201 and one end of the b contact 120. The wiring 230 is provided to electrically connect the other end of the b contact 120 and the wiring 220 and is grounded. The wiring 230 is further electrically connected to the wiring 192. Test resistance element 210 is connected between nodes N 1 and N 2 on wiring 220.

  Node N 2 is electrically connected to the input node of multiplexer 152. Therefore, the voltage of the node N2 can be taken in by the A / D converter 154 via the multiplexer 152. That is, the arithmetic processing unit 150 can detect the voltage V2 at the node N2. Since the wiring 192 is grounded, the voltage across the b-contact 120 can be detected by the voltage V2. Alternatively, the voltage across the b contact 120 may be directly detected. The “detecting means” is realized by the configuration for detecting the voltage V2.

  The power supply unit 250 is configured to supply power from the external power supply 290 connected to the test terminals 201 and 202 to the power supply line 195. For example, the power supply unit 250 can be configured by a combination of wiring and a diode. As a result, even in the test mode, it is possible to secure an operation power supply for the arithmetic processing unit 150 and an excitation power supply for the b contact 120.

  Zener diode 240 is connected between node N1 and wiring 230 (GND). Thereby, the voltage V1 of the node N1 is made constant by the Zener diode 240. Note that another circuit element (for example, a three-terminal regulator) may be provided instead of the Zener diode 240 as long as the node N1 can be a constant voltage. That is, during the test, the voltage V1 is maintained at a constant level. Since the voltage V1 corresponds to the breakdown voltage of the Zener diode or the output voltage of the regulator, it can be treated as a known constant. Therefore, the voltage V1 can be stored in the memory 156 in advance.

  Alternatively, for the sake of high accuracy, it is possible to detect the voltage V1 in the test mode similarly to the voltage V2 of the node N2 by electrically connecting the node N1 and the multiplexer 152.

  Further, the switch 160 is configured to be able to input a user instruction related to the test mode. For example, the switch 160 is configured to be able to input a test mode start instruction and an excitation instruction (open instruction) for the b contact 120 during the test mode.

  The configuration of the other parts of the overcurrent relay 100A is the same as that of the overcurrent relay 100 # shown in FIG. That is, also in the overcurrent relay 100A, overcurrent detection and circuit breaker operation control other than in the test mode are performed in the same manner as described with reference to FIGS.

  When the overcurrent relay 100A operates, the circuit breaker 50 (FIG. 1) is tripped and the electric circuit of the distribution line 10 is interrupted. As part of the confirmation work before the circuit breaker 50 is turned on again and power transmission is resumed, a test mode for confirming the soundness of the overcurrent relay 100A is executed. That is, no current flows through the distribution line 10 and the external power source (dry battery pack) 290 is connected to the test terminals 201 and 202 from the state where the secondary current I2 = 0. The test mode for measuring is ready to start.

  4 and 5 show circuit states in the test mode of the overcurrent relay 100A.

  Referring to FIG. 4, since secondary current I <b> 2 does not flow after tripping breaker 50, b contact 120 is de-energized. As a result, the b contact 120 is closed. In this state, when the external power supply 290 is connected, the circuit state of FIG. 4 is obtained.

  Referring to FIG. 4, a path of test current It1 is formed between external power supply 290 and b contact 120 via test terminals 201 and 202 and test resistance element 210. In the normal b-contact 120, the contact resistance value Rb in the closed state is almost zero. Therefore, even if the trip coil 60 is connected to the terminals 103 and 104, the test current It1 passes only through the b-contact 120 as shown in FIG.

  However, strictly speaking, when the trip coil 60 is connected to the terminals 103 and 104, the contact resistance value Rb of the b contact 120 and the DC impedance (impedance value Rt) indicating the DC resistance component of the trip coil 60 are connected in parallel. The test current It1 passes through the circuit (DC resistance value R2). Since the wiring 230 is grounded, the voltage V2 is equal to the voltage drop due to the DC resistance value R2. In general, Rt = about 30Ω. The DC impedance value Rt varies depending on the type of the circuit breaker, the length of the cable to be connected, and the like, and is a value unique to the trip coil 60.

  For example, as shown in FIG. 6, a DC impedance value Rt set or measured in advance can be stored in the nonvolatile memory 157 of the memory 156. In this way, the DC impedance value Rt can be read from the nonvolatile memory 157 when the overcurrent relay 100A is started or when the test mode is started.

  A relationship of It1 = V1 / (R1 + R2) is established between the DC resistance value R2 and the test current It1. Since the voltage V2 corresponding to the voltage drop due to the DC resistance value R2 is represented by It1 × R2, by solving for V1 / (R1 + R2) × R2 = V2, the following equation (1) is obtained as a calculation formula of the DC resistance value R2. can get.

R2 = V2 / (V1-V2) × R1 (1)
In the equation (1), the DC resistance value R2 can be calculated as the measurement result of the contact resistance of the b contact based on the voltage V1, the resistance value R1, and the detected value of the voltage V2.

  In the normal b-contact 120, since the contact resistance value Rb in the closed state is substantially zero, the DC resistance value R2 is also substantially zero (Rb = R2). On the other hand, when the contact resistance value Rb increases due to contact damage or the like, the DC resistance value R2 increases toward the DC impedance value Rt.

  Therefore, the soundness of the contact in the closed state of the b contact 120 can be confirmed based on the contact resistance from the DC resistance value R2. In particular, the allowable upper limit value of the DC resistance value R2 can be obtained according to the DC impedance (Rt) connected in parallel and the upper limit value (closed state) of the allowable contact resistance.

  Further, the DC resistance value R2 in which the contact resistance (Rb) and the DC impedance (Rt) are connected in parallel is represented by R2 = Rb × Rt / (Rb + Rt). By solving this for Rb, the following equation (2) is obtained.

Rb = R2 × Rt / (Rt−R2) (2)
Therefore, by using both equations (1) and (2), the contact resistance value Rb itself of the b-contact 120 is calculated from the detected value of the voltage V2 according to the known V1, R1, and Rt read from the memory 156. It is also possible.

  If the test mode is performed with the trip coil 60 disconnected from the terminals 103 and 104, the DC resistance value R2 calculated by the equation (1) indicates the contact resistance value Rb itself.

  FIG. 5 shows a circuit state in the test mode when the b contact 120 is opened.

  Referring to FIG. 5, when the arithmetic processing unit 150 generates an excitation command So in response to a user operation of the switch 160, the b contact 120 is opened. As described with reference to FIG. 4, in practice, a circuit (DC resistance value R2) in which the contact resistance (resistance value Rb) of the b contact 120 and the DC impedance (Rt) of the trip coil 60 are connected in parallel is represented by the test current It2. pass. Since the wiring 230 is grounded, the voltage V2 is equal to the voltage drop due to the DC resistance value R2.

  In the normal b-contact 120, the contact resistance value Rb = ∞ in the closed state. Therefore, since the test current It2 passes through the trip coil 60 connected to the terminals 103 and 104 as shown in FIG. 5, R2 = Rt. On the other hand, when the contact resistance of the b contact 120 is increased due to damage such as welding, R2 is lower than Rt.

  Therefore, the soundness of the contact in the open state of the b contact 120 can be known from the calculated DC resistance value R2. Furthermore, the allowable upper limit value of the DC resistance value R2 can be obtained according to the DC impedance (Rt) connected in parallel and the lower limit value (open state) of the allowable contact resistance.

  Further, as described above, the contact resistance value Rb of the b-contact 120 is calculated from the detected value of the voltage V2 according to the known V1, R1, and Rt read from the memory 156 by further using the expression (2). Is also possible.

  When the test mode is performed with the trip coil 60 disconnected from the terminals 103 and 104, the DC resistance value R2 calculated by the equation (1) is the contact resistance value Rb of the b contact 120 itself. Show.

  Here, in the circuit state of FIG. 5, the test current It2 flows through the trip coil 60 when the b contact 120 is normal. In the test mode, it is necessary to prevent the circuit breaker 50 from tripping due to the test current It2 at this time in order to perform a confirmation test of the overcurrent relay alone. That is, It2 = V1 / (R1 + Rt) needs to be a level at which the circuit breaker 50 cannot be excited. Therefore, it is necessary to appropriately design the resistance value R1 of the test resistance element 210 in consideration of the voltage V1 and the DC impedance value Rt. For example, assuming that V1 = 4.5V and Rt = 30Ω, if R1 is set to several tens of Ω, the test current It1 is normally set to a current of 0.5 A or less at which a general circuit breaker does not operate. be able to.

  On the other hand, since the contact resistance of the b-contact 120 is measured based on the voltage V2 obtained by dividing the voltage V1 by the resistance values R1 and R2, if the resistance value R1 is too large, V2 is lowered and measurement accuracy is increased. It will be difficult to ensure. The resistance value R1 of the test resistance element 210 needs to be designed in consideration of these points.

  4 and 5, when the main current transformer 30 is connected to the input terminals 101 and 102, the main current transformer 30 is connected to the b contact 120 in parallel. However, since the input impedance of the main current transformer 30 viewed from the overcurrent relay 100A side is very large, the test currents It1 and It2 flowing into the main current transformer 30 can be ignored. That is, the influence of the resistance value based on the voltage V2 generated by the test currents It1 and It2 on the measurement accuracy can be ignored.

  FIG. 7 is a flowchart illustrating the procedure of the control process in the test mode of overcurrent relay 100A according to the first embodiment. Each step of the flowchart shown in FIG. 7 is mainly executed by software processing by the arithmetic processing unit 150.

  Referring to FIG. 7, operation processing unit 150 receives an input of a test mode start instruction from the user in step S100. This instruction is accepted on condition that the external power source 290 is connected to the test terminals 201 and 202.

  In step S110, the arithmetic processing unit 150 converts the voltage V2 into a digital signal by the multiplexer 152 and the A / D conversion unit 154. Thereby, the voltage V2 is detected. The “detecting means” is realized by the processing in step S110.

  Further, in step S120, the arithmetic processing unit 150 measures the contact resistance of the b-contact 120 based on the detected voltage V2. Specifically, the DC resistance value R2 including the contact resistance is calculated based on the voltage V2 according to the equation (1) using the known voltage V1 and the resistance value R1. Alternatively, it is possible to further calculate the contact resistance value Rb of the b-contact 120 according to the equation (2) further using the DC impedance value Rt of the trip coil 60. The “measuring means” is realized by the processing in step S110.

  In step S130, the arithmetic processing unit 150 issues an instruction for displaying the calculated electric resistance value (R2 or Rb) to the display unit 170 as the measurement result of the contact resistance of the b-contact 120 in step S120. Thereby, the electrical resistance value (R2 or Rb) is visually recognized by the user by the display unit 170 as information based on the measurement result of the contact resistance.

  If the excitation instruction (opening instruction) for the b contact 120 is further input by the switch 160, the arithmetic processing unit 150 issues the excitation command for the b contact 120 to measure the contact resistance in the circuit state of FIG. Can do. On the other hand, when the excitation instruction is not input, the b-contact 120 is closed, so the contact resistance in the circuit state of FIG. 4 is measured. That is, by a series of processes according to the flowchart of FIG. 6, an electrical resistance value indicating a contact resistance measurement result can be displayed to the user separately for each of the b contact 120 being excited and not excited.

  As described above, according to the overcurrent relay according to the first embodiment, the b contact 120 can be connected in a test mode in which the external power source 290 is connected with a simple circuit configuration in which the test terminals 201 and 202 and the test circuit 200 are added. Contact resistance can be measured. As a result, the soundness of the internal contact (b contact) that operates when the circuit breaker is tripped can be confirmed based on the contact resistance of the b contact by the test mode after the occurrence of the circuit breaker trip.

  In particular, even when the main current transformer 30 and the trip coil 60 are connected, the test mode of the overcurrent relay 100A can be executed. Furthermore, the contact resistance value Rb of the b-contact 120 can be directly calculated by obtaining the DC impedance value Rt of the trip coil 60 in advance.

  In addition, since the test mode can be executed using a DC power source to which a dry battery pack can be applied, a confirmation test can be performed more easily as compared with a configuration that requires an AC current input (for example, Patent Document 1). .

[Modification of Embodiment 1]
In the first embodiment, the example in which the electrical resistance value (R2 or Rb) itself is displayed on the display unit 170 as the measurement result of the contact resistance of the b contact has been described. However, in this example, there is a concern that the user may further need to refer to a written value such as an instruction manual as to whether or not the contact resistance value of the b contact is a normal value. In particular, in a product such as a relay that has a long replacement cycle, there is a concern that the user's convenience may be reduced due to the reference work. Therefore, in the modification of the first embodiment, the abnormality / normal determination result is output to the display unit 170 as the measurement result of the contact resistance of the b contact.

  FIG. 8 is a flowchart illustrating a control processing procedure in the overcurrent relay according to the modification of the first embodiment.

  Referring to FIG. 8, operation processing unit 150 receives a test mode start instruction from the user in step S100 similar to FIG. At this time, the switch 160 can further input an excitation instruction (open instruction) for the b contact 120.

  The arithmetic processing unit 150 performs the detection of the voltage V2 and the measurement of the contact resistance of the b-contact 120 based on the voltage V2 through steps S110 and S120 similar to FIG. As a result, as in FIG. 6, the DC resistance value R2 or the contact resistance value Rb including the contact resistance is calculated as the measurement result of the contact resistance of the b-contact 120.

  When the excitation instruction for the b contact 120 is input, the b contact 120 is opened, so that the contact resistance is measured in the circuit state of FIG. On the other hand, when the excitation instruction for the b contact 120 is not input, the b contact 120 is closed, so that the contact resistance is measured in the circuit state of FIG. Therefore, the normal range of the contact resistance differs between when the b contact 120 is excited and when it is not excited.

  In step S150, the arithmetic processing unit 150 determines whether or not the b contact 120 is being excited.

  When the b contact 120 is excited (YES in S150), the arithmetic processing unit 150 determines whether or not the measured contact resistance value is within the normal range at the time of excitation in step S160. With respect to the contact resistance value Rb in which the state of Rb = ∞ is ideal at the time of excitation, the normal range can be set in advance so as to correspond to a range where there is no practical problem. Furthermore, when the direct current impedance (Rt) of the trip coil 60 is further taken into consideration, the normal range at the time of non-excitation corresponding to the normal range of the contact resistance value Rb can also be set in advance for the direct current resistance value R2. Or, more simply, for the voltage V2, it is possible to set in advance a normal range at the time of non-excitation corresponding to the normal range of the contact resistance value Rb by back calculation from the above formulas (1) and (2). It is.

  In step S160, it is determined whether or not the measured value or the calculated value is within the normal range at the time of non-excitation for any one of the contact resistance value Rb, the DC resistance value R2, and the voltage V2.

  When the b-contact 120 is not excited (when NO is determined in S150), the arithmetic processing unit 150 determines whether or not the measured contact resistance value is within the normal range during the non-excited state in step S170. . With respect to the contact resistance value Rb in which the state of Rb = 0 is ideal at the time of non-excitation, the normal range can be set in advance in correspondence with a range in which there is no practical problem. Furthermore, considering the DC impedance (Rt) of the trip coil 60, the normal range at the time of non-excitation corresponding to the normal range of the contact resistance (Rb) can also be set in advance for the DC resistance value R2. Or, more simply, a normal range at the time of non-excitation corresponding to the normal range of the contact resistance (Rb) may be set in advance for the voltage V2 by back calculation from the above formulas (1) and (2). Is possible.

  In step S170, it is determined whether or not the measured value or the calculated value is within the normal range at the time of non-excitation for any one of the contact resistance value Rb, the DC resistance value R2, and the voltage V2.

  In step S180, the arithmetic processing unit 150 confirms the determination result in step S160 or S170. When the measurement result indicating that the contact resistance is within the normal range is obtained (when YES is determined in S180), the arithmetic processing unit 150 proceeds with the process to step S190, and states that “the contact resistance is normal. Is output to the display unit 170 as information based on the measurement result of the contact resistance.

  On the other hand, if the measurement result indicating that the contact resistance is within the normal range is not obtained (NO determination in S180), the arithmetic processing unit 150 proceeds with the process to step S195, “Abnormal” is output to the display unit 170 as information based on the measurement result of the contact resistance.

FIG. 9 shows a display example on the display unit 170 in steps S190 and S195.
FIG. 9A shows a display example when the contact resistance is within the normal range (step S190), while FIG. 9B shows a case where the contact resistance is not within the normal range (step S195). A display example of is shown.

  As described above, according to the overcurrent relay according to the modification of the first embodiment, the same test mode as in the first embodiment is executed, and the contact resistance of the b contact is normal / The result of which of the abnormalities can be clearly notified to the user separately for each of the b-contact excitation time and non-excitation time.

[Embodiment 2]
In the second embodiment, another example of the storage method of the DC impedance value Rt of the trip coil 60 in the first embodiment or the modification example 1 will be described.

  FIG. 10 is a conceptual diagram showing a DC coil setting method for a trip coil in the overcurrent relay test mode according to the second embodiment.

  Referring to FIG. 10, in the overcurrent relay according to the second embodiment, at least a part of nonvolatile memory 157 is configured by a memory area (for example, flash ROM or the like) 157 # in which stored contents can be updated. Further, a memory area for DC impedance value Rt is provided in memory area 157 #.

  With such a configuration, the stored value of the DC impedance value Rt can be updated based on the measured value obtained by the test after the installation of the overcurrent relay. For example, when the test mode in which an excitation instruction is input to the b contact 120 is executed when the soundness of the b contact 120 can be confirmed with the trip coil 60 connected to the terminals 103 and 104, the measured DC resistance The value R2 can be used as the DC impedance value Rt. That is, DC impedance value Rt obtained by normal measurement can be stored in memory area 157 # in advance.

  In the subsequent test mode after occurrence of the circuit breaker trip, the DC impedance value Rt stored in advance in the memory area 157 # can be read out and used for the calculation related to the equation (2).

  Therefore, in the overcurrent relay according to the second embodiment, the DC impedance value required for calculating the contact resistance value Rb of the b-contact 120 or setting the normal range of the measurement result in the first embodiment or the modification 1 thereof. Rt can be set with higher accuracy. As a result, contact resistance measurement and normal / abnormal determination can be performed with high accuracy.

[Embodiment 3]
In the overcurrent relay according to the first embodiment and the modification thereof and the second embodiment, each time the test mode is executed, the b contact is excited (open state) and non-excited (closed state). The contact resistance of the contact 120 can be measured.

  In the overcurrent relay according to the third embodiment, the transition of the measurement result of the contact resistance of the b-contact 120 in these test modes is accumulated.

  FIG. 11 is a conceptual diagram for explaining the storage contents of the memory in the overcurrent relay according to the third embodiment.

  Referring to FIG. 11, in the overcurrent relay according to the third embodiment, DC resistance value R2 including the contact resistance or the contact resistance calculated as a result of the contact resistance measurement in the test mode execution using memory region 157 # The resistance value Rb is stored sequentially. For example, for the latest N test modes (N: a predetermined natural number), the electrical resistance value (R2 or Rb) indicating the measurement result of the contact resistance is stored in the memory area 157 #.

  Based on these stored data, the deterioration management of the b-contact 120 can be performed based on the change amount or change rate of the electrical resistance value. For example, when the latest test mode is executed, even if the contact resistance of the b-contact 120 is within the normal range, information such as “part replacement time is approaching” based on the change amount or change rate of the electrical resistance value. Can be notified to the user.

  As described above, according to the overcurrent relay according to the third embodiment, the internal contact (b) that operates when the circuit breaker is tripped in the same test mode as the overcurrent relay according to the first embodiment and the modified example thereof and the second embodiment. In addition to being able to confirm the soundness of the contact), it is further possible to manage the progress of contact deterioration based on the contact resistance.

[Embodiment 4]
FIG. 12 is a circuit diagram showing a configuration of an overcurrent relay 100B according to the fourth embodiment.

Referring to FIG. 12, the overcurrent relay 100B according to the fourth embodiment is wired with the power supply voltage output by the control power supply circuit 190 in the test mode, compared to the overcurrent relay 100A according to the first embodiment (FIG. 3). The difference is that a power supply unit 235 for supplying power to 220 is further provided. For example, the power supply unit 235 can be configured by a combination of wiring and switch elements that are turned on in the test mode. Since the structure of the other part of overcurrent relay 100B is the same as that of overcurrent relay 100A (FIG. 3), detailed description will not be repeated.

  As described with reference to FIG. 3, the control power supply circuit 190 has a function of converting the alternating current input to the input terminals 101 and 102 into an operating power supply inside the overcurrent relay. Therefore, in the overcurrent relay 100B according to the fourth embodiment, the test currents It1 (FIG. 4) and It2 (FIG. 5) flowing through the test circuit 200 can be secured by inputting an alternating current to the input terminals 101 and 102.

  In other words, in the overcurrent relay 100B according to the fourth embodiment, even when the external power source 290 is not connected to the test terminals 201 and 202, the test mode is executed by inputting an alternating current to the input terminals 101 and 102. Is possible.

  Since the Zener diode 240 is provided, the voltage of the node N1 in the test mode is supplied when power is supplied from any of the input terminals 101 and 102 (alternating current) and the test terminals 201 and 202 (dry battery pack). It is possible to keep V1 at the same value. In addition, calculation processing and measurement result management in the test mode may be the same as those in the first embodiment and its modification examples and the second and third embodiments, and thus detailed description thereof will not be repeated.

  As described above, according to the overcurrent relay according to the fourth embodiment, the application range of the external power supply for executing the test mode can be expanded, so that convenience for the user is improved.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 distribution lines, 30 main current transformers, 50 circuit breakers, 60 trip coils, 100, 100A, 100B, 100 # overcurrent relays, 101, 102 input terminals, 103, 104 terminals, 110 input converters, 120 contacts, 125 Excitation unit, 130 analog filter circuit, 150 arithmetic processing unit, 152 multiplexer, 154 conversion unit, 154 digital conversion unit, 156 memory, 157 nonvolatile memory, 157 # memory area, 160 switch, 170 display unit, 180 transistor, 190 control Power supply circuit, 191,192,220,230 wiring, 195 power supply line, 200 test circuit, 201,202 test terminal, 210 resistor element, 240 Zener diode, 250 power supply unit, 290 external power supply, I2 secondary current, Is current , It1, It2 test current, N1, N2 node, R1, Rb resistance value, R2 DC resistance value, Rb contact resistance value (b contact), Rt DC impedance value (trip coil), So excitation command, V1, V2 voltage.

Claims (8)

An overcurrent relay for generating a trip command for a circuit breaker inserted and connected to the distribution line when an overcurrent occurs in the distribution line,
First and second terminals for electrical connection with a current transformer installed in the distribution line;
Third and fourth terminals for electrical connection with the exciting coil of the circuit breaker;
A b-contact arranged so that one end is electrically connected to the first and third terminals and the other end is electrically connected to the second and fourth terminals;
A control circuit for controlling opening and closing of the b-contact;
A control power supply circuit for generating an operating power supply for the control circuit from currents input to the first and second terminals;
A test terminal for connecting an external power supply of the overcurrent relay in a test mode;
In the test mode, a test circuit configured to form a test current path including a test resistance element between the external power source and the b contact via the test terminal;
In the test mode, detection means for detecting a voltage across the b-contact in the test current path;
In the test mode, the voltage detected by the detection means, the voltage drop amount in the trial Ken抵 anti elements, and for measuring the contact resistance of the contact b on the basis of the known resistance value of the trial Ken抵 anti element Measuring means,
An overcurrent relay comprising: a display unit for displaying information based on the measurement result of the contact resistance in the test mode. Means for determining whether or not the contact resistance measured when the b-contact is in a closed state is within a first normal range;
The display unit displays the first display content when the contact resistance measured when the b contact is in the closed state is within the first normal range, while the b contact is in the closed state. 2. The overcurrent relay according to claim 1, wherein the second display content is displayed when the contact resistance measured in step 1 is not within the first normal range.   The overcurrent relay according to claim 1, further comprising means for supplying operating power of the control circuit by power from the external power source connected to the test terminal in the test mode. Means for determining whether or not the contact resistance measured when the b-contact is in a closed state is within a first normal range;
Means for determining whether or not the contact resistance measured when the b-contact is in an open state is in a second normal range;
The display unit is configured such that when the first contact resistance measured when the b contact is in the closed state is within a first normal range, or when the b contact is in the open state, the second measured. When the first contact resistance is not in the first normal range, the first display content is displayed when the first contact resistance is in the second normal range, or the second display range is displayed. The overcurrent relay according to claim 3, wherein when the contact resistance is not within the second normal range, the second display content is displayed. A first storage means for storing in advance the DC impedance value of the exciting coil;
The measurement means includes means for calculating a contact resistance value of the b-contact based on the DC impedance value and a voltage detected by the detection means when the b-contact is in an open state. 3. The overcurrent relay according to 3. The external power source is connected to the test terminal after the trip of the circuit breaker,
The overcurrent relay is
Before the trip of the circuit breaker, further comprising first storage means for storing a DC impedance value of the exciting coil in a state where the b contact is opened,
The measurement means includes means for calculating a contact resistance value of the b-contact based on the DC impedance value and a voltage detected by the detection means when the b-contact is in an open state. 3. The overcurrent relay according to 3. The measurement means includes means for measuring a contact resistance when the b contact is in an open state and a contact resistance when the b contact is in a closed state every time the test mode is executed,
The overcurrent relay is
The apparatus further comprises second storage means for storing a history of contact resistance when the b contact is in an open state and contact resistance when the b contact is in a closed state, measured in the past test mode. Item 7. The overcurrent relay according to any one of Items 3 to 6.   The overcurrent relay according to any one of claims 1 to 7, further comprising means for guiding an output voltage of the control power supply circuit to the test current path in the test mode.

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