JP2010042784A - Direct current high-voltage grounding relay and circuit for preventing malfunction of relay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct current high-voltage grounding relay without having an adverse influence on travel of a train, preventing the occurrence of malfunction due to a disturbance such as a lightening strike, and to provide a circuit for preventing the malfunction of the relay. <P>SOLUTION: This invention relates to the direct current high-voltage grounding relay 1 with a potential difference detecting section 10 operated by the potential difference between a ground mat 7 and a return line 4, arranged between the ground mat 7 and the return line 4 of a direct current substation 2 for an electric railroad. It is provided with an electric discharge circuit 15 discharging electric charge charged between the ground mat and the return line with stray capacitance C due to application of an impulse voltage so that the potential difference becomes below the operating voltage within the operating time of the potential difference detecting section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC high-voltage ground relay and a relay malfunction prevention circuit, and more particularly, a DC high-voltage ground having high reliability that does not malfunction even when a high impulse voltage is generated due to a disturbance such as lightning. The present invention relates to a relay and a malfunction prevention circuit for the relay.

  Conventionally, in a DC substation for electric railways, when a serious failure such as a ground fault occurs in a DC bus, a fault such as burning of the substation equipment occurs due to a large ground fault current flowing. Therefore, the voltage between the grounding mat and the return line (rail) of the DC substation for electric railway is detected, and when this voltage exceeds a predetermined level, the substation is powered off as quickly as possible. In order to prevent damage to substation facilities and protect substations, DC high-voltage ground relays are installed.

  FIG. 4 is a diagram showing a configuration of the DC substation 90 for electric railway. This substation 90 supplies electric power between a return line 94 and a DC bus 95 via a circuit breaker 91, a transformer 92 and a rectifier 93. Further, 95a is a DC high speed circuit breaker, 96 is a power filter, 97 is a grounding mat buried under the substation 90, and 98 is a grounding resistance of the grounding mat 97. The DC high-voltage grounding relay 99 is provided between the grounding mat 97 and the return line (rail R), and operates when the grounding mat 97 is at a positive potential with respect to the return line 94 to cut off the circuit breaker 91. It is what The DC high-voltage grounding relay 99 can detect a failure within a predetermined operating time of, for example, about 40 ms when the potential of the grounding mat 97 with respect to the return line 94 is, for example, about 500 V or more.

  As described above, it is a common practice to provide a protective device for quickly detecting a failure at a substation and interrupting the failure current when a ground fault occurs. Patent Document 1 describes a ground fault protection system that does not cause an unnecessary operation (malfunction) even when a ground fault occurs in a nearby substation in a distribution substation.

JP 2005-192305 A

  However, in the conventional DC substation 90 for electric railways, for example, when a high impulse voltage due to a disturbance such as lightning is applied to the grounding mat 97 or the rail R has a high negative impulse with respect to the grounding mat 97. When a voltage is applied, the DC high-voltage ground relay 99 may erroneously detect the occurrence of a ground fault due to this disturbance, which causes the circuit breaker 91 of the substation 90 to be erroneously cut off, resulting in a long time connection to the train. There was a problem that the power supply stopped.

  FIG. 3 is a diagram illustrating an example in which the potential of the grounding mat 97 with respect to the retrace line 94 is measured when the impulse voltage of, for example, 20 kV is applied to the grounding mat 97 due to disturbance such as lightning in the substation 90 having the above configuration. As shown by the phantom line Lp in FIG. 3, the high voltage of the impulse applied to the ground mat 97 is attenuated, but when the electric charge charged in the floating capacitance between the return line 94 and the ground mat 97 is discharged. Since the constant is large, the attenuation is slow. From the measurement results, it can be seen that the voltage of, for example, 500 V or more is maintained as the operating voltage of the DC high-voltage ground relay 99 for 17.1 ms after application of the impulse voltage.

  In general, the higher the applied voltage, the shorter the operation time of the relay, and although there are individual differences, the operation time is about 15 to 25 ms. Therefore, the high-voltage grounding relay 99 enters the operating range. That is, the potential difference between the return line 94 and the grounding mat 97 exceeds the operating voltage during the operating time of the DC high voltage grounding relay 99, a malfunction due to this disturbance occurs, and the DC high voltage grounding relay 99 malfunctions. In this case, in order to change the state of the substation 90 to a state of total power failure, there arises a problem that much time is required for restoration and a great obstacle is caused to the operation of the train.

  The present applicant has stated that the reason for the slow decay is that the product of the floating capacitance due to the ground capacitance and the like existing in the main circuits 91 to 98 of the substation 90 and the impedance of the discharge circuit is large. We have determined that there is a possibility that the constant is large and that the operating voltage and operating time that cause the relay to malfunction are maintained.

  The present invention has been made in consideration of the above-mentioned matters, and the purpose of the present invention is to provide a DC high-voltage grounded relay and a relay that do not malfunction due to disturbance such as lightning strikes and do not adversely affect train operation. It is to provide a malfunction prevention circuit.

  In order to solve the above-mentioned problem, the first invention is a DC high-voltage grounding having a potential difference detection unit which is provided between a grounding mat and a return line of a DC substation for electric railways and operates by a potential difference between the grounding mat and the return line. A relay that is charged between an earthing mat having a floating capacitance and a return line by applying an impulse voltage so that the potential difference becomes less than the operating voltage within the operating time of the potential difference detecting unit. Provided is a DC high-voltage ground relay comprising a discharge circuit for discharging. (Claim 1)

  According to the DC high-voltage grounded relay having the above-described configuration, the electric charge charged between the grounding mat having the floating capacitance and the retrace line by applying the impulse voltage is operated within the operating time of the potential difference detecting unit. Since it has a discharge circuit that discharges to less than the voltage, it is charged between the grounding mat that has stray capacitance due to ground capacitance due to disturbance such as lightning strike to the substation or near the substation and the return line The discharged electric charge can be quickly discharged to a voltage of a certain level or less by the discharge circuit. On the other hand, since the discharge circuit is of a level that discharges the charge charged by applying the impulse voltage, the impedance of the discharge circuit is sufficiently higher than the impedance from the DC bus to the ground mat when a ground fault occurs. That is, the DC high-voltage grounding relay can reliably detect the occurrence of a ground fault, prevent the DC high-voltage grounding relay from malfunctioning due to disturbance, and prevent a train operation failure.

  The impulse voltage is caused by disturbance such as lightning, and for example, a high voltage impulse of about 20 kV is assumed. The discharge circuit may be a surge absorber having a threshold voltage higher than the operating voltage of the potential difference detection unit and lower than the impulse voltage, but is preferably a resistor having a resistance value in accordance with the floating capacitance, More preferably, the resistance value can be changed by a single element, such as a variable resistance or a semi-fixed resistance. The discharge circuit is preferably connected between the ground mat and the return wire. Note that the discharge circuit may be connected in parallel to the potential difference detection unit.

  A capacitance measuring unit that measures the floating capacitance between the grounding mat and the return line, and a discharge resistor configured to be able to adjust a resistance value according to the capacitance measured by the capacitance measuring unit; (Claim 2), the capacitance measuring unit measures the floating capacitance between the grounding mat and the return line, so that the ground capacitance existing in the main circuit of the substation is dominant. The magnitude of the stray capacitance that has a negative effect is measured, and the resistance value of the discharge resistance is adjusted according to the magnitude. Therefore, the optimum discharge resistance value can be set at any substation, and The electric charge charged in the electric capacity can be quickly discharged. Moreover, even when the substation equipment is changed, it is possible to respond flexibly and quickly to the change.

  The capacitance measuring unit preferably measures the capacitance by measuring the advance of the current phase when an AC voltage is applied, for example, and the capacitance is measured every day, every week. It may be performed intermittently after a long time such as every month. Alternatively, the power supply state to the substation is monitored, and a start detection unit that can detect the start time to start power supply from the state where power supply is stopped is provided, and when the start detection unit detects the start time, the substation By determining that the configuration may have changed and performing capacitance measurement, the best effect can be obtained with the minimum necessary operation. The discharge resistance is preferably a variable resistance, a semi-fixed resistance, or a resistance value that can be adjusted by selectively switching a plurality of resistance elements.

  The second invention is provided between a grounding mat and a return line of a DC substation for electric railway, and is attached to a DC high-voltage grounding relay having a potential difference detection unit that operates by a potential difference between the grounding mat and the return line, and an impulse voltage A discharge circuit that discharges the electric charge charged between the grounding mat having a floating capacitance and the retrace line by applying a voltage so that the potential difference becomes less than the operating voltage within the operating time of the potential difference detecting unit. A malfunction prevention circuit for a relay is provided. (Claim 3)

  By attaching the relay malfunction prevention circuit to an existing DC high-voltage grounded relay, this DC high-voltage grounded relay can be used for lightning even when there is a large floating capacitance between the grounding mat to which it is connected and the return line. It is possible to prevent malfunction due to disturbance.

As described above, according to the present invention, a charge charged between a grounding mat having a floating capacitance due to a ground capacitance or the like due to a disturbance and a return line can be quickly converted into a voltage of a certain level by a discharge circuit. Since it can be discharged to the following, the potential difference detection unit does not malfunction due to the influence of disturbance. Accordingly, when a disturbance such as lightning occurs, the substation circuit breaker is not unnecessarily disconnected, and the reliability is increased accordingly.
When adjusting the resistance value of the discharge circuit by measuring the stray capacitance between the grounding mat and the return line, the magnitude of the resistance value of the discharge circuit is automatically adjusted as needed even when the substation configuration changes. can do.

Next, an embodiment showing a specific configuration of the DC high-voltage grounding relay of the present invention will be described in detail with reference to the drawings.
1 to 2 are diagrams for explaining the configuration of a DC high-voltage grounded relay 1 according to an embodiment of the present invention, and FIG. FIG. 2 shows a circuit configuration of the DC high-voltage ground relay 1 according to the first embodiment.

  As shown in FIG. 1, a DC substation 2 for electric railway (hereinafter simply referred to as a substation 2) includes a circuit breaker 3a configured to cut off power supply to the substation 2 as a power supply unit 3, and for example, 22 kV A transformer 3b that lowers the transmission voltage to 1.2 kV and a rectifier 3c that performs AC / DC conversion are provided, and a DC voltage is supplied between the return line 4 and the DC bus 5. Reference numeral 6 denotes a power filter that cuts an AC component so that no alternating current flows through the bus 5, 7 is a grounding mat embedded in the basement of the substation 2, and 8 is a grounding resistance of the grounding mat 7.

  The return line 4 is evenly connected to the rail R through the impedance bond Ra, and a rail leakage resistance Rb exists between each rail R and the ground E. The bus 5 is connected to the trolley line via a DC high-speed circuit breaker (not shown) to supply electric power to the electric railway vehicle.

  The power filter 6 includes, for example, a capacitor 6a and a coil 6b. The capacitor 6a is covered with a capacitor case 6c grounded through the ground mat 7. The ground mat 7 is a mesh made of a conductor embedded under the substation 2 so that the ground resistance 8 with respect to the ground E is 1Ω or less.

  C1 represents a capacitance between the capacitor 6a and the capacitor case 6c constituting the power filter 6 of the substation 2 (capacitance to the ground because the capacitor case 6c is grounded), and C2 represents a return line 4 Represents the electrostatic capacitance of The ground capacitances C1 and C2 existing on the capacitor 6a and the return line 4 occupy a dominant part of the floating capacitance C between the ground mat 7 and the return line 4, but other parts (for example, coils) 6b, rail R, bus 5) including the return line 4 and the grounding mat 7, the sum of the ground capacitances C1, C2,... Of the main circuits 4 to 7 of the substation 2 is returned to the grounding mat 7. It affects the stray capacitance C between the lines 4.

  As shown in FIG. 2, the DC high-voltage ground relay 1 outputs a potential difference detection unit 10 and a cutoff signal Bk for shutting off the circuit breaker 3a when a predetermined potential difference is detected by the potential difference detection unit 10. And an output unit 11. The potential difference detection unit 10 includes a voltage dividing circuit 10a that divides a voltage applied between the return line 4 and the grounding mat 7, and a rectifier connected in parallel to the potential difference detection unit 10 with the grounding mat 7 from the return line 4 in the forward direction. 10b.

  The DC high-voltage grounding relay 1 of the present invention includes a capacitance measuring unit 14 that measures a floating capacitance C between the return line 4 and the grounding mat 7, and a discharge circuit 15 that is connected in parallel to the capacitance measuring unit 14. And a discharge resistance adjusting unit 16 for adjusting the resistance value of the discharge circuit 15. The capacitance measuring unit 14, the discharge circuit 15, and the discharge resistance adjusting unit 16 are the malfunction prevention circuit 1 a of the DC high-voltage ground relay 1.

  The discharge resistance adjusting unit 16 adjusts the resistance value of the discharge circuit 15 in accordance with the measured value D of the floating capacitance C measured by the capacitance measuring unit 14, and more specifically, such as lightning strikes. The electric charge charged between the grounding mat 7 and the return line 4 when an impulse high voltage (for example, 20 kV) is applied due to disturbance, and the potential difference from the return line 4 to the grounding mat 7 is the potential difference of the potential difference detection unit 10. The resistance value of the discharge circuit 15 is adjusted (Set) so that it can be discharged so as to be less than the operating voltage within the operating time.

  The voltage dividing circuit 10a in the present embodiment is, for example, a resistance voltage dividing circuit, and the potential difference detection unit 10 and the determination output unit 11 are, for example, a coil and a contact of one electromagnetic relay. The capacitance measuring unit 14 applies, for example, an alternating voltage between the return line 4 and the ground mat 7, and measures the advance of the phase of the alternating current flowing with respect to the applied voltage at this time. The capacitance between the ground mats 7 is measured. Further, the discharge circuit 15 is a variable resistor, and the discharge resistance adjuster 16 includes an actuator (not shown) that mechanically adjusts the size of the variable resistor 15 (Set). That is, in this embodiment, the manufacturing cost of the DC high-voltage grounded relay 1 can be reduced by simplifying the configuration of each part of the DC high-voltage grounded relay 1.

  The potential difference detection unit 10 can omit the voltage dividing circuit 10a if it can withstand a high voltage of impulse (impulse voltage) applied to the ground E due to a disturbance such as a lightning strike. In this case, the potential difference detection unit 10 is directly connected between the return line 4 and the grounding mat 7. The potential difference detection unit 10 of the present embodiment operates when the grounding mat 7 has a positive potential with respect to the return line 4, and basically the potential of the grounding mat 7 with respect to the return line 4 is, for example, about 500V. When the operating voltage is equal to or higher than the operating voltage, for example, the occurrence of a failure is detected within an operating time of about 40 ms, and the determination signal output unit 11 outputs the cutoff signal Bk. As a result, the breaker 3a is cut off, so that damage caused by the flow of a fault current can be minimized.

  On the other hand, when an impulse voltage caused by a disturbance such as a lightning strike is applied to the ground E, a high voltage of about 20 kV is applied to the potential difference detection unit 10 (including the voltage dividing circuit 10a in this embodiment). It may take. In general, the higher the applied voltage, the shorter the operating time of the relay. That is, when an impulse voltage is applied to the DC high-voltage ground relay 1, it operates faster than when the potential difference detection unit 10 detects a normal failure voltage, and the operation time may be 15 to 25 ms. .

  Since the discharge circuit 15 quickly discharges the charge charged between the return line 4 and the ground mat 7 to a certain level voltage or less in accordance with the application of the impulse voltage, the operable region of the potential difference detection unit 10 (The operation time and the operation voltage) can be removed.

  FIG. 3 shows a comparison of discharge characteristics (measured values) between the DC high-voltage grounded relay 1 of the present invention and the conventional DC high-voltage grounded relay 99. As shown by a solid line L in FIG. 3, the DC high voltage ground relay 1 of the present invention is charged between the ground mat 7 and the return line 4 by applying the impulse voltage even when the impulse voltage of 20 kV is applied. The electric charge can be quickly discharged by the discharge circuit 15, and the potential difference between the return line 4 and the grounding mat 7 becomes less than the operating voltage of 500 V within the operating time 15 to 25 ms of the potential difference detecting circuit 11.

  More specifically, in the actual measurement value of FIG. 3, the time during which the operating voltage of the potential difference detecting unit 10 can be maintained at a voltage of 500 V or higher is 17.1 ms in the conventional case, whereas in the present embodiment, it is 7. The maintenance time is less than half of 5 ms. That is, in the DC high-voltage ground relay 1 according to the embodiment, even when an impulse voltage is applied to the ground E, the potential difference between the return line 4 and the ground mat 7 deviates from the operable region of the potential difference detection circuit 11. The high-voltage ground relay 1 does not operate.

  When a ground fault occurs, a large current flows through the ground E, so there is almost no influence of the discharge by the discharge circuit 15, and the presence of the discharge circuit 15 adversely affects the normal operation of the DC high-voltage ground relay 1. Never give.

  In the case of the present embodiment, the capacitance measuring unit 14 measures the magnitude of the floating capacitance C caused by the ground capacitance between the main circuit of the substation and the ground at each substation 2 and discharges it. Since the resistance adjustment unit 16 is configured to adjust the resistance value of the discharge circuit 15 that is optimal for discharge according to the measured floating capacitance C, the resistance value of the discharge circuit 15 is optimal. Adjusted to the value. That is, the DC high-voltage grounded relay 1 of the present embodiment adjusts the resistance value of the discharge circuit 15 according to the environment of the substation 2 that grounds it, so that it can be installed without being affected by the configuration of the substation 2. it can.

  The measurement of the floating capacitance C by the capacitance measuring unit 14 and the adjustment of the resistance value of the discharge circuit 15 by the discharge resistance adjusting unit 16 are performed unless the configuration of the main circuits 3 to 8 of the substation 2 is changed. There is no need. For this reason, the interval for adjusting the resistance value of the discharge circuit 15 may be intermittent such as daily, weekly, or monthly. Alternatively, an activation detection unit that can detect the activation time point at which power supply to the bus 5 is started is provided, and when the activation detection unit detects the activation time point, the electrostatic capacitance measurement unit 14 measures the floating capacitance C and adjusts the discharge resistance. The resistance value of the discharge circuit 15 may be adjusted by the unit 16.

  In addition, since the discharge circuit 15 of the present embodiment is a variable resistor, the resistance value can be adjusted steplessly. However, the discharge circuit 15 of the present invention connects a plurality of resistors having different sizes by switching. The resistance value may be adjusted step by step.

  In addition, the malfunction prevention circuit 1a including the capacitance measuring unit 14, the discharge circuit 15, the discharge resistance adjusting unit 16, and the like (including the start detection unit in some cases) is configured to be attachable to an existing DC high-voltage ground relay. It may be what was done. In this case, since there is no need to replace the existing DC high-voltage grounding relay, there is an advantage that installation is easy.

  Furthermore, taking into account that the configuration of the substation 2 is not frequently changed, the capacitance measuring unit 14 and the discharge resistance adjusting unit 16 are omitted, and a discharge circuit 15 having a fixed resistance value is provided. It may be formed. As a result, the configuration of the DC high-voltage ground relay 1 or the malfunction prevention circuit 1a can be greatly simplified, and the manufacturing cost can be reduced.

  The discharge circuit 15 is not limited to a resistor. For example, the voltage applied to the DC high-voltage ground relay 1 when a ground fault occurs and the operating voltage of the potential difference detector 10 are higher than the impulse voltage during a lightning strike. May be a surge absorber that operates at a sufficiently low threshold voltage, or a combination thereof.

It is a figure which shows the structure of the substation which attaches the DC high voltage grounding relay of this invention. It is a figure which shows the structure of the said DC high voltage grounding relay. It is a figure explaining operation | movement of a direct current | flow high voltage | pressure grounding relay. It is a figure which shows the structure of the conventional substation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC high voltage earthing relay 1a Relay malfunction prevention circuit 2 Electric railway DC substation 4 Return line 7 Grounding mat 10 Potential difference detection part 14 Capacitance measurement part 15 Discharge circuit 16 Discharge resistance adjustment part C Floating capacitance

Claims (3)

  A DC high-voltage grounding relay provided between a grounding mat and a return line of a DC substation for electric railways and having a potential difference detection unit that operates by a potential difference between the grounding mat and the return line. A direct current circuit comprising: a discharge circuit that discharges a charge charged between a grounding mat having a capacitance and a return line so that the potential difference becomes less than an operating voltage within an operating time of the potential difference detecting unit. High voltage grounding relay.   A capacitance measuring unit that measures the floating capacitance between the grounding mat and the return line, and a discharge resistor configured to be able to adjust a resistance value according to the capacitance measured by the capacitance measuring unit; The DC high-voltage grounding relay according to claim 1. It is installed between a grounding mat and a return line of a DC substation for electric railways, and is attached to a DC high-voltage grounding relay having a potential difference detection unit that operates according to the potential difference between the grounding mat and the return line. A relay comprising: a discharge circuit that discharges a charge charged between a grounding mat having a capacitance and a return line so that the potential difference becomes less than the operating voltage within an operating time of the potential difference detecting unit. Malfunction prevention circuit.

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