DC high voltage ground relay

Abstract

To provide an erroneous detection prevention type DC voltage ground relay having a high reliability so as to prevent train operations from being affected without malfunction due to ground faults on a secondary side line of high-voltage distribution transformers installed in DC substations for electric railways, and so on.SOLUTION: A DC high voltage ground relay includes: a potential difference measurement unit 5 that is provided between a ground mat 3 and a return line 4 of a DC substation 2 for an electric railway and measures the potential difference; a DC ground fault determination output unit 6 that determines a DC ground fault using the potential difference and outputs a DC ground fault signal Fd; and a malfunction prevention unit 13 that prevents the DC ground fault determination output unit 6 from outputting the determination of the DC ground fault signal Fd when the potential difference occurred between the ground mat 3 and the return line 4 is due to a ground fault in an AC electric circuit 2A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a DC high-voltage grounding relay. Specifically, it relates to a DC high-voltage grounding relay with high reliability that is installed in a DC substation for electric railways and does not malfunction when an AC high-voltage distribution line other than the DC bus of the electric railway experiences a ground fault.

Background Art

[0002] Conventionally, in a DC substation for electric railways, when a serious fault such as a ground fault occurs in the DC bus, a large ground fault current flows, resulting in faults such as burnout of substation equipment. Therefore, a DC high-voltage grounding relay is installed to detect the potential difference between the grounding mat and the return line (rail) of the DC substation for electric railways, and when this potential difference exceeds a predetermined magnitude, the substation is de-energized as quickly as possible to suppress damage to the substation equipment and protect the substation.

[0003] Figure 8 is a diagram showing the configuration of a DC substation for electric railways where a conventional DC high-voltage grounding relay 90 is installed. Figure 8 As shown in, in a DC substation for electric railways, a high-voltage distribution line 91A that branches from the bus of the extra-high-voltage distribution line and supplies power to each facility such as a signal, lighting, escalator, and ticket vending machine via a transformer Ta for high-voltage distribution lines, and a DC distribution line (DC bus) 91B that is DC-converted by a rectifier B via a transformer Tb for rectifiers and supplies power to the catenary wire.

[0004] Figure 9 is a diagram showing the configuration of a conventional DC high-voltage grounding relay represented by Patent Document 1. Figure 9 The DC high-voltage grounding relay 90 shown in is installed between the grounding mat 92 of the substation and the return line 93 (rail R), and has a potential difference measurement unit 94A that measures the potential difference between them. When the potential difference measurement unit 94A detects a potential difference equal to or greater than the threshold value, the ground fault determination output unit 94B determines a DC ground fault, and an AC circuit breaker 90A ( Figure 8It sends a trip signal (DC ground fault signal) to the AC breaker 90A (for reference) and the DC high-speed breaker 90B to cut off the power supply to the electric wire 95 and the DC bus 91B.

[0005] When a ground fault occurs in the DC bus 91B, due to the influence of the ground fault, the potential of the grounding mat 92 becomes higher with respect to the return line 93. Therefore, when this potential difference exceeds the threshold value, the ground fault determination output unit 94B can detect the fault within an extremely short operation time of, for example, about 40 ms. Thus, by tripping the AC breaker 90A and the DC high-speed breaker 90B as quickly as possible, damage to the equipment can be minimized.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when a ground fault occurs in the secondary side line (high-voltage power distribution line 91A) of the high-voltage power distribution transformer Ta of a conventional DC substation for electric railways, an AC high voltage is applied to the grounding mat 92, and the DC high-voltage ground relay 90 may erroneously detect an AC ground fault.

[0008] That is, generally, an AC ground fault in the secondary side line (high-voltage power distribution line 91A) of the high-voltage power distribution transformer Ta should be interrupted and protected by a ground fault protection relay for high-voltage power reception and distribution (not shown) and the AC breakers 96, 96A to 96C. However, when a ground fault occurs in the high-voltage power distribution line 91A of a DC substation for electric railways, the potential of the grounding mat 92 of the substation fluctuates due to the ground fault voltage, so a relatively large potential difference occurs between the grounding mat 92 and the return line 93 connected to the rail R at a location far from the grounding mat 92.

[0009] Figure 10This is a diagram showing the AC voltage waveform of a 50Hz 6600V system. Figure 10 To explain more specifically using this, when a ground fault occurs in the high-voltage power distribution line 91A, assuming that the full voltage is applied between the grounding mat and the return line (rail) depending on the grounding situation, for example, an AC half-wave voltage is applied to the potential difference measurement unit 94A of the DC high-voltage ground relay 90 with a set value of 500V.

[0010] Therefore, an AC voltage of the upper half-wave of the circuit is applied to the potential difference measurement unit 94A of the DC high-voltage ground relay 90 due to the potential difference (AC voltage), and a DC voltage equivalent of 500V or more, which is approximately the set threshold value, is continuously applied for about 9.7ms. For this reason, when the ground fault voltage is high, the DC high-voltage ground relay 90 malfunctions, and the AC circuit breaker 90A and the DC high-speed circuit breaker 90B of the substation are erroneously tripped, resulting in a problem that the power supply to the train stops.

[0011] In this way, when an AC ground fault occurs on the high-voltage power distribution line 91A side and the DC high-voltage ground relay 90 malfunctions, due to its function, the state of the substation becomes a total power outage state, so it takes a lot of time to restore, causing a great obstacle to the operation of the train.

[0012] The applicant of the present application has, through years of intensive research, pursued the cause of the malfunction of the conventional DC high-voltage ground relay 90 installed in the DC substation for electric railways due to a ground fault in the secondary side line of the high-voltage power distribution transformer Ta installed in the same substation, and has found that the above-mentioned phenomena are related to this malfunction.

[0013] Therefore, it can be easily considered that by deliberately slowing down the reaction speed of the ground fault determination output unit 94B, the occurrence of malfunction can be prevented. That is, when an AC ground fault occurs on the high-voltage distribution line 91A side, this AC ground fault is detected on the high-voltage distribution line 91A side and the transformer Ta for high-voltage distribution lines is cut off in about 100 ms, and the influence of the AC ground fault becomes small. Therefore, the reaction speed of the ground fault determination output unit 94B is deliberately slowed down, and only when a potential difference of 400 to 600 V or more, which is the setting value, can be confirmed after exceeding about 100 ms, the ground fault determination output unit 94B detects a ground fault in the DC distribution line 91B, sends a cutoff signal to the AC circuit breaker 90A and the DC high-speed circuit breaker 90B, and cuts off the power supply to the DC bus 91B to prevent malfunction.

[0014] However, in this case, although malfunction of the DC high-speed circuit breaker 90B can be avoided, even when a DC ground fault occurs in the DC distribution path 91B, after the influence of the ground fault current occurs, it will operate with a delay of at least 100 ms or more. Therefore, there is a problem that the possibility of damage such as facility damage becomes extremely high because a large fault current continues to flow for 100 ms or more.

[0015] The present invention has been made in consideration of the above matters, and its object is to prevent malfunction due to a ground fault in the secondary side line of a transformer for high-voltage distribution installed in a DC substation for electric railways, and when a ground fault occurs in the DC distribution path, it is possible to cut off the fault current as quickly as possible. An object of the present invention is to provide a malfunction detection prevention type DC high-voltage earthing relay having high reliability.

Means for Solving the Problems

[0016] The first invention provides a false detection prevention type DC high-voltage grounding relay, which is characterized in that it includes a potential difference measurement unit provided between a grounding mat and a return line of a DC substation for an electric railway to measure this potential difference, a DC ground fault determination output unit that determines a DC ground fault using the potential difference and outputs a DC ground fault signal, an auxiliary power supply unit that is charged using the rail potential generated between the grounding mat and the return line, a fast Fourier transform unit that performs a fast Fourier transform operation on the output of the potential difference measurement unit using the power charged in this auxiliary power supply unit, an AC ground fault determination unit that determines an AC ground fault when the commercial frequency component calculated by this fast Fourier transform unit exceeds a threshold value for determining a ground fault in an AC circuit, and a malfunction prevention unit that blocks the determination output of the DC ground fault by the DC ground fault determination output unit when the AC ground fault determination unit determines an AC ground fault. (Claim 1)

[0017] The grounding mat is grounded to the grounding potential of the substation through a grounding resistance. In contrast, the potential of the return line connected to a rail at a location distant from this grounding mat has some rail potential generated between the grounding mat and the return line because current flows through the train running above. The auxiliary power supply unit is charged using this rail potential and is constantly charged. Note that the auxiliary power supply unit may be a rechargeable secondary battery, but it is preferable to use a capacitor with a simpler configuration. More preferably, an electric double layer capacitor is used to increase the capacity.

[0018] The power charged in the auxiliary power supply unit is used for the fast Fourier transform operation of the potential difference measured by the potential difference measurement unit by the fast Fourier transform unit. This fast Fourier transform unit is considered to be an FFT circuit that combines electronic circuits to obtain at least the frequency components of the commercial power supply. However, for example, it may be an arithmetic processing unit and a fast Fourier transform program executable by this arithmetic processing unit. Also, the frequency components obtained by the fast Fourier transform are at least commercial frequency components (frequency components of the commercial power supply), which are 60 Hz in the Kansai region of Japan and 50 Hz in the Kanto region. The output of this fast Fourier transform unit can obtain an accuracy sufficient to reliably detect the ground fault of the AC power supply based on the calculation result for a time corresponding to one wavelength of the commercial frequency (16.7 ms in the case of Kansai and 20 ms in the case of Kanto).

[0019] Since the AC ground fault determination unit determines an AC ground fault when the commercial frequency components frequency-analyzed by the fast Fourier transform operation exceed the threshold for determining a ground fault in the AC circuit, it is possible to reliably determine an AC ground fault in a short time of about 16.7 to 20 ms from the occurrence time of the AC ground fault. Needless to say, since this ground fault determination unit is also realized by an AC ground fault determination program executable by the same arithmetic processing unit as the fast Fourier transform unit, the configuration can be simplified and the manufacturing cost can be reduced.

[0020] The malfunction prevention unit blocks the determination output of the DC ground fault by the DC ground fault determination output unit from the time when the AC ground fault determination unit determines an AC ground fault. For example, a switch unit that does not output a DC ground fault signal while the AC ground fault is being determined at the output unit of the DC ground fault determination output unit, or a switch unit that does not input a potential difference signal to the DC ground fault determination output unit while the AC ground fault is being determined, can be considered.

[0021] Therefore, when a ground fault occurs in the high-voltage power distribution line of a substation, by making full use of the fast Fourier transform, the AC ground fault determination unit can quickly and reliably determine the ground fault, and the malfunction prevention unit can prevent the malfunction of the DC ground fault determination output unit. Thus, the DC high-voltage ground relay will not malfunction due to the ground fault in the high-voltage power distribution line within the substation, and the reliability is improved accordingly.

[0022] A second invention provides a false detection prevention type DC high-voltage ground relay, comprising: a potential difference measurement unit provided between a grounding mat and a return line of a DC substation for an electric railway to measure this potential difference; a DC ground fault determination output unit that determines a DC ground fault using the potential difference and outputs a DC ground fault signal; a current measurement unit that measures the current flowing in the circuit between the grounding mat and the return line; an auxiliary power supply unit that is charged using the rail potential generated between the grounding mat and the return line; a fast Fourier transform unit that performs a fast Fourier transform operation on the output of the current measurement unit using the power charged in this auxiliary power supply unit; an AC ground fault determination unit that determines an AC ground fault when the commercial frequency component calculated by this fast Fourier transform unit exceeds a threshold value for determining the ground fault of the AC circuit; and a malfunction prevention unit that blocks the determination output of the DC ground fault by the DC ground fault determination output unit when the AC ground fault determination unit determines an AC ground fault. (Claim 2)

[0023] The current measurement unit measures the current flowing in the circuit between the grounding mat and the return line. For example, it is preferable to use a current transformer that is excited by the current flowing through the primary side by electromagnetic induction and has a current flowing through the secondary side, and converts the magnitude of the current on the secondary side to a measurable magnitude for measurement. That is, when there is a change in the current flowing through the primary side of the current transformer, due to the change in the magnetic flux density excited thereby, a current of a magnitude divided by the turns ratio flows through the secondary side. Therefore, when an AC ground fault occurs, a secondary current proportional to the magnitude of the AC ground fault flows, and this can be measured.

[0024] The grounding mat is grounded to the grounding potential of the substation through the grounding resistance. In contrast, the potential of the return line connected to the rails at a location far from this grounding mat has some rail potential generated between the grounding mat and the return line because current flows through the train running on it. The auxiliary power supply unit is constantly charged by utilizing this rail potential. Note that the auxiliary power supply unit may be a rechargeable secondary battery, but it is preferable to use a capacitor with a simpler configuration. More preferably, an electric double layer capacitor is used to increase the capacity.

[0025] The power charged in the auxiliary power supply unit is used for the high-speed Fourier transform operation of the current measured by the current measurement unit by the high-speed Fourier transform unit. This high-speed Fourier transform unit may be an FFT circuit that combines electronic circuits to obtain at least the frequency component of the commercial power supply. However, for example, it may be an arithmetic processing unit and a high-speed Fourier transform program executable by this arithmetic processing unit. Also, the frequency component obtained by the high-speed Fourier transform is at least the commercial frequency component (the frequency component of the commercial power supply), which is 60 Hz in the Kansai region of Japan and 50 Hz in the Kanto region. The output of this high-speed Fourier transform unit can obtain an accuracy sufficient to reliably detect the ground fault of the AC power supply based on the calculation result for one wavelength time of the commercial frequency (16.7 ms in the case of Kansai and 20 ms in the case of Kanto).

[0026] Since the AC ground fault determination unit determines the AC ground fault when the commercial frequency component frequency-analyzed by the high-speed Fourier transform operation exceeds the threshold for determining the ground fault of the AC circuit, it is possible to reliably determine the AC ground fault in a short time of about 16.7 to 20 ms from the occurrence time of the AC ground fault. Needless to say, since this ground fault determination unit is also realized by an AC ground fault determination program executable by the same arithmetic processing unit as the high-speed Fourier transform unit, the configuration can be simplified and the manufacturing cost can be reduced.

[0027] The malfunction prevention unit blocks the determination output of DC ground fault from the DC ground fault determination output unit from the time when the AC ground fault determination unit determines an AC ground fault. For example, there may be a switch unit that does not output a DC ground fault determination while an AC ground fault is being determined at the output unit of the DC ground fault determination output unit, or a switch unit that does not input a potential difference signal to the DC ground fault determination output unit while an AC ground fault is being determined.

[0028] Therefore, when a ground fault occurs in the high-voltage distribution line of a substation, by making full use of the fast Fourier transform, the AC ground fault determination unit can quickly and surely determine the ground fault, and the malfunction prevention unit can prevent the malfunction of the DC ground fault determination output unit. Thus, the DC high-voltage ground relay will not malfunction due to a ground fault in the high-voltage distribution line within the substation, and the reliability is improved accordingly.

[0029] The third invention provides a false detection prevention type DC high-voltage ground relay, comprising: a potential difference measurement unit provided between the grounding mat and the return line of a DC substation for an electric railway to measure this potential difference; a DC ground fault determination output unit that determines a DC ground fault using the potential difference and outputs a DC ground fault signal; a current measurement unit that measures the current flowing in the circuit between the grounding mat and the return line; an auxiliary power supply unit that is charged using the rail potential generated between the grounding mat and the return line; an effective value calculation unit that calculates the effective value from at least the output of the current measurement unit using the power charged in this auxiliary power supply unit; an AC ground fault determination unit that determines an AC ground fault when the effective value calculated by this effective value calculation unit exceeds a threshold value for determining a ground fault in the AC circuit; and a malfunction prevention unit that blocks the determination output of DC ground fault by the DC ground fault determination output unit when the AC ground fault determination unit determines an AC ground fault. (Claim 3)

[0030] The current measurement unit measures the current flowing in the circuit between the grounding mat and the return wire. For example, it preferably uses a current transformer that is excited by the current flowing on the primary side by electromagnetic induction and causes a current to flow on the secondary side, and converts the magnitude of the current on the secondary side to a measurable magnitude for measurement. That is, when there is a change in the current flowing through the primary side of the current transformer, due to the change in the magnetic flux density excited thereby, a current of a magnitude divided by the turns ratio flows on the secondary side. Therefore, when an AC ground fault occurs, a secondary current proportional to the magnitude of the AC ground fault flows, and this can be measured.

[0031] The grounding mat is grounded to the ground potential of the substation via a grounding resistance, whereas the potential of the return wire connected to a rail at a location distant from this grounding mat has some rail potential generated between the grounding mat and the return wire because current flows through the train running thereon. The auxiliary power supply unit is constantly charged by utilizing this rail potential. The auxiliary power supply unit may be a secondary battery capable of charge and discharge, but it is preferable to use a capacitor with a simpler configuration. More preferably, an electric double layer capacitor is used to increase the capacity.

[0032] The power charged in the auxiliary power supply unit is used for the effective value calculation unit to perform the calculation of the effective value using the current measured by the current measurement unit. Also, it goes without saying that the effective value calculation unit can improve the measurement accuracy by obtaining the average value of the obtained instantaneous effective values as the effective value. The effective value calculation unit may be, for example, an arithmetic processing device and an effective value calculation program executable by this arithmetic processing device. The effective value obtained by the effective value calculation unit is such that the magnitude of the AC ground fault current can be accurately determined in a short time of about half of 16.7 to 20 ms in one cycle from the occurrence time of the AC ground fault.

[0033] Since the AC ground fault determination unit determines an AC ground fault when the effective value exceeds the threshold for determining a ground fault in the AC power line, it can surely determine an AC ground fault within a short time of several milliseconds to several tens of milliseconds from the occurrence time of the AC ground fault. Note that this ground fault determination unit is also realized by an AC ground fault determination program that can be executed by the same arithmetic processing unit as the high-speed Fourier transform unit. Needless to say, this makes it possible to simplify the configuration and reduce the manufacturing cost.

[0034] The malfunction prevention unit blocks the determination output of the DC ground fault from the time when the AC ground fault determination unit determines an AC ground fault. For example, there may be considered a switch unit that does not output a DC ground fault determination while the AC ground fault is being determined at the output unit of the DC ground fault determination output unit, or a switch unit that does not input a potential difference signal to the DC ground fault determination output unit while the AC ground fault is being determined.

[0035] Therefore, when a ground fault occurs in the high-voltage distribution line of a substation, by making full use of the calculation of the effective value, the AC ground fault determination unit can quickly and surely determine the ground fault, and the malfunction prevention unit can prevent the malfunction of the DC ground fault determination output unit. Thus, the DC high-voltage earthing relay will not malfunction due to a ground fault in the high-voltage distribution line within the substation, and the reliability is improved accordingly. It follows that

[0036] No. 4 The invention provides a false detection prevention type DC high-voltage earthing relay, comprising: a potential difference measurement unit provided between the earthing mat and the return line of a DC substation for an electric railway to measure this potential difference; a DC ground fault determination output unit that determines a DC ground fault using the potential difference and outputs a DC ground fault signal; and an AC ground fault voltage suppression circuit that attenuates the potential difference caused by the AC ground fault so that it is not erroneously detected by the DC ground fault determination output unit when the potential difference generated between the earthing mat and the return line is due to a ground fault in the AC power line, and is interposed between the earthing mat, the return line and the DC ground fault determination output unit, and a malfunction prevention unit that blocks the determination output of the DC ground fault. ( Claim 4 )

[0037] Preferably, the AC ground fault voltage suppression circuit is an attenuation circuit that attenuates the potential difference generated between the ground mat and the return wire to such an extent that it is not misdetected by the DC ground fault determination output unit when it is a ground fault of the AC power line, and it is preferably a passive filter such as a low-pass filter or a notch filter that can attenuate 6600V of 50 to 60Hz of the commercial power supply frequency to at least 2000V or less, preferably 400V or less. However, an active filter may also be used.

[0038] The malfunction prevention unit can prevent the determination output of DC ground fault by causing the AC ground fault voltage suppression circuit to be interposed between the ground mat, the return wire, and the DC ground fault determination output unit, and inputting the potential difference between the ground mat and the return wire generated by the ground fault of the AC power line to the DC ground fault determination output unit in a state where it is sufficiently attenuated.

[0039] Therefore, even when a ground fault occurs in the high-voltage distribution line of the substation, the malfunction of the DC ground fault discrimination output unit can be prevented by inputting the ground fault AC voltage attenuated by the AC ground fault voltage suppression circuit of the malfunction prevention unit to the DC ground fault determination output unit. Thus, the DC high-voltage ground relay does not malfunction due to the ground fault of the high-voltage distribution line in the substation, and the reliability is improved accordingly. It follows that

Advantages of the Invention

[0040] As described above, according to the false detection prevention type DC high-voltage ground relay of the present invention, the influence of a ground fault in the secondary side line of the high-voltage distribution transformer can be quickly determined, and the malfunction prevention unit can prevent the output of the DC ground fault determination of the DC ground fault determination output unit. Therefore, the malfunction of the DC high-voltage ground relay can be prevented, and the obstacle to the operation of the train can be prevented.

[0041] According to the misdetection prevention type DC high-voltage grounding relay of the first invention, the high-speed Fourier transform unit performs frequency analysis on the potential difference generated between the grounding mat and the return line by high-speed Fourier transform, and the AC ground fault determination unit can accurately and quickly determine the ground fault due to AC ground fault using the magnitude of the frequency component of the commercial power supply. The malfunction prevention unit can block the determination output of DC ground fault when a ground fault due to AC ground fault occurs.

[0042] According to the misdetection prevention type DC high-voltage grounding relay of the second invention, the high-speed Fourier transform unit performs frequency analysis on the current flowing between the grounding mat and the return line by high-speed Fourier transform, and the AC ground fault determination unit can accurately and quickly determine the ground fault due to AC ground fault using the magnitude of the frequency component of the commercial power supply. The malfunction prevention unit can block the determination output of DC ground fault when a ground fault due to AC ground fault occurs.

[0043] According to the misdetection prevention type DC high-voltage grounding relay of the third invention, the effective value calculation unit calculates the effective value using the current flowing between the grounding mat and the return line, and can accurately and quickly determine the ground fault due to AC ground fault using the magnitude of this effective value. The malfunction prevention unit can block the determination output of DC ground fault when a ground fault due to AC ground fault occurs It follows that

[0044] The 4 According to the misdetection prevention type DC high-voltage grounding relay of the invention, the potential difference due to AC ground fault can be attenuated by the AC ground voltage suppression circuit of the malfunction prevention unit, so that it cannot be misdetected by the DC ground fault determination output unit. Therefore, the determination output of DC ground fault can be blocked when a ground fault due to AC ground fault occurs It follows that

Brief Description of Drawings

[0045]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying out the Invention

[0046] FIG. 1 is a diagram showing the configuration of a DC electric railway substation where the false detection prevention type DC high-voltage grounding relay of the present invention is installed, and FIG. 2 is a diagram showing the configuration of such a false detection prevention type DC high-voltage grounding relay according to the first embodiment. Hereinafter, with reference to FIGS. 1 to 2, the specific embodiments of the false detection prevention type DC high-voltage grounding relay according to the first embodiment of the present invention will be described in detail with reference to the drawings.

[0047] As shown in Fig. 1, the false detection prevention type DC high-voltage grounding relay 1 is provided between the grounding mat 3 of the substation 2 and the return line 4, and has a potential difference measurement unit 5 that measures the potential difference between the grounding mat 3 and the return line 4, and a DC ground fault determination output unit 6 that determines a ground fault using the measured potential difference. Also, the circuit in the substation 2 is divided into a high-voltage power line 2A that supplies AC power to the loads R of various facilities such as signal lights, lighting, escalators, and ticket vending machines via the high-voltage distribution transformer 7A, and a DC distribution line (DC bus bar) 2B that supplies the power DC-converted by the rectifier 8 to the feeding wire 9 via the rectifier transformer 7B. Ba is a circuit breaker that shuts off the power supply to the high-voltage distribution transformer 7A, Bb is a circuit breaker that shuts off the power supply to the rectifier transformer 7B, and 8A is a DC high-speed circuit breaker for quickly shutting off the power supply to the feeding wire 9.

[0048] As shown in Fig. 2, the false detection prevention type DC high-voltage grounding relay 1 of the present invention, in addition to the potential difference measurement unit 5 and the DC ground fault determination output unit 6, has an auxiliary power supply unit 10 that is charged using the rail potential generated between the grounding mat 3 and the return line 4, a fast Fourier transform unit 11 that performs a fast Fourier transform operation on the output of the potential difference measurement unit 5 using the power charged in this auxiliary power supply unit 10, an AC ground fault determination unit 12 that determines an AC ground fault when the commercial frequency component calculated by this fast Fourier transform unit 11 exceeds the threshold value for determining a ground fault in the AC circuit, and a malfunction prevention unit 13 that blocks the DC ground fault signal Fd of the DC ground fault by the DC ground fault determination output unit 6 when the AC ground fault determination unit 12 determines an AC ground fault.

[0049] Since the grounding mat 3 is buried underground in the substation 2, it can be considered that it is connected to the true ground point G via a resistance value 3R. On the other hand, the return line 4, which is a rail arranged far from the substation 3, can be considered to be connected to the true ground point G via a rail leakage resistance 4R. Here, assuming that a ground fault occurs at the fault location F in the high-voltage power line 2A, this fault location F is considered to be connected to the nearest grounding mat 3 and the resistance 2R.

[0050] The potential difference measurement unit 5 includes a voltage dividing resistor 5A that divides the voltage applied between the return wire 4 and the grounding mat 3, and a rectifier 5B connected in parallel to the potential difference measurement unit 5 in the forward direction from the return wire 4 to the grounding mat 3, and measures the positive-polarity potential difference of the grounding mat 3 with reference to the return wire 4.

[0051] The DC ground fault determination output unit 6 includes a DC ground fault determination unit 6A that determines that the potential difference measured by the potential difference measurement unit 5 has reached a setting value that is the reference for DC ground faults and that there is a DC ground fault, and a ground fault determination output unit 6B that outputs the determination result determined by this DC ground fault determination unit 6A as a DC ground fault signal Fd. The malfunction prevention unit 13 is formed at the output unit of the DC ground fault signal Fd by the ground fault determination output unit 6B. Note that 6C is a ground fault display unit formed using an LED or the like so that the DC ground fault signal Fb can be visually confirmed.

[0052] The auxiliary power supply unit 10 includes, for example, an electric double layer capacitor and a charge and discharge control circuit for this electric double layer capacitor, and is preferably always charged and has a long lifespan. That is, during train operation, a rail voltage of approximately 200 to 300 V is generated between the grounding mat 3 and the return wire 4, and it is possible to charge the electric double layer capacitor using this rail voltage. Thereby, the high-speed Fourier transform unit 11 can perform the arithmetic processing of high-speed Fourier transform using the power charged in the auxiliary power supply unit 10. Also, in this embodiment, power is supplied to the AC ground fault determination unit 12, the malfunction prevention unit 13, and the DC ground fault determination output unit 6 using the power charged in the auxiliary power supply unit 10. Thereby, it becomes possible to correctly determine a ground fault even when the power supply from the outside is interrupted.

[0053] The fast Fourier transform unit 11 performs a fast Fourier transform on the output of the potential difference measurement unit 5 and supplies the output to the AC ground fault determination unit 12. This arithmetic processing of the fast Fourier transform is performed at least in the frequency component of the commercial power supply (i.e., the commercial frequency component), which is a frequency component of 60 Hz in the Kansai region of Japan and 50 Hz in the Kanto region. The commercial frequency component obtained by performing this fast Fourier transform on the time corresponding to one cycle of the commercial power supply (i.e., 16.7 ms or 20 ms) serves as a guideline for determining that the AC voltage due to the ground fault of the high-voltage power line 2A is surely included in the potential difference between the grounding mat 3 and the return wire 4, which contains various noise components. Note that the fast Fourier transform unit 11 may be formed by making full use of hardware such as a programmable logic device (FPGA), but by realizing it with a fast Fourier transform program executable by an arithmetic processing device such as a microcomputer, the manufacturing cost can be reduced.

[0054] Similarly, each of the above units 6, 12, and 13 may also be realized by using a program (not shown, such as a DC ground fault determination program, an AC ground fault determination program, and a malfunction prevention program) executable by an arithmetic processing device such as a microcomputer.

[0055] The AC ground fault determination unit 12 determines the ground fault of the high-voltage power line 2A. When the magnitude of the commercial frequency component calculated by the fast Fourier transform unit 11 exceeds the threshold for determining the ground fault of the AC circuit, it determines an AC ground fault. This threshold reaches 2000 V far exceeding the setting value of 400 to 600 V, which is the setting value for the DC ground fault determination unit 6A to determine a DC ground fault, so there is a possibility of false detection. Therefore, this AC ground fault is determined. Note that by using the commercial frequency component obtained by performing the fast Fourier transform, it is possible to surely determine the ground fault of the high-voltage power line 2A in a short time of about several tens of ms. However, the fast Fourier transform unit 11 may be made to calculate the double-frequency component of the commercial frequency and use the magnitude of the double-frequency component as a determination criterion to further speed up the process.

[0056] When the malfunction prevention unit 13 is at the output of the DC ground fault signal Fd by the DC ground fault determination output unit 6, if the AC ground fault determination unit 12 determines a ground fault in the high-voltage power line 2A, it blocks the DC ground fault signal Fd of the DC ground fault. More specifically, it cuts off the DC ground fault signal Fd using a switch circuit. Thus, even if the DC ground fault determination unit 6A may determine the fluctuation of the potential difference due to the ground fault of the high-voltage power line 2A as the occurrence of a DC ground fault, it is configured so that the DC ground fault signal Fd of the DC ground fault is not output.

[0057] Note that the malfunction prevention unit 13 only needs to be able to block the DC ground fault signal Fd by the DC ground fault determination output unit 6, and it may block the signal between the DC ground determination unit 6A and the potential difference measurement unit 5, or between the DC ground fault determination unit 6A and the ground fault determination output unit 6B.

[0058] By using the false detection prevention type DC high-voltage grounding relay 1 with the above configuration, when a DC ground fault occurs in the DC distribution line (DC bus) 2B, due to the influence of the resulting ground fault current, the potential of the grounding mat 3 with respect to the return line 4 rapidly increases, and the potential difference measurement unit 5 measures this potential difference. When this potential difference exceeds the setting value for ground fault determination (for example, 400V to 600V), the DC ground fault determination output unit 6 outputs the DC ground fault signal Fd of the DC ground fault, thereby quickly cutting off the high-speed circuit breaker 8A and the circuit breaker Bb to minimize the damage caused by the flow of a large fault current. Therefore, it has no adverse effect on the high-voltage power line 2A.

[0059] On the other hand, when an AC ground fault occurs at the fault location F of the high-voltage power line 2A of the substation 2, the power supplied to this fault location F is supplied to the grounding mat 3 via the resistor 2R, and an AC voltage close to the power supply voltage (3300V or 6600V) is applied to the grounding mat 3. At this time, the potential difference measurement unit 5 measures an extremely large AC potential difference (a waveform half-wave rectified by the rectifier 5B).

[0060] The high-speed Fourier transform unit 11 constantly analyzes the commercial frequency components of the potential difference measured by the potential difference measurement unit 5. When an AC ground fault occurs, the commercial frequency components of the AC ground fault will appear significantly for at least one cycle (16.6 ms to 20 ms) of the commercial power supply from the time of occurrence. When the commercial frequency components obtained by the high-speed Fourier transform unit 11 exceed a predetermined threshold value, the AC ground fault determination unit determines the ground fault in the high-voltage power line 2A, and the malfunction prevention unit 13 blocks the DC ground fault signal Fd of the DC ground fault by the DC ground fault determination output unit 6.

[0061] Therefore, when an AC ground fault occurs, the malfunction prevention unit 13 determines the ground fault in the high-voltage power line 2A first. Even if the DC ground fault determination output unit 6 may malfunction due to a large AC potential difference, the malfunction can be prevented by blocking the DC ground fault signal Fd of the DC ground fault. Although not shown in the figure, since the ground fault is also detected on the high-voltage power line 2A side and the circuit breaker Ba is tripped, when the circuit breaker Ba is tripped, the AC voltage is no longer applied to the grounding mat 3, and the potential of the grounding mat returns to a state where it is equal to or lower than the setting value of the DC ground fault by the DC ground fault determination output unit 6, and the detection of the DC ground fault can be performed.

[0062] That is, in the malfunction detection prevention type DC high-voltage grounding relay 1 of the present embodiment, the malfunction of outputting the DC ground fault signal Fd of the DC ground fault due to the ground fault in the high-voltage power line 2A can be eliminated. Therefore, the power supply to the DC power line 2B is not interrupted due to the ground fault in the high-voltage power line 2A, and the operation of the train is not adversely affected.

[0063] FIG. 3 is a diagram showing the configuration of the malfunction detection prevention type DC high-voltage grounding relay 15 according to the second embodiment. In FIG. 3, the differences from the malfunction detection prevention type DC high-voltage grounding relay 1 shown in FIG. 2 are that it includes a current measurement unit 16 that measures the current flowing in the circuit between the grounding mat 3 and the return line 4, and the high-speed Fourier transform unit 11 performs frequency analysis of the AC current measured by the current measurement unit 16. Since the other components are the same as or equivalent to those already described in detail with reference to FIG. 2, detailed description thereof is omitted.

[0064] The current measurement unit 16 preferably uses, for example, a current transformer that is excited by the current flowing through the primary-side circuit by electromagnetic induction and has a current flowing through the secondary side, and converts and measures the magnitude of the current on the secondary side to a measurable magnitude. That is, when there is a change in the current flowing through the primary side of the current transformer, due to the change in the magnetic flux density excited thereby, a current of a magnitude divided by the turns ratio flows through the secondary side. Therefore, when an AC ground fault occurs, a secondary current proportional to the magnitude of the AC ground fault flows, and this can be measured.

[0065] According to the current transformer, when an alternating current that constantly fluctuates flows through the circuit between the grounding mat 3 and the return wire 4, this current can be efficiently converted and measured. Also, when a direct current flows through the circuit between the grounding mat 3 and the return wire 4, the current transformer does not transmit the direct current, so the direct current is not detected. In addition, since the current flowing through the circuit between the grounding mat 3 and the return wire 4 flows in both the forward and reverse directions, the commercial frequency component of the alternating current generated when a ground fault occurs in the high-voltage power line 2A can be accurately analyzed.

[0066] That is, the AC ground fault determination unit 6 can more reliably determine a ground fault in the high-voltage power line 2A, and the malfunction prevention unit 13 can quickly and surely prevent the determination output due to a malfunction associated with an AC ground fault from the DC ground fault determination output unit 6.

[0067] FIG. 4 is a diagram showing the configuration of the false detection prevention type DC high-voltage grounding relay 20 according to the third embodiment. In FIG. 4, the difference from the false detection prevention type DC high-voltage grounding relay 1 shown in FIG. 3 is that it includes an effective value calculation unit 21 that calculates the effective value from the current measured by the current measurement unit 16, and the AC ground fault determination unit 12 determines an AC ground fault when the effective value calculated by the effective value calculation unit 21 exceeds the threshold for determining a ground fault in the AC circuit. Since the other components are the same as or equivalent to those already described in detail with reference to FIGS. 2 to 3, detailed description thereof is omitted.

[0068] The effective value calculation unit 21 performs effective value calculation processing using the power charged in the auxiliary power supply unit 10, so that the effective value calculation can be always performed even in a situation where the external power supply is interrupted. Note that the effective value is always a positive value and varies with a period that is twice the commercial frequency. Therefore, by obtaining the average value of the effective value of the alternating current measured by the current measurement unit 16 by the effective value calculation unit 21, an index indicating the magnitude of the ground fault in the high-voltage power line 2A can be obtained more quickly.

[0069] In addition, although it is conceivable that the effective value calculation unit 21 obtains the effective value by combining electronic circuits, for example, by realizing it with an arithmetic processing device and an effective value calculation program executable by this arithmetic processing device, the manufacturing cost can be reduced. Yes.

[0070] Figure 5 is incorrect Detection prevention type DC high-voltage ground relay 40 For reference is a diagram shown. Figure 5 In General DC high-voltage ground relay device and The difference is that when a ground fault occurs in the high-voltage power line 2A, the DC ground fault determination output unit 6 is completely disconnected from the grounding mat 3 and the return line 4 so that the DC ground fault determination output unit 6 does not malfunction.

[0071] This The false detection prevention type DC high-voltage ground relay 40 includes an AC ground fault determination unit 41 that determines an AC ground fault when the potential difference generated between the grounding mat 3 and the return line 4 exceeds a threshold value (for example, a DC offset voltage of 1500 V) for determining a ground fault in the AC circuit, and a switch unit 42A that disconnects the connection between the grounding mat 3 and the return line 4 and the DC ground fault determination output unit 6 when the AC ground fault determination unit 41 determines an AC ground fault, and a malfunction prevention unit 42 that prevents the determination output of the DC ground fault signal Fd by the DC ground fault determination output unit 6.

[0072] More specifically, the malfunction prevention unit 42 is a relay circuit. An AC voltage is applied to the relay coil 41B of the AC excitation via the voltage dividing circuit 41A. When the AC voltage supplied to the relay coil 41B exceeds the threshold value, the b contact of the switch unit 42A opens, disconnecting the potential difference measurement unit 5 from the ground mat 3 and the return wire 4.

[0073] This According to the false detection prevention type DC high-voltage grounding relay 40, when no AC voltage due to a ground fault of the high-voltage power line 2A is applied between the ground mat 3 and the return wire 4, no potential difference is applied to the relay coil 41B. Since the switch unit 42A connects the potential difference measurement unit 5 between the ground mat 3 and the return wire 4, when a ground fault occurs in the DC distribution line 2B, the DC ground fault determination output unit 6 detects this and outputs a DC ground fault signal Fd.

[0074] On the other hand, when an AC voltage due to a ground fault of the high-voltage power line 2A is applied between the ground mat 3 and the return wire 4, when this AC voltage exceeds the operating threshold value of the relay coil 41B, the b contact of the switch unit 42A opens before the DC ground fault determination output unit 6 operates. That is, the malfunction prevention unit 42 can surely prevent the malfunction by disconnecting the DC ground fault determination unit 6 from between the ground mat 3 and the return wire 4.

[0075] Figure 6 is Fourth Embodiment a diagram showing the configuration of the false detection prevention type DC high-voltage grounding relay 45 according to this. Figure 6 In, Fig. 5 The difference from the false detection prevention type DC high-voltage grounding relay 40 shown in is that, instead of the AC ground fault determination unit 41 and the malfunction prevention unit 42, when the potential difference generated between the ground mat 3 and the return wire 4 is due to a ground fault of the AC circuit, an AC ground fault voltage suppression circuit 47 that outputs a potential difference Vo attenuated to such an extent that the potential difference Vi due to this AC ground fault is not falsely detected by the DC ground fault determination output unit 6 is interposed between the ground mat 4 and the return wire 3 and the DC ground fault determination output unit 5, and a malfunction prevention unit 46 that blocks the determination output of the DC ground fault signal Fd is provided. Other parts are shown in Fig. 5Since it is the same as that already described in detail using, the detailed description is omitted by attaching the same reference numerals to the same or equivalent members.

[0076] Figure 7 is a diagram showing an example of the AC ground fault voltage suppression circuit 47. Figure 7 As shown in, it is conceivable that the AC ground fault voltage suppression circuit 47 attenuates, for example, the AC voltage of a commercial power supply with a potential difference Vi. For example, at the frequency of the commercial power supply, even if an AC potential difference Vi of 6600 V is applied, it is a filter circuit that converts it into a potential difference Vo attenuated to a level below the setting value of the DC ground fault determination output unit 6.

[0077] Figure 7 (A) is a diagram showing the configuration of a low-pass filter circuit as an example of the AC ground fault voltage suppression circuit.

[0078] Figure 7 As shown in (A), the low-pass filter circuit 47A as an example of the AC ground fault voltage suppression circuit 47 includes a variable resistor R and a capacitor C connected in series, and a coil L connected between one end and the midpoint of the variable resistor R. According to this low-pass filter circuit 47A, the AC component of the potential difference Vi can be attenuated with characteristics determined by the magnitudes of the resistors R1, R1 divided by the midpoint of the variable resistor R, the magnitude of the coil L, and the capacitance of the capacitor C. Note that the magnitudes of the elements R1, R2, L, and C are adjusted so that the AC output potential difference Vo at the commercial frequency is equal to or less than the setting value of the DC ground fault determination output unit 6 even when a 6600 V commercial power supply is applied to the potential difference Vi, and the rise delay of the potential difference Vi when a DC ground fault occurs is minimized.

[0079] Also, in this example, a coil L is provided in parallel with the resistor R1 so as to minimize the load resistance of the DC component, but it is also possible to omit this coil L. That is, it goes without saying that the AC ground fault voltage suppression circuit 47 of the present invention may have a configuration obtained by removing the coil L from the circuit configuration of the low-pass filter circuit 47A.

[0080] Figure 7 (B) is a diagram showing an example of a π-type low-pass filter circuit as an example of the AC ground voltage suppression circuit.

[0081] Figure 7 As shown in (B), the π-type low-pass filter circuit 47B as an example of the AC ground voltage suppression circuit 47 includes a resistor R3, an inductor L1, a capacitor C1, a resistor R4, an inductor L2, and a capacitor C2 that are sequentially connected, and the resistor R4 and the inductor L2 are sequentially connected in parallel to the capacitor C1. The potential difference Vi across both ends of the capacitor C1 is output.

[0082] By using the π-type low-pass filter circuit 47 in which a plurality of low-pass filter circuits are combined in stages as in this example, the attenuation rate depending on the frequency can be increased. That is, it is possible to efficiently attenuate the potential difference Vi due to the AC ground of the commercial power supply and convert it to the potential difference Vo that is sufficiently attenuated so as not to be detected reliably, and at the same time, it is possible to suppress the attenuation of the DC potential difference.

[0083] Figure 7 (C) is a diagram showing an example of a notch filter circuit as an example of the AC ground voltage suppression circuit.

[0084] Figure 7 As shown in (C), the notch filter circuit 47C as an example of the AC ground voltage suppression circuit 47 includes resistors R5 and R6 connected in sequence, a capacitor C3 connected between these resistors R5 and R6, capacitors C4 and C5 connected in sequence in parallel to these resistors R5 and R6, and a resistor R7 connected between these capacitors C4 and C5, and efficiently attenuates only the commercial power supply frequency. Therefore, it is possible to efficiently attenuate the potential difference Vi due to the AC ground of the commercial power supply and sufficiently attenuate it so as not to be detected reliably, and at the same time, it is possible to suppress the attenuation of the DC potential difference to such an extent that almost no attenuation occurs. It follows that

Explanation of symbols

[0085] 1, 15, 20 ,45False Detection Prevention Type DC High Voltage Ground Relay 2 Substations 2A High Voltage Power Line 2B DC Distribution Line 3 Ground Mats 4 Return Lines 5 Potential Difference Measurement Unit 6 DC Ground Fault Judgment Output Unit 7 Transformer for Rectifier 8 Rectifier 10 Auxiliary Power Supply Unit 11 Fast Fourier Transform Unit 1 2 AC Ground Fault Judgment Unit 13 ,46 Malfunction Prevention Unit 16 Current Measurement Unit 21 Effective Value Calculation Unit 4 7 AC Ground Fault Voltage Suppression Circuit Fd DC Ground Fault Signal

Claims

1. a potential difference measuring unit that is provided between the ground mat and the return line of the electric railway DC substation and measures the potential difference; and a DC earth fault determination output unit that uses the potential difference to determine a DC earth fault and output a DC earth fault signal. an auxiliary power supply unit that is charged using a rail potential generated between the ground mat and the return line; a fast Fourier transform unit that performs fast Fourier transform calculation on the output of the potential difference measuring unit using the power charged in the auxiliary power supply unit; an AC ground fault determination unit that determines an AC ground fault when the commercial frequency component calculated by the fast Fourier transform unit exceeds a threshold value for determining a ground fault in the AC power line; An erroneous detection prevention type DC high voltage ground relay characterized by comprising a malfunction prevention unit that prevents the DC ground fault judgment output unit from judging a DC ground fault when this AC ground fault judgment unit judges an AC ground fault.

2. a potential difference measuring unit that is provided between the ground mat and the return line of the electric railway DC substation and measures the potential difference; and a DC earth fault determination output unit that uses the potential difference to determine a DC earth fault and output a DC earth fault signal. a current measuring unit for measuring a current flowing in an electric circuit between the ground mat and the return line; an auxiliary power supply unit that is charged using a rail potential generated between the ground mat and the return line; a fast Fourier transform unit that performs a fast Fourier transform operation on the output of the current measuring unit using the power charged in the auxiliary power supply unit; an AC ground fault determination unit that determines an AC ground fault when the commercial frequency component calculated by the fast Fourier transform unit exceeds a threshold value for determining a ground fault in the AC power line; An erroneous detection prevention type DC high voltage ground relay characterized by comprising a malfunction prevention unit that prevents the DC ground fault judgment output unit from judging a DC ground fault when this AC ground fault judgment unit judges an AC ground fault.

3. a potential difference measuring unit that is provided between the ground mat and the return line of the electric railway DC substation and measures the potential difference; and a DC earth fault determination output unit that uses the potential difference to determine a DC earth fault and output a DC earth fault signal. a current measuring unit for measuring a current flowing in an electric circuit between the ground mat and the return line; an auxiliary power supply unit that is charged using a rail potential generated between the ground mat and the return line; an effective value calculation unit that calculates an effective value from at least the output of the current measurement unit using the power charged in the auxiliary power supply unit; an AC ground fault determination unit that determines an AC ground fault when the effective value calculated by the effective value calculation unit exceeds a threshold value for determining a ground fault in the AC electric circuit; An erroneous detection prevention type DC high voltage ground relay characterized by comprising a malfunction prevention unit that prevents the DC ground fault judgment output unit from judging a DC ground fault when this AC ground fault judgment unit judges an AC ground fault.

4. A potential difference measuring unit that is provided between a ground mat and a return line of an electric railway DC substation and measures this potential difference, and a DC ground fault determination output unit that uses the potential difference to determine a DC ground fault and output a DC ground fault signal, This invention relates to a fault detection prevention type DC high voltage ground relay, and is characterized in that it comprises an AC ground fault voltage suppression circuit, which is interposed between the ground mat and the return line and the DC ground fault judgment output unit, and which attenuates the potential difference caused by the AC ground fault when the potential difference caused by the AC ground fault is due to a ground fault in an AC circuit, to a level that does not cause the DC ground fault judgment output unit to erroneously detect it, and a fault prevention unit which prevents the judgment output of a DC ground fault signal.

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