KR100602914B1 - Ground overcurrent protective relaying schemes for ungrounded DC power supply system and the controlling method for the system - Google Patents

Abstract

The present invention relates to a ground fault protection relay system for detecting a ground fault occurrence (ground fault zone detection) and a ground fault line in a non-grounded DC power supply system of a train.

The present invention comprises a current control means for varying the resistance characteristics according to the voltage difference between the both ends of the ground fault protection relay, the current control means of the ground fault protection relay is installed between the negative bus of the rectifier and the ground of high resistance during normal operation It is intended to provide a ground fault protection relay which exhibits characteristics to limit the leakage current to a reference value or less and exhibit a characteristic of very small resistance in case of a ground fault so that a ground fault current of sufficient magnitude is required for detection. Determining the ground fault current through the current control means to determine whether there is a ground fault (accident section), and comparing the change (increase amount) of the current flowing in the feed line with the change amount of the ground fault current at the same time so that the accident feeder can be identified. To provide a ground fault protection relay system and its control method.

Ground, Ungrounded, Power Supply System, Electric Train, Ground Protection Relay, Electric

Description

Ground overcurrent protective relaying schemes for ungrounded DC power supply system and the controlling method for the system}

1 is a view showing the problem of the ground current flow and the conventional ground fault protection relay.

2 is a diagram showing an installation configuration of a conventional ground fault protection relay.

3 is a schematic diagram of a power supply system for showing a change amount of ground current flowing into a substation;

Figure 4 is a graph showing the time delay element of the relay device in the system of the present invention.

5 is a diagram showing an equivalent circuit for calculating a fault current in the system of the present invention.

6 is a graph of the amount of change in the energized current and the amount of change in the feeder current of the current control means for explaining an accident catenary discrimination method in the system of the present invention;

Fig. 7 is a diagram showing the current control means grounding configuration of the ground fault protection relay in the system of the present invention.

8 is a diagram showing a feed line for indicating the position of a current sensor in the ground fault protection relay system of the present invention.

9 is a block diagram showing the configuration of the ground fault protection relay system of the present invention.

10 is a flow chart showing the operational flow of the system of the present invention.

Fig. 11 is a diagram showing general current-voltage characteristics of the current control means in the system of the present invention.

The present invention relates to a ground fault protection relay system for detecting a ground fault occurrence (ground fault zone detection) and a ground fault line in a non-grounded DC power supply system of a train.

In general, the electric power feeding system is installed along railroad lines to supply electric power to trains. In order to stably supply the prescribed voltage to the end of a long tramway, electric substations are equipped with substation facilities at appropriate sections. AC power is rectified to DC and DC power is supplied to trains through DC switchboards and feeders.

In the electric power supply system for electric railways, a ground fault protection relay is installed to protect various equipments and secure public safety in case of ground faults due to unexpected accidents during normal operation. The supply is shut off.

The urban railway DC power supply system is operated ungrounded to prevent electrical breakdown.

Therefore, ground fault protection relay of DC feeding system uses voltage type relay rather than current type because ground current does not flow even if ground fault occurs.

The problem with the voltage relay is that the relay determines whether there is an accident but cannot determine the accident section.

Therefore, the power supply is interrupted in the accident section as well as in the health section, which may cause a problem for the safety of the train passengers.

As in FIG. 1, when a ground fault occurs at the location of the first train, the power supply breakers B ₁ , B ₂ , B ₃ , and B _{4 of} all substations A, B, C, and D are tripped to provide a sound zone. The power supply is also interrupted by train No. 2, which can cause a risk to passenger safety.

Reference numerals RL1 to RL4, which are not explained, are conventional ground fault protection relays and are installed as shown in FIG.

The ground fault protection relay is provided with a resistor between the earth and the negative bus of the rectifier so that the ground current flows through the resistor, and measures the voltage across the resistor and compares it with a predetermined value to determine whether there is a ground fault. And, according to the determination result, the power supply feeder circuit breaker (B ₁ , B ₂ , B ₃ , B ₄ ) installed in the substation is operated to cut off the power supply.

However, in the conventional ground fault protection relay device, since the ground current flows into not only the substation of the accident section but also all other substations, it is difficult to determine the accident section.

The present invention has been made in consideration of such a point, and the current control means for varying the resistance characteristics according to the voltage difference between both ends is configured in the ground fault protection relay, the current control of the ground fault protection relay between the negative bus and the ground of the rectifier Provides ground fault protection relay that provides means of high resistance in normal operation by limiting the leakage current to below standard value, and in case of ground fault, it shows very small resistance so that ground fault current of sufficient size for detection can flow. It would be.

In the present invention, the magnitude of the ground fault current flowing through the current control means is determined to determine whether there is a ground fault (accident section), and the change of the ground fault current at the same time is compared with the change (increase amount) of the current flowing in the feed line. The purpose of the present invention is to provide a ground fault protection relay system and a control method for identifying a feeder line.

The present invention is characterized by a ground fault protection relay having a configuration in which the current control means of the ground fault protection relay is configured on the negative bus of the rectifier for ground fault current detection, and the current control means is grounded to the ground.

The current control means is composed of a device that varies the resistance characteristics according to the voltage difference between the two ends, the current control means exhibits a high resistance characteristics when the voltage at both ends is low (normal operation state) to limit the leakage current to the reference value or less The current control means is characterized in that it is configured so that the voltage of both ends is high (when a ground fault occurs) so as to exhibit a characteristic of low resistance so that the amount of the ground current is not limited by the current control means.

The relay system of the present invention using the ground fault protection relay device,

Current measuring means for measuring the current flowing through the current control means configured between the negative bus and the ground of the rectifier, feeder current measuring means for measuring all feeder currents going up, down, left and right from the substation, and the current measurement It judges whether a ground fault has occurred according to the current value flowing through the current control means measured from the means, compares the current value measured from the current control means and the current measurement means of the feeder line, determines the fault line, and trips the control signal of the circuit breaker. It comprises a control means for controlling the output.

The control means compares the ground fault current measured by the current measuring means with a predetermined set current value to determine whether a ground fault has occurred, and the change amount or waveform of the ground fault current measured by the current measuring means and the feeder current measured by the feed line measuring means. It is characterized in that the fault line is judged by comparing for a predetermined time, and output control of the trip control signal of the fault line breaker after a predetermined delay time.

The present invention as such

* Determination of accident section (Judged whether ground fault occurred)

The discrimination of the accident section is judged as the magnitude of the current flowing through the current control means of the substation.

In other words, in the substation of the accident section, a large ground fault current always flows than the substation outside the accident section.

Figure 3 shows a schematic feed system, only the system in the left direction from the accident point is shown for simplicity of circuit analysis.

FIG. 3 is to show that the ground current I _b flowing into the substation B from the accident point is always greater than the ground current I _a flowing into the substation A which is relatively far from the accident point.

Since the load current does not flow through the current control means, it is omitted.

As shown in FIG. 3, when the loop equation of the feed system is established, the following equations (1) and (2) may be represented.

Where R _s is the source resistance, R _a , R _b are the resistance components of the feed line, and I _a , I _b are the loop current. The load current is omitted because it does not flow through the current control means.

When Equation 1 is calculated (−), Equation 1 is arranged as Equation 3 below, and when the Equation 2 is arranged again, Equation 4 is expressed as Equation 4 below.

As such, the ground fault current I _b is always greater than the ground fault current I _a , which means that the ground fault current I _b flowing into the substation B close to the accident point flows to the substation A relatively far from the accident point. It shows that it is always larger than the incoming ground current I _a .

Figure 4 also shows the time delay element characteristics of the relay.

, 변전소(B)의 계전기가 변전소(A) 계전기 보다 항상 먼저 동작하여 사고전류를 차단한다. When a ground fault occurs in the right direction of the substation B, the substation A always sees a smaller ground current than that of the substation B.

, Relay of substation (B) always operates before substation (A) relay to cut off the fault current.

이고

이다. In Figure 4,

ego

to be.

In addition, when the relay of the substation B fails to operate due to a failure, the substation A relay operates after a time delay, thereby naturally performing the post-protection function.

Accordingly, the accident section (ground fault occurrence) is determined using the amount of current flowing through the current control means.

 * Discrimination of accident track

In the substation of the accident zone, whether the accident tramline is left, right or up and down is determined by a ground fault in the feeder line by comparing the change amount or waveform of the ground current with the change amount or waveform of each feeder line current.

5 shows an equivalent circuit for calculating the ground fault current, showing a simplified power supply system.

Here, R _s represents the resistance component of the source, R _l {R} _ {l} represents the resistance component of the feeder, L _s represents the inductance component of the source, L ₁ represents the inductance component of the feeder.

In FIG. 5, the ground fault current may be represented by Equation 5 below.

Ground fault current in Equation 5 is a ground fault current flowing from the accident line to the ground.

The ground fault current flowing through the substation's current control means may be less than this value because the ground fault current flows into the current control means of each substation.

 In the fault feeder, since the fault current value of Equation 5 will increase in addition to the load current, the fault feeder may be determined by comparing the current amount of the current control means with the current amount of the feeder.

FIG. 6 shows the current change of the accident feeder and the current change of the current control means in FIG. 3 on the same time axis.

Here, it is necessary to pay attention to the size t _w of the window for comparing the amount of current change.

The size of the comparison window is t shown in Equation 5.

In other words, the magnitude of the current variation is a function of t. In order to obtain a sufficient amount of current change for comparison, a sufficient magnitude of t is required, and this value will be the size of the minimum comparison window.

)의 22% 정도가 된다. For example, if the comparison window t _w is 5ms in a system with a time constant of 20ms, the amount of current change is represented by the equation of 'Steady State' ground current (

22% of).

Whether this value is large enough to measure the current increase due to a ground fault should be considered when setting the relay.

In consideration of the above, the present invention system may be configured as follows.

7 is a view showing the grounding configuration of the ground fault protection relay device of the present invention, Figure 8 is a view showing a feed line of the train for indicating the position of the current sensor of the ground fault protection relay system, Figure 9 is a ground fault protection relay system of the present invention Is a block diagram showing the configuration of a.

The current control means 10 configured between the negative bus and the ground of the rectifier, the current sensor I _g for measuring the current of the current control means 10, and the left and right, phase out of the substation for measuring the current of the feed line. It is determined whether a ground fault has occurred according to the current value flowing through the current sensors I ₁ to I ₄ and the current control means 10 measured by the current sensor I _g installed in the downward line, and the current sensor I _g and Including a control unit 20 for outputting the trip control signal of the circuit breaker (B ₁ ~ B ₄ ) by determining the fault line by comparing the current change amount or waveform measured from the feeder current sensor (I ₁ ~ I ₄ ) It is composed.

And said control means is a current sensor (I _g) by a ground current measured from the comparison with the predetermined current value set in the ground fault occurs to determine whether an earth fault occurrence determining unit 21, a measurement from the current sensor (I _g) An accident line judgment unit 22 and a ground fault accident that compare an amount or waveform of a current flowing through the feed line measured by the ground current and the feed line current sensors I ₁ to I ₄ for a predetermined time period to determine an accident line. It is configured to include a breaker control unit 23 for output control of the trip control signal of the breaker (B ₁ ~ B ₄ ) of the generated accident line.

In the ground fault protection relay system of the present invention

Current sensors I ₁ to I ₄ that measure all the feeder line currents going up, down, left and right from the substation at all times are configured.

In addition, the negative bus of the substation DC switchboard is grounded through the current control means 10, and a sensor I _g for measuring the current flowing through the current control means 10 is configured.

As described above, the characteristics of the current control means 10 show high resistance characteristics in the normal operation state, thereby limiting the leakage current of the negative train line to a reference value or less and in case of a ground fault, that is, the terminal of the current control means 10. When the voltage is high, the characteristics of low resistance should be exhibited so that the amount of ground current should not be limited by the current control means 10.

Typical voltage-current characteristics of this current limiting means 10 are shown in FIG.

As described above, the current control means 10 may be an arrestor as an apparatus for varying the resistance characteristics according to the voltage difference between both ends, or may be made by applying a power semiconductor.

The ground fault protection relay system of the present invention has the following operation control process.

Comparing the ground current measured from the current sensor I _g with a predetermined current value Iset to determine whether a ground fault has occurred;

Comparing the ground current measured from the current sensor I _g with the feeder current change amount or waveform measured from the feeder current sensors I ₁ to I ₄ for a predetermined time, and determining an accident line;

After determining whether a ground fault has occurred, a process of outputting the trip control signal of the corresponding accident line breaker after a predetermined delay time is performed.

Referring to the operation process of controlling the breaker through the determination of the accident section and the determination of the accident line in the present invention as follows.

10 is a flowchart showing the operation flow of the ground fault protection relay.

The current I ₁ to I ₄ of each substation feed line and the current I _g flowing through the current control means 10 are always measured.

The current I _g of the current control means 10 measured as described above is compared with a predetermined set value Iset.

As a result of the comparison, when the current I _g of the current control means 10 is greater than the setting value Iset, it is determined that a ground fault has occurred.

In this way, if it is determined that the ground fault has occurred, the predetermined time DELTA T begins to accumulate from this time.

The accumulated time T _d is compared with the set time T _set of the time delay characteristic shown in FIG. 4 incorporated in the relay.

The set time T _set means a delay time determined in response to a ground current value on a time delay characteristic curve.

When the accumulated time T _d is greater than the _set time T _set , the trip signal of the breakers B ₁ to B ₄ is emitted.

The outgoing from the incident catenary i.e. substation before exporting the trip signal, down, left, and select the catenary of the incident right four catenary and sends out a signal to the trip (either the B ₁ ~ B ₄₎ the circuit breaker.

As described above, the identification of the accident tank line is a change amount of ground fault current (I _g ) or a change amount of the waveform and each feed line current (I ₁ to I ₄ ), or the waveform thereof, as shown in FIG. Compared to the accident tank line.

Such a system of the present invention does not have to perform reclosing, and further includes a reclosing circuit control unit in the reclosing reclosing control unit 20 to selectively determine whether to perform the reclosing.

The present invention does not require a sensor for measuring the current of the feedback circuit for discriminating the accident section and the accident line, and also eliminates the need for a device for transmitting and receiving an accident detection signal with an adjacent substation.                     

In addition, the determination of the accident tank line is conventionally made in the re-closing process, but in the relay system of the present invention, the fault is detected along with the ground fault detection, so that only the breaker of the accident tank line is tripped, thereby increasing the reliability of the power supply system.

Claims (7)

delete The current control means of the ground protection relay is configured on the negative bus of the rectifier for ground fault current detection, and the negative bus is grounded to the ground through the current control means, the current control means having different resistance characteristics according to the voltage difference between both ends. It is composed of a device, and it shows high resistance when the terminal voltage of the current control means is low (normal operation state), limiting the leakage current to below the reference value, and low when the terminal voltage of the current control means is high (under ground fault). A ground fault over-current protection relay device characterized in that it is configured such that the amount of ground current is not limited by the current control means so as to exhibit the characteristics of the resistance. Current measuring means for measuring the current flowing through the current control means configured between the negative bus and the ground of the rectifier, feeder current measuring means for measuring all feeder currents going up, down, left and right from the substation, and the current measurement The current value flowing through the current control means measured from the means is compared with the time-current characteristics of the relay to determine the occurrence of the ground fault and the accident section, and the current value measured from the current measurement means of the current control means and the feeder line is compared with each other. A ground fault over-current protection relay system of a non-grounded DC power supply system, characterized in that it comprises a control means for judging the line and output control of the trip control signal of the circuit breaker. 4. The ground fault detection unit according to claim 3, wherein the control means compares the ground fault current measured by the current measuring means with a predetermined current value to determine whether a ground fault has occurred, and the ground fault current measured by the current measuring means; An accident line judging unit for judging an accident line by comparing the change amount of the feeder line current measured from the feeder line measuring unit for a predetermined time period, and a circuit breaker control unit for outputting a trip control signal of the circuit breaker of the accident line where a ground fault has occurred. A ground fault over-current protection relay system of an ungrounded DC power supply system, comprising: a. 4. The ground fault detection unit according to claim 3, wherein the control means compares the ground fault current measured by the current measuring means with a predetermined current value to determine whether a ground fault has occurred, and the ground fault current measured by the current measuring means; An accident line judging unit comparing the feeder current waveforms measured from the feeder measuring unit for a predetermined time period and judging an accident line, and a circuit breaker control unit outputting a trip control signal of a corresponding circuit breaker of an accident line having a ground fault A ground fault over-current protection relay system for an ungrounded DC power supply system. Comparing the ground current flowing through the current control means measured by the current measuring means with a predetermined set current value Iset to determine whether a ground fault has occurred; Comparing the change amount of the ground fault current measured by the current control means with the change amount of the feeder line current measured by the feeder current measuring means for a predetermined time, and determining an accident line; And a step of output control of a trip control signal of the breaker of the accident line to the ground overcurrent protection relay control method of a non-grounded DC power supply system. According to claim 6, In the process of determining the accident track, A ground fault of an ungrounded DC power supply system characterized by comparing the current waveform of the ground current measured from the current control means with the feeder current waveform measured from the feeder current measuring means for a predetermined time. Over current protection relay control method.

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