Method for adjusting protection range in electric railway feeder line distance protection

Abstract

This invention belongs to the field of electrified railway traction power supply technology, specifically relating to a method for adjusting the protection range in the distance protection of electrified railway feeders. This invention proposes a method for adjusting the protection range of electrified railway feeder distance protection. When the feeder distance protection is activated, if the harmonic distortion rate of the feeder current exceeds the set value, the distance protection range is adjusted. This ensures that when the protection enters its original operating zone under heavy load, the distance protection range is reduced, avoiding maloperation of the protection. This effectively solves the problem of traditional integrated harmonic suppression elements in current traction substation feeder distance protection failing under AC / DC / AC train loads.

Description

Technical Field

[0001] This invention belongs to the field of electrified railway traction power supply technology, specifically relating to a method for adjusting the protection range in the distance protection of electrified railway feeders. Background Technology

[0002] Distance protection is the primary protection for feeder protection in electrified railways. With the rapid development of my country's society and economy, the density of various electric locomotives or EMUs operating on electrified railways is increasing, and the load current is also increasing, leading to frequent feeder overload phenomena. This can easily cause maloperation of the distance protection of traction substation feeders. By identifying the load characteristics of electric locomotives and appropriately adjusting the setting value of the distance protection, the protection operating range can be narrowed, which helps to prevent maloperation of feeder distance protection.

[0003] Currently, time-domain analysis-based methods primarily identify inrush currents based on the differences between them and standard sine waves. For example, mathematical methods such as mathematical morphology, least squares, and waveform complexity are used to identify the specific characteristics of inrush currents. In the feeder protection of traction substations in electrified railways, the combined harmonic content of the 2nd, 3rd, and 5th harmonics is calculated. When the combined harmonic content exceeds the setting value, the distance protection operating zone is adaptively reduced; this is called "combined harmonic suppression."

[0004] In reality, due to the widespread use of AC-DC-AC type electric locomotives and EMUs, the locomotive load current has low harmonic content. As the load on the power supply arm increases, the comprehensive harmonic content of the 2nd, 3rd, and 5th harmonics of traditional feeder protection generally cannot meet the suppression conditions, thus the suppression function of the protection operating zone is basically ineffective.

[0005] It is necessary to propose a method that adapts to the load characteristics of electric locomotives and EMUs in my country, effectively identify faults and loads, and reduce the feeder distance protection operating zone under heavy load conditions, thereby improving the sensitivity and reliability of relay protection. Summary of the Invention

[0006] To address the problem that current electrified railway feeder protection devices cannot effectively identify large loads and prevent maloperation of distance protection, this invention provides a method for adjusting the protection range of electrified railway feeder distance protection. When the harmonic distortion rate of the feeder protection calculated current exceeds the set value, the distance protection resistor setting value is adjusted, thereby narrowing the distance protection operating range. This effectively solves the problem of traditional integrated harmonic suppression elements in current traction substation feeder distance protection failing under AC-DC-AC train loads.

[0007] The technical solution adopted in this invention is:

[0008] A method for adjusting the protection range in distance protection for electrified railway feeders includes the following steps:

[0009] S1. Obtain the statistical average value of the harmonic distortion rate of the steady-state load current of the power supply arm feeder at the maximum train operating density. Statistical average value of harmonic distortion rate of steady-state short-circuit current of feeder during contact network short-circuit fault ;

[0010] S2, when At that time, set the feeder current harmonic distortion rate setting. Otherwise, the method ends.

[0011] S3. Enter the distance protection logic judgment process. After the feeder distance protection is activated, if the feeder current harmonic distortion rate... satisfy:

[0012] ,

[0013] The resistance setting value is then multiplied by the adjustment coefficient K to narrow the resistance protection range, where Otherwise, the method ends; the harmonic distortion rate of the feeder current. The definition of is:

[0014] ,

[0015] in, , ... These are the effective values ​​of the 2nd, 3rd, ..., nth harmonic currents, respectively. This is the effective value of the fundamental current, and the value of n is determined based on the highest value that the current relay protection device can calculate.

[0016] Furthermore, in S1, in obtaining and At that time, the sampling frequency was set to 128 points / cycle or higher, which was used to calculate the effective value of harmonics with a maximum number of harmonics up to 60.

[0017] Furthermore, in S2, The set value is:

[0018] ,

[0019] in, For the reliability coefficient, and ,at the same time The harmonic distortion rate of the steady-state fault waveform of the feeder current is higher than that when the traction network experiences a fault and there is no load. .

[0020] The beneficial effects of this invention are: This invention proposes a method for adjusting the protection range of feeder distance protection in electrified railways. When the feeder distance protection is activated, if the harmonic distortion rate of the feeder current is greater than the setting value, the distance protection range is adjusted to ensure that the distance protection range is reduced when the protection enters the original operating zone under heavy load, thus avoiding maloperation of the protection. Attached Figure Description

[0021] Figure 1 This is a flowchart of the steps of the present invention.

[0022] Figure 2 This is for the distance protection operating zone and the measurement impedance trajectory. Detailed Implementation

[0023] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings:

[0024] like Figure 1 As shown, the present invention includes the following steps:

[0025] S1. Obtain the statistical average value of the harmonic distortion rate of the steady-state load current of the power supply arm feeder at maximum train operating density. Statistical average value of harmonic distortion rate of steady-state short-circuit current of feeder during contact network short-circuit fault .

[0026] S2. When Set the feeder current harmonic distortion rate setpoint ;

[0027] S3. After the feeder distance protection is activated, the protection logic judgment process begins. If the feeder current harmonic distortion rate... If equation (1) is satisfied, then the resistance setting value is multiplied by the adjustment coefficient K, where This is to reduce the protection range of the resistor side.

[0028] (1)

[0029] Furthermore, it is recommended that the sampling frequency in S1 be 128 points / cycle or higher, in order to calculate the effective value of harmonics up to the 60th order, thereby reducing the impact of frequency aliasing on the criterion.

[0030] Furthermore, the harmonic distortion rate of the feeder current is defined as:

[0031] (2)

[0032] in, , ... These are the effective values ​​of the 2nd, 3rd, ..., nth harmonic currents, respectively. This represents the effective value of the fundamental current. The value of n is determined based on the highest harmonic order that the current relay protection device can calculate; it is recommended that the harmonic order be 60 or higher. Fourier transform algorithms are used for both the fundamental and all harmonic calculations.

[0033] Furthermore, the setting value for the harmonic distortion rate of the feeder current in S2 is:

[0034] (3)

[0035] in, For reliability coefficient, and . It should be higher than the harmonic distortion rate of the steady-state fault waveform of the feeder current when the traction network experiences a fault and there is no load. .

[0036] The specific implementation method is as follows:

[0037] The current recording and analysis of the feeder of a power supply arm in a traction substation was performed. The sampling frequency of the recording device was 128 points / cycle.

[0038] The statistical average harmonic distortion rate of the steady-state load current of the power supply arm feeder under maximum train operating density is 1.6%.

[0039] Three short-circuit tests were conducted on the power supply arm at the traction substation, and the statistical average value of the harmonic distortion rate of the steady-state fault current of the power supply arm feeder was 0.2%.

[0040] The current harmonic distortion rate setting value is taken if the statistical average value of the load current harmonic distortion rate is greater than the statistical average value of the short-circuit fault current harmonic distortion rate. .

[0041] The power supply arm malfunctioned due to a heavy load, causing the distance section I of the traction substation feeder to trip. The resistance setting value of distance section I was 7.21Ω, and the reactance setting value was 5.74Ω.

[0042] The harmonic distortion rate of the feeder current during a steady-state fault is recorded as 2.18%, which satisfies equation (2). Therefore, it was determined that the protection was activated due to a heavy load. The resistance setting adjustment coefficient K was set to 0.85, and the resistance setting was adjusted to... This is to reduce the distance protection range.

[0043] The trajectory of the feeder measured impedance changing over time within the distance protection operating zone is as follows: Figure 2 As shown, during a fault, the measured impedance at the distance protection output is 9.1∠28.9°Ω, entering the original protection operating range. However, after reducing the distance protection resistance setting value by 0.85 times, the resistance-side protection range is reduced (e.g., Figure 2(As shown by the dashed line in the middle), the measured impedance falls outside the protection operating zone, so the distance protection will not malfunction.

Claims

1. A method for adjusting the protection range in distance protection of electrified railway feeders, characterized in that, Includes the following steps: S1. Obtain the statistical average value of the harmonic distortion rate of the steady-state load current of the power supply arm feeder at the maximum train operating density. Statistical average value of harmonic distortion rate of steady-state short-circuit current of feeder during contact network short-circuit fault ; S2, when At that time, set the feeder current harmonic distortion rate setting. ; Otherwise, the method ends; S3. Enter the distance protection logic judgment process. After the feeder distance protection is activated, if the feeder current harmonic distortion rate... satisfy: ， The resistance setting value is then multiplied by the adjustment coefficient K to narrow the resistance protection range, where ; Otherwise, the method ends; the harmonic distortion rate of the feeder current. The definition of is: ， in, , ... These are the effective values ​​of the 2nd, 3rd, ..., nth harmonic currents, respectively. This is the effective value of the fundamental current, and the value of n is determined based on the highest value that the current relay protection device can calculate.

2. The method for adjusting the protection range in the distance protection of an electrified railway feeder according to claim 1, characterized in that, In S1, in obtaining and At that time, the sampling frequency was set to 128 points / cycle or higher, which was used to calculate the effective value of harmonics with a maximum number of harmonics up to 60.

3. The method for adjusting the protection range in distance protection of electrified railway feeders according to claim 1, characterized in that, In S2, The set value is: ， in, For reliability coefficient, and ,at the same time The harmonic distortion rate of the steady-state fault waveform of the feeder current is higher than that when the traction network experiences a fault and there is no load. .

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