High-precision inspection platform of urban rail transit steel rail transition resistance test equipment

Abstract

The invention discloses a high-precision test platform of urban rail transit steel rail transition resistance test equipment. The high-precision test platform specifically comprises an uplink steel rail and a downlink steel rail which are simulated by using four metal plates, a stray current collection net / ground which is simulated by using one metal plate, and a transition resistance between the steel rail and the stray current collection net / ground which is simulated by using a precision resistor. Short current-equalizing lines are connected between the steel rails in the same row, and long current-equalizing lines are connected between the upper steel rails and the lower steel rails; the transition resistors are divided into a plurality of groups, each group comprises four precision resistors, the precision resistors are connected between the four simulated steel rails and the metal plate of the stray current collecting net / ground, the relative positions connected on the metal plate are the same, and each group of precision resistors are uniformly distributed on the metal plate of the simulated steel rail. The invention has the characteristics of high precision, low temperature drift, high reliability and high stability.

Description

Technical Field

[0001] The invention belongs to the technical field of rail transit, and in particular relates to a high-precision inspection platform for urban rail transit rail transition resistance testing equipment. Background Art

[0002] There is a problem that the test equipment for the transition resistance of urban rail transit rails lacks a convenient and feasible high-precision testing platform.

[0003] The principle of transition resistance detection in engineering practice is as follows: the detection equipment injects a current of about 100A between the rail to be tested and the through-ground flat steel or the terminal of the stray current collection network, and accurately measures the current flowing in or out at both ends of the rail transition resistance test interval, and finally obtains the current leaking from the rail to the ground. The average value of the rail-to-ground potential sampled in the test interval is divided by the leakage current to calculate the rail transition resistance in the test interval.

[0004] At present, there are many inconveniences in conducting rail transition resistance test equipment verification experiments in tunnels. There is a lack of a convenient and feasible high-precision inspection platform for the test equipment of urban rail transit rail transition resistance. Summary of the invention

[0005] In view of the above problems, the present invention provides a high-precision inspection platform for urban rail transit rail transition resistance testing equipment. The inspection platform has the characteristics of high precision, low temperature drift, high reliability and high stability.

[0006] The invention discloses a high-precision inspection platform for testing equipment for transition resistance of urban rail transit rails, comprising up and down rails simulated by four metal plates, a stray current collection network / earth simulated by one metal plate, and a precision resistor to simulate the transition resistance between the rails and the stray current collection network / earth; short equalizing flow lines are connected between the same rails, and long equalizing flow lines are connected between the up and down rails.

[0007] The transition resistors are divided into several groups, each group of 4 precision resistors, connected between 4 simulated rails and the metal plate of the stray current collection network / earth. The relative positions of the connections on the metal plates are the same, and each group of precision resistors is evenly distributed on the metal plates simulating the rails.

[0008] The cross-sectional area of ​​the metal plate is selected to simulate the longitudinal resistance of the rail.

[0009] The test section of the inspection platform needs to span at least one set of precision resistors. When current is injected on the metal plate, the current flowing in and out of the metal plate in the test section is measured, and the current leaking through the precision resistors spanning the test section to the simulated stray current collection network / earth is calculated; the average potential of the metal plate in the test section relative to the metal plate simulating the stray current collection network / earth is measured, and the transition resistance of the rail is calculated using the transition resistance calculation formula.

[0010] Furthermore, the cross-sectional area of ​​the metal plate simulating the rail and the stray current collection network / ground is determined by the following formula:

[0011]

[0012] Where: S is the cross-sectional area of ​​the metal plate, d is the length of the metal plate between the positive and negative electrodes of the sensor when measuring the longitudinal voltage drop U, ρ is the resistivity of the selected metal material, I is the current designed to flow through the metal plate, and U is the longitudinal voltage drop formed by the metal plate of length d when the current I flows through the metal plate.

[0013] Furthermore, the transition resistor determines the resistance value and the number of resistors by the following formula:

[0014]

[0015] Where: R r is the resistance value of the high-precision resistor; R g and L are the transition resistance and interval length of the rail to the stray current collection network / earth respectively; n is the number of high-precision resistors.

[0016] Furthermore, the calculation method of the current limit through the metal plate is shown in the following formula:

[0017]

[0018] Where: Q l is the convection heat dissipation of the conductor, Q f is the heat dissipated by conductor radiation, I w is the metal plate current limit, R w For flow through I w The resistance, Q l and Q f It is expressed as:

[0019] Q l =a l (θ w -θ0)F l (4)

[0020]

[0021] Among them: a lis the total heat dissipation coefficient, F l is the heat transfer area of ​​the conductor, θ w is the temperature of the conductor, θ0 is the temperature of the surrounding air, ε is the radiation coefficient of the conductor material, the surface of the polished metal material is 0.039~0.057, the surface of the rough metal material is 0.055, F f is the radiation heat dissipation surface area per unit length.

[0022] The beneficial technical effects of the present invention are:

[0023] 1. The present invention can realize the inspection of the performance and effectiveness of rail transition resistance testing equipment.

[0024] 2. The present invention can quantitatively evaluate the test range and test capability of the rail transition resistance test equipment and measure the accuracy of the rail transition resistance test equipment.

[0025] 3. The present invention is conducive to the research and development of rail transition resistance testing equipment, thereby promoting the management of stray currents in urban rail transit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a high-precision inspection platform for the urban rail transit rail transition resistance testing equipment of the present invention.

[0027] In the figure: 1-transition resistor; 2-rail; 3-long average flow line; 4-short average flow line; 5-grounding.

[0028] Figure 2 This is an equivalent circuit diagram of a high-precision inspection platform for the urban rail transit rail transition resistance testing equipment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0030] The present invention provides a high-precision inspection platform for urban rail transit rail transition resistance testing equipment, such as Figure 1 As shown, it includes up and down rails 2 simulated by 4 metal plates, a stray current collection network / earth simulated by 1 metal plate, and a transition resistance 1 between the rails 2 and the stray current collection network / earth simulated by a precision resistor; a short equalizing flow line 4 is connected between the same rails, and a long equalizing flow line 3 is connected between the up and down rails.

[0031] The transition resistor 1 is divided into several groups, each group of 4 precision resistors, connected between the 4 simulated rails 2 and the metal plates of the stray current collection network / earth 1, the relative positions of the connections on the metal plates are the same, and each group of precision resistors is evenly distributed on the metal plates of the simulated rails 2. The precision resistors can be adjusted to simulate different rail-to-ground transition resistances. The selection of precision resistors should take into account the current carrying capacity of each resistor in parallel. If the current carrying capacity exceeds the allowable value, the number of resistor groups needs to be increased.

[0032] The cross-sectional area of ​​the metal plate is selected to simulate the longitudinal resistance of the rail 2 .

[0033] The equivalent circuit diagram of the present invention is as follows: Figure 2 As shown. The test section of the inspection platform needs to cross at least one set of precision resistors. When current is injected on the metal plate, the current flowing in and out of the metal plate in the test section is measured, and the current leaking to the simulated stray current collection network / earth through the precision resistors across the tested section is calculated; the average potential of the metal plate in the test section to the metal plate simulating the stray current collection network / earth is measured, and the transition resistance of the rail is calculated using the transition resistance calculation formula. Comparing the measured value with the actual value can give the accuracy and effectiveness of the transition resistance test equipment.

[0034] In the rail transition resistance test, injecting a current of 100A into the rail will form a longitudinal voltage drop of about 10mV on the rail with a length of D=10m. Applying a current of 100A on a 20cm metal plate will also form a voltage drop of 10mV. The parameter design table of the metal plate is shown in Table 1.

[0035] Table 1 Design parameters of metal plates

[0036]

[0037] Table 1 gives the design parameters of metal plates made of aluminum and iron. The calculation of the design parameters is shown in formula (1):

[0038]

[0039] Where: S is the cross-sectional area of ​​the metal plate, d is the length of the metal plate between the positive and negative electrodes of the sensor when measuring the longitudinal voltage drop U, ρ is the resistivity of the selected metal material, I is the current designed to flow through the metal plate, and U is the longitudinal voltage drop formed by the metal plate of length d when the current I flows through the metal plate.

[0040] The resistance values ​​of several simulated transition resistors are given by formula (2):

[0041]

[0042] Where: R r is the resistance value of the high-precision resistor; Rg and L are the transition resistance and interval length of the rail to the stray current collection network / earth respectively; n is the number of high-precision resistors.

[0043] Table 2 gives several simulated resistance values.

[0044] Table 2 Simulated resistance values

[0045] <![CDATA[Transition resistance R g Ω·km]]> Number of resistors n Simulation interval length L km <![CDATA[Resistance value R r Ω]]> 1 4 2 2 3 4 2 6 15 4 2 30 150 4 2 300

[0046] Through formulas (3) to (5), taking the geometric parameters of the metal plate made of iron in Table 1 as an example, the maximum current carrying capacity I of the metal plate is verified. w . Maximum allowable temperature θ w is 85℃, the ambient temperature θ0 is 25℃, and the air natural convection a l 5~25, gas forced convection a l It is 20 to 100. See Table 3 for details.

[0047] Table 3 Verification results using iron as an example

[0048]

[0049] The calculation method is as follows:

[0050]

[0051] Where: Q l is the convection heat dissipation of the conductor, Q f is the heat dissipated by conductor radiation, I w is the metal plate current limit, R w For flow through I w The resistance, Q l and Q f It is expressed as:

[0052] Q l =a l (θ w -θ0)F l (4)

[0053]

[0054] Among them: a l is the total heat dissipation coefficient, F l is the heat transfer area of ​​the conductor, θ w is the temperature of the conductor, θ0 is the temperature of the surrounding air, ε is the radiation coefficient of the conductor material, the surface of the polished metal material is 0.039~0.057, the surface of the rough metal material is 0.055, F f is the radiation heat dissipation surface area per unit length.

Claims

1. A high-precision inspection platform for urban rail transit rail transition resistance testing equipment, characterized in that: The method comprises using four metal plates to simulate the up and down rails (2), using one metal plate to simulate the stray current collection network / earth, and using a precision resistor to simulate the transition resistance (1) between the rails (2) and the stray current collection network / earth; connecting a short flow line (4) between the same rails, and connecting a long flow line (3) between the up and down rails; The transition resistors (1) are divided into several groups, each group of 4 precision resistors are connected between the 4 simulated rails (2) and the metal plates of the stray current collection network / earth (1), the relative positions of the connections on the metal plates are the same, and the groups of precision resistors are evenly distributed on the metal plates of the simulated rails (2); The cross-sectional area of ​​the metal plate is selected so as to simulate the longitudinal resistance of the rail (2); The test interval of the inspection platform needs to span at least one set of precision resistors. When current is injected on the metal plate, the current flowing into and out of the metal plate in the test interval is measured, and the current leaking through the precision resistors spanning the tested interval to the simulated stray current collection network / earth is calculated; the average potential of the metal plate on the test interval relative to the metal plate simulating the stray current collection network / earth is measured, and the transition resistance of the rail is calculated using the transition resistance calculation formula.

2. The high-precision inspection platform for urban rail transit rail transition resistance testing equipment according to claim 1 is characterized in that: The cross-sectional area of ​​the metal plate simulating the steel rail (2) and the stray current collection network / earth is determined by the following formula: Where: S is the cross-sectional area of ​​the metal plate, d is the length of the metal plate between the positive and negative electrodes of the sensor when measuring the longitudinal voltage drop U, ρ is the resistivity of the selected metal material, I is the current designed to flow through the metal plate, and U is the longitudinal voltage drop formed by the metal plate of length d when the current I flows through the metal plate.

3. The high-precision inspection platform for urban rail transit rail transition resistance testing equipment according to claim 1 is characterized in that: The resistance value and the number of the transition resistor (1) are determined by the following formula: Where: R r is the resistance value of the high-precision resistor; R g and L are the transition resistance and interval length of the rail to the stray current collection network / earth respectively; n is the number of high-precision resistors.

4. The high-precision inspection platform for urban rail transit rail transition resistance testing equipment according to claim 1 is characterized in that: The calculation method of the current limit through the metal plate is as follows: Where: Q l is the convection heat dissipation of the conductor, Q f is the heat dissipated by conductor radiation, I w is the metal plate current limit, R w For flow through I w The resistance, Q l and Q f It is expressed as: Q l =a l (i w -θ0)F l (4) Among them: a l is the total heat dissipation coefficient, F l is the heat transfer area of ​​the conductor, θ w is the temperature of the conductor, θ0 is the temperature of the surrounding air, ε is the radiation coefficient of the conductor material, the surface of the polished metal material is 0.039~0.057, the surface of the rough metal material is 0.055, F f is the radiation heat dissipation surface area per unit length.

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