CN112255501A - Method for accurately extracting fault current during traction network fault - Google Patents

Method for accurately extracting fault current during traction network fault Download PDF

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Publication number
CN112255501A
CN112255501A CN202011085402.8A CN202011085402A CN112255501A CN 112255501 A CN112255501 A CN 112255501A CN 202011085402 A CN202011085402 A CN 202011085402A CN 112255501 A CN112255501 A CN 112255501A
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fault
current
locomotive
traction network
measuring device
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CN202011085402.8A
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CN112255501B (en
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葛海波
庄晓明
任雪涛
范红疆
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Chengdu Southwest Jiaotong University Xuji Electric Co ltd
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Chengdu Southwest Jiaotong University Xuji Electric Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0046—Arrangements for measuring currents or voltages or for indicating presence or sign thereof characterised by a specific application or detail not covered by any other subgroup of G01R19/00
    • G01R19/0053—Noise discrimination; Analog sampling; Measuring transients
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
    • G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
    • G01R19/16547—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies voltage or current in AC supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

The invention discloses a method for accurately extracting fault current during traction network fault, which comprises the following steps: collecting key data of a traction network at a fault moment; judging whether a locomotive gets a current before the traction network fault based on the key data at the moment of collecting the traction network fault; if the current is taken by the inorganic vehicle before the traction network fails, the fault current is the sampling current of the fault distance measuring device at the moment of the failure; judging whether the collected current of the fault distance measuring device contains locomotive load current or not under the condition that a locomotive gets current before the traction network fault; if the collected current of the fault distance measuring device does not contain locomotive load current, the fault current is the sampled current of the fault distance measuring device at the fault moment; if the collected current of the fault distance measuring device comprises locomotive load current, the fault current is the sampled current of the fault distance measuring device minus the locomotive load current; the method calculates the fault distance by using the fault current after the locomotive load current is eliminated, and greatly improves the fault distance measurement precision.

Description

Method for accurately extracting fault current during traction network fault
Technical Field
The invention relates to the technical field of high-speed railway fault location, in particular to a method for accurately extracting fault current when a traction network fails.
Background
An electric locomotive used in a high-speed railway in China usually adopts an 'alternating current-direct current-alternating current' electricity taking mode, when the locomotive runs, in order to prevent the locomotive equipment from being damaged due to too low traction network voltage, low-voltage protection is usually arranged inside the locomotive, and when the working voltage of the traction network is lower than 19kV, the locomotive operates under the low-voltage protection, and electricity is stopped to be taken from the traction network. When the traction network has high-resistance fault, the voltage of the traction network can change along with the change of the transition resistance value. When the transition resistor causes that the voltage of a traction network at the fault moment is larger than 19kV, the sampling current of the fault distance measuring device comprises the fault current and the locomotive current, when the fault distance measuring device adopts the fault moment sampling current to calculate the fault distance, the sampling current is the composite current of the locomotive load current and the fault current, the sampling current is directly used for calculating the fault distance, the fault distance measuring error is increased, and the fault distance measuring precision requirement cannot be met.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: in the existing fault location method, the sampling current is directly used for calculating the fault distance, and the fault location error is increased because the sampling current is a composite current of the load current and the fault current, so that the fault location precision requirement cannot be met. The scheme provides a method for separating locomotive load current from sampled current when a traction network fails, and the fault distance is calculated by adopting the fault current after the locomotive load current is removed, so that the fault distance measurement precision is greatly improved.
The invention is realized by the following technical scheme:
the scheme provides a method for accurately extracting fault current during traction network fault, which comprises the following steps:
according to whether the sampling current of the fault distance measuring device contains load current, the fault of the traction network is divided into the following steps:
the first situation is as follows: no locomotive runs before the fault, and the current sampled by the fault distance measuring device at the fault moment does not contain locomotive current;
case two: the locomotive runs before the fault, the voltage of a traction network is lower than 19kV when the fault occurs, the locomotive trips, and the sampling current of the fault distance measuring device at the fault moment does not contain the locomotive current;
case three: the locomotive runs before the fault, the voltage of a traction network is higher than 19kV when the fault occurs, the locomotive does not trip, and the sampling current of the fault distance measuring device at the fault moment comprises the locomotive current;
when the traction network fails to work in the first situation or the second situation: sampling current by a fault distance measuring device;
when the traction network fails, the method is as follows: the fault current is the current sampled by the fault distance measuring device, namely the load current before the fault.
The further optimization scheme is that the method records key data of the traction network at the fault moment:
the current value at the two-cycle time before the protection element of the fault distance measuring device is started is marked as I1；
The current value of the fault distance measuring device at the moment of one cycle after the protection element is started is recorded as I2；
The current value at the action time of the protection element of the fault distance measuring device is marked as I3；
The no-load current value of the traction network is marked as Ikz。
The working principle of the scheme is as follows: when fault location calculation is used at present, the directly used sampling current may be a composite current of a load current and a fault current, which can cause that a fault location error becomes large and cannot meet the fault location precision requirement; according to the scheme, after collected key current data are judged based on three states of sampling current (the collected current is no-load current, the collected current is locomotive load current, and the collected current is mixed current of the locomotive load current and fault current), the fault current after the locomotive load current is removed is obtained, the fault current data are used for participating in fault distance calculation more accurately, and the precision of fault distance measurement is greatly improved.
The further optimization scheme is that when I1＝IkzIn time, no locomotive runs before the traction network fails;
when I is1＞IkzIn time, the locomotive is operated before the traction network fails.
The further optimization scheme is that when the formula I3-I2|＞IkzWhen the locomotive current sampling device is in the fault state, the fault distance measuring device samples current which does not contain locomotive current at the fault moment;
when formula I3-I2|＞IkzWhen the fault is not established, the fault distance measuring device samples current including locomotive current at the fault moment.
The further optimization scheme is that when the formula I3-I2|＞IkzWhen the current collected by the fault distance measuring device does not contain the locomotive load current,
fault current as I3；
When formula I3-I2|＞IkzIf the fault distance measuring device is not in operation and the collected current of the fault distance measuring device comprises the locomotive load current,
fault current as I3-I1。
Generally, the variable acquisition current has only three states: collecting current as no-load current, collecting current as locomotive load current, and collecting current as mixed current of locomotive load current and fault current; current value I at two-cycle time before starting protection element of fault distance measuring device1Namely the locomotive load current, and the current value is I at the moment of one cycle after the protection element of the fault distance measuring device is started2And the current value at the action moment of the protection element of the fault distance measuring device is I3The current is the mixed current of the load current and the fault current of the locomotive, and the fault distance measuring device protects the component and starts the later one cycle time I2May also contain a part of the transient quantity not eliminated, so to ensure the effect of the transient quantity here, I is used3-I1To calculate the fault current.
A further optimization scheme is that each cycle is 20 ms.
The invention also provides a device for accurately extracting fault current when a traction network fails based on the method, which comprises the following steps: the device comprises an analysis module, a first calculation module and a second calculation module;
the analysis module is according to whether contain load current in the fault range unit sampling current, divide into the traction network trouble:
the first situation is as follows: no locomotive runs before the fault, and the current sampled by the fault distance measuring device at the fault moment does not contain locomotive current;
case two: the locomotive runs before the fault, the voltage of a traction network is lower than 19kV when the fault occurs, the locomotive trips, and the sampling current of the fault distance measuring device at the fault moment does not contain the locomotive current;
case three: the locomotive runs before the fault, the voltage of a traction network is higher than 19kV when the fault occurs, the locomotive does not trip, and the sampling current of the fault distance measuring device at the fault moment comprises the locomotive current;
when the traction network fails in the first situation or the second situation, the first calculation module outputs a fault current which is a sampling current of the fault distance measuring device;
when the traction network fails, the second calculation module outputs a fault current, namely a sampling current of the fault distance measuring device-a load current before the fault.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the method for separating the load current from the sampled current in the case of the traction network fault, provided by the invention, can greatly improve the fault distance measurement precision by adopting the fault current after the load current is removed to calculate the fault distance.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention.
Fig. 1 is a schematic diagram of a fault waveform and a fault current extraction timing.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1
The first step is as follows: recording critical data
The fault distance measuring device is provided with a protection element, and when a fault occurs, the protection element of the fault distance measuring device is started to trigger data recording and record current data at three moments.
As shown in FIG. 1, the first critical current data is the current value at the two-cycle (40ms) time before the protection device is started, and is marked as I1(ii) a The second key current data is the current value recorded as I at the time of one cycle (20ms) after the protection element is started2(ii) a The third key current data is the current value of the protective element at the action moment and is marked as I3。
The second step is that: judging whether a locomotive runs before the traction network is in fault
When the first critical current data I1＝IkzIn time, no locomotive is running before the fault;
when the first critical current data I1When the current value is greater than the no-load current of the traction network, i.e.
I1＞Ikz (3)
Judging that a locomotive runs before the traction network fails; and when the formula (3) is not met, judging that no locomotive runs before the traction network fails.
In the formula (3), IkzIs the no-load current of the traction network.
The third step: when the locomotive runs before the traction network fails, judging whether the current at the moment of protection action of the protection element of the fault distance measuring device contains load current or not;
the method comprises the following steps that a traction network is operated by a locomotive before a fault, if the voltage of the traction network is smaller than 19kV when the fault occurs, the locomotive is in low-voltage protection action, the locomotive stops taking current from the traction network within a short time (about 30-40 ms), and when a fault distance measuring element acts (about 100ms), the sampling current of the device does not contain locomotive load current; if the voltage of the traction network is larger than 19kV when the fault occurs, the locomotive still draws current from the traction network when the fault occurs, and when the protection element of the fault distance measuring device acts, the sampling current of the device comprises locomotive load current.
Second critical current data I recorded by the device2Is not cut for locomotiveThird key current data I recorded by the device except the current at the moment3The current is used for protecting the action moment of the element of the fault distance measuring device.
If I2And I3The sizes are basically consistent, the locomotive can be judged to still take current from the traction network when in fault, and the sampling current of the protection element at the moment of action contains load current. The judgment logic is shown in formula (4).
When the formula (4) is satisfied, the sampling current at the fault moment does not contain the load current; when the formula (4) is not satisfied, the sampling current at the fault moment contains the load current.
|I3-I2|＞Ikz (4)
The fourth step: extracting fault current
And extracting fault current according to the judgment results of the second step and the third step.
When no locomotive runs before the traction network fails or a locomotive runs but the locomotive stops taking the current from the traction network when the traction network fails, the calculation is carried out according to the formula (5)
Igz＝I3 (5)
When a locomotive runs before the fault of the traction network and the locomotive still takes current from the traction network at the moment of protection action, calculating according to the formula (6)
Igz＝I3-I1 (6)
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A method for accurately extracting fault current when a traction network is in fault is characterized by comprising the following steps:
according to whether the sampling current of the fault distance measuring device contains load current, the fault of the traction network is divided into the following steps:
the first situation is as follows: no locomotive runs before the fault, and the current sampled by the fault distance measuring device at the fault moment does not contain locomotive current;
case two: the locomotive runs before the fault, the voltage of a traction network is lower than 19kV when the fault occurs, the locomotive trips, and the sampling current of the fault distance measuring device at the fault moment does not contain the locomotive current;
case three: the locomotive runs before the fault, the voltage of a traction network is higher than 19kV when the fault occurs, the locomotive does not trip, and the sampling current of the fault distance measuring device at the fault moment comprises the locomotive current;
when the traction network fails to work in the first situation or the second situation: sampling current by a fault distance measuring device;
when the traction network fails, the method is as follows: the fault current is the current sampled by the fault distance measuring device, namely the load current before the fault.
2. The method for accurately extracting the fault current during the fault of the traction network according to claim 1, is characterized in that key data of the fault moment of the traction network are recorded:
the current value at the two-cycle time before the protection element of the fault distance measuring device is started is marked as I1；
The current value of the fault distance measuring device at the moment of one cycle after the protection element is started is recorded as I2；
The current value at the action time of the protection element of the fault distance measuring device is marked as I3；
The no-load current value of the traction network is marked as Ikz。
3. The method for accurately extracting the fault current during the fault of the traction network according to claim 2,
when I is1＝IkzIn time, no locomotive runs before the traction network fails;
when I is1＞IkzIn time, the locomotive is operated before the traction network fails.
4. The method for accurately extracting the fault current during the fault of the traction network according to claim 2,
when formula I3-I2|>IkzWhen the locomotive current sampling device is in the fault state, the fault distance measuring device samples current which does not contain locomotive current at the fault moment;
when formula I3-I2|>IkzWhen the fault is not established, the fault distance measuring device samples current including locomotive current at the fault moment.
5. The method for accurately extracting the fault current during the fault of the traction network according to claim 4,
when formula I3-I2|>IkzWhen the current collected by the fault distance measuring device does not contain the locomotive load current,
fault current as I3；
When formula I3-I2|>IkzIf the fault distance measuring device is not in operation and the collected current of the fault distance measuring device comprises the locomotive load current,
fault current as I3-I1。
6. The method for accurately extracting the fault current during the fault of the traction network according to claim 2,
each cycle is 20 ms.
7. A device for accurately extracting fault current when a traction network fails is characterized by comprising: the device comprises an analysis module, a first calculation module and a second calculation module;
the analysis module is according to whether contain load current in the fault range unit sampling current, divide into the traction network trouble:
the first situation is as follows: no locomotive runs before the fault, and the current sampled by the fault distance measuring device at the fault moment does not contain locomotive current;
case two: the locomotive runs before the fault, the voltage of a traction network is lower than 19kV when the fault occurs, the locomotive trips, and the sampling current of the fault distance measuring device at the fault moment does not contain the locomotive current;
case three: the locomotive runs before the fault, the voltage of a traction network is higher than 19kV when the fault occurs, the locomotive does not trip, and the sampling current of the fault distance measuring device at the fault moment comprises the locomotive current;
when the traction network fails in the first situation or the second situation, the first calculation module outputs a fault current which is a sampling current of the fault distance measuring device;
when the traction network fails, the second calculation module outputs a fault current, namely a sampling current of the fault distance measuring device-a load current before the fault.
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