CN112630686A - Method and system for identifying single-phase earth fault line of urban rail medium-voltage system - Google Patents
Method and system for identifying single-phase earth fault line of urban rail medium-voltage system Download PDFInfo
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- CN112630686A CN112630686A CN202011631820.2A CN202011631820A CN112630686A CN 112630686 A CN112630686 A CN 112630686A CN 202011631820 A CN202011631820 A CN 202011631820A CN 112630686 A CN112630686 A CN 112630686A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/52—Testing for short-circuits, leakage current or ground faults
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Abstract
The invention discloses a method and a system for identifying a single-phase earth fault line of an urban rail medium-voltage system, wherein the method comprises the following steps: measuring zero sequence voltage and zero sequence current in real time; sending each zero sequence current and zero sequence voltage to each power direction identification device; and respectively calculating the real-time zero sequence power of each branch line by each power direction identification device, judging the direction of the real-time zero sequence power of each branch line, and if a certain real-time zero sequence power direction is a branch line flow direction bus, determining that the branch line has a single-phase earth fault. The method and the system for identifying the single-phase earth fault line of the urban rail medium-voltage system utilize each power direction identification device to calculate the zero sequence power in real time, and identify that the branch line has the single-phase earth fault when the direction of the zero sequence power is judged to be that the branch line flows to the bus, so that the branch line with the single-phase earth fault can be conveniently and quickly disconnected from the bus, and the normal operation of other branch lines can be maintained.
Description
Technical Field
The invention relates to a single-phase earth fault line identification method and a single-phase earth fault line identification system, in particular to a single-phase earth fault line identification method and a single-phase earth fault line identification system for an urban rail medium-voltage system by adopting an earth transformer.
Background
In the conventional power system, as shown in fig. 3, T1 is a power supply transformer, A, B, C is a three-phase bus, F1, F2, … …, Fn-1, and Fn are lead wires, C01, C02, … …, C0n-1, and C0n are zero-sequence capacitors to ground of the corresponding lines, Rf is a single-phase grounded transition resistor, X0 is a zero-sequence impedance of a grounded transformer, and RN is a grounded current-limiting resistor.
When the system runs normally, the ABC three phases are balanced and symmetrical, so that the current flowing through the grounding capacitor is relatively small, and the system does not have serious harm to the insulation of the system and the safe operation of equipment. Once the system is earthed in a single phase, the voltage of the same phase connected with the bus is limited to be fault voltage, and the power network is seriously operated in a non-full phase, so that the fault line is determined and tripped in time in a short time, and the reliability and the safety of the system are significant.
Disclosure of Invention
The purpose of the invention is as follows: the method and the system for identifying the single-phase earth fault line of the urban rail medium-voltage system can identify and judge whether each branch line on the bus has the single-phase earth fault, so that the branch line with the single-phase earth fault can be conveniently and quickly disconnected from the bus, and the normal operation of other branch lines is maintained.
The technical scheme is as follows: the invention relates to a method for identifying a single-phase earth fault line of an urban rail medium-voltage system, which comprises the following steps:
step 2, correspondingly sending each zero sequence current to each power direction identification device, and sending the zero sequence voltage measured in real time to each power direction identification device;
and 3, respectively calculating the real-time zero sequence power of each branch line by each power direction identification device, judging the direction of the real-time zero sequence power of each branch line, and if a certain real-time zero sequence power direction is a branch line flow direction bus, determining that the branch line has a single-phase earth fault.
As a further scheme of the method, the method also comprises the following steps:
and 4, the power direction identification device sends an opening signal to the circuit breaker on the corresponding branch line with the single-phase earth fault, so that the branch line is disconnected from the bus.
As a further development of the method, the power direction detection device is a power direction relay and/or a microcomputer protection device.
The invention also provides a single-phase earth fault line identification system of the urban rail medium-voltage system, which comprises a voltage transformer, each zero-sequence current transformer and each power direction identification device;
the voltage transformer is used for being installed on a bus and measuring the zero sequence voltage of the bus in real time;
each zero sequence current transformer is used for being respectively installed on each branch line of the bus and measuring the zero sequence current of each branch line in real time;
each power direction identification device is electrically connected with a voltage transformer and is used for acquiring the zero sequence voltage of the bus;
each power direction identification device is also electrically connected with each zero sequence current transformer respectively and is used for acquiring the zero sequence current of each branch circuit;
each power direction identification device is used for calculating the real-time zero sequence power of each branch line according to the zero sequence voltage and each zero sequence current, judging the direction of the real-time zero sequence power of each branch line, and sending a turn-off signal that a single-phase earth fault exists in the branch line if a certain real-time zero sequence power direction is that the branch line flows to the bus.
As a further scheme of the system, the system also comprises various circuit breakers;
each circuit breaker is used for being respectively connected in series on each branch line and is used for controlling the on-off of each branch line according to the turn-off signal;
each power direction recognition device is also electrically connected with each circuit breaker respectively, and is used for sending a turn-off signal to the corresponding circuit breaker when judging that the single-phase earth fault exists.
As a further development of the system, the power direction detection device is a power direction relay and/or a microcomputer protection device.
Compared with the prior art, the invention has the beneficial effects that: the method comprises the steps of utilizing each power direction identification device to calculate zero sequence power in real time, and identifying that a branch line has a single-phase earth fault when the direction of the zero sequence power is judged to be that the branch line flows to a bus, so that the branch line with the single-phase earth fault can be conveniently and quickly disconnected from the bus, and the normal operation of other branch lines is maintained.
Drawings
FIG. 1 is a schematic diagram of a signal acquisition architecture of the present invention;
FIG. 2 is a schematic diagram of the operation of the present invention;
FIG. 3 is a prior art electrical power system architecture;
fig. 4 is a single-phase zero-sequence current system diagram of a power system in the prior art.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.
In the existing power system, as shown in fig. 3 and 4, F1, F2, … …, Fn-1, Fn are lead-out lines, C01, C02, … …, Cn-1, Cn are zero-sequence capacitors to ground of corresponding lines, I01, I02, … …, I0n-1, I0n, I0N are zero-sequence capacitors to ground of corresponding lines, Rf is a transition resistor of single-phase grounding, X0 is zero-sequence impedance of a grounding transformer, RN is a grounding current-limiting resistor, and Vf is a virtual zero-sequence voltage source. According to the characteristics of the ordered components, only the zero sequence power of the fault line flows to the bus, and the rest zero sequence power flows out of the bus, so that the direction of the zero sequence power can be used for determining the fault line.
Example 1:
as shown in fig. 1 and 2, the method for identifying the single-phase earth fault line of the urban rail medium-voltage system disclosed by the invention comprises the following steps:
step 2, correspondingly sending each zero sequence current to each power direction identification device, and sending the zero sequence voltage measured in real time to each power direction identification device;
and 3, respectively calculating the real-time zero sequence power of each branch line by each power direction identification device, judging the direction of the real-time zero sequence power of each branch line, and if a certain real-time zero sequence power direction is a branch line flow direction bus, determining that the branch line has a single-phase earth fault.
The method comprises the steps of utilizing each power direction identification device to calculate zero sequence power in real time, and identifying that a branch line has a single-phase earth fault when the direction of the zero sequence power is judged to be that the branch line flows to a bus, so that the branch line with the single-phase earth fault can be conveniently and quickly disconnected from the bus, and the normal operation of other branch lines is maintained.
As a further scheme of the method, the method also comprises the following steps:
and 4, the power direction identification device sends an opening signal to the circuit breaker on the corresponding branch line with the single-phase earth fault, so that the branch line is disconnected from the bus.
And the power direction recognition device is used for linkage control with the corresponding circuit breaker, so that the branch line is timely disconnected from the bus when the single-phase earth fault is recognized, and the normal operation of other branch lines is maintained.
As a further development of the method, the power direction detection device is a power direction relay and/or a microcomputer protection device. The power direction relay and the microcomputer protection device can be installed at the same time, and the operation reliability of the method can be ensured.
As shown in fig. 1 and 2, the single-phase earth fault line identification system of the urban rail medium-voltage system disclosed by the invention comprises: the power direction identification device comprises a voltage transformer, each zero sequence current transformer and each power direction identification device;
the voltage transformer is used for being installed on a bus and measuring the zero sequence voltage of the bus in real time;
each zero sequence current transformer is used for being respectively installed on each branch line of the bus and measuring the zero sequence current of each branch line in real time;
each power direction identification device is electrically connected with a voltage transformer and is used for acquiring the zero sequence voltage of the bus;
each power direction identification device is also electrically connected with each zero sequence current transformer respectively and is used for acquiring the zero sequence current of each branch circuit;
each power direction identification device is used for calculating the real-time zero sequence power of each branch line according to the zero sequence voltage and each zero sequence current, judging the direction of the real-time zero sequence power of each branch line, and sending a turn-off signal that a single-phase earth fault exists in the branch line if a certain real-time zero sequence power direction is that the branch line flows to the bus.
As a further scheme of the system, the system also comprises various circuit breakers;
each circuit breaker is used for being respectively connected in series on each branch line and is used for controlling the on-off of each branch line according to the turn-off signal;
each power direction recognition device is also electrically connected with each circuit breaker respectively, and is used for sending a turn-off signal to the corresponding circuit breaker when judging that the single-phase earth fault exists.
As a further development of the system, the power direction detection device is a power direction relay and/or a microcomputer protection device. The power direction relay and the microcomputer protection device can be installed at the same time, and the operation reliability of the system can be ensured.
As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A single-phase earth fault line identification method for an urban rail medium-voltage system is characterized by comprising the following steps:
step 1, installing a voltage transformer on a bus to measure zero sequence voltage in real time, and installing a zero sequence current transformer on each branch line of the bus to measure zero sequence current in real time;
step 2, correspondingly sending each zero sequence current to each power direction identification device, and sending the zero sequence voltage measured in real time to each power direction identification device;
and 3, respectively calculating the real-time zero sequence power of each branch line by each power direction identification device, judging the direction of the real-time zero sequence power of each branch line, and if a certain real-time zero sequence power direction is a branch line flow direction bus, determining that the branch line has a single-phase earth fault.
2. The method for identifying the single-phase earth fault line of the urban rail medium-voltage system according to claim 1, characterized by further comprising the following steps:
and 4, the power direction identification device sends an opening signal to the circuit breaker on the corresponding branch line with the single-phase earth fault, so that the branch line is disconnected from the bus.
3. The method for identifying single-phase earth fault lines of an urban rail medium-voltage system according to claim 1, wherein the power direction identification device is a power direction relay and/or a microcomputer protection device.
4. A single-phase earth fault line identification system of an urban rail medium-voltage system is characterized by comprising voltage transformers, zero-sequence current transformers and power direction identification devices;
the voltage transformer is used for being installed on a bus and measuring the zero sequence voltage of the bus in real time;
each zero sequence current transformer is used for being respectively installed on each branch line of the bus and measuring the zero sequence current of each branch line in real time;
each power direction identification device is electrically connected with a voltage transformer and is used for acquiring the zero sequence voltage of the bus;
each power direction identification device is also electrically connected with each zero sequence current transformer respectively and is used for acquiring the zero sequence current of each branch circuit;
each power direction identification device is used for calculating the real-time zero sequence power of each branch line according to the zero sequence voltage and each zero sequence current, judging the direction of the real-time zero sequence power of each branch line, and sending a turn-off signal that a single-phase earth fault exists in the branch line if a certain real-time zero sequence power direction is that the branch line flows to the bus.
5. The urban rail medium voltage system single-phase ground fault line identification system according to claim 4, further comprising individual circuit breakers;
each circuit breaker is used for being respectively connected in series on each branch line and is used for controlling the on-off of each branch line according to the turn-off signal;
each power direction recognition device is also electrically connected with each circuit breaker respectively, and is used for sending a turn-off signal to the corresponding circuit breaker when judging that the single-phase earth fault exists.
6. The urban rail medium voltage system single-phase ground fault line identification system according to claim 4, characterized in that the power direction identification means are power direction relays and/or microcomputer protection means.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011631820.2A CN112630686A (en) | 2020-12-31 | 2020-12-31 | Method and system for identifying single-phase earth fault line of urban rail medium-voltage system |
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| CN202011631820.2A CN112630686A (en) | 2020-12-31 | 2020-12-31 | Method and system for identifying single-phase earth fault line of urban rail medium-voltage system |
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Cited By (1)
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| CN114019312A (en) * | 2021-11-10 | 2022-02-08 | 国网山东省电力公司临沂供电公司 | Decentralized small-current grounding line selection device and method |
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