Dry-type reactor turn-to-turn short circuit fault monitoring method and system

Abstract

The invention discloses a dry-type reactor turn-to-turn short circuit fault monitoring method and system. The method comprises the following steps: S1, obtaining a zero-sequence voltage 3V0 on a bus of a dry-type reactor; s2, obtaining an evaluation current I0diff of a loop where the dry-type reactor is located; s3, obtaining the zero-sequence current and the negative-sequence current of each phase of the dry-type reactor, and obtaining the phase angle difference between the zero-sequence current and the negative-sequence current of each phase; and S4, according to the zero-sequence voltage 3V0, the evaluation current I0diff and the phase angle difference, judging whether each phase of the dry-type reactor has a turn-to-turn short circuit fault or not. The method has the advantages of high fault monitoring sensitivity and the like.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of dry-type air-core reactors, and in particular to a method and system for monitoring inter-turn short-circuit faults of dry-type reactors. Background Art

[0002] Dry-type air-core reactors have the advantages of low loss, stable parameters, and simple maintenance, and are increasingly widely used in power systems. As a component of reactive power compensation equipment, dry-type air-core reactors are often used in outdoor environments. For areas with complex operating environments, dry-type air-core reactors may suffer from short circuits, fires, and other faults under multiple stresses. According to relevant data, most of the inter-turn short-circuit insulation faults of reactors originate from the damage of local insulation of the coil, which in turn causes the coil to become damp, local discharge to increase, and local overheating to eventually lead to complete destruction of the coil insulation. Considering the outdoor humid and hot operating environment of the reactor, as the service time increases, its surface insulation will inevitably deteriorate to varying degrees, forming tiny partial discharges. As the partial discharge develops, the tiny partial discharge may evolve into tree branch discharge, which in turn leads to the formation of inter-turn short circuits.

[0003] Compared with oil-filled reactors, dry-type air-core reactors do not have mechanical protection devices and gas monitoring to detect turn-to-turn short-circuit faults, but dry-type air-core reactors do not have such protection devices and can only rely on simple directional ground overcurrent to detect such faults.

[0004] The process of dry-type air-core reactor inter-turn short-circuit fault develops rapidly and will cause great harm to the reliability of the power system, so fault diagnosis is very important. However, the dry-type air-core reactor fault diagnosis methods currently used at home and abroad still mainly rely on regular power outages for maintenance. These methods are not time-effective and often advance or lag behind the occurrence time of the fault state, resulting in waste of manpower and financial resources or leaving safety hazards. The research on dry-type air-core reactor fault diagnosis is currently mainly divided into magnetic field, temperature and electrical quantity detection. Among them, the magnetic field and temperature detection methods are often greatly affected by the environment, rely on external facilities, and have poor sensitivity and stability. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a method and system for monitoring inter-turn short-circuit faults of dry-type reactors with high sensitivity.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for monitoring a dry-type reactor turn-to-turn short-circuit fault comprises the following steps:

[0008] S1, obtain the zero-sequence voltage 3V0 on the busbar of the dry-type reactor;

[0009] S2. Obtain the evaluation current I0 of the circuit where the dry-type reactor is located diff ;

[0010] S3, obtaining the zero-sequence current and negative-sequence current of each phase of the dry-type reactor, and obtaining the phase angle difference between the zero-sequence current and the negative-sequence current of each phase;

[0011] S4, based on the zero sequence voltage 3V0, evaluate the current I0 diff The phase angle difference can be used to determine whether a turn-to-turn short-circuit fault occurs in each phase of the dry-type reactor.

[0012] Preferably, the evaluation current I0 in step S2 diff Calculated by the following formula:

[0013]

[0014] Where: CTR is the current transformer ratio; PTR is the potential transformer ratio; I0 is the zero-sequence current of the reactor under test; V0 is the zero-sequence voltage of the reactor under test; R Lim is the calculation coefficient.

[0015] Preferably, the calculation coefficient R Lim The calculation formula is as follows:

[0016]

[0017] Where: V0 ref is the reactor voltage value before the fault; I0 ref is the reactor current value before the fault.

[0018] Preferably, in step S3, the calculation formula of the phase angle difference is:

[0019] θ fault =θ I0 -θ I2 (3)

[0020] Where: θ fault is the phase angle difference; θ I0 is the phase angle of the zero-sequence current flowing through phase A when the turns are short-circuited; θ I2 is the phase angle of the negative sequence current flowing through phase A.

[0021] Preferably, the specific process of step S4 is:

[0022] When the zero-sequence voltage 3V0=0 and the evaluation current I0 diff Greater than the preset standard value I0 diff_ref , the phase angle difference is within the preset threshold and lockout86 is in the locked state, it is determined that a turn-to-turn short circuit fault occurs in the corresponding phase.

[0023] Preferably, in step S4, the corresponding turn-to-turn short-circuit fault signal is outputted after a preset delay time.

[0024] Preferably, the preset threshold is between -5 and +5 degrees.

[0025] The present invention also discloses a computer program product, comprising a computer program, wherein the computer program executes the steps of the method described above when executed by a processor.

[0026] The present invention further discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described above are executed.

[0027] The present invention also discloses a computer device, comprising a memory and a processor connected to each other, wherein a computer program is stored in the memory, and when the computer program is run by the processor, the steps of the method described above are executed.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] The present invention discloses a method for monitoring short-circuit faults of dry-type air-core reactors based on changes in neutral point current. The method uses the changes in current flowing through the neutral point of the dry-type reactor during normal and faulty operation to identify whether a fault has occurred. First, the zero-sequence voltage 3V0 on the bus is measured to determine whether it is an internal fault. Then, the evaluation current I0 is calculated. diff The evaluation current is compared with the pickup current; the phase difference between the zero-sequence current and the negative-sequence current is calculated; finally, 3V0, the difference between the evaluation current and the pickup current, the phase difference between the negative-sequence current and the zero-sequence current, and lockout86 are logically ANDed. If the logic signal is true, it indicates that the fault is a turn-to-turn short circuit fault.

[0030] The fault detection method proposed by the present invention based on the change of neutral point current has higher sensitivity than general methods, can ensure the safe and stable operation of dry-type air-core reactors, and is also suitable for turn-to-turn short-circuit fault monitoring of dry-type shunt reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a circuit diagram of the reactor and busbar of the present invention.

[0032] Figure 2 for Figure 1 Norton equivalent change graph.

[0033] Figure 3 This is a logical diagram of the A-phase fault judgment in the present invention.

[0034] Figure 4The present invention is a flow chart of a dry-type reactor turn-to-turn short-circuit fault monitoring method in an embodiment. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0036] like Figure 4 As shown, the dry-type reactor turn-to-turn short-circuit fault monitoring method according to the embodiment of the present invention comprises the following steps:

[0037] S1. Obtain the zero-sequence voltage 3V0 on the busbar of the dry-type reactor; determine whether it is an internal fault or an external fault of the reactor by whether 3V0 is equal to 0; if 3V0=0, it is an internal fault of the reactor, and if 3V0≠0, it is an external fault of the reactor;

[0038] S2. Obtain the evaluation current I0 of the circuit where the dry-type reactor is located diff ; By evaluating the current I0 diff Compared with the standard value I0 diff_ref (Experience value) to compare to determine whether a fault occurs;

[0039] S3, obtaining the zero-sequence current and negative-sequence current of each phase of the dry-type reactor, and obtaining the phase angle difference between the zero-sequence current and the negative-sequence current of each phase; and determining which phase has a fault by comparing the phase angle difference with a preset threshold;

[0040] S4, based on the zero sequence voltage 3V0, evaluate the current I0 diff The phase angle difference is used to determine whether a turn-to-turn short circuit fault occurs in each phase of the dry-type reactor; the phase of the reactor that fails is determined by combining the above conditions.

[0041] Specifically, Figure 1 The circuit diagram of the reactor and busbar is shown in Figure 1. First, the zero-sequence voltage 3V0 on the busbar is used to determine whether the fault is an internal fault of the dry-type reactor. For an independently operated dry-type reactor, the change of 3V0 on the busbar is caused by the change of the external power system, rather than the small change caused by the internal fault of the reactor. Because in the case of internal fault, 3V0 is 0, and the current flowing through R Lim The current of the dry reactor is I0, the relay resistance is not 0, but no current flows. The left power supply is open because 3V0 is zero because for a three-phase system, the zero-sequence voltage V0 on the bus will only appear due to three-phase imbalance, not due to a small fault inside the reactor. Therefore, 3V0 can be used as a discriminant for internal and external faults of the reactor. That is, for a three-phase system, Figure 2The power supply on the left side is 0. The reason can only be caused by three-phase imbalance outside the reactor, and it will not be caused by minor faults inside the reactor (including inter-turn short circuit). For example, only when three-phase imbalance occurs outside the reactor will 3v0 not be 0, and it will be 0 in all other cases.

[0042] That is to say, for a three-phase system, the zero-sequence voltage (3V0) on the bus is likely to be caused by a single-phase grounding fault, unbalanced load (usually, the zero-sequence voltage caused by unbalanced load is small and can be ignored), insulation damage between transformer windings, system configuration and other faults. For independently operated dry-type reactors, when a small fault such as an inter-turn short circuit occurs inside, a zero-sequence voltage will not appear on the bus. However, when a serious fault occurs on the bus, zero-sequence current and zero-sequence voltage may appear inside the dry-type reactor. At this time, the situation shown by the reactor is consistent with the inter-turn short circuit. Therefore, in order to distinguish that the inter-turn short circuit inside the reactor is not caused by an external fault, an internal and external fault judgment basis 3V0 is set.

[0043] In step S2, Figure 1 The circuit diagram of the reactor and busbar is transformed into the Norton equivalent circuit diagram Figure 2 From this circuit analysis, the calculation formula for evaluating the current can be obtained. Evaluation current I0 diff can be Figure 2 Calculate and get, Figure 2 The leftmost current source is open circuit because 3V0 is zero, so the evaluation current can be calculated by the following formula:

[0044]

[0045] Where: CTR is the current transformer ratio; PTR is the potential transformer ratio; I0 is the zero-sequence current of the reactor under test; V0 is the zero-sequence voltage of the reactor under test.

[0046] Where R Lim To calculate the coefficient, the calculation formula is as follows:

[0047]

[0048] Where: V0 ref is the reactor voltage value before the fault; I0 ref is the reactor current value before the fault; at the same time, a standard value I0 is set diff_ref , which is usually an empirical value.

[0049] In step S3, when determining which phase the fault occurs in, the zero-sequence current of the reactor is independent of the reference system, while the negative-sequence current will change based on the reference system. For example, if a turn-to-turn short circuit occurs in phase A, and the calculation of the zero-sequence current and the negative-sequence current is performed with phase A as the reference system, the phase angles of the zero-sequence current and the negative-sequence current will be approximately the same. However, when the fault occurs on phase B, if the calculation is performed under the same reference system, the negative-sequence current is offset from the zero-sequence current by approximately 120°. Therefore, the calculation formula for identifying the fault phase is shown in Formula 3:

[0050] θ fault =θ I0 -θ I2 (3)

[0051] Where: θ fault is the phase angle difference; θ I0 is the phase angle of the zero-sequence current flowing through phase A when the turns are short-circuited; θ I2 is the phase angle of the negative sequence current flowing through phase A.

[0052] Taking phase A as an example, when a turn-to-turn short circuit fault occurs, the phase angle difference θ fault The value should be between -5 and +5 degrees. If the calculated value is within this range, it can be determined that the fault occurs on phase A.

[0053] In step S4, Figure 3 As shown, a logical AND is performed based on the comparison result of the evaluation current and the pickup current, 3V0, the phase angle difference and the lockout86 lockout signal, and the fault is determined based on the result of the logical AND. Lockout86 is the relay's own lockout signal, and its normal state is 0, in order to avoid false operation due to the relay's own fault. A time delay is introduced after the differential result of the evaluation current and the pickup current to allow the reactor external fault protection function to work first.

[0054] That

[0055] After the A phase fault occurs, the phase angle difference between the zero-sequence and negative-sequence currents is 0°±5°, and 3V0 is measured from the bus to ensure that there is no external fault.

[0056] Taking the inter-turn fault of reactor A phase as an example, when the internal and external fault discrimination value 3V0 is 0, the difference between the evaluation current and the pickup current is greater than the preset value, θ fault If the value is between -5 and +5 and lockout86 is in the locked state, it means that a turn-to-turn short circuit fault has occurred on phase A of the reactor. That is, if the above conditions are met at the same time, a trip signal is issued.

[0057] The present invention discloses a method for monitoring short-circuit faults of dry-type air-core reactors based on changes in neutral point current. The method uses the changes in current flowing through the neutral point of the dry-type reactor during normal and faulty operation to identify whether a fault has occurred. First, the zero-sequence voltage 3V0 on the bus is measured to determine whether it is an internal fault. Then, the evaluation current I0 is calculated. diff The evaluation current is compared with the pickup current; the phase difference between the zero-sequence current and the negative-sequence current is calculated; finally, 3V0, the difference between the evaluation current and the pickup current, the phase difference between the negative-sequence current and the zero-sequence current, and lockout86 are logically ANDed. If the logic signal is true, it indicates that the fault is a turn-to-turn short circuit fault.

[0058] The fault detection method proposed by the present invention based on the change of neutral point current has higher sensitivity than general methods, can ensure the safe and stable operation of dry-type air-core reactors, and is also suitable for turn-to-turn short-circuit fault monitoring of dry-type shunt reactors.

[0059] The present invention also discloses a computer program product, including a computer program, which executes the steps of the above method when executed by a processor. The present invention further discloses a computer-readable storage medium, on which a computer program is stored, which executes the steps of the above method when executed by a processor. The present invention also discloses a dry-type reactor turn-to-turn short-circuit fault monitoring system, including an interconnected memory and a processor, on which a computer program is stored, which executes the steps of the above method when executed by a processor. The product, medium and system of the present invention correspond to the above method and also have the advantages described in the above method.

[0060] The present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiment when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable storage media include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. The memory is used to store computer programs and / or modules, and the processor implements various functions by running or executing computer programs and / or modules stored in the memory, and calling data stored in the memory. The memory may include high-speed random access memory and may also include non-volatile memory, such as a hard disk, an internal memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0061] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A dry-type reactor turn-to-turn short-circuit fault monitoring method, characterized in that: Includes steps: S1, obtain the zero-sequence voltage 3V0 on the busbar of the dry-type reactor; S2. Obtain the evaluation current I0 of the circuit where the dry-type reactor is located diff ; S3, obtaining the zero-sequence current and negative-sequence current of each phase of the dry-type reactor, and obtaining the phase angle difference between the zero-sequence current and the negative-sequence current of each phase; S4, based on the zero sequence voltage 3V0, evaluate the current I0 diff The phase angle difference can be used to determine whether a turn-to-turn short-circuit fault occurs in each phase of the dry-type reactor.

2. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 1, characterized in that: Evaluation current I0 in step S2 diff Calculated by the following formula: Where: CTR is the current transformer ratio; PTR is the potential transformer ratio; I0 is the zero-sequence current of the reactor under test; V0 is the zero-sequence voltage of the reactor under test; R Lim is the calculation coefficient.

3. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 2 is characterized in that: The calculation coefficient R Lim The calculation formula is as follows: Where: V0 ref is the reactor voltage value before the fault; I0 ref is the reactor current value before the fault.

4. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 1, 2 or 3, characterized in that: In step S3, the calculation formula of the phase angle difference is: i fault =θ I0 -θ I2 (3) Where: θ fault is the phase angle difference; θ I0 is the phase angle of the zero-sequence current flowing through phase A when the turns are short-circuited; θ I2 is the phase angle of the negative sequence current flowing through phase A.

5. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 1, 2 or 3, characterized in that: The specific process of step S4 is: When the zero-sequence voltage 3V0=0 and the evaluation current I0 diff Greater than the preset standard value I0 diff_ref , the phase angle difference is within the preset threshold and lockout86 is in the locked state, it is determined that a turn-to-turn short circuit fault occurs in the corresponding phase.

6. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 5, characterized in that: In step S4, the corresponding turn-to-turn short-circuit fault signal is outputted after a preset delay time.

7. The dry-type reactor turn-to-turn short-circuit fault monitoring method according to claim 5, characterized in that: The preset threshold is between -5 and +5 degrees.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are performed.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 7.

10. A dry-type reactor inter-turn short-circuit fault monitoring system, comprising a memory and a processor connected to each other, wherein a computer program is stored in the memory, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 7.

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