Method for judging power-on state of line in medium-voltage distribution transformer

Abstract

The invention discloses a power-on state judgment method for a line in a medium-voltage distribution transformer, and relates to a judgment method capable of monitoring and recognizing the power-on state of a line in a high-voltage winding of the distribution transformer in real time. According to the technical scheme, the method for judging the power-on state of the line in the medium-voltage distribution transformer comprises the following steps of 1, collecting monitoring data in real time; 2, the amplitude and phase of the three-phase current of the high-voltage side of the transformer are calculated in real time through monitoring data; an identification basis is established; and step 3, making a corresponding judgment by judging the identification basis, and sending prompt information under the condition that the fault point is identified. The method provided by the invention fills the monitoring blind area of the traditional power distribution network fault alarm technology, can monitor the operation state of the high-voltage winding of the power distribution transformer in real time, can accurately give an alarm for the internal broken line fault of the winding of the power distribution transformer, gives an alarm at the early stage of fault development, avoids accident expansion, and guarantees the safety of line equipment of the power distribution network.

Description

Technical Field

[0001] The present invention relates to a method for determining the energization status of internal circuits in a medium-voltage distribution transformer, which is capable of real-time monitoring and identification of the energization status of internal circuits in the high-voltage winding of a distribution transformer. Background Technology

[0002] Currently, medium-voltage distribution networks (20kV / 10kV) can alarm and isolate short-circuit and ground faults on feeders. When the fault voltage or current characteristic value reaches the set value, the terminal detection of the substation or feeder can easily detect the fault signal and isolate the fault point in a timely manner according to the protection configuration.

[0003] In practical applications, when a break occurs inside the high-voltage winding of a distribution transformer, the high-voltage side current and low-voltage side voltage will exhibit characteristic numerical and angular changes. Specifically, the three-phase current on the high-voltage side of the distribution transformer will change in amplitude and angle, while the voltage on one phase of the low-voltage side will return to zero. Because distribution transformers generally contain insulating media (such as transformer oil and insulating components), a break in the high-voltage winding will not immediately lead to grounding or a short circuit. Over time, it may further develop into a single-phase grounding or phase-to-phase short-circuit fault, posing a safety hazard that could escalate the accident. This invention proposes a method that can monitor breakage faults inside the high-voltage winding of distribution transformers in real time and issue an alarm in the early stages of fault development, preventing the accident from escalating and ensuring the safety of distribution network lines and equipment. Summary of the Invention

[0004] This invention proposes a method for determining the energization status of lines within a medium-voltage distribution transformer. By monitoring the high-voltage side current and low-voltage side voltage of the distribution transformer in real time, it can accurately alarm for high-voltage winding open circuit faults inside the distribution transformer, issuing alarms in the early stages of fault development to prevent the accident from escalating into single-phase grounding or phase-to-phase short circuits, ensuring the safety of distribution network lines and equipment, and filling the monitoring blind spots of traditional distribution network fault monitoring and alarm technologies.

[0005] Based on the above actual situation, the technical solution of the present invention for a method for determining the energization status of lines inside a medium-voltage distribution transformer is as follows:

[0006] Step 1: Collect monitoring data in real time;

[0007] Step 2: Calculate the amplitude and phase of the three-phase current on the high-voltage side of the transformer in real time using monitoring data; and establish identification criteria.

[0008] Step 3: Make a corresponding judgment based on the identification criteria, and send a prompt message if the fault point is identified.

[0009] Specifically, in step 1, the monitoring data includes high-voltage side voltage, low-voltage side voltage, and current flow.

[0010] More specifically, the high-voltage side voltage and low-voltage side voltage are acquired through voltage transformers, and the energizing current is acquired through current transformers; the low-voltage side voltage can also be acquired through meters or low-voltage fusion terminals.

[0011] The voltage transformers and current transformers mentioned are all commercially available products.

[0012] The aforementioned meters or low-voltage fusion terminals are all commercially available products.

[0013] Specifically, in step 2, the amplitude and phase of the three-phase current on the high-voltage side of the transformer are calculated in real time by collecting the high-voltage side voltage, low-voltage side voltage and energizing current;

[0014] When the amplitude and phase change in accordance with the conditions, first determine whether there is a single-phase grounding. After eliminating the single-phase grounding fault, start the high-voltage winding inside the distribution transformer to determine the open circuit. The zero-sequence voltage of a single-phase grounding can also be directly measured through the open delta of the secondary circuit of the voltage transformer, and the single-phase grounding is used as identification condition 1.

[0015] The three-phase voltage on the low-voltage side is collected synchronously. If there is a line break inside the high-voltage winding, the voltage of one phase on the low-voltage side should be zero. Depending on the location of the break point, the phase with zero voltage value is also different. When a phase winding of the high-voltage winding has no terminal voltage, the corresponding phase terminal voltage of the low-voltage winding is zero. The corresponding situation is used as identification condition 2.

[0016] Specifically, in step 3, the identification condition 1 for the change in amplitude and angle of the three-phase current on the high-voltage side is compared with the identification condition 2 for the three-phase voltage value on the low-voltage side.

[0017] If both occur simultaneously and the corresponding values ​​meet the conditions, it is determined that there is a fault point of high-voltage winding disconnection in the high-voltage winding inside the transformer. At this time, an alarm message can be sent to the equipment operator to eliminate the fault as soon as possible.

[0018] An electronic device includes one or more processors for storing one or more programs, which, when executed by the one or more processors, cause the one or more processors to perform the aforementioned method for determining the energization status of lines within a medium-voltage distribution transformer.

[0019] A storage medium storing a computer program, wherein the computer program is configured to execute the aforementioned method for determining the energization status of lines within a medium-voltage distribution transformer when it is run.

[0020] The method proposed in this invention fills the monitoring blind spot of traditional power distribution network fault alarm technology. It can monitor the operating status of the high-voltage winding of the distribution transformer in real time, accurately alarm the internal open circuit fault of the distribution transformer winding, issue alarms in the early stage of fault development, avoid the accident from escalating, and ensure the safety of the power distribution network line equipment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the working process of the method for determining the energization status of the circuits inside the medium-voltage distribution transformer in this invention;

[0022] Figure 2 This is a schematic diagram of a medium-voltage distribution network feeder in an embodiment of the method for determining the energization status of lines within a medium-voltage distribution transformer according to the present invention;

[0023] Figure 3 This is a schematic diagram of an internal disconnection and grounding of a distribution transformer in an embodiment of the method for determining the energization status of internal circuits in a medium-voltage distribution transformer according to the present invention.

[0024] Figure 4 This is a schematic diagram of the current phasors before and after a wire breakage inside the distribution transformer in an embodiment of the method for determining the energization state of the internal circuits of the medium-voltage distribution transformer of the present invention (the left side is before the wire breakage, and the right side is after the wire breakage). Detailed Implementation

[0025] See attached document Figure 1-4 The present invention provides a further explanation of the method for determining the energization status of the circuits within the medium-voltage distribution transformer.

[0026] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The technical solution of the present invention, a method for determining the energization status of lines within a medium-voltage distribution transformer, is as follows:

[0028] Step 1: Collect monitoring data in real time;

[0029] Step 2: Calculate the amplitude and phase of the three-phase current on the high-voltage side of the transformer in real time using monitoring data; and establish identification criteria.

[0030] Step 3: Make a corresponding judgment based on the identification criteria, and send a prompt message if the fault point is identified.

[0031] Specifically, in step 1, the monitoring data includes high-voltage side voltage, low-voltage side voltage, and current flow.

[0032] More specifically, the high-voltage side voltage and low-voltage side voltage are acquired through voltage transformers, and the energizing current is acquired through current transformers; the low-voltage side voltage can also be acquired through meters or low-voltage fusion terminals.

[0033] The voltage transformers and current transformers mentioned are all commercially available products.

[0034] The aforementioned meters or low-voltage fusion terminals are all commercially available products.

[0035] Specifically, in step 2, the amplitude and phase of the three-phase current on the high-voltage side of the transformer are calculated in real time by collecting the high-voltage side voltage, low-voltage side voltage and energizing current;

[0036] When the amplitude and phase change in accordance with the conditions, first determine whether there is a single-phase grounding. After eliminating the single-phase grounding fault, start the judgment of the high-voltage winding disconnection inside the distribution transformer and use it as identification condition 1.

[0037] The three-phase voltage on the low-voltage side is collected synchronously. If there is a line break inside the high-voltage winding, the voltage of one phase on the low-voltage side should be zero. Depending on the location of the break point, the phase with zero voltage value is also different. When a phase winding of the high-voltage winding has no terminal voltage, the corresponding phase terminal voltage of the low-voltage winding is zero. The corresponding situation is used as identification condition 2.

[0038] Specifically, in step 3, the identification condition 1 for the change in amplitude and angle of the three-phase current on the high-voltage side is compared with the identification condition 2 for the three-phase voltage value on the low-voltage side.

[0039] If both occur simultaneously and the corresponding values ​​meet the conditions, it is determined that there is a fault point of high-voltage winding disconnection in the high-voltage winding inside the transformer. At this time, an alarm message can be sent to the equipment operator to eliminate the fault as soon as possible.

[0040] An electronic device includes one or more processors for storing one or more programs, which, when executed by the one or more processors, cause the one or more processors to perform the aforementioned method for determining the energization status of lines within a medium-voltage distribution transformer.

[0041] A storage medium storing a computer program, wherein the computer program is configured to execute the aforementioned method for determining the energization status of lines within a medium-voltage distribution transformer when it is run.

[0042] See attached document Figure 2In the following schematic diagram of a medium-voltage distribution network feeder, a section of the substation busbar has multiple medium-voltage 10kV outgoing lines A, B, and C. Taking outgoing line A as an example, the line has multiple branch lines, each with multiple distribution transformers. If an internal open-circuit fault occurs in the high-voltage winding of one of the transformers (assuming it is transformer No. 02, with a connection group of Dyn11), in the early stages of fault development, the high-voltage side current and low-voltage side voltage will exhibit characteristic numerical and angular changes. At this time, the three-phase voltage and current on the line side cannot trigger a single-phase ground fault alarm or short-circuit alarm, and the faulty distribution transformer cannot be accurately located.

[0043] When an internal open-circuit fault occurs in the high-voltage winding of a transformer, the amplitude and phase of the three-phase current on the high-voltage side will change according to certain conditions (identification condition 1). At this time, the three-phase voltage on the low-voltage side can be collected, and the voltage of one phase on the low-voltage side should be zero (identification condition 2). Depending on the location of the open-circuit fault, the phase with the zero voltage value will also be different. When a phase winding of the high-voltage side has no terminal voltage, the corresponding phase terminal voltage of the low-voltage winding will be zero. If identification conditions 1 and 2 occur simultaneously, and the corresponding values ​​meet the conditions, it can be determined that there is a fault point (open-circuit fault) in the high-voltage winding of the transformer.

[0044] The phasor relationship formula between the phase current on the high-voltage line side and the line current on the load side of the distribution transformer is as follows, where , , For the phase current phasor on the line side, , , This is the phasor of the line current in the high-voltage winding of the transformer.

[0045] (Formula 1)

[0046] (Formula 2)

[0047] (Formula 3)

[0048] Before an internal disconnection occurs in the high-voltage winding of a distribution transformer, the no-load current is typically 3% to 8% due to internal losses. Load side line current... , , Not zero. After the connection is lost, It becomes zero. , The phasors of the phase currents on the line side before and after the line break are as follows: Figure 4 As shown.

[0049] Depend on Figure 4 It can be seen that, under the condition that the transformer load is basically symmetrical, the amplitude of the two-phase current on the line side is reduced to approximately the original value. (Internal disconnection associated phases, i.e., phases A and C), one phase remains basically unchanged (non-disconnection associated phase, i.e., phase B). Originally, the angle difference between the three phase currents was about 120°. After the internal disconnection, the current of phase B is about 150° different from phases A and C respectively, and the angle difference between phases A and C is about 60°.

[0050] If the three-phase load is unbalanced, according to operational requirements, the three-phase load imbalance of the Dyn series distribution transformer is generally no greater than 25%. After an internal disconnection, the current in phase B on the line side differs from that in phases A and C by approximately 120° to 180°, and the angle difference between phases A and C is between 0° and 120°. The line-side current and the low-voltage load-side voltage before and after the disconnection are shown in the table below.

[0051]

[0052] According to the table above, the internal winding breakage can be determined by comparing the changes in line current and low-voltage load voltage before and after the breakage.

Claims

1. A method for identifying the energized state of a line in a medium-voltage distribution transformer, characterized in that, Step 1, real-time acquisition of monitoring data; Step 2, real-time calculation of the amplitude and phase of the three-phase current at the high-voltage side of the transformer through the monitoring data; and establishing the basis for identification; Step 3, making a corresponding judgment through the identification of the basis, and sending a prompt message in the case of identifying the fault point.

2. The method for identifying the energized state of a line in a medium-voltage distribution transformer according to claim 1, characterized in that, In step 1, the monitoring data includes the high-voltage side voltage, the low-voltage side voltage, and the energized current.

3. The method for identifying the energized state of a line in a medium-voltage distribution transformer according to claim 2, characterized in that, The high-voltage side voltage and the low-voltage side voltage are collected by a voltage transformer, and the energized current is collected by a current transformer; the low-voltage side voltage can also be collected by a meter or a low-voltage fusion terminal.

4. The method for identifying the energized state of a line in a medium-voltage distribution transformer according to claim 1, characterized in that, In step 2, the amplitude and phase of the three-phase current at the high-voltage side of the transformer are calculated in real time through the collected high-voltage side voltage, low-voltage side voltage, and energized current; When the amplitude and phase change in accordance with the conditions, first determine whether there is a single-phase grounding, and after excluding the single-phase grounding fault, start the high-voltage winding breakage judgment inside the distribution transformer, and take it as identification condition 1; Synchronously collect the three-phase voltage at the low-voltage side, if there is a line break in the high-voltage winding, the voltage of one phase at the low-voltage side should be zero; according to the different positions of the break point, the phase with zero voltage value is also different, when there is no terminal voltage for a certain phase of the high-voltage winding, the corresponding low-voltage winding phase terminal voltage is zero, and the corresponding condition is taken as identification condition 2.

5. The method for identifying the energized state of a line in a medium-voltage distribution transformer according to claim 4, characterized in that, In step 3, the identification condition 1 of the amplitude and angle change of the three-phase current at the high-voltage side is compared with the identification condition 2 of the three-phase voltage value at the low-voltage side; If both occur at the same time, and the corresponding values meet the conditions, it is determined that there is a high-voltage winding breakage fault point in the high-voltage winding inside the transformer, at which time an alarm message can be sent to the equipment operator to achieve the fastest fault elimination.

6. An electronic device comprising one or more processors for storing one or more programs, characterized in that, When the one or more programs are executed by the one or more processors, the one or more processors execute the aforementioned method for identifying the energized state of a line in a medium-voltage distribution transformer.

7. A storage medium having a computer program stored therein, characterized in that, wherein The computer program is configured to execute the aforementioned method for identifying the energized state of a line in a medium-voltage distribution transformer when running.

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