Method for preventing tripping of power supply loop of transformer substation

Abstract

The invention relates to a tripping prevention method for a power supply loop of a transformer substation, and belongs to the technical field of short circuit testing by measuring electrical variables in testing. The method comprises the following steps: firstly, setting interval time to divide moments and setting a threshold value; when each moment is reached, whether load transfer needs to be carried out on the individual terminal box or not is judged according to comparison between the load and the maximum current of the individual terminal box and a threshold value, and a special terminal box is found out; comparing the overall load and the maximum current of the power supply loop with a threshold value to judge whether load transfer needs to be carried out on the special terminal box or not; according to the method, the power supply loop is checked in real time, local load adjustment is performed according to a specific judgment formula, and tripping of the power supply loop of the transformer substation can be timely and effectively prevented.

Description

Technical Field

[0001] This invention relates to a method for preventing tripping in a substation power supply loop, belonging to the technical field of short circuit testing by measuring electrical variables during testing (G01R31 / 52). Background Technology

[0002] In substation power supply systems, such as Figure 1 As shown, typically, two independent power supplies are drawn from the two busbars in the AC room of a substation. These two power supplies are connected to different feeder panels in the AC room, and then connected in series through terminal boxes to form a closed-loop power supply circuit with the two feeder panels as the starting and ending points. However, with the increasingly complex operating environment of substations, power supply loops often trip. Once a terminal box in the loop trips, all the terminal boxes connected in series after it will lose their load, posing a serious threat to the reliability of power supply.

[0003] Currently, traditional power supply loop anti-tripping mechanisms mostly rely on whether the loop current value exceeds the standard as the judgment criterion, but ignore the overall load of the loop. This deficiency often leads to false alarms and missed tripping warnings in the power supply system, ultimately making it difficult to avoid tripping accidents. Summary of the Invention

[0004] The technical problem to be solved by this invention is: how to prevent power supply loop tripping in substations.

[0005] The technical solution proposed by this invention to solve the above-mentioned technical problems is: a method for preventing tripping in a substation power supply loop, comprising the following steps:

[0006] Step 1: Set the interval time m for checking the power supply loop. Record the time of the first check of the power supply loop as the first moment, and the time of the second check of the power supply loop after one interval as the second moment, and so on up to the nth moment.

[0007] Set the first load threshold of the terminal box and the first current threshold ;

[0008] Set the second load threshold for the power supply loop. Second current threshold ;

[0009] Step 2: When the power supply loop reaches time n, based on the incoming three-phase currents of the N terminal boxes collected from time n-1 to time n. , , and outgoing three-phase current , , , the N first integrated three-phase differential currents of the N terminal boxes are obtained by integrating the following formula (1) 、 and

[0010] (1);

[0011] In formula (1), t is a time variable; and are the incoming line A-phase, B-phase and C-phase currents of the i-th terminal box at time variable t within the n-1th moment to the n-th moment, respectively; and are the outgoing line A-phase, B-phase and C-phase currents of the i-th terminal box at time variable t within the n-1th moment to the n-th moment, respectively; is an integrated microelement;

[0012] The maximum value in the N first integrated three-phase differential currents is recorded as , respectively ;

[0013] Step 3: the N first load values of the N terminal boxes are calculated according to the following formula (2)

[0014] (2);

[0015] In all terminal boxes, at least one terminal box is taken as a special terminal box;

[0016] The load connected to the phase with the maximum current in the terminal box is reconnected to the phase with the minimum current, respectively and ;

[0017] Step 4: the second integrated three-phase currents 、 and are obtained by integrating the incoming three-phase currents of the terminal box at the head of the power supply loop within the n-1th moment to the n-th moment according to the following formula (3) 、 and

[0018] (3);

[0019] The maximum value in the second integrated three-phase currents is recorded as ;

[0020] Step 5: the second load value of the power supply loop is calculated according to the following formula (4)

[0021] (4);

[0022] like and In each special terminal box, the load connected to the phase with the maximum current is reconnected to the phase with the minimum current.

[0023] like or It was determined that the power supply loop would not trip.

[0024] Furthermore, the first load threshold Set to 0.8, the first current threshold. Set it to 0.5, the second load threshold. Set to 0.4, the second current threshold. Take 16.

[0025] The beneficial effects of this invention are as follows: First, it reflects the three-phase imbalance of each terminal box based on the individual terminal box load calculation formula, and implements local load adjustment in conjunction with the maximum phase current value of each terminal box. Then, it reflects the overall three-phase imbalance of the power supply loop through the overall loop load calculation formula, and performs precise load transfer in conjunction with the maximum phase current value of the overall loop. Through this dual judgment and transfer mechanism, it is possible to prevent power supply loop tripping in a timely and effective manner. Attached Figure Description

[0026] The following description, in conjunction with the accompanying drawings, further illustrates a method for preventing tripping in a substation power supply loop according to the present invention.

[0027] Figure 1 This is a schematic diagram of the power supply loop in a substation. Detailed Implementation

[0028] Example

[0029] This embodiment of a substation power supply loop tripping prevention method includes the following steps:

[0030] Step 1: Set the interval time for checking the power supply loop to m=1s. Record the time of the first check of the power supply loop as the first moment, and the time of the second check of the power supply loop after one interval as the second moment, and so on up to the nth moment.

[0031] Set the first load threshold of the terminal box =0.8 and the first current threshold =0.5A.

[0032] Set the second load threshold for the power supply loop. =0.4 and the second current threshold =16A.

[0033] Step 2: When the power supply loop reaches the 4th moment, the incoming three-phase currents of the 10 terminal boxes collected between the 3rd and 4th moments are used as the basis. , , and outgoing three-phase current , , The 10 first integral three-phase differential currents of the 10 terminal boxes are obtained by integrating according to the following formula (1). , and

[0034] (1);

[0035] In equation (1), t is a time variable; and These are the incoming A-phase, B-phase, and C-phase currents of the i-th terminal box at time t, from time 3 to time 4. and These are the outgoing phases A, B, and C of the i-th terminal box at time t, from time 3 to time 4. It is an integral infinitesimal element.

[0036] The maximum value among the 10 first integral three-phase differential currents is denoted as: , obtained They are 0.6A, 0.7 A, 0.8 A, 0.9 A, 1.0 A, 0.5 A, 0.4 A, 0.3 A, 0.6 A, 0.7 A respectively.

[0037] Step 3: Calculate the 10 first load values ​​for the 10 terminal boxes according to formula (2).

[0038] (2);

[0039] In all Of the terminal boxes, at least one terminal box is randomly selected as a special terminal box.

[0040] Each and The load connected in the terminal box with the maximum current phase should be reconnected to the phase with the minimum current phase.

[0041] The first load threshold can reflect the three-phase imbalance of the terminal box. The closer the first load threshold is to 1, the more unbalanced the load inside the terminal box is. It is calculated according to formula (2). The values ​​are 0.4, 0.5, 0.6, 0.85, 0.9, 0.3, 0.2, 0.1, 0.55, and 0.65, respectively. Therefore, the loads connected to the phase with the maximum current in the fourth and fifth terminal boxes need to be reconnected to the phase with the minimum current.

[0042] In this embodiment, the first load value is selected. and The corresponding third and fourth terminal boxes are designated as two special terminal boxes.

[0043] Step 4: Based on the incoming three-phase current of the power supply loop terminal box collected between time 3 and time 4. , and The second integral three-phase current is obtained by integrating the equation (3) as follows. =3A、 =3A and =15A

[0044] (3);

[0045] Let the maximum value of the three-phase current in the second integral be denoted as... =15A.

[0046] Step 5: Calculate the second load value of the power supply loop according to formula (4). =0.571

[0047] (4);

[0048] like and In each special terminal box, the load connected to the phase with the maximum current is reconnected to the phase with the minimum current.

[0049] like or It was determined that the power supply loop would not trip.

[0050] The second load threshold can reflect the overall three-phase imbalance of the loop. The closer the second load threshold is to 1, the more unbalanced the overall load of the loop is.

[0051] In this embodiment, due to the second load value =0.571> and Therefore, the loads connected to the maximum current phase in each of the two special terminal boxes were reconnected to the minimum current phase; after the reconnection was completed, the second integral three-phase current... Change to 6A Become 3A and It becomes 12A, and

[0052] ,

[0053] It can be seen that after the load transfer, the maximum phase current of the power supply loop drops to 12A, and the three phases of the loop as a whole tend to be balanced, effectively preventing loop tripping and ensuring the continuity of loop power supply.

[0054] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. All equivalent substitutions or modifications made to the concepts and technical solutions of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preventing tripping in a substation power supply loop, characterized in that... Includes the following steps: Step 1: Set the interval time m for checking the power supply loop. Record the time of the first check of the power supply loop as the first moment, and the time of the second check of the power supply loop after one interval as the second moment, and so on up to the nth moment. Set the first load threshold of the terminal box and the first current threshold ; Set the second load threshold for the power supply loop. Second current threshold ; Step 2: When the power supply loop reaches time n, based on the incoming three-phase currents of the N terminal boxes collected from time n-1 to time n. , , and outgoing three-phase current , , The N first integral three-phase differential currents of the N terminal boxes are obtained by integrating according to the following formula (1). , and （1）； In equation (1), t is a time variable; and These are the incoming A-phase, B-phase, and C-phase currents of the i-th terminal box at time t from time n-1 to time n. and These are the outgoing phases A, B, and C of the i-th terminal box at time t, from time n-1 to time n. It is an integral infinitesimal element; Let the maximum value of each of the N first integral three-phase differential currents be denoted as . Get N ; Step 3: Calculate the N first load values ​​of the N terminal boxes according to the following formula (2). （2）； In all Of the terminal boxes, at least one terminal box may be selected as a special terminal box; Each and The load connected in the terminal box with the maximum current phase should be reconnected to the phase with the minimum current. Step 4: Based on the incoming three-phase current of the power supply loop terminal box collected from time n-1 to time n. , and The second integral three-phase current is obtained by integrating the equation (3) as follows. , and （3）； Let the maximum value of the second integral three-phase current be denoted as... ; Step 5: Calculate the second load value of the power supply loop according to formula (4). （4）； like and In each special terminal box, the load connected to the phase with the maximum current is reconnected to the phase with the minimum current. like or It was determined that the power supply loop would not trip.

2. The substation power supply loop tripping prevention method according to claim 1, characterized in that: First load threshold Set to 0.8, the first current threshold. Set it to 0.5, the second load threshold. Set to 0.4, the second current threshold. Take 16.

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