Section switch FTU current direction self-adaption method for eliminating regular phase jump

Abstract

The invention discloses a section switch FTU current direction self-adaption method for eliminating regular phase jump. The method comprises the following steps that 1, the FTU of a certain section switch collects # imgabs0 # and # imgabs1 # on the two sides of the section switch under the condition that the section switch is closed, calculates # imgabs2 # in real time, collects # imgabs3 # in real time, calculates a three-phase current phase angle # imgabs4 #, and records the phase angle # imgabs4 #; 2, calculating the phase angle of the three-phase current of the section switch FTU, judging which quadrant of a rectangular coordinate system is operated according to the active power P and reactive power Q flowing through the FTU, and judging and screening load properties; step 3, according to the load change, further screening whether jumping is caused by regular load; and step 4, when the angles of the three-phase current are all crossed quadrant phase jumping of 180 degrees at a certain moment, screening as a power supply mode that the A transformer substation line is transferred to the B transformer substation, and realizing automatic phase reversal in the reference direction of each phase current of each section switch FTU.

Description

Technical Field

[0001] The invention relates to a current direction self-adaptation method for a segmented switch FTU excluding regular phase jumps, and belongs to the technical field of protection and control of power distribution networks. Background Art

[0002] In the ungrounded system, arc suppression coil grounding system, and low resistance grounding system, the 10kV distribution line is divided into several segments by using a section switch to facilitate maintenance and fault isolation. The distribution automation terminal (FTU) is set on the section switch and the tie switch as a device for protecting the 10kV distribution line from faults and realizing distribution network automation (FA). Tie lines m and n are set between the two substations, and m and n are connected through a tie switch, such as Figure 1As shown, when the switch compartment equipment of line m of substation A is under maintenance or part of line m is under maintenance, the line m or the remaining downstream line after the fault is cut off is transferred to substation B for power supply (abbreviated as: power transfer) through the connecting switch; usually, the connecting switches of the two connecting lines m and n are generally in hot standby state (the isolating switches on both sides of the switch are closed and the connecting switches are disconnected). When a section of the distribution line m of the A substation fails, the downstream line of the faulty line m needs to be transferred to the B substation for power supply through the tie switch after the protection and FTU isolate the fault, or the A substation line m and the B substation line n are closed through the tie switch and the corresponding sections are opened (referred to as closing and opening), so that the A substation line is transferred to the B substation for power supply; the power supply has changed, that is, the topological relationship of each section switch on the line m has changed. In order to further correctly identify the fault, the three-phase current of the section switch FTU on the A substation line m or the downstream line after the fault cuts off part of the line segment and the reference direction of the zero-sequence current collected by the zero-sequence current transformer (CT) need to be changed from the A substation bus pointing to the line to the B substation bus pointing to the line (referred to as current reference direction inversion), that is, the power supply has changed, and the current reference direction of the FUT on the corresponding section switch also needs to be changed (inversion). The purpose of this current reference direction inversion is to enable the FUT to correctly measure and identify the fault on these remaining line section switches, otherwise it is easy to misjudge and cause malfunction. Regarding the inversion of the reference direction of the current, although the prior art proposes to automatically adapt to the change in power supply to adjust the inversion of each phase current according to the order in which the voltage transformers (PT) on both sides of the switch are energized; however, for the closing and opening operation to adjust the power supply mode, it is impossible to sense the order in which the PTs are energized, so it cannot be implemented. At present, the main method is still manual adjustment, and full self-adaptation has not been achieved. The present invention proposes a method for a 10kV system that is an ungrounded system, a grounded system through an arc suppression coil, and a low-resistance grounded system, which uses real-time calculation of the phase of each phase current of each segment switch FTU of the 10kV interconnection line. After excluding the phase jump caused by the phase of each phase current caused by the regular load, when it is confirmed that the phase of each phase current of each segment switch FTU has a phase change of about 180°, the reference direction of each phase current of each segment switch FTU is automatically inverted, which serves as the technical basis for the subsequent relay protection scheme. Summary of the invention

[0003] The purpose of the present invention is to calculate the phase of each phase current of each section switch FTU of a 10kV interconnection line in real time in a 10kV system that is an ungrounded system, an arc suppression coil grounded system, or a low-resistance grounded system, and after excluding the phase jump caused by the regular load, confirming that the phase of each phase current of each section switch FTU has a phase change of about 180°, realize automatic inversion of the reference direction of each phase current of each section switch FTU.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for current direction adaptation of a segmented switch FTU eliminating regular phase jumps comprises the following steps:

[0006] Step 1: The FTU of a certain sectionalizer collects the voltage of two single-phase PTs on both sides of the sectionalizer when the sectionalizer is closed. and Calculate the third line voltage in real time Real-time acquisition of phase A current Phase B current Phase C current Calculate the phase angle of the three-phase current of phase A, phase B, and phase C The phase angles of the three-phase currents of phase A, phase B, and phase C are recorded every 15 minutes every day for t1 days;

[0007] Step 2: Calculate the phase angles of the three-phase currents of phases A, B, and C of a certain section switch FTU of the substation line on one side every 15 minutes every day for t1 days, and determine the quadrant of the rectangular coordinate system with P as the horizontal coordinate and Q as the vertical coordinate based on the active power P and reactive power Q flowing through the FTU, and determine and select the nature of the load during this period:

[0008] The positive direction of current, active power P and reactive power Q is from the busbar to the line.

[0009] ⑴ When the active power P and reactive power Q of a certain section switch of the detected line m are both positive, it means that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the first quadrant angle Then the screening line load is the common inductive load.

[0010] ⑵When the active power P of a certain section switch is detected to be negative and the reactive power Q is positive, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of this section switch appears in the second quadrant angle. Then select the active loads of this line that have active power fed back to the grid;

[0011] ⑶ When the active power P and reactive power Q of a certain section switch of the detected line are both negative, it indicates that the phase angles of the three-phase currents of phases A, B and C of the section switch are all in the third quadrant. Then select the active loads of this line that have both active power P and reactive power Q fed back to the grid;

[0012] (4) When the active power P of a certain section switch of the detected line m is positive and the reactive power Q is negative, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the fourth quadrant. Then select the load of this line that has reactive power fed back to the grid;

[0013] Step 3: Based on the load change, further screen whether the load change is caused by a regular load and the current phase has a 180° jump:

[0014] The specific screening methods are as follows;

[0015] (1) When the load changes between adjacent quadrants, it is screened as no 180° jump in current occurs;

[0016] (2) When the load changes as a change between cross quadrants, it is screened as a 180° jump in current;

[0017] ⑶ Check whether the 180° jump of load current is caused by regular load:

[0018] ① Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the third quadrant. When a certain period of time, it changes to run in the first quadrant angle In another period, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the third quadrant angle Or vice versa; the screening produces a regular 180° jump in the current;

[0019] ② Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the second quadrant. When a certain period of time, it changes to run in the fourth quadrant angle In another period, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the second quadrant angle Or vice versa; the screening produces a regular 180° jump in the current;

[0020] Step 4: When at a certain moment, the angles of the three-phase currents of phases A, B, and C of a certain section switch on the calculated line all show a 180° jump in the cross-quadrant phase angle, and the cross-quadrant phase angle jump of the three-phase currents of phases A, B, and C caused by the load law described in step 3 (3) is excluded, the power supply mode of the A substation line transferred to the B substation is selected:

[0021] (1) Delay t2 and send an alarm signal to the dispatching master station;

[0022] (2) Delay t3, the section switch FTU sends a command to execute:

[0023] ① Reverse the polarity of the three-phase current and zero-sequence current of phase A, phase B, and phase C of this section switch;

[0024] ② Enable the protection setting when the three-phase current direction is reversed.

[0025] The purpose of the present invention can also be further achieved by the following technical measures:

[0026] The above-mentioned method for excluding the regular phase jump segment switch FTU current direction adaptation,

[0027] Furthermore, step 1 requires and Voltage, calculate the third line voltage in real time for:

[0028]

[0029] (1) Where: It is the single-phase PT secondary voltage on the segmented switching power supply side. It is the single-phase PT secondary voltage on the load side of the section switch.

[0030] Furthermore, steps 1 to 4 require calculation of phase A Phase B Phase C current The current phase angle calculation formula is:

[0031]

[0032] (2) Phase A or B phase or C phase current The phase angle, The voltage of two single-phase PTs on both sides of the sectionalizer or Or calculate the third line voltage in real time A phase current Or B phase current or C phase current ΦΦ represents AB or BC or CA, and Φ represents phase A or phase B or phase C.

[0033] Furthermore, the calculation formula of the active power P of the switch in this section in steps 2 to 4 is:

[0034] P=P fh -P fd (3)

[0035] (3) In the formula, P fh is the actual active power load of the downstream of the section switch minus the power station load, P fd is the active power generated by the power station downstream of this section switch; when P fh >Pfd , then P is positive; when P fh <P fd , then P is negative;

[0036] The calculation formula of the reactive power Q of this section switch is:

[0037] Q=Q fh -Q fd (4)

[0038] (4) In the formula, Q fh The actual reactive power load of the downstream of the section switch minus the power station load, Q fd is the reactive power generated by the power station downstream of this section switch (including the reactive power compensation capacitor of the substation); when Q fh >Q fd , then Q is positive; when Q fh <Q fd , then Q is negative.

[0039] Preferably, the number of days t1 for detection required in step 1 and step 2 is 3 to 7 days; the delay time t2 required in step 4 is 1 to 2 minutes, and the delay time t3 is 10 to 30 minutes.

[0040] Preferably, the voltage level of the distribution line to which the present invention is applicable is 6kV to 35kV, and the grounding methods used in the 6kV to 35kV system are an ungrounded system, a grounding system via an arc suppression coil, and a low-resistance grounding system.

[0041] By means of the above scheme, the present invention has at least the following advantages:

[0042] 1. The present invention determines whether the power supply of the line is transferred from substation A to substation B by detecting the change of the phase angle of the three-phase current of phase A, phase B and phase C of the sectional switch. The judgment is very accurate, which is conducive to the safe and stable operation of the power grid.

[0043] 2. The present invention can determine whether active power or reactive power is being fed back to the grid in this line by detecting the changing pattern of the phase angle of the three-phase current of phase A, phase B and phase C of the segmented switch, and further distinguish and exclude that the phase angle jump of the three-phase current of phase A, phase B and phase C is caused by the regular jump of the three-phase current phase angle of the regular load, so that the change of the phase angle of the three-phase current of phase A, phase B and phase C when the power supply is transferred from substation A to substation B can be determined more clearly, and the implementation plan is simple and easy.

[0044] 3. The present invention can also verify whether the phase of the line voltage and current is correct and determine the power consumption nature of the line load by detecting the phase angle of the three-phase current of the segment switch A phase, B phase, and C phase.

[0045] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a single line diagram of two 10kV distribution lines of the present invention;

[0047] Figure 2 It is a flow chart of the reverse phase determination of three-phase current in a 10kV power distribution line of the present invention;

[0048] Figure 3 It is a relationship diagram of the phase angles of the currents of each phase of the circuit of the present invention in four quadrants. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0050] In the 10kV system, which is an ungrounded system, a grounding system with arc suppression coils, or a low-resistance grounding system, when a section of the distribution line fails, the downstream line of the faulty line needs to be transferred to another substation for power supply through a connecting switch after the FTU isolates the fault, or some equipment on the line is overhauled. After the power supply is changed, that is, the topology changes, in order to further identify the fault, it is necessary to reverse the three-phase current reference direction of the section switches FTU on these downstream lines to ensure that these section switches FTU can correctly measure, handle faults, and operate FA correctly; the phase of each phase current of each section switch FTU of the 10kV line is calculated in real time, and when the phase jump caused by the regular load is eliminated and it is confirmed that the phase of each phase current of each section switch FTU has a phase change of about 180°, a relay protection method is implemented to automatically reverse the reference direction of each phase current of each section switch FTU. To achieve the above purpose, with Figure 1 Taking substation A line m as an example, the method for substation B line n is the same.

[0051] The circuit used by the present invention has:

[0052] ⑴ Each segmented switch is equipped with single-phase voltage transformers (PT) on the AB phase on the power supply side and the BC phase on the load side;

[0053] ⑵Each section switch is equipped with current transformer (CT) and FTU. FTU is equipped with protection and distribution network automation (FA) functions.

[0054] like Figure 2 As shown, the current direction adaptation method of the segmented switch FTU excluding the regular phase jump includes the following steps:

[0055] Step 1: The FTU of a certain sectionalizer collects the voltage of two single-phase PTs on both sides of the sectionalizer when the sectionalizer is closed. and Calculate the third line voltage in real time Real-time acquisition of phase A current Phase B current Phase C current Calculate the phase angle of the three-phase current of phase A, phase B, and phase C The phase angles of the three-phase currents of phase A, phase B, and phase C are recorded every 15 minutes every day for t1 days;

[0056] Step 2: Calculate the phase angle of the three-phase current of phase A, phase B, and phase C of a certain section switch FTU of line m every 15 minutes every day for t1 days, and determine the quadrant of the rectangular coordinate system with P as the horizontal coordinate and Q as the vertical coordinate based on the active power P and reactive power Q flowing through the FTU, and determine and select the nature of the load during this period:

[0057] The positive direction of current, active power P and reactive power Q is from the busbar to the line.

[0058] ⑴ When the active power P and reactive power Q of a certain section switch of the detected line m are both positive, it means that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the first quadrant angle (See Figure 3 a), the screening line load is a common inductive load.

[0059] ⑵When the active power P of a certain section switch is detected to be negative and the reactive power Q is positive, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of this section switch appears in the second quadrant angle. (See Figure 3 b), then select active loads that have active power fed back to the grid (for example, photovoltaic power stations: generate electricity during the day and not at night);

[0060] ⑶ When the active power P and reactive power Q of a certain section switch of the detected line m are both negative, it indicates that the phase angles of the three-phase currents of phases A, B, and C of the section switch are all in the third quadrant. (See Figure 3 b); then select the active loads of this line whose active power P and reactive power Q are both fed back to the grid (for example, there are power stations such as hydroelectric power generation, which have active power P and reactive power Q fed back to the grid during off-peak hours);

[0061] (4) When the active power P of a certain section switch of the detected line m is positive and the reactive power Q is negative, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the fourth quadrant. (See Figure 3 d); then filter out the loads on this line that have reactive power fed back to the grid (for example, the load is low at night, and the capacitors of reactive power compensation in the user's substation are not removed, which will cause reactive power Q to be fed back to the grid);

[0062] Step 3: Based on the load change, further screen whether the load change is caused by a regular load and the current phase has a 180° jump:

[0063] The specific screening methods are as follows;

[0064] (1) When the change of regular load appears as a change between adjacent quadrants, it is screened as no 180° jump of current occurs;

[0065] ① When the phase angle of the three-phase current of phase A, phase B and phase C of the line m segment switch is running in the first quadrant At some point, it changes to run in the second quadrant angle or vice versa;

[0066] ② When the phase angle of the three-phase current of phase A, phase B and phase C of the line m segment switch is running in the first quadrant At some point, it changes to run in the fourth quadrant angle For example, there is no reactive power reverse transmission during the day, but the capacitor is not removed at night, and reactive power reverse transmission occurs; or vice versa;

[0067] (2) When the change of regular load appears as a change between cross quadrants, it is screened as a 180° jump in current;

[0068] ① When the phase angle of the three-phase current of phase A, phase B and phase C of the line m segment switch is running in the first quadrant At some point, it changes to run in the third quadrant angle or vice versa;

[0069] ② When the phase angle of the three-phase current of phase A, phase B and phase C of the line m segment switch is running in the second quadrant At some point, it changes to run in the fourth quadrant angle or vice versa;

[0070] ⑶ Check whether the 180° jump of load current is caused by regular load:

[0071] ① Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the third quadrant. In the morning or at a certain time, it changes to run in the first quadrant angle In the evening or at another time, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the third quadrant angle Or vice versa; the screening produces a regular 180° jump in the current;

[0072] ② Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the second quadrant. When in the morning or at a certain time, it changes to run in the fourth quadrant angle In the evening or at another time, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the second quadrant angle Or vice versa; the screening produces a regular 180° jump in the current;

[0073] Step 4: When at a certain moment, the angles of the three-phase currents of phases A, B, and C of a certain section switch on the calculated line all show a 180° jump in the cross-quadrant phase angle, and the cross-quadrant phase angle jump of the three-phase currents of phases A, B, and C caused by the load law described in step 3 (3) is excluded, the power supply mode of the A substation line transferred to the B substation is selected:

[0074] (1) Delay t2 and send an alarm signal to the dispatching master station;

[0075] (2) Delay t3, the section switch FTU sends a command to execute:

[0076] ① Reverse the polarity of the three-phase current and zero-sequence current of phase A, phase B, and phase C of this section switch;

[0077] ② Enable the protection setting when the three-phase current direction is reversed.

[0078] The above-mentioned method for excluding the regular phase jump segment switch FTU current direction adaptation,

[0079] Furthermore, step 1 requires and Voltage, calculate the third line voltage in real time for:

[0080]

[0081] (5)Where: It is the single-phase PT secondary voltage on the segmented switching power supply side. It is the single-phase PT secondary voltage on the load side of the section switch.

[0082] Furthermore, steps 1 to 4 require calculation of phase A Phase B Phase C current The current phase angle calculation formula is:

[0083]

[0084] (6) Phase A or B phase or C phase current The phase angle, The voltage of two single-phase PTs on both sides of the sectionalizer or Or calculate the third line voltage in real time A phase current Or B phase current or C phase current ΦΦ represents AB or BC or CA, and Φ represents phase A or phase B or phase C.

[0085] The first quadrant angle in steps 1 to 4 above The range is 0 to 90°, the second quadrant angle The range is 90-180°, the third quadrant angle The range is 180-270°, the fourth quadrant angle The range is 270~360° or -90~0°, and Φ is expressed as A, B, or C.

[0086] Furthermore, the calculation formula of the active power P of the switch in this section in steps 2 to 4 is:

[0087] P=P fh -P fd (7)

[0088] (7) In the formula, P fh is the actual active power load of the downstream of the section switch minus the power station load, P fd is the active power generated by the power station downstream of this section switch; when P fh >P fd , then P is positive; when P fh <P fd , then P is negative;

[0089] The calculation formula of the reactive power Q of this section switch is:

[0090] Q=Q fh -Q fd (8)

[0091] (8) In the formula, Q fh The actual reactive power load of the downstream of the section switch minus the power station load, Q fh is the reactive power generated by the power station downstream of this section switch; when Q fh >Q fd , then Q is positive; when Q fh <Q fd, then Q is negative.

[0092] Taking into account the grid phase error, a 180° phase angle change occurs in step 3 and step 4. When there is no 30° angle difference between the interconnecting switch power supplies, the 180° phase angle is 180°±20°; when there is a 30° angle difference between the interconnecting switch power supplies, the 180° phase angle is 150±20° or 210±20°.

[0093] Preferably, the number of days t1 for detection required in step 1 and step 2 is 3 to 7 days; the delay time t2 required in step 4 is 1 to 2 minutes, and the delay time t3 is 10 to 30 minutes.

[0094] The voltage level of the distribution line applicable to the present invention is 6kV-35kV, and the grounding modes used in the 6kV-35kV system are an ungrounded system, a grounding system through an arc suppression coil, and a low-resistance grounding system.

[0095] The following embodiments all take 10 kV as an example.

[0096] Embodiment 1

[0097] Combination Figure 1 On the basis of the above embodiment, the 10kV line m of the A substation and the 10kV line n of the B substation are connected to each other through a tie switch, and a plurality of section switches ( Figure 1 Three are drawn on the diagram, but there may be more than three in reality). FTU is set on each switch. Normally, the contact switch is disconnected, and the 10kV line m of substation A and the 10kV line n of substation B are powered by their respective substations. Take the sectionalizer 3 on the 10kV line m of substation A as an example:

[0098] The specific embodiments are as follows:

[0099] ⑴ When a ground fault or interphase fault occurs between section switch 1 and section switch 2 on the 10kV line m of substation A, the corresponding protection will trip section switch 1 after necessary delay, and distribution network automation (FA) will trip section switch 2 after necessary delay. FA will close the interconnecting switch after a long delay. Section switch 3 calculates the phase of each phase current, and the phase angle of each phase current of this switch has a 180° (or 150°) phase jump. Within the delay t2, the 180° jump of the phase angle of each phase current is continuously confirmed, and an alarm message is sent to the dispatcher; within the delay t3, continuous judgment is made, and the 180° jump of the phase angle of each phase current is continuously confirmed, eliminating the angle jump and jump period caused by the regular load phase angle change of each phase current, and it is judged that the interconnecting switch has been closed, confirming that this section switch has been powered by substation B through the interconnecting line, and automatically adjusting the current phase and protection setting.

[0100] ⑵When the power supply mode of the 10kV line m of substation A is adjusted through the interconnecting switch, the 10kV line m of substation A is adjusted to supply power to substation B (close the interconnecting switch and open the section switch 1). Section switches 2~3 on the 10kV line m of substation A calculate the current of each phase and determine that a 180° phase jump has occurred in the phase angle of each phase current of this switch. Within the delay t2, it is continuously confirmed that a 180° phase jump has occurred in the phase angle of each phase current, and an alarm message is sent to the dispatcher; within the delay t3, continuous judgment is made and it is continuously confirmed that a 180° phase jump has occurred in the phase angle of each phase current, eliminating the angle jump caused by regular changes in the phase angle of each phase current, and confirming that this section switch has been powered by substation B through the interconnecting line, and automatically performs current phase adjustment and protection setting adjustment.

[0101] ⑶ When the power supply mode of the 10kV line m of substation A is adjusted through the connecting switch, the 10kV line m of substation A, which was originally supplied by substation B, is adjusted to return to substation A (close the section switch 1 and open the connecting switch), the section switches 2~3 on the 10kV line m of substation A, through the calculation of the current of each phase, determine that the phase angle of each phase current of this switch has a 180° phase jump. Within the delay t2, it is continuously confirmed that the phase angle of each phase current has a 180° jump, and an alarm message is sent to the dispatcher; within the delay t3, continuous judgment is made and it is continuously confirmed that the phase angle of each phase current has a 180° jump, which eliminates the angle jump caused by the regular changes in the phase angle of each phase current, confirms that the section switch is powered by substation A, and automatically adjusts the current phase and the protection setting.

[0102] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for current direction adaptation of a segmented switch FTU that eliminates regular phase jumps, characterized in that: The following steps are involved: Step 1: The FTU of a certain sectionalizer collects the voltage of two single-phase PTs on both sides of the sectionalizer when the sectionalizer is closed. and Calculate the third line voltage in real time Real-time acquisition of phase A current Phase B current Phase C current Calculate the phase angle of the three-phase current of phase A, phase B, and phase C The phase angles of the three-phase currents of phase A, phase B, and phase C are recorded every 15 minutes every day for t1 days; Step 2: Calculate the phase angles of the three-phase currents of phases A, B, and C of a certain section switch FTU of the substation line on one side every 15 minutes every day for t1 days, and determine the quadrant of the rectangular coordinate system with P as the horizontal coordinate and Q as the vertical coordinate based on the active power P and reactive power Q flowing through the FTU, and determine and select the nature of the load during this period: The positive direction of current, active power P and reactive power Q is from the busbar to the line. ⑴ When the active power P and reactive power Q of a certain section switch of the detected line m are both positive, it means that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the first quadrant angle The filter line load is a common inductive load, and the first quadrant angle is The range is 0 to 90°; ⑵When the active power P of a certain section switch is detected to be negative and the reactive power Q is positive, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of this section switch appears in the second quadrant angle. Then filter the active loads that have active power fed back to the grid; the second quadrant angle The range is 90 to 180°; ⑶ When the active power P and reactive power Q of a certain section switch of the detected line are both negative, it indicates that the phase angles of the three-phase currents of phases A, B and C of the section switch are all in the third quadrant. Then select the active loads of this line that have both active power P and reactive power Q fed back to the grid; the third quadrant angle The range is 180-270°; (4) When the active power P of a certain section switch of the detected line m is positive and the reactive power Q is negative, it indicates that the phase angle of the three-phase current of phase A, phase B and phase C of the section switch appears in the fourth quadrant. Then filter the load of the line that has reactive power fed back to the grid; the fourth quadrant angle The range is 270 to 360° or -90 to 0°; Step 3: Based on the load change, further screen whether the load change is caused by a regular load and the current phase has a 180° jump: The specific screening methods are as follows; (1) When the load changes between adjacent quadrants, it is screened as no 180° jump in current occurs; (2) When the load changes as a change between cross quadrants, it is screened as a 180° jump in current; ⑶ Check whether the 180° jump of load current is caused by regular load: ① Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the third quadrant. When a certain period of time, it changes to run in the first quadrant angle In another period, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the third quadrant angle Or vice versa; the screening produces a regular 180° jump in the current; ② Within 24 hours, the phase angle of the three-phase current of phase A, phase B and phase C of the switch in this section of the line is originally in the second quadrant. When a certain period of time, it changes to run in the fourth quadrant angle In another period, the phase angle of the three-phase current of phase A, phase B, and phase C of this segment switch returns to the second quadrant angle Or vice versa; the screening produces a regular 180° jump in the current; Step 4: When at a certain moment, the angles of the three-phase currents of phases A, B, and C of a certain section switch on the calculated line all show a 180° jump in the cross-quadrant phase angle, and the cross-quadrant phase angle jump of the three-phase currents of phases A, B, and C caused by the load law described in step 3 (3) is excluded, the power supply mode of the A substation line transferred to the B substation is selected: (1) Delay t2 and send an alarm signal to the dispatching master station; (2) Delay t3, the section switch FTU sends a command to execute: ① Reverse the polarity of the three-phase current and zero-sequence current of phase A, phase B, and phase C of this section switch; ② Enable the protection setting when the three-phase current direction is reversed.

2. The method for current direction adaptation of a segmented switch FTU eliminating regular phase jumps according to claim 1, characterized in that: Step 1 requires and Voltage, calculate the third line voltage in real time for: (1) Where: It is the single-phase PT secondary voltage on the segmented switching power supply side. It is the single-phase PT secondary voltage on the load side of the section switch.

3. The method for current direction adaptation of a segmented switch FTU eliminating regular phase jumps according to claim 1, characterized in that: Steps 1 to 4 require calculation of phase A Phase B Phase C current The current phase angle calculation formula is: (2) Phase A or B phase or C phase current The phase angle, The voltage of two single-phase PTs on both sides of the sectionalizer or Or calculate the third line voltage in real time A phase current Or B phase current or C phase current ΦΦ represents AB or BC or CA, and Φ represents phase A or phase B or phase C.

4. The method for current direction adaptation of a segmented switch FTU eliminating regular phase jumps according to claim 1, characterized in that: The calculation formula for the active power P of the subsection switch in steps 2 to 4 is: P=P fh -P fd (3) (3) In the formula, P fh is the actual active power load of the downstream of the section switch minus the power station load, P fd is the active power generated by the power station downstream of this section switch; when P fh >P fd , then P is positive; when P fh <P fd , then P is negative; The calculation formula of the reactive power Q of this section switch is: Q=Q fh -Q fd (4) (4) In the formula, Q fh The actual reactive power load of the downstream of the section switch minus the power station load, Q fd is the reactive power generated by the power station downstream of this section switch; when Q fh >Q fd , then Q is positive; when Q fh <Q fd , then Q is negative.

5. The method for current direction adaptation of segmented switch FTU eliminating regular phase jump according to claim 1, characterized in that: The number of days t1 required for testing in step 1 and step 2 is 3 to 7 days; the delay time t2 required in step 4 is 1 to 2 minutes, and the delay time t3 is 10 to 30 minutes.

6. The method for current direction adaptation of a segmented switch FTU eliminating regular phase jumps according to claims 1-5, characterized in that: The applicable voltage level of the distribution line is 6kV~35kV. The grounding methods used in the 6kV~35kV system are ungrounded system, arc suppression coil grounding system, and low resistance grounding system.

Images