Polarity verification method for differential protection device of auxiliary power line

Abstract

The invention discloses a polarity verification method for a differential protection device of an auxiliary power line. A verification device comprises a first interconnection switch, a second interconnection switch and a third interconnection switch which are led out from a first bus, and a fourth interconnection switch, a fifth interconnection switch and a sixth interconnection switch which are led out from a second bus. The third interconnection switch is electrically connected with the fourth interconnection switch; the transformer is electrically connected with the sixth interconnection switch; transformer switching-on impact current is adopted, the wave recording functions of protection devices on the two sides of a first bus and a second bus are synchronously started, and the polarity of a line differential protection device is verified by analyzing and comparing the phase relation between wave recording current and voltage. The problem that a traditional method cannot verify the polarity of the auxiliary power protection device is solved from the source, the method is suitable for all scenes, the situation that verification cannot be conducted does not exist, and the accuracy of polarity verification of the protection device is improved. And the safety and the reliability of the operation of the station service power system of the power station are further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of line verification, and relates to a polarity verification method for a differential protection device of a power line used in an industrial plant. Background Art

[0002] The important power lines of the power plant are equipped with optical fiber differential protection. When the differential protection device is put into operation for the first time after modification, the polarity of the differential protection on both sides of the line needs to be verified. Sometimes, the load current in the trial operation mode is too small, and the phase angle or differential current information cannot be directly read through the device sampling, and the polarity cannot be verified. If the polarity is wrong, it will cause the protection device to malfunction, affecting the safe and stable operation of the power station.

[0003] At present, the polarity check of the differential protection device of the power line adopts a small load current, such as Figure 2 In the process, bus 1M is energized and bus 2M is powered off for standby; close the tie switch 1L2 and tie switch 2L1, and use bus 1M to charge bus 2M through tie switch 1L2 and tie switch 2L1. Differential protection device verification: Initial state: bus 1M is energized and normally loaded, tie switch 101 is closed, tie switch 102 is closed, and tie switch 1L2 is open. Bus 2M is powered off, tie switch 2L1 is open, tie switch 201 is open, and tie switch 202 is open. Step 1: Close tie switch 1L2; Step 2: Close tie switch 2L1, and let bus 1M charge bus 2M; Step 3: Read the current and voltage sampling and differential current values ​​of tie switch 1L2 and tie switch 2L1 protection devices; Step 4: Compare the phase value and differential current value of current and voltage. If the angle difference between the current of tie switch 1L2 protection device and the current of tie switch 2L1 protection device is close to 0 degrees, instead of 180 degrees, the polarity of the protection devices on both sides is correct.

[0004] The problem is that when the factory power bus is short, the voltage level is not high, the impedance is small, and when the bus 1M carries the bus 2M, the load current is very small. When the current sampling amplitude is close to 0, the angle often jumps and is unreliable. The collected data cannot guarantee reliability, so the polarity cannot be verified. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a polarity verification method for a differential protection device of a power line in an industrial plant, so as to solve the problems that the current sampling amplitude is small, the angle reading is unreliable, and the polarity verification cannot be performed.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for checking the polarity of a differential protection device for a power plant line, wherein the checking device includes a first contact switch, a second contact switch and a third contact switch derived from a first bus, and a fourth contact switch, a fifth contact switch and a sixth contact switch derived from a second bus; the third contact switch is electrically connected to the fourth contact switch; the transformer is electrically connected to the sixth contact switch; the transformer closing impact current is used to synchronously start the recording function of the protection devices on both sides of the first bus and the second bus, and the polarity of the line differential protection device is checked by analyzing and comparing the phase relationship between the recorded current and the voltage.

[0007] The polarity verification method of the auxiliary power line differential protection device as described above comprises the following steps: S1, initial state, the first busbar is energized and normally loaded, the first and second contact switches are closed, and the third contact switch is open; the second busbar is powered off, and the fourth, fifth and sixth contact switches are open; S2, close the third contact switch; S3, close the fourth connecting switch to allow the first bus to charge the second bus; S4, close the sixth contact switch with transformer, use the transformer impact current to synchronously cause the line protection devices on both sides of the third contact switch and the fourth contact switch to start, and form a wave recording file; S5, relative to the third tie switch, the inrush current flows to the first bus, and the angle between UI is x degrees; relative to the fourth tie switch, the inrush current flows to the second bus, and the angle between UI is x+180 degrees; S6, respectively compare the UI phase angles of the first bus and the second bus to determine whether the polarity of the protection device is correct.

[0008] The main beneficial effects of the present invention are: The transformer closing impact current is used to synchronously start the recording of the protection devices on both sides of the line. By comparing the phase relationship between the recorded current and voltage on both sides, the polarity of the line differential protection device is verified. This solves the problem that the traditional method cannot verify the polarity of the power plant protection device from the source. It is applicable to all scenarios, and there is no situation where verification cannot be performed, which improves the accuracy of the polarity verification of the protection device. This in turn improves the safety and reliability of the power plant power system operation.

[0009] The invention solves the problems that the current sampling amplitude of the original polarity verification device is small, the angle reading is unreliable, and the polarity verification cannot be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0011] Figure 1It is a schematic structural diagram of the polarity verification device of the present invention.

[0012] Figure 2 It is a structural schematic diagram of the original polarity verification device.

[0013] In the figure: a first busbar 1; a first connecting switch 11; a second connecting switch 12; a third connecting switch 13; a second busbar 2; a fourth connecting switch 21; a fifth connecting switch 22; a sixth connecting switch 23; and a transformer 3. DETAILED DESCRIPTION

[0014] like Figure 1~Figure 2 A method for checking the polarity of a differential protection device for a power plant line is disclosed, wherein the checking device comprises a first contact switch 11, a second contact switch 12 and a third contact switch 13 derived from a first busbar 1, and a fourth contact switch 21, a fifth contact switch 22 and a sixth contact switch 23 derived from a second busbar 2; the third contact switch 13 is electrically connected to the fourth contact switch 21; a transformer 3 is electrically connected to the sixth contact switch 23; a transformer closing impact current is used to synchronously start the wave recording function of the protection devices on both sides of the first busbar 1 and the second busbar 2, and the polarity of the line differential protection device is checked by analyzing and comparing the phase relationship between the wave recording current and the voltage.

[0015] Preferably, to perform polarity verification, reliable current sampling data must be obtained. However, for a newly modified protection device, it is not suitable to carry conventional loads on the second bus 2, so as to avoid the extreme situation where there is a fault in the line and the protection device does not function properly and cannot cut off the fault, causing serious consequences. Therefore, it is not possible to obtain current sampling data by increasing conventional loads.

[0016] Preferably, in the configuration of factory power supply, there is often a transformer on the busbar to supply power to the load of the next voltage level. When charging the transformer, there will be a closing impact current. The characteristics of the impact current are: large amplitude, which can reach 6 to 8 times the rated current; the current is biased to one side of the time axis; the decay is fast, and the peak value appears at the first spike and then decreases rapidly. The impact current has a large amplitude, so that usable data can be obtained stably; it is biased to one side of the time axis, which is more conducive to comparing phase relationships; the decay is fast, so there is no need to maintain the power-on state for a long time, which reduces the damage caused by faults in the route.

[0017] In a preferred solution, the polarity verification method of the auxiliary power line differential protection device as described above comprises the following steps: S1, initial state, the first busbar 1 is energized and normally loaded, the first contact switch 11 and the second contact switch 12 are closed, and the third contact switch 13 is open; the second busbar 2 is powered off, and the fourth contact switch 21, the fifth contact switch 22 and the sixth contact switch 23 are open; S2, close the third contact switch 13; S3, close the fourth connecting switch 21, so that the first bus 1 charges the second bus 2; S4, close the sixth contact switch 23 with the transformer 3, and use the impulse current of the transformer 3 to synchronously cause the line protection devices on both sides of the third contact switch 13 and the fourth contact switch 21 to start, forming a wave recording file; S5, relative to the third contact switch 13, the inrush current flows to the first bus 1, and the angle between UI is x degrees; relative to the fourth contact switch 21, the inrush current flows to the second bus 2, and the angle between UI is x+180 degrees; S6, respectively compare the UI phase angles of the first bus 1 and the second bus 2 to determine whether the polarity of the protection device is correct.

[0018] In the above method, based on the characteristics of the closing impact current generated when the transformer is charged, which has a large amplitude, the current is biased to one side of the time axis and decays quickly, the transformer closing impact current is used to synchronously start the recording of the protection devices on both sides of the line. By comparing the phase relationship between the recorded current and the voltage on both sides, the polarity of the line differential protection device can be verified. The accuracy of the polarity verification of the protection device is improved. In turn, the safety and reliability of the operation of the power plant power system are improved.

[0019] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for polarity verification of a differential protection device for a power supply line in an industrial plant, characterized in that: The verification device comprises a first connecting switch (11), a second connecting switch (12) and a third connecting switch (13) derived from a first busbar (1), and a fourth connecting switch (21), a fifth connecting switch (22) and a sixth connecting switch (23) derived from a second busbar (2); the third connecting switch (13) is electrically connected to the fourth connecting switch (21); the transformer (3) is electrically connected to the sixth connecting switch (23); the transformer closing impact current is used to synchronously start the wave recording function of the protection devices on both sides of the first busbar (1) and the second busbar (2); and the polarity of the line differential protection device is verified by analyzing and comparing the phase relationship between the wave recording current and the voltage.

2. The polarity verification method for the differential protection device of the auxiliary power line according to claim 1 is characterized in that: The steps include: S1, initial state, the first busbar (1) is energized and normally loaded, the first contact switch (11) and the second contact switch (12) are closed, and the third contact switch (13) is open; the second busbar (2) is powered off, and the fourth contact switch (21), the fifth contact switch (22) and the sixth contact switch (23) are open; S2, close the third contact switch (13); S3, closing the fourth connecting switch (21) to allow the first busbar (1) to charge the second busbar (2); S4, closing the sixth contact switch (23) with the transformer (3), using the impulse current of the transformer (3) to synchronously cause the line protection devices on both sides of the third contact switch (13) and the fourth contact switch (21) to start, and forming a wave recording file; S5, relative to the third contact switch (13), the impulse current flows toward the first busbar (1), and the angle between UIs is x degrees; relative to the fourth contact switch (21), the impulse current flows toward the second busbar (2), and the angle between UIs is x+180 degrees; S6, respectively comparing the UI phase angles of the first busbar (1) and the second busbar (2) to determine whether the polarity of the protection device is correct.

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