An AC voltage sampling device for a capacitor, a capacitor protection device and a method

Abstract

The present application discloses a capacitor AC voltage sampling device, a capacitor protection device and a method. The capacitor AC voltage sampling device includes: three groups of voltage transformers; wherein, each group of voltage transformers includes: two primary coils and two secondary coils; the polar ends of each primary coil are respectively used for connecting the corresponding polar ends of the secondary sides of the discharge coils of the corresponding phase capacitors; the non-polar ends of each primary coil are used for connecting the non-polar ends of the secondary sides of the discharge coils of the corresponding phase capacitors; the non-polar ends of the two secondary coils are both grounded, and the polar ends output the acquisition voltage corresponding to the polar ends of the primary coils. When facing different types of capacitor discharge coils, only the connection relationship between the two primary coils and the discharge coils needs to be changed, and there is no need to replace the AC voltage sampling plug-in in the prior art, thereby reducing the operation and maintenance costs and effectively improving the operation and maintenance efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power system safety, and particularly relates to a capacitor AC voltage sampling device, a capacitor protection device and a method. Background Art

[0002] In the prior art, the functions of a capacitor protection device are generally divided into: unbalanced voltage protection and differential pressure protection; when a voltage imbalance fault or a differential pressure fault occurs in a capacitor, the corresponding capacitor protection device can play a corresponding protection role.

[0003] However, due to the different structures of the corresponding capacitor discharge coils under the two protections, the AC voltage sampling plug-in of the capacitor protection device is matched with the discharge coil; when the discharge coil and the AC voltage sampling plug-in are not matched, the capacitor protection device cannot work properly, which increases the probability of capacitor failure.

[0004] If the type of the discharge coil of the capacitor is replaced, the AC voltage sampling plug-in also needs to be replaced accordingly, which will increase the workload of on-site staff and also increase the operation and maintenance costs, resulting in low operation and maintenance efficiency. Summary of the Invention

[0005] In view of this, the present invention provides a capacitor AC voltage sampling device, a capacitor protection device and a method, so that the capacitor protection device can achieve the purpose of detecting various voltage faults without disassembly.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a capacitor AC voltage sampling device, including: three groups of voltage transformers; wherein,

[0008] Each group of the voltage transformers includes: two primary coils and two secondary coils;

[0009] The polar ends of each of the primary coils are respectively used to connect the corresponding polar ends of the secondary sides of the corresponding-phase capacitor discharge coils;

[0010] The non-polar ends of each of the primary coils are used to connect the non-polar ends of the secondary sides of the corresponding-phase capacitor discharge coils;

[0011] The non-polar ends of the two secondary coils are both grounded, and the polar ends output the collected voltages corresponding to the polar ends of the primary coils.

[0012] Optionally, the two primary coils are respectively: a first primary coil and a second primary coil;

[0013] The polar end of the first primary coil is used to connect to the corresponding phase capacitor phase line connection end at the same-name end on the secondary side of its discharge coil;

[0014] The polar end of the second primary coil is used to connect to the corresponding phase capacitor midpoint at the same-name end on the secondary side of its discharge coil;

[0015] The non-polar end of the first primary coil and the non-polar end of the second primary coil are both used to connect to the corresponding phase capacitor neutral point connection end at the same-name end on the secondary side of its discharge coil.

[0016] Optionally, the two secondary coils include: a first secondary coil and a second secondary coil;

[0017] The first secondary coil corresponds to the first primary coil and is used to output the acquisition voltage value of the upper half-branch capacitor of the corresponding phase capacitor;

[0018] The second secondary coil corresponds to the second primary coil and is used to output the acquisition voltage value of the lower half-branch capacitor of the corresponding phase capacitor.

[0019] Optionally, it further includes: a terminal block; wherein,

[0020] The terminal block is fixed on the outer shell of the capacitor protection device;

[0021] The outside of the terminal block is used to connect to the corresponding port on the secondary side of the discharge coil of the corresponding phase capacitor;

[0022] The inside of the terminal block is used to connect to both ends of the corresponding primary coil of each group of the voltage transformers.

[0023] Optionally, it further includes: a support member; wherein,

[0024] The terminal block is arranged on the support member and is fixed on the outer shell of the capacitor protection device through the support member;

[0025] Each group of the voltage transformers is arranged inside the support member.

[0026] The second aspect of the present application provides a capacitor protection device, including: an outer shell, a protection module main body, and the capacitor AC voltage sampling device according to any one of the above first aspects;

[0027] The capacitor AC voltage sampling device is used to collect the voltage of the corresponding port on the secondary side of the discharge coil of each phase capacitor;

[0028] The capacitor AC voltage sampling device outputs the detected voltage to the protection module main body.

[0029] Optionally, the protection module main body is configured to implement differential voltage protection between each phase of capacitors or voltage imbalance protection between each phase of capacitors.

[0030] The third aspect of the present application provides a capacitor protection method, which is applied to the protection module main body of the capacitor protection device as described in the second aspect above. The capacitor protection method includes:

[0031] Obtain each detected voltage output by the capacitor AC voltage sampling device in the capacitor protection device;

[0032] When at least one of the detected voltages exceeds a first preset value, perform differential voltage protection judgment and imbalance protection judgment;

[0033] According to the results of the two judgments, perform corresponding protection or determine that the capacitor is normal.

[0034] Optionally, when performing the differential voltage protection judgment, each of the detected voltages is respectively: the secondary side voltage of the discharge coil corresponding to each of the two series segments of each phase of the capacitor; when performing the imbalance protection judgment, each of the detected voltages is respectively: the secondary side voltage of the discharge coil of each phase of the capacitor; the performing of the differential voltage protection judgment includes:

[0035] Perform a difference calculation on the secondary side voltages of the discharge coils corresponding to each of the two series segments of each phase of the capacitor, and determine whether the absolute value of the corresponding difference of each phase is greater than a second preset value;

[0036] If there is at least one phase where the absolute value of the corresponding difference is greater than the second preset value and the duration of maintenance exceeds a first preset duration, perform a differential voltage protection action;

[0037] If the absolute values of the corresponding differences of each phase are all less than or equal to the second preset value, determine that the capacitor is normal.

[0038] Optionally, the performing of the imbalance protection judgment includes:

[0039] Calculate the absolute value of the sum of each of the detected voltages, and determine whether the absolute value is greater than a third preset value;

[0040] If the absolute value is greater than the third preset value and the duration of maintenance exceeds a second preset duration, perform an imbalance protection action;

[0041] If the absolute value is less than or equal to the third preset value, determine that the capacitor is normal.

[0042] Optionally, each of the detected voltages is respectively: the secondary side detection voltage of the discharge coil corresponding to the upper half branch of each phase of the capacitor and the secondary side detection voltage of the discharge coil corresponding to the lower half branch of each phase of the capacitor;

[0043] After obtaining the respective detected voltages output by the capacitor AC voltage sampling device in the capacitor protection device, it further includes:

[0044] Determine whether the absolute values of the detected voltages on the secondary sides of the discharge coils corresponding to the upper half branches of each phase of the capacitor are all less than the first preset value;

[0045] If there is at least one phase where the absolute value of the detected voltage on the secondary side of the discharge coil corresponding to the upper half branch of the capacitor is greater than or equal to the first preset value, then before the capacitor closing time arrives, determine whether the absolute value of the sum of the detected voltages on the secondary sides of the discharge coils corresponding to the upper half branches of each phase of the capacitor, or the absolute value of the sum of the detected voltages on the secondary sides of the discharge coils corresponding to the lower half branches of each phase of the capacitor, is greater than the third preset value and the duration exceeds the second preset duration; if so, perform a protection action; if not, then after the capacitor closing time arrives, determine whether the absolute value of the detected voltage on the secondary side of the discharge coil corresponding to the lower half branch of each phase of the capacitor exceeds the first preset value; if so, perform the steps of differential voltage protection judgment and unbalance protection judgment;

[0046] If the absolute values of the detected voltages on the secondary sides of the discharge coils corresponding to the upper half branches of each phase of the capacitor are all less than the first preset value, then determine whether the absolute values of the detected voltages on the secondary sides of the discharge coils corresponding to the lower half branches of each phase of the capacitor are all less than the first preset value; if so, return to perform the step of determining whether the absolute values of the detected voltages on the secondary sides of the discharge coils corresponding to the upper half branches of each phase of the capacitor are all less than the first preset value; if not, output a voltage abnormality alarm signal.

[0047] The present invention provides a capacitor AC voltage sampling device, which is composed of three groups of voltage transformers. Each group of voltage transformers includes two primary coils and two secondary coils; wherein, the polar ends of each primary coil are respectively used to connect the corresponding polar ends of the secondary sides of the discharge coils of the corresponding phase of the capacitor; the non-polar ends of each primary coil are used to connect the non-polar ends of the secondary sides of the discharge coils of the corresponding phase of the capacitor; the non-polar ends of the two secondary coils are both grounded, and the polar ends output the acquisition voltages corresponding to the polar ends of the primary coils. When facing different types of capacitor discharge coils, only the connection relationship between the two primary coils and the discharge coils needs to be changed, and there is no need to replace the AC voltage sampling plug-in in the prior art, thereby reducing the operation and maintenance costs and effectively improving the operation and maintenance efficiency. Description of the Drawings

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0049] Figure 1 Structural schematic diagram of a capacitor AC voltage sampling device provided by an embodiment of the present invention;

[0050] Figure 2a Wiring diagram of a capacitor AC voltage sampling device and the secondary side of a capacitor provided by an embodiment of the present invention;

[0051] Figure 2b Another wiring diagram of a capacitor AC voltage sampling device and the secondary side of a capacitor provided by an embodiment of the present invention;

[0052] Figure 3 Another structural schematic diagram of a capacitor AC voltage sampling device provided by an embodiment of the present invention;

[0053] Figure 4 Another structural schematic diagram of a capacitor AC voltage sampling device provided by an embodiment of the present invention;

[0054] Figure 5 Another structural schematic diagram of a capacitor AC voltage sampling device provided by an embodiment of the present invention;

[0055] Figure 6 Structural schematic diagram of a capacitor protection device provided by an embodiment of the present invention;

[0056] Figure 7 Flowchart of a capacitor protection method provided by an embodiment of the present invention;

[0057] Figure 8 Flowchart of a capacitor protection method provided by an alternative embodiment of the present invention;

[0058] Figure 9 Flowchart of a capacitor protection method provided by another alternative embodiment of the present invention. Detailed implementation manners

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0060] The present invention provides a capacitor AC voltage sampling device, and its circuit structure is as Figure 1 shown, including: three groups of voltage transformers. Among them:

[0061] The three groups of voltage transformers are respectively a phase-A voltage transformer, a phase-B voltage transformer, and a phase-C voltage transformer.

[0062] A voltage transformer is an indispensable electrical appliance in power generation plants, substations and other power transmission and supply systems. By using a voltage transformer, high voltage can be transformed into a standard secondary voltage of 100V or a lower level according to a proportional relationship for use in protection, metering, and instrument devices. At the same time, using a voltage transformer can also isolate the high voltage from electrical workers, thus ensuring the safety of the workers.

[0063] Each group of voltage transformers includes: two primary coils 101 and two secondary coils 102; Figure 1 Taking the phase-A voltage transformer as an example for display.

[0064] The polarity ends of the primary coil 101 are respectively used to connect the corresponding polarity ends of the secondary side of the capacitor discharge coil of the corresponding phase.

[0065] The non-polarity ends of the primary coil 101 are used to connect the non-polarity ends of the secondary side of the capacitor discharge coil of the corresponding phase.

[0066] See Figure 1 , where * indicates that this is the polarity end. Inside the phase-A voltage transformer, the polarity ends of its primary coil 101 are respectively A1 and A2, and the non-polarity end is AX; inside the phase-B voltage transformer, the polarity ends of its primary coil 101 are respectively B1 and B2, and the non-polarity end is BX; inside the phase-C voltage transformer, the polarity ends of its primary coil 101 are respectively C1 and C2, and the non-polarity end is CX.

[0067] Specifically, in each group of voltage transformers, its two primary coils 101 can be respectively denoted as: the first primary coil 201 and the second primary coil 202 ( Figure 2a and Figure 2b shown).

[0068] Taking the phase-A as an example, the polarity end of the first primary coil 201 is used to connect the same-name end of the secondary side of the corresponding-phase capacitor phase wire connection end in its discharge coil.

[0069] The polarity end of the second primary coil 202 is used to connect the same-name end of the secondary side of the corresponding-phase capacitor midpoint in its discharge coil.

[0070] The non-polarity end of the first primary coil 201 and the non-polarity end of the second primary coil 202 are both used to connect the same-name end of the secondary side of the corresponding-phase capacitor neutral point connection end in its discharge coil.

[0071] Specifically, among each group of voltage transformers, taking the voltage transformer of phase A as an example for illustration, as Figure 2a shown, the polar end A1 of its first primary coil 201 is used to connect the corresponding phase capacitor phase line connection end 205 to the secondary side homonymous end 206 of its discharge coil, and is the homonymous end with the polar end of a secondary coil 203; the polar end A2 of its second primary coil 202 is used to connect the corresponding phase capacitor midpoint to the secondary side homonymous end 207 of its discharge coil, and is the homonymous end with the polar end of another secondary coil 204; the non-polar end AX of the second primary coil 202 is used to connect the capacitor neutral point N connection end 208 to the secondary side homonymous end 209 of its discharge coil.

[0072] Moreover, the non-polar ends of the two secondary coils 102 are both grounded, and the polar ends output the acquisition voltage corresponding to the polar end of the primary coil 101 (as Figure 1 shown, the end with "*" is the polar end, and the end without "*" is the non-polar end).

[0073] Specifically, the two secondary coils 102 include: the first secondary coil 203 and the second secondary coil 204 ( Figure 2a and Figure 2b shown).

[0074] The first secondary coil 203 corresponds to the first primary coil 201 and is used to output the acquisition voltage value of the upper half-branch capacitor of the corresponding phase capacitor.

[0075] The second secondary coil 204 corresponds to the second primary coil 202 and is used to output the acquisition voltage value of the lower half-branch capacitor of the corresponding phase capacitor.

[0076] The specific working principle is as follows:

[0077] For the protection of the capacitor, first use the capacitor AC voltage sampling device to sample the voltage of each phase capacitor, and then judge and process the sampling result through the subsequent equipment of the capacitor protection device, and perform corresponding protection when a fault is determined. The capacitor protection device is divided into an unbalanced voltage protection device and a differential pressure protection device.

[0078] Taking the voltage transformer of phase A as an example, the current of the capacitor AC voltage sampling device during operation can be as Figure 2a and Figure 2b shown by the dotted line with an arrow in the figure, where the primary current is represented by i1 and the secondary current is represented by i2.

[0079] As Figure 2a shown, when performing differential pressure protection, the capacitor AC voltage sampling device is correspondingly connected to the secondary side of the discharge coil of each phase capacitor (as Figure 2aAs shown by the dashed lines in each case, still taking the A-phase voltage transformer as an example, the polar end A1 of its first primary coil 201 is connected to the corresponding-phase capacitor phase wire connection end 205, which is the same-named end 206 of the secondary side of the discharge coil. The polar end A2 of its second primary coil 202 is used to connect to the midpoint of the corresponding-phase capacitor, which is the same-named end 207 of the secondary side of its discharge coil. The non-polar end AX of its second primary coil 202 is connected to the neutral point N connection end 208 of the capacitor, which is the same-named end 209 of the secondary side of its discharge coil. At this time, the primary current i1 flows into from the polar ends A1 and A2 of the two primary coils 101 respectively, and the secondary current i2 flows out from the polar ends of the two secondary coils 102 respectively, and the voltage values of each phase are collected, where the polar ends of the two primary coils 101 and the polar ends of the two secondary coils 102 are the same-named ends. At this time, this capacitor AC voltage sampling device can detect the voltage of two series segments X C / 2 of each phase capacitor (such as Figure 2a shown as Ua1, Ua2, Ub1, Ub2, Uc1 and Uc2 in C ); then, the corresponding subsequent equipment in the differential protection device can calculate the voltage difference ΔU A , ΔU B and ΔU C between two series segments X A / 2 of each phase capacitor, where ΔU B =|Ua1 - Ua2|, ΔU C =|Ub1 - Ub2|, ΔU A =|Uc1 - Uc2|; then compare ΔU B , ΔU C with zero respectively; if any voltage difference is not zero, it means that the capacitor of this phase has a fault. After a delay time t, the protection action can be executed.

[0080] As Figure 2b shown, when performing unbalance protection, the capacitor AC voltage sampling device is correspondingly connected to the secondary side of the capacitor discharge coil (such as Figure 2bAs shown by the dotted lines in each figure, still taking the A-phase voltage transformer as an example, the polar end A1 of its first primary coil 201 is connected to the corresponding-phase capacitor phase wire connection end 205 at the same-name end 206 on the secondary side of its discharge coil. The non-polar ends AX of its two primary coils 101 are connected to the capacitor neutral point N connection end 207 at the same-name end 208 on the secondary side of its discharge coil. And the polar end A2 of its first primary coil 201 is placed in an empty state and is not connected to other terminals correspondingly. At this time, the primary current i1 flows into from the polar end A1 of the first primary coil 201, and the secondary current i2 flows out from the polar end of the first secondary coil 203 corresponding to the polar end A1, and the voltage values of each phase are collected. Among them, the polar end of the first primary coil 201 and the polar end of the first secondary coil 203 are the same-name ends. At this time, this capacitor AC voltage sampling device can detect the terminal voltage on each-phase capacitor X C and the corresponding characterization values of (such as Ua1, Ub1, and Uc1 shown in Figure 2b ); then the Ua1, Ub1, and Uc1 obtained are connected in an open delta through the secondary coil of the voltage transformer to obtain the zero-sequence voltage value U0; if the zero-sequence voltage value U0 is not zero, it indicates that the capacitor X C has a fault. After a delay time t, the protection action can be executed.

[0081] The capacitor AC voltage sampling device provided in this embodiment can, according to different capacitor fault detection requirements, obtain the voltage values of each-phase capacitor by changing the wiring method for real-time monitoring; it can improve the efficiency of detecting capacitor faults.

[0082] On the basis of the above embodiment, in this capacitor AC voltage sampling device, connection terminals can also be added. The connection terminals are fixed on the outer shell of the capacitor protection device and specifically include Figure 3 the interfaces A1, A2, AX, B1, B2, BX, C1, C2, and CX shown in Figure 2a ; the outside of the connection terminals is used to connect the corresponding ports on the secondary side of the discharge coil of the corresponding-phase capacitor; the inside of the connection terminals is used to connect both ends of the corresponding primary coil of each group of voltage transformers (such as

[0083] the interfaces A1, A2, and AX shown in Figure 3 ). In actual application, when this capacitor protection device is an unbalance protection device, Figure 3 the interfaces A2, B2, and C2 in Figure 3 are all suspended. When this capacitor protection device is a differential pressure protection device, Figure 3 the interfaces A2, B2, and C2 in Figure 3 are also in a connected state. Whether it is unbalance protection or differential pressure protection, Figure 3 the interfaces A1, AX, B1, BX, C1, and CX in Figure 3 are all in a connected state.

[0084] Specifically, by inserting the wires at the corresponding ports on the secondary side of the external capacitor discharge coil into the corresponding interfaces of this terminal block, the connection between the capacitor AC voltage sampling device and the secondary side of the capacitor discharge coil can be achieved.

[0085] Furthermore, in this capacitor AC voltage sampling device, a support member 301 can be added. As Figure 4 shown, this terminal block is arranged on the support member 301 and fixed to the outer shell of the capacitor protection device through the support member 301.

[0086] Moreover, each group of voltage transformers in this capacitor AC voltage sampling device can be arranged inside the support member 301, so that the entire capacitor AC voltage sampling device can be installed on the corresponding outer shell of the capacitor protection device in the form of a plug-in.

[0087] Specifically, the support member 301 can be a support plate, a steel plate, an aluminum plate, or other components with a support function.

[0088] Using the support member 301 can facilitate the installation and disassembly between this terminal block and the outer shell of the capacitor protection device, and improve the assembly and maintenance speed of the capacitor protection device.

[0089] Even further, in this capacitor AC voltage sampling device, a fixing member 401 can be added. As Figure 5 shown, the fixing member 401 is used to fix the support member 301 on the outer shell of the capacitor protection device.

[0090] Specifically, the fixing member 401 includes: a series of components with a fixing function such as screws or tenons.

[0091] Using the fixing member 401 can fix the support member 301 more firmly on the outer shell of the capacitor protection device, and increase the safety and reliability during use.

[0092] Another embodiment of this application also provides a capacitor protection device, which is as Figure 6 shown, and specifically includes: an outer shell 501, a protection module main body 502, and a capacitor AC voltage sampling device 503 as described in any one of the above first aspects; wherein:

[0093] This capacitor AC voltage sampling device 503 is used to collect the voltages at the corresponding ports on the secondary side of each phase of the capacitor discharge coil.

[0094] This capacitor AC voltage sampling device 503 outputs the sampled voltage to the protection module main body 502 ( Figure 6 the wiring between the two is not shown).

[0095] In practical applications, the capacitor AC voltage sampling device 503 can be installed on the housing 501 of the capacitor protection device in the form of a plug, which is convenient for installation and maintenance.

[0096] Optionally, the protection module main body 502 is used to implement: differential protection between each phase of capacitors, or voltage imbalance protection between each phase of capacitors.

[0097] When performing differential protection, the capacitor AC voltage sampling device 503 samples the voltages of two series segments X / 2 of each phase of capacitors (such as Ua1, Ua2, Ub1, Ub2, Uc1, and Uc2 shown in C ), and outputs them to the protection module main body 502; then, the protection module main body 502 calculates the voltage differences ΔU Figure 2a , ΔU C , and ΔU A , ΔU B , and ΔU C between two series segments X / 2 of each phase of capacitors; and when any voltage difference is not zero, it is determined that the capacitor of this phase has a fault, and after a delay time t, a differential protection action is executed.

[0098] When performing imbalance protection, the capacitor AC voltage sampling device 503 collects the corresponding characterization values of the terminal voltages of each phase of capacitors and (such as Ua1, Ub1, and Uc1 shown in Figure 2b ), and outputs them to the protection module main body 502; then, the protection module main body 502 connects the obtained Ua1, Ub1, and Uc1 in an open delta to obtain a zero-sequence voltage value U0; and when the zero-sequence voltage value U0 is not zero, it is determined that the capacitor bank has a fault, and after a delay time t, an imbalance protection action is executed.

[0099] For the capacitor protection device provided in this embodiment, for different capacitor fault detection requirements, by changing the wiring mode between its capacitor AC voltage sampling device 503 and external devices, the voltage values of each phase of capacitors can be obtained for real-time monitoring, thereby improving the efficiency of detecting capacitor faults.

[0100] Another embodiment of the present application further provides a capacitor protection method, as shown in Figure 7 , which is applied to the protection module main body of the capacitor protection device in the previous embodiment. The capacitor protection method includes:

[0101] S601. Obtain each detection voltage output by the capacitor AC voltage sampling device in the capacitor protection device.

[0102] Specifically, when performing differential pressure protection judgment, the detected voltages are respectively: the secondary side voltages of the discharge coils corresponding to the two series segments of each phase capacitor (such as Figure 2a Ua1, Ua2, Ub1, Ub2, Uc1, and Uc2 shown in

[0103] Specifically, when performing unbalance protection judgment, the detected voltages are respectively: the secondary side voltages of the discharge coils of each phase capacitor (such as Figure 2b Ua1, Ub1, and Uc1 shown in

[0104] In practical applications, this step S601 can be executed in real time or periodically, depending on its specific application environment, and all are within the protection scope of this application.

[0105] S602. When there is at least one detected voltage exceeding the first preset value U1, perform differential pressure protection judgment and unbalance protection judgment.

[0106] Optionally, this step S602 includes two judgment processes, namely: differential pressure protection judgment and unbalance protection judgment.

[0107] When performing differential pressure protection judgment, it specifically includes the following process:

[0108] (1) Calculate the difference of the secondary side voltages of the discharge coils corresponding to the two series segments of each phase capacitor (such as Figure 2a Ua1, Ua2, Ub1, Ub2, Uc1, and Uc2 shown in A ΔU B and ΔU C , where ΔU A =|Ua1 - Ua2|, ΔU B =|Ub1 - Ub2|, ΔU C =|Uc1 - Uc2|; then compare the absolute value of the corresponding difference of each phase, ΔU A or ΔU B or ΔU C with the second preset value U2 respectively.

[0109] (2) If there is at least one absolute value of the corresponding difference, ΔU A , ΔU B and ΔU C is greater than the second preset value U2 and the duration is longer than the first preset duration t1, then perform the differential pressure protection action.

[0110] Specifically, dt1 is the duration when |Ua1 - Ua2| > U2, or |Ub1 - Ub2| > U2, or |Uc1 - Uc2| > U2, and dt1 calculates the time difference starting from 0 each time. If there is at least one phase where |Ua1 - Ua2| > U2, or |Ub1 - Ub2| > U2, or |Uc1 - Uc2| > U2 and dt1 >= t1 (as shown in Figure 9 step S807 in

[0111] ), the protection module main body of the capacitor protection device performs a differential pressure protection action.

[0112] (3) If the absolute value of each corresponding difference is less than or equal to the second preset value U2, it is determined that the capacitor is normal.

[0113] Specifically, when |Ua1 - Ua2| <= U2, |Ub1 - Ub2| <= U2, and |Uc1 - Uc2| <= U2 all hold, the protection module main body of the capacitor protection device determines that the capacitor is normal.

[0114] When performing unbalance protection judgment, it specifically includes the following process: Figure 2b (1) Calculate the absolute value of the sum of each detected voltage (such as Ua1, Ub1, and Uc1 shown in

[0115] ), and determine whether this absolute value is greater than the third preset value U3.

[0116] (2) If this absolute value |Ua1 + Ub1 + Uc1| is greater than the third preset value U3 and the duration exceeds the second preset duration t2, perform an unbalance protection action.

[0117] Specifically, dt2 is the duration when |Ua1 + Ub1 + Uc1| > U3, and dt2 calculates the time difference starting from 0 each time. If |Ua1 + Ub1 + Uc1| > U3 and dt2 >= t2 (as shown in Figure 9 step S806 in

[0118] (3) If this absolute value is less than or equal to the third preset value, it is determined that the capacitor is normal.

[0119] Specifically, when |Ua1 + Ub1 + Uc1| <= U2 holds, the protection module main body of the capacitor protection device determines that the capacitor is normal.

[0120] S603. According to the results of the two judgments, perform corresponding protection or determine that the capacitor is normal.

[0121] Specifically, according to the comparison result obtained by comparing the difference or sum of the detection voltages of differential protection and unbalance protection with the preset value in step S602, it is determined whether the capacitor performs a protection action or determines that the capacitor is normal. For specific details, please refer to the above content.

[0122] In this embodiment, by comparing each detection voltage output by the capacitor AC voltage sampling device with the first preset value U1, it is determined whether to perform differential protection and unbalance protection. Further, according to the judgment result, corresponding protection is determined or it is determined that the capacitor is normal. Through this capacitor protection method, the detected voltage value can be judged, so as to make corresponding protection actions, which can ensure the safety and reliability of the capacitor during operation, and further effectively improve the efficiency of the capacitor during operation and maintenance.

[0123] Based on the previous embodiment, this embodiment describes the process of obtaining each detection voltage output by the capacitor AC voltage sampling device in the capacitor protection device in step S601. Specifically, when performing differential protection judgment, each detection voltage is respectively: the secondary side voltage of the discharge coil corresponding to the two series segments of each phase capacitor; when performing unbalance protection judgment, each detection voltage is respectively: the secondary side voltage of the discharge coil of each phase capacitor. After obtaining each detection voltage output by the capacitor AC voltage sampling device in the capacitor protection device in this embodiment, it may specifically further include Figure 8 Another flowchart of the capacitor protection method as shown in, specifically including the following steps:

[0124] S701. Judge whether the absolute value of the secondary side detection voltage of the discharge coil corresponding to the upper half branch of each phase capacitor is less than the first preset value.

[0125] Specifically, the absolute values of the secondary side detection voltages of the discharge coils corresponding to the upper half branches of each phase capacitor are |Ua1|, |Ub1|, and |Uc1|. Compare |Ua1|, |Ub1|, and |Uc1| with the first preset value U1 to judge whether it is less than the first preset value U1.

[0126] Specifically, if there is at least one phase capacitor whose absolute value of the secondary side detection voltage of the discharge coil corresponding to the upper half branch is greater than or equal to the first preset value, then execute step S702.

[0127] S702. Before the capacitor closing time arrives, judge whether the absolute value of the sum of the secondary side detection voltages of the discharge coils corresponding to the upper half branches of each phase capacitor, or the absolute value of the sum of the secondary side detection voltages of the discharge coils corresponding to the lower half branches of each phase capacitor, is greater than the third preset value and the duration exceeds the second preset duration.

[0128] Specifically, if any of the following conditions is met: |Ua1| >= U1 or |Ub1| >= U1 or |Uc1| >= U1, when before the capacitor closing time arrives (i.e., as shown in Figure 9 "t < T" in

[0129] ), determine the relationship between the absolute value of the sum of the detected voltages |Ua1 + Ub1 + Uc1| and the third preset value U3 and maintain it for a duration exceeding the second preset duration t2. If so, execute step S703; if not, execute step S704.

[0130] S703. Execute the protection action.

[0131] Specifically, if the conditions in step S702 are met, execute the protection action; if not and when after the capacitor closing time arrives (i.e., as shown in Figure 9 "t >= T" in

[0132] ), determine whether the absolute values of the detected voltage values |Ua2|, |Ub2|, and |Uc2| exceed the first preset value U1. If so, execute step S705; if not, execute step S706.

[0133] S705. Execute the steps of performing differential pressure protection judgment and unbalance protection judgment.

[0134] Specifically, if the conditions |Ua2| < U1, |Ub2| < U1, and |Uc2| < U1 are met, execute step S602.

[0135] Specifically, if the conditions |Ua1| < U1 & |Ub1| < U1 & |Uc1| < U1 are met, determine whether the following conditions |Ua2| < U1 & |Ub2| < U1 & |Uc2| < U1 are satisfied. If so, execute step S707; if not, execute step S708.

[0136] S707. Execute the step of determining whether the absolute values of the detected voltages on the secondary sides of the discharge coils corresponding to the upper half branches of each phase of the capacitor are all less than the first preset value.

[0137] S708. Output a voltage abnormality alarm signal.

[0138] Specifically, if the following conditions are met: |Ua2| < U1 & |Ub2| < U1 & |Uc2| < U1, execute step S601; if not, output a voltage abnormality alarm signal.

[0139] Through this embodiment, the protection action can be adaptively executed and the "voltage abnormality" signal can be reported through the capacitor protection device, which can facilitate on-site staff to understand the working status of the capacitor and facilitate subsequent operation and maintenance.

[0140] In order to facilitate a better understanding of the capacitor protection method proposed in this application, Figure 9 A specific embodiment is shown for illustration.

[0141] The method includes:

[0142] S801, obtaining the detection voltages Ua1, Ua2, Ub1, Ub2, Uc1 and Uc2 output by the capacitor AC voltage sampling device in the capacitor protection device (this step corresponds to step S601 in the above embodiment).

[0143] S802, determine whether the following conditions are met: |Ua1| <U1&|Ub1|<U1&|Uc1|<U1(此步骤对应上述实施例中的步骤S701)。

[0144] Specifically, the modulus values |Ua1|, |Ub1|, |Uc1| of Ua1, Ub1, and Uc1 are respectively compared with the first preset value U1; if the values of |Ua1|, |Ub1|, |Uc1| are all smaller than the first preset value U1, proceed to step S803; if not, proceed to step S804; and take this moment as the starting point for timing, set t=0, and start calculating the time from 0 each time.

[0145] S803, determine whether the following conditions are met: |Ua2| <U1&|Ub2|<U1&|Uc2|<U1(此步骤对应上述实施例中的步骤S706)。

[0146] Specifically, the modulus values |Ua2|, |Ub2|, |Uc2| of Ua2, Ub2, and Uc2 are respectively compared with the first preset value U1; if the values of |Ua2|, |Ub2|, and |Uc2| are all less than the first preset value U1, step S802 or step S801 ( Figure 9 It is just an exemplary case), specifically, the step of determining whether the absolute value of the secondary side detection voltage of the discharge coil corresponding to the upper half branch of each phase capacitor is less than the first preset value or continuing to collect the voltage value at the next moment (this step corresponds to step S601 in the above embodiment); if not, the protection module body of the capacitor protection device reports "voltage abnormality" (this step corresponds to step S708 in the above embodiment).

[0147] S804. When t < T, determine whether the following conditions are met: |Ua1 + Ub1 + Uc1| > U3 and dt2 >= t2; or |Ua2 + Ub2 + Uc2| > U3 and dt3 >= t2 (this step corresponds to step S702 in the above embodiment).

[0148] Specifically, when the time t is less than the capacitor closing time T, compare the modulus value |Ua1 + Ub1 + Uc1| of the vector sum of the voltage quantities Ua1, Ub1, and Uc1 with the third preset value U3 in the unbalance protection, or compare the modulus values |Ua2 + Ub2 + Uc2| of the voltage quantities Ua2, Ub2, and Uc2 with the third preset value U3 in the unbalance protection. If the duration dt2 during which |Ua1 + Ub1 + Uc1| > U3 is greater than or equal to the second preset duration t2 in the unbalance protection, that is, |Ua1 + Ub1 + Uc1| > U3 and dt2 >= t2, or if the duration dt3 during which |Ua2 + Ub2 + Uc2| > U3 is greater than or equal to the second preset duration t2 in the unbalance protection, that is, |Ua2 + Ub2 + Uc2| > U3 and dt3 >= t2, the protection module main body of the capacitor protection device performs a protection action and the capacitor trips out; otherwise, proceed to step S805.

[0149] S805. When t >= T, determine whether the following conditions are met: |Ua2| < U1 & |Ub2| < U1 & |Uc2| < U1 (this step corresponds to step S704 in the above embodiment).

[0150] Specifically, when the time t is less than the capacitor closing time T, compare the modulus values |Ua2|, |Ub2|, and |Uc2| of Ua2, Ub2, and Uc2 with the first preset value U1 respectively. If the values of |Ua2|, |Ub2|, and |Uc2| are all less than the first preset value U1, proceed to step S806; otherwise, proceed to step S807.

[0151] S806. Determine whether the following conditions are met: |Ua1 + Ub1 + Uc1| > U3 and dt2 >= t2 (this step corresponds to the necessary condition for performing unbalance protection in step S602 of the above embodiment).

[0152] Specifically, compare the modulus value |Ua1 + Ub1 + Uc1| of the vector sum of the voltage quantities Ua1, Ub1, and Uc1 with the third preset value U3 in the secondary unbalance protection. If |Ua1 + Ub1 + Uc1| > U3 and dt2 >= t2, the protection module main body of the capacitor protection device performs an unbalance protection action and the capacitor trips out; otherwise, the protection module main body of the capacitor protection device reports "capacitor normal"; where dt2 is the duration during which |Ua1 + Ub1 + Uc1| > U3.

[0153] S807. Determine whether the following conditions are met: |Ua1 - Ua2| > U2 or |Ub1 - Ub2| > U2 or |Uc1 - Uc2| > U2 and dt1 >= t1 (this step corresponds to the necessary conditions for performing differential pressure protection in step S602 of the above embodiment).

[0154] Specifically, perform vector subtraction on the voltage quantities Ua1, Ua2 and Ub1, Ub2 and Uc1, Uc2 respectively, and compare their modulus values with the second preset value U2 in differential pressure protection; if |Ua1 - Ua2| > U2 or |Ub1 - Ub2| > U2 or |Uc1 - Uc2| > U2 and dt1 >= t1, the protection module main body of the capacitor protection device performs differential pressure protection action and the capacitor trips out; otherwise, the protection module main body of the capacitor protection device reports "capacitor normal"; where dt1 is the duration of |Ua1 - Ua2| > U2 or |Ub1 - Ub2| > U2 or |Uc1 - Uc2| > U2, and dt1 calculates the time difference starting from 0 each time.

[0155] This application passes the Figure 9 shown flowchart to more comprehensively and clearly represent the capacitor protection method. Compare each detected voltage with the preset value to obtain that the protection module main body in the capacitor protection device reports "capacitor normal" or performs differential pressure protection and unbalance protection actions, ensuring that when the capacitor replaces the discharge coil type, the AC voltage sampling plug-in also needs to be replaced accordingly, improving the work efficiency of the staff, and thus reducing the cost of capacitor operation and maintenance.

[0156] Finally, it should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0157] Each embodiment in this specification focuses on the differences from other embodiments. The embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0158] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An AC voltage sampling device for a capacitor, characterized in that, Comprising: Three groups of voltage transformers; wherein, Each group of the voltage transformers includes: two primary coils and two secondary coils; The polar ends of each of the primary coils are respectively used to connect the corresponding polar ends of the secondary sides of the capacitor discharge coils of the corresponding phases; The non-polar ends of each of the primary coils are used to connect the non-polar ends of the secondary sides of the capacitor discharge coils of the corresponding phases; The non-polar ends of the two secondary coils are both grounded, and the polar ends output the acquisition voltages corresponding to the polar ends of the primary coils.

2. The capacitor AC voltage sampling device according to claim 1, characterized in that The two primary coils are respectively: a first primary coil and a second primary coil; The polar end of the first primary coil is used to connect the same-named end of the secondary side of the discharge coil of the corresponding phase capacitor phase wire connection end; The polar end of the second primary coil is used to connect the same-named end of the secondary side of the discharge coil of the corresponding phase capacitor midpoint; The non-polar end of the first primary coil and the non-polar end of the second primary coil are both used to connect the same-named end of the secondary side of the discharge coil of the corresponding phase capacitor neutral point connection end.

3. The capacitor AC voltage sampling device according to claim 2, characterized in that, The two secondary coils include: a first secondary coil and a second secondary coil; The first secondary coil corresponds to the first primary coil and is used to output the acquisition voltage value of the upper half-branch capacitor of the corresponding phase capacitor; The second secondary coil corresponds to the second primary coil and is used to output the acquisition voltage value of the lower half-branch capacitor of the corresponding phase capacitor.

4. The capacitor AC voltage sampling device according to any one of claims 1 to 3, characterized in that, Further comprising: A terminal block; wherein, The terminal block is fixed on the outer shell of the capacitor protection device; The outside of the terminal block is used to connect the corresponding ports of the secondary sides of the capacitor discharge coils of the corresponding phases; The inside of the terminal block is used to connect both ends of the corresponding primary coil of each group of the voltage transformers.

5. The capacitor AC voltage sampling device according to claim 4, wherein Further comprising: A support member; wherein, The terminal block is arranged on the support member and is fixed on the outer shell of the capacitor protection device through the support member; Each group of the voltage transformers is arranged inside the support member.

6. A capacitor protection device, characterized in that, Comprising: An outer shell, a protection module main body and the capacitor AC voltage sampling device according to any one of claims 1 to 5; The capacitor AC voltage sampling device is used to collect the voltages of the corresponding ports of the secondary sides of the capacitor discharge coils of each phase; The capacitor AC voltage sampling device outputs the detection voltage to the protection module main body.

7. The capacitor protection device according to claim 6, wherein The protection module main body is used to implement: differential protection between each phase capacitor, or voltage imbalance protection between each phase capacitor.

8. A capacitor protection method, characterized in that, Applied to the protection module main body of the capacitor protection device according to claim 6 or 7, the capacitor protection method includes: Obtaining each detection voltage output by the capacitor AC voltage sampling device in the capacitor protection device; When there is at least one of the detection voltages exceeding a first preset value, performing differential protection judgment and imbalance protection judgment; According to the results of the two judgments, performing corresponding protection or determining that the capacitor is normal.

9. The capacitor protection method according to claim 8, characterized in that, When performing the differential protection judgment, each of the detection voltages is respectively: the secondary side voltages of the discharge coils corresponding to the two series segments of each phase capacitor; When performing the imbalance protection judgment, each of the detection voltages is respectively: the secondary side voltages of the discharge coils of each phase capacitor.

10. The capacitor protection method according to claim 9, wherein, The performing of the differential protection judgment includes: Calculate the difference between the secondary side voltages of the discharge coils corresponding to the two series segments of each phase capacitor respectively, and determine whether the absolute value of the corresponding difference of each phase is greater than the second preset value; If there is at least one phase with the absolute value of the corresponding difference greater than the second preset value and the duration exceeds the first preset duration, then perform the differential pressure protection action; If the absolute values of the corresponding differences of each phase are all less than or equal to the second preset value, it is determined that the capacitor is normal.

11. The capacitor protection method according to claim 9, wherein, The above-mentioned judgment for unbalance protection includes: Calculate the absolute value of the sum of the detected voltages, and determine whether the absolute value is greater than the third preset value; If the absolute value is greater than the third preset value and the duration exceeds the second preset duration, then perform the unbalance protection action; If the absolute value is less than or equal to the third preset value, it is determined that the capacitor is normal.

12. The capacitor protection method according to any one of claims 8 to 11, characterized in that, Each of the detected voltages is: the secondary side detected voltage of the discharge coil corresponding to the upper half branch of each phase capacitor, and the secondary side detected voltage of the discharge coil corresponding to the lower half branch of each phase capacitor; After obtaining each of the detected voltages output by the capacitor AC voltage sampling device in the capacitor protection device, it further includes: Determine whether the absolute values of the secondary side detected voltages of the discharge coils corresponding to the upper half branches of each phase capacitor are all less than the first preset value; If there is at least one phase with the absolute value of the secondary side detected voltage of the discharge coil corresponding to the upper half branch of the capacitor greater than or equal to the first preset value, then before the capacitor closing time arrives, determine whether the absolute value of the sum of the secondary side detected voltages of the discharge coils corresponding to the upper half branches of each phase capacitor, or the absolute value of the sum of the secondary side detected voltages of the discharge coils corresponding to the lower half branches of each phase capacitor, is greater than the third preset value and the duration exceeds the second preset duration; if so, perform the protection action; if not, after the capacitor closing time arrives, determine whether the absolute value of the secondary side detected voltage of the discharge coil corresponding to the lower half branch of each phase capacitor exceeds the first preset value; if so, perform the steps of the differential pressure protection judgment and the unbalance protection judgment; If the absolute values of the secondary side detected voltages of the discharge coils corresponding to the upper half branches of each phase capacitor are all less than the first preset value, then determine whether the absolute values of the secondary side detected voltages of the discharge coils corresponding to the lower half branches of each phase capacitor are all less than the first preset value; if so, return to execute the step of determining whether the absolute values of the secondary side detected voltages of the discharge coils corresponding to the upper half branches of each phase capacitor are all less than the first preset value; if not, output a voltage abnormal alarm signal.

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