Capacitor rack
By electrically connecting the housing of the capacitor module to the common node in the supercapacitor rack and forming a high impedance path with resistors, the fault current problem caused by insulation failure is solved, and effective limiting and protection of the fault current is achieved, avoiding the Serious consequences occur.
Patent Information
- Application Number
- CN202322958964.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-31
- Publication Date
- 2025-01-07
- Estimated Expiration
- 2033-10-31
AI Technical Summary
The high peak of fault current caused by insulation failure in the supercapacitor rack may cause serious consequences such as arcs, explosions and fires, and the existing technology is difficult to effectively solve this problem.
A capacitor rack is designed to form a high-impedance fault current path by electrically connecting the housing of the capacitor module to the common node and connecting the central node to the common node through a resistor to optimize the flow of the fault current and limit the fault current. Peak.
It effectively reduces the peak of fault current, provides protection for insulation faults, prevents arcs, explosions and fires, and ensures the safety and stability of the capacitor rack.
Smart Images
Figure CN222321118U_ABST
Abstract
Description
Technical Field
[0001] The present disclosure generally relates to a grounding system for mitigating insulation fault currents generated within a capacitor rack. More particularly, the present invention relates to a method for providing protection for a capacitor rack by limiting insulation fault currents between a housing of the capacitor rack and corresponding capacitor cells in capacitor modules of the capacitor rack. Background Art
[0002] Capacitor modules or supercapacitor modules are widely used in STATCOM projects. Several number of capacitor modules constitute a capacitor rack, and several number of such capacitor racks are connected in series to build a capacitor string, as shown in Figure 1. Several number of such capacitor strings are used to form a supercapacitor energy storage system (SCESS).
[0003] For the supercapacitor rack, the ground bus is connected to the midpoint of its corresponding voltage potential. The chassis of each of the capacitor modules is connected to the ground bus. The insulation level between the chassis of the capacitor module and the capacitor unit inside the capacitor module is about 1500V, but flashover and insulation failure may occur due to electrolyte leakage from the capacitor unit. If there is an insulation failure between the chassis of the capacitor module and the terminals of the same capacitor module, as shown in Figure 2, the fault current caused by the insulation failure flows through one or more capacitor modules in the capacitor rack, and the peak value of the fault current may be 40kA or even higher. High fault current may lead to serious consequences, including arcing, explosion and fire.
[0004] Therefore, there is a need for an improved device for grounding a supercapacitor rack. Utility Model Content
[0005] It is therefore an object of the present disclosure to provide an improved capacitor rack for a plurality of capacitor modules to mitigate, alleviate or eliminate all or at least some of the above discussed disadvantages of currently known solutions.
[0006] This and other objects are achieved by a protective device as defined in the appended claims.The term "exemplary" is in this context to be understood as serving as an example, instance or illustration.
[0007] According to a first aspect of the present disclosure, a capacitor rack for a plurality of capacitor modules CM is provided. The capacitor rack comprises a first branch of at least one CM connected in series and a second branch of at least one CM connected in series, the first branch and the second branch being connected in series via a central node. Further, the capacitor rack has a grounding network comprising a housing encapsulating the CM and a grounding branch electrically connecting the housing of each of the CMs in the first branch and the second branch to a common node. The central node is connected to the common node via a resistor, and / or each grounding branch (120) comprises a resistor, and the central node is connected to the common node, and the connection of the resistors allows the fault current to flow through the resistor when any insulation fault exists, thereby optimizing the fault current generated within the capacitor rack.
[0008] According to one embodiment, the number of CMs in the first branch is equal to the number of CMs in the second branch.
[0009] According to one embodiment, the number of CMs in the first branch is more or less than the number of CMs in the second branch.
[0010] According to one embodiment, the common node is a ground bus.
[0011] According to one embodiment, where when the center node is connected to the common node via a resistor, the resistor is connected to one of the polarities of the CM.
[0012] According to one embodiment, the housing of each of the CMs is insulated from the capacitor frame.
[0013] According to an embodiment, the resistor comprises a combination of two or more resistors.
[0014] According to an embodiment, the two or more resistors include resistors having the same value or resistors having different values.
[0015] Advantageously, the proposed invention provides an effective protection device against leakage fault currents.
[0016] Other advantages may be apparent to those skilled in the art. Certain embodiments may have some or all of the enumerated advantages. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The foregoing will become apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings, in which like reference numerals refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead being placed upon illustrating example embodiments.
[0018] FIG1 discloses an example capacitor rack according to the prior art;
[0019] FIG. 2 discloses an example fault current flow in a capacitor rack according to the prior art;
[0020] Figure 3 Disclosed is a block diagram representation of a capacitor rack according to the present invention, the capacitor rack comprising a first branch and a second branch of capacitor modules, a grounding network and a resistor;
[0021] Figure 4A and Figure 4B A capacitor rack according to the present invention is disclosed;
[0022] Figure 5 Disclosed is a leakage fault current flow in a capacitor rack according to the present invention;
[0023] Fig. 6A and Figure 6B A capacitor rack according to one embodiment is disclosed;
[0024] Figure 7 Disclosed is a leakage fault current flow in a capacitor rack according to one embodiment; and
[0025] Figure 8 An equivalent circuit of a capacitor rack and fault current flow according to the present invention is shown.
[0026] Fig. 9 An equivalent circuit of a capacitor rack and fault current flow is shown according to one embodiment.
[0027] FIG. 10 illustrates an equivalent circuit of a capacitor rack and fault current flow according to one embodiment. DETAILED DESCRIPTION
[0028] The various aspects of the present disclosure will be described more fully below with reference to the accompanying drawings. However, the devices disclosed herein can be implemented in many different forms and should not be construed as limited to the various aspects set forth herein. The same numbers in the accompanying drawings always refer to the same elements.
[0029] The terms used herein are only for describing specific aspects of the present disclosure and are not intended to limit the present invention. It should be emphasized that the term "includes / comprising" is used to specify the presence of stated features, integers, steps or components when used in this specification, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to also include plural forms, unless the context clearly indicates otherwise.
[0030] Fault current: As used herein, "fault current" may refer to the current flowing through a circuit during an electrical fault condition.
[0031] Generally speaking, supercapacitors are storage devices that were originally classified as capacitors. Compared with other electrical energy storage devices, capacitors have lower energy density (the amount of energy stored per unit mass or volume). But capacitors are more excellent due to their output density (instantaneous power output per unit mass or volume). Capacitors can withstand low performance degradation caused by repeated charging and discharging at high currents, and therefore capacitors have a more excellent service life.
[0032] Generally speaking, supercapacitor banks are used for energy storage that undergoes frequent charge and discharge cycles at high currents and short durations.
[0033] According to the prior art, as shown in FIGS. 1 and 2 , a supercapacitor bank includes a plurality of capacitor modules (CMs) arranged in series. The housing of each CM is connected to a ground bus. Further, the polarity of the CM is also connected to the ground bus. In this configuration, if an insulation failure occurs between the CM chassis and any terminal of the same CM, a fault current due to the insulation failure will flow through the CM, and this fault current peak may be about 40 kA or even higher. As shown in FIG. 2 , a high fault current flows through the affected CM. The fault current leads to serious consequences, including arcing, explosion, and fire, resulting in damage to the supercapacitor bank.
[0034] Embodiments herein provide a rack of ultracapacitor banks or capacitor racks with improved protection against fault currents due to insulation failure.
[0035] Figure 3 A supercapacitor rack 100 is disclosed. The supercapacitor bank 100 mentioned herein may be used in a STATCOM project.
[0036] like Figure 3 As shown, the supercapacitor bank or capacitor rack 100 includes a first branch having at least one capacitor module CM 105, a second branch having at least one CM 105, and a grounding network. The first branch and the second branch are connected in series to each other via a central node 110.
[0037] The grounding network includes a housing 125 encapsulating the corresponding CM 105, and a grounding branch 120 that electrically connects the housing 125 of each of the CMs 105 in the first branch and each of the CMs 105 in the second branch to a common node 130. The housing 125 of each of the CMs 105 is insulated from the capacitor rack 100. The central node 110 is also connected to the common node 130 via a resistor 135A, and / or each of the grounding branches 120 includes a resistor 135B and the central node 110 is connected to the common node 130. The resistors 135A, 135B may include a combination of two or more resistors having the same value or different values. In an example, the resistor 135B may be embedded inside the CM 105.
[0038] The first branch includes one or more CMs 105 connected in series with each other. Similarly, the second branch includes one or more CMs 105 connected in series with each other. When any insulation fault exists, the connection of the resistors 135A, 135B allows the fault current to flow through the resistors 135A, 135B, thereby optimizing the fault current generated within the capacitor rack 100.
[0039] Each CM 105 includes a plurality of cells combined into a group structure and embedded circuits to prevent voltage inconsistency between each of the plurality of cells. The CM 105 may also be a special module that may be characterized by advanced vibration resistance and shock resistance.
[0040] The central node 110 is a node at the center of the plurality of CMs 105. The central node 110 may also be considered as the approximate center of the plurality of CMs 105, that is, the central node 110 should be as close to the center as possible. In the example, if there are n CMs 105 and n is an even number, the central node will be after the (n / 2)th CM. Therefore, the number of CMs 105 in the first branch is equal to the number of CMs 105 in the second branch. However, if the number of CMs 105 in the first branch is more or less than the number of CMs 105 in the second branch, that is, if n is an odd number, the central node will be before or after the (n+1 / 2)th CM.
[0041] The common node 130 is a ground bus used to create an equipotential plane between the capacitor rack and its service ground during fault and transient conditions. The equipotential plane provides a near zero voltage difference and protects people and the capacitor rack during such events.
[0042] Figure 4A and Figure 4BIt is disclosed that the capacitor rack 100 includes a plurality of capacitor units in the form of CMs 105. The CMs 105 are connected in series with each other by positive / negative polarity. Each of the CMs 105 is enclosed in a respective housing 125. The housing 125 may be a metal frame enclosure surrounding the CMs 105. The metal frame enclosure protects the public and personnel from accidentally contacting the energized CMs 105. Each of the housings 125 of the CMs 105 is directly connected to a common node 130 using a ground branch 120. Further, an auxiliary 0 volt is also connected to the common node 130. According to an embodiment, the frame of the capacitor rack 100 is also connected to the common node 130.
[0043] The central node 110 of a series of CMs 105 is connected to a common node 130 through a resistor 135A. The resistor 135A provides a high impedance current path for a fault current generated due to an insulation failure of the CM 105. The resistor 135A is connected to one of the polarities (i.e., positive or negative) of the CM 105. According to an example, the resistance 135A provided in the current path can be up to 10 kΩ. The resistor 135A is placed such as to limit the fault current of a single point insulation fault. The fault current or leakage current or short circuit current should generally be as small as possible. Therefore, in the event of an insulation failure in the capacitor rack 100, an effective protection device is provided to protect against the fault current.
[0044] The resistor 135A is selected so that it can withstand a certain power range, for example 50 W. The resistor 135A is designed to be low cost and compact, and thus does not require additional space in the size of the capacitor rack 100 .
[0045] Figure 5 The flow path of the fault current in the case of an insulation failure in the capacitor rack 100 is disclosed. In the example, the fault current starts from the faulty CM and follows the path through the resistor 135A via the central node 110 to reach the faulty CM, thereby completing the flow circuit. The resistor 135A with a high impedance is able to limit the fault current flowing through it. Since the RC time constant of the circuit is high, the discharge time of the capacitor in the CM is long, and the capacitor rack 100 can still function as usual until the insulation fault is detected and the affected fault area is bypassed. Therefore, implementing the resistor 135A provides effective protection against the fault current.
[0046] According to an embodiment, Fig. 6A and Figure 6BA capacitor rack 100 is disclosed that includes a plurality of CMs 105 connected to each other in series via positive / negative polarity. A central node 110 of a series of CMs 105 is directly connected to a common node 130 to allow current to flow directly through the common node. Each of the housings 125 of the CMs 105 is connected to the common node 130 through a resistor 135B. Thus, there are a plurality of resistors 135B, at least one in each of the ground branches 120. Further, an auxiliary 0 volt is also connected to the common node 130. According to an embodiment, the frame of the capacitor rack 100 is also connected to the common node 130.
[0047] Resistor 135B provides a high impedance current path for fault current generated due to insulation failure of CM 105. Resistor 135B is connected to housing 125 of CM 105. Resistor 135B is placed such as to limit the fault current of single point insulation fault and double point insulation fault. Therefore, in the event of insulation failure in capacitor rack 100, an effective protection device is provided to protect against fault current. Resistor 135B is selected so that it can withstand a certain power range, such as 50W. Resistor 135B is designed to be low cost and compact, and therefore does not require additional space in the size of capacitor rack 100.
[0048] Figure 7 The flow path of the fault current in the case of an insulation failure in the capacitor rack 100 is disclosed. In an example, the fault current starts from the faulty CM and follows the path through the central node 110 to the common node 130. The faulty CM is also connected to the common node 130 through the grounding branch 120 including the resistor 135B. The resistor 135B with high impedance can limit the fault current flowing through the grounding branch 120. Therefore, implementing the resistor 135B provides effective protection against the fault current. In an example, the resistor 135B can be embedded inside the CM 105.
[0049] Figure 8 Publicly disclosed Figure 5 1 shows an equivalent circuit of a capacitor rack 100 with a single insulation failure fault. In the event of a single insulation failure fault in the capacitor rack 100, the fault current follows a path through the resistor 135A via the central node. The resistor 135A provides a high impedance current path for the flow of the fault current, thereby providing effective protection against the fault current.
[0050] Fig. 9 Publicly disclosed Figure 5FIG. 1 is an equivalent circuit diagram of a capacitor rack 100 with a double insulation failure fault. In the case of a double insulation failure fault in the capacitor rack 100, the first fault current caused by the first fault point follows the path through the resistor 135A via the central node and is mitigated by the resistor 135A. Further, as Fig. 9 As shown, there is a second fault current caused by the second fault point, and the second fault current still circulates between the second fault points of the double insulation failure fault. The second fault current still circulating between the second fault points may cause serious damage to the supercapacitor bank or capacitor rack 100. Fig. 6A and Figure 6B As shown, the second fault current that is still circulating is mitigated by the resistor 135B of the capacitor rack 100 .
[0051] Understandably, Figure 4A and Figure 4B In the above, a single insulation failure is considered. However, if a double insulation failure occurs, the fault current circulates between the second fault point of the double insulation failure. In this scenario, the following options can be used based on Figure 7 A capacitor rack 100 of an embodiment.
[0052] Fig. 10A A capacitor rack 100 having a double insulation failure fault is disclosed. Fig. 10B An equivalent circuit of a capacitor rack 100 with a double insulation failure fault is disclosed. Fig. 10A and Fig. 10B In the case of a double insulation failure in the capacitor rack 100, the fault current flowing due to the first fault point in the capacitor rack 100 follows the resistor 135B in the first grounding branch 120. 1 path, and is resistor 135B 1 Further, the second fault current flowing due to the second fault point in the capacitor rack 100 follows the resistor 135B in the second grounding branch 120. 2 path, and is resistor 135B 2 Similarly, using corresponding resistors from a set of resistors 135B in a corresponding ground branch 120 of the capacitor rack 100, any number of faults, such as Fig. 10A shown.
[0053] Resistor 135B 1 and 135B 2 The resistance values of resistor 135B are preferably the same. However, according to an embodiment, resistor 135B 1 and 135B 2 The resistance values are different.
[0054] like Figure 4A and Figure 4B The functions disclosed in the first embodiment shown can be combined with Fig. 6A and Figure 6B The functions disclosed in the second embodiment shown are performed.
[0055] The foregoing description of specific embodiments will fully reveal the general nature of the embodiments herein so that others can easily modify and / or adapt such specific embodiments for various applications by applying current knowledge without departing from the general concepts, and therefore, such adaptations and modifications should and are intended to be understood within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes. Therefore, although the embodiments herein have been described according to preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the scope of the present disclosure.
Claims
1. A capacitor rack (100), the capacitor rack being used for a plurality of capacitor modules (105), characterized in that: The capacitor rack comprises: a first branch of at least one capacitor module (105) connected in series; a second branch of at least one capacitor module (105) connected in series, wherein the first branch and the second branch are connected in series via a central node (110); and A grounding network, the grounding network comprising: a housing (125) encapsulating the capacitor module (105); and a grounding branch (120) electrically connecting the housing (125) of each of the capacitor modules (105) in the first branch and the second branch to a common node (130); wherein the central node (110) is connected to the common node (130) via a resistor (135A), and / or wherein each ground branch (120) comprises a resistor (135B), and the central node (110) is connected to the common node (130), and Wherein when there is any insulation fault, the connection of the resistors (135A, 135B) allows the fault current to flow through the resistors (135A, 135B), thereby optimizing the fault current generated in the capacitor rack (100).
2. The capacitor rack (100) according to claim 1, characterized in that: The number of capacitor modules (105) in the first branch is equal to the number of capacitor modules (105) in the second branch.
3. The capacitor rack (100) according to claim 1, characterized in that: The number of capacitor modules (105) in the first branch is greater or less than the number of capacitor modules (105) in the second branch.
4. The capacitor holder (100) according to any one of the preceding claims, characterized in that The common node (130) is a ground bus.
5. The capacitor rack (100) according to any one of claims 1 to 3, characterized in that: When the central node (110) is connected to the common node (130) via the resistor (135A), the resistor (135A) is connected to one of the polarities of the capacitor module (105).
6. The capacitor rack (100) according to any one of claims 1 to 3, characterized in that: The housing (125) of each of the capacitor modules (105) is insulated from the capacitor rack (100).
7. The capacitor rack (100) according to any one of claims 1 to 3, characterized in that: The resistor (135A, 135B) includes a combination of two or more resistors.
8. The capacitor rack (100) according to claim 7, characterized in that: The two or more resistors include resistors having the same value or resistors having different values.