Power transmission

Abstract

To provide a protection apparatus improved for capacitive cables, to thereby continuously provide connection, while the cables are protected.SOLUTION: A feeding network comprises: a power source connected to a first node; the first node connected to a second node through two or more conductors separated by a dielectric body; the second node; and a control system. The two or more conductors can transmit power between the first node and the second node, via galvanic connection in a first mode, or as a capacitive cable in a second mode. The control system can switch the two or more conductors between the first node and the second mode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to power transmission.

Background Art

[0002] Fuses and electromagnetic devices are known for protecting circuits from overvoltage and overcurrent. They are provided for most commercial voltages and currents, such as low voltages as seen in fuses of hand-held devices, power supplies as seen in household appliances equipped with circuit breakers, or medium-voltage and high-voltage power grids equipped with distribution circuit breakers.

[0003] Protection devices are also known for specific elements in certain circuits. For example, the abstract of Japanese Patent Laid-Open No. 11-275872 describes as follows: "[Problem] To protect a capacitor from overvoltage without increasing the processing energy of a non-linear resistance element and the overcurrent duty of a power converter when an accident such as a line-to-line short circuit or an arm short circuit occurs. [Solution] In a power conversion circuit having series capacitors 31 to 33 connected between the AC terminals of a power converter and an AC power supply 2, non-linear resistance elements 41 to 43, switch means (51 to 53) for short-circuiting between the capacitor terminals, and voltage detection means (61 to 63) for detecting the voltage between the capacitor terminals are connected between the capacitor terminals, and control means 200 is provided to turn on the short-circuit switch after delaying for about one cycle from the time when the overvoltage is detected by the voltage detection means. In the case of a line-to-line short-circuit current that continues for one cycle or more, the line-to-line short-circuit current is bypassed to the short-circuit switch, and in the case of an arm short circuit for one cycle, the arc pulse of the power converter stops before the short-circuit switch is turned on, and the short-circuit current is suppressed by the capacitors 31 to 33."

[0004] Capacitive cables, such as those described in International Publication No. 2019 / 234449, benefit from protective equipment, just like ordinary power grid cables, not only for the protection of the equipment to which they are connected, but also for their own protection. Such cables benefit from further protection, as described below. The cable comprises two capacitive plates separated by a dielectric material. This is either a strip-like physical plate as described in International Publication No. 2010 / 026380, or a composite plate composed of multiple adjacent and connected wires forming a plate as described in International Publication No. 2019 / 234449. Such cables can transmit overvoltage from one end to the other and therefore require ordinary protective equipment to avoid the application of such overvoltage, as well as the dielectric material of the cable being susceptible to damage if overvoltage is applied to both ends. This overvoltage is indicated by excessively high voltages across the conductors constituting the plates of the cable. Such voltages are easily monitored by extending the power supply voltage conductor to measure the voltage between that conductor and the load voltage conductor. If the monitored voltage exceeds a threshold, the cable may be disconnected from the relevant equipment to protect it from the monitoring voltage exceeding the dielectric breakdown threshold. Disconnection can be performed by protective equipment that sets the distribution voltage to its rated voltage. This solution not only increases the cost of installing capacitive cables but also undermines the economic advantages of capacitive cables and is prone to unnecessary disconnections. Furthermore, it may be too slow to protect the dielectric material of capacitive cables. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide an improved protective device for capacitive cables, enabling the cables to continue providing a connection while remaining protected. [Means for solving the problem]

[0006] According to one aspect of the present invention, a power transmission cable protection and control configuration for a capacitive power transmission cable, the configuration comprising: At one end of the cable, • Load terminals or power terminals for load cables or power cables, A pair of cable terminals for a pair of conductors of the capacitive power transmission cable, wherein the conductors are connected directly or via extension conductors of the terminals when in use. One of the pair of cable terminals is connected to the load terminal or power terminal by a rail or busbar, - The rail or busbar and the other of the pair of cable terminals are provided with an electromagnetic switch or electronic switch, At one end or the other end of the cable, • Means for measuring the differential voltage between the pair of cable terminals, i.e., between the capacitive cable conductors, during use. • Means for controlling the switch to close when the differential voltage exceeds a threshold below the dielectric breakdown of the capacitive cable. A power transmission cable protection and control configuration is provided that includes the following:

[0007] Preferably, in one modified example, The switch control means is configured to control the switch in a second or third event, or alternatively, a separate switch control means is provided. The second event is that the current in the busbar or rail falls below a certain threshold. The third event is that the current in the busbar or rail exceeds a certain threshold.

[0008] In another modified example, The second switch control means is configured to control the second switch between the rail or busbar and the other of the pair of cable terminals in a second or third event. The second event described above is that the current in the busbar or rail falls below a certain threshold. The third event described above is that the current in the busbar or rail exceeds a certain threshold.

[0009] In a further configuration, a capacitor is provided that provides or increases the capacitance between the conductors of the capacitive cable.

[0010] In a preferred modification, the configuration is a connection and protection device housed in a grounded or groundable conductive case or cabinet, the terminals are isolated from the transmission voltage, and the switch has the differential breakdown voltage as its rated voltage.

[0011] Preferably, the measuring means and control means are housed together with the terminals and switches in a case or cabinet.

[0012] The protection and control device may be provided in combination with a second such device for the other end of the capacitive cable, which is configured for wireless communication, wired communication, or optical fiber communication.

[0013] Typically, the device includes an autonomous device between the rail or busbar and the other of the pair of cable terminals, preferably configured to conduct and reduce the differential voltage faster than the switch can close, by preferably at least one of a metal oxide varistor, spark gap, and thyristor that functions as a surge arrester. More preferably, the device includes all of the metal oxide varistor and thyristor that function as surge arresters.

[0014] Furthermore, typically both an electromagnetic switch and an electronic switch are provided, and the electronic switch is configured to close faster than the electromagnetic switch.

[0015] Preferably, The aforementioned connecting means is · Set the rated voltage to 20% or less, preferably 15% or less, of the voltage transmitted by the capacitive cable, and · Be configured to operate with lower voltage control, · The event detection means includes means for detecting that the voltage between the pair of cables exceeds a threshold value that is more than 20%, preferably more than 15%, of the transmitted voltage. · The device · A low-voltage power supply within the case or cabinet, · A low-voltage controller within the housing for causing the connection means to make the connection when it is detected that the voltage has exceeded the threshold value.

[0016] Note that the case or cabinet may be inside or near a substation having an isolated DC power supply.

[0017] The connection and control device may be combined with one or more capacitors connected between the pair of cable terminals outside the device.

[0018] Usually, the cable includes a pair of conductors that are capacitively related along its length.

[0019] In another aspect of the present invention, the connection and protection device is provided in combination with a power transmission cable having two capacitively connected conductors that are connected to a power supply cable at one end and a load cable at the other end during use.

[0020] In such a combination, the cable may include a pair of normal step-up power transmission cables that are capacitively connected at one end or the other by one or more normal capacitors housed as circuit elements of the connection and protection device or housed separately. Alternatively, the cable may include a pair of conductors that are capacitively related along its length, and additional capacitors are provided as circuit elements within the device.

[0021] According to a third aspect of the present invention, there is provided a connection and protection device for a power transmission cable having two capacitively connected conductors that are respectively connected to a power cable at one end and a load cable at the other end during use, · a conductive housing that can be grounded, and · three connection terminals each having a rated voltage that provides a termination in step-up voltage insulation from the housing and an internal connection point within the housing, · one of the connection terminals is for the insulated termination and internal connection of either the power cable or the load cable, · the other cable terminal is a pair for the insulated termination and internal connection of each capacitively connected conductor, or one of the cable interconnecting portions from the terminal to each conductor, and three connection terminals, · a direct connection between one of the connection terminals within the housing and one of the pair of cable terminals, wherein the other of the pair of cable terminals is not normally connected to the connection terminal, and a direct connection, · means within the housing for connecting the other of the pair of cable terminals to the connection terminal in order to protect the capacitive connection of the two conductors when the voltage between the pair of cable terminals exceeds a threshold value A connection and protection device is provided.

[0022] Preferably, event detection means including means for detecting that the voltage between the pair of cables has exceeded a threshold value is included.

[0023] In a fourth aspect of the present invention, there is provided a connection and protection device combined with a power transmission cable having two capacitively connected conductors that are respectively connected to a power cable at one end and a load cable at the other end during use, · a conductive housing that can be grounded, and · three connection terminals each having a rated voltage that provides a termination in step-up voltage insulation from the housing and an internal connection point within the housing, One of the connection terminals is for the insulated termination and internal connection of either the power cable or the load cable. The other cable terminals consist of three connectors, which are either pairs for the insulated termination and internal connections of the respective capacitively connected conductors, or one of the interconnecting portions of the cable from the terminal to the respective conductors. A direct connection between one of the connection terminals within the housing and one of the pair of cable terminals, wherein the other of the pair of cable terminals is not normally connected to the connection terminal. - Means within the housing for connecting the other of the pair of cable terminals to the connection terminal in order to protect the capacitive connection of the two conductors when the voltage between the pair of cable terminals exceeds a threshold, The connection means is set to a rated voltage of 20% or less of the boosted voltage. The connection means is configured to operate by low-voltage control, and includes a connection means. • Event detection means including means for detecting that the voltage between the pair of cables exceeds a threshold of 20% of the boosted voltage, • Low-voltage power supply within the housing, A connection and protection device is provided, comprising a low-voltage controller in the housing for causing the connection means to make the connection when it detects that the voltage has exceeded a threshold.

[0024] One aspect of the present invention relates to a power grid that is switched between a capacitive operating mode and a conventional (galvanic) operating mode to supply power. The selection between modes may relate to the load on the power grid or the load on a region of the power grid, because a single network generally includes individual sections as appropriate, and each section can operate conventionally or capacitively. This selection may be made to avoid damage to equipment in the network, such as damage to cables or cable components.

[0025] The selection between modes may be performed manually by manually operating a switch to change modes. This selection may also be performed by an automated device that monitors, for example, the load or network-related factors. The network control system may also include both of these, namely, a manually operated switch and a control device that operates the switch according to a predetermined trigger.

[0026] In a fifth aspect of the present invention, therefore, • Power supply connected to the first node, The first node is connected to the second node by two or more conductors separated by a dielectric, The second node and, A power supply network comprising a control system, The two or more conductors are capable of transmitting power between the first node and the second node via a galvanic connection in the first mode, or as a capacitive cable in the second mode. The control system provides a power grid capable of switching the two or more conductors between the first node and the second mode.

[0027] The power grid, more specifically, (i) Power supply connected to the first node, (ii) The first node connected to the second node by two or more cables separated by dielectrics as necessary, (iii) The second node and, (iv) It may also include a control system, The two or more cables are capable of transmitting power between the first node and the second node via a galvanic connection in the first mode, or as capacitive cables in the second mode. The control system is capable of switching the two or more cables between the first node and the second mode.

[0028] References to capacitive cables are as described elsewhere in this specification and therefore include references in embodiments to capacitive cables having two constituent conductors or constituent cables in a capacitive configuration. Two ordinary cables connected at the ends by a capacitor can also function as a capacitive conductive cable, but two separated by a dielectric The above Capacitive cables with internal cables are preferred.

[0029] As previously mentioned, the switching between the two or more conductors can be performed manually by an operator.

[0030] A dielectric protection device capable of switching between the two or more conductors in response to a trigger event may be optionally included. A signal from the device may then initiate the switching between modes. An example of a trigger event includes an overvoltage between each conductor when operating as a capacitive cable. A further example of a trigger event is a safety warning that the operating mode of the conductor in the current mode is inappropriate. A trigger event may further include a reduction in load indicating that a galvanic connection is preferable to a capacitive mode.

[0031] An external monitoring system may be provided to estimate when a trigger threshold is reached. This threshold may be set to avoid damage to the dielectric in the capacitive cable. Another suitable threshold is when power transmission at low loads is delivered more efficiently by normal means. A further threshold may be when extreme weather conditions indicate a switch between modes. Thus, the switch may occur as a result of light winds.

[0032] The monitoring system may include artificial intelligence to make decisions regarding the operating mode at the network level or at the subsection level of the network.

[0033] In embodiments of the present invention, the two or more conductors include a first conductor and a second conductor, In the first mode, the first end of the first conductor is connected to the first node, the second end of the first conductor is connected to the second node, and / or the first end of the second conductor is connected to the first node, the second end of the second conductor is connected to the second node, In the second mode described above, the first conductor is connected to the first node at its first end but not to the second node at its second end, and the second conductor is not connected to the first node at its first end but is connected to the second node at its second end.

[0034] Preferably, the control system includes control circuits at both the first and second nodes, so that switching between the first and second modes involves simultaneously operating relays at both nodes.

[0035] Furthermore, this invention is applicable to power transmission cables across various transmission voltages and relates to the voltage between two capacitively connected conductors within a power transmission cable. This voltage is lower than the transmitted voltage. Such a transmitted voltage will be referred to as the “boost voltage” below, while other voltages will be referred to as low voltage, medium voltage, high voltage (by various terms) or even higher voltage. In short, a distinction is made between “boost voltage” and “low” voltage. The term “rated voltage” may be used as appropriate instead of transmitted voltage and boost voltage, as long as the boost voltage is the voltage to which the entire device is rated for connection to the power grid. So ru.

[0036] Alternatively, a capacitive connection conductor connected to the power supply and / or load by a connection and protection device may be one of the following: • A pair of cables having a capacitive relationship along their length, as described in International Publication No. 2019 / 234449, or • This may be a pair of ordinary power transmission cables that are capacitively connected at one or both ends and have one or more conventional capacitors interposed as needed.

[0037] Such capacitors may be housed as circuit elements of the connection and protection device, or separately. In the first option, the threshold voltage is set to protect the dielectric between the capacitively connected cables, and in the latter option, the threshold voltage is set to protect the dielectric between the plates of the capacitor (wherever it is located and housed). In either option, the two capacitively connected cables are referred to as "capacitive cables" for convenience. Note that there may be other cases in which the present invention is applicable and the term "capacitive cables" is appropriate.

[0038] This is the case where the pair of cables described above have a capacitive relationship along their length, but the length is short, and the capacitance between the cables is conveniently increased by an additional capacitor included as a circuit element inside or actually outside the connection and protection device.

[0039] Connection and protection devices can be connected to the load or power end of a capacitive cable. They are typically connected to both ends of a long circuit. At each end, the power / load connection terminal is connected via one of a pair of terminals to a conductor of the capacitive cable that is not connected to a power cable or load cable at the other end. The power cable at one end is capacitively connected to the load cable at the other end by the conductors of the capacitive cable and / or a separate capacitor.

[0040] When connection and protection devices are installed at both ends of a long circuit of a capacitive cable, they are usually configured to communicate with each other and thereby operate together.

[0041] Under normal use, the connectors and protective devices simply provide a straight connection from the power source or load to each conductor of the capacitive cable.

[0042] Typically, a connection and protection device includes two rails or busbars. One rail or busbar, having power / load connection terminals at one end and one of a pair of cable terminals at the other end, constitutes the direct connection in the device. The other rail or busbar is isolated at one end, with the other of the pair of cable terminals connected to the other end. The connection means is positioned between the rails. While this rail / busbar configuration is convenient, other configurations may also be convenient.

[0043] In general, events that cause voltage or current thresholds to be exceeded are transient events such as lightning or, for example, prolonged durations associated with cable damage (which may be caused by a tree falling onto a power line at some other point in the power grid). Lightning can generate impulses that make dielectrics susceptible to damage due to overvoltage across the dielectric.

[0044] Cable damage can generate current surges, which can heat the cable conductors through resistance and thus damage the dielectric. Other abnormal or normal events, such as switching that causes voltage or current thresholds to be exceeded, are also possible.

[0045] If a voltage surge occurs in either the load cable or the power cable, or possibly one of the capacitive cables, for example, due to lightning, the voltage between the pair of terminals, and consequently the voltage across both ends of the capacitive cable plate, will rise. When the connection means detects that this voltage has exceeded a threshold, the three terminals are directly connected to each other by the connection means, by rails / busbars being connected to each other (if provided).

[0046] Since impulses such as lightning are very steep events in terms of voltage rise, the connection means conveniently includes a spark gap component between a pair of terminals, conveniently via a rail. This component conducts as soon as the voltage across its gap exceeds a threshold, limiting the voltage between conductors.

[0047] To accommodate high-energy impulses that could overwhelm the spark gap components, surge arrester components may be connected in parallel with the spark gap. The surge arresters allow more current to flow through primary conduction of the semiconductor material while maintaining the voltage across them below dielectric breakdown levels.

[0048] In addition to the spark gap and surge arrester, the device may also include another passive component, i.e., a component not operated by a controller, a metal oxide varistor between a pair of terminals, conveniently via a rail.

[0049] Furthermore, impulses can persist in such currents as long as the voltages across them are too high. To address this, the terminal connection means may include one or more active components, such as switches, between a pair of terminals, conveniently via rails. The switches may be physical switches such as relays, or electronic switches such as thyristors.

[0050] As a result, the conductors of the capacitive cable are short-circuited to each other, there is no voltage between the conductors, and there is no voltage across the dielectric material between the plates of the capacitor, and the power cable is directly connected to the load cable. This protects the dielectric material from voltages across its ends that could cause damage.

[0051] If a current surge occurs in either the load cable or the power cable, or possibly one of the capacitive cables, the current in the direct connection between the connection terminal and one of the pair of cable terminals within the device increases. When the connection means detects that this exceeds a threshold, these three terminals are conveniently directly connected to each other by the connection means, preferably via a switch. As a result, the conductors of the capacitive cables are short-circuited to each other, and with current shared between the two capacitively connected conductors, the power cable is directly connected to the load cable.

[0052] The connecting means may be rated to the rated voltage of the power grid to which the connection and protective devices are connected, provided that the means for connecting other cable terminals to the connecting terminals properly includes a switch, and the switch normally maintains the voltage between its contacts before closing at the rated voltage. However, surprisingly, it has been found that the actual voltage between terminals that are switched to each other is usually an order of magnitude lower than the rated voltage. This is because the voltage between the rails depends on the cable current acting on the capacitance between the plate elements of the capacitor. Thus, the voltage in question, which is proportional only to capacitance and current and not to the rated voltage, is lower than the rated voltage.

[0053] In practice, this makes it possible to set the voltage of the components of the connecting means, including the switch, to a voltage lower than the rated voltage of the device itself, as long as applicable safety standards are maintained.

[0054] Therefore, given that the rated voltage is practically the ground insulation rating, preferably the voltage threshold at which the connection is made is less than 20% of the ground insulation rating voltage of the connection and protection device, and the connection means consists of components whose rated voltage is less than 20% of the ground insulation rating. Typically, the above figure of 20% may be 15% in any case.

[0055] The rated operating current (due to minimized losses and low skin / proximity effect) is equal to or slightly (5% to 10%) higher than that of a typical cable with equivalent cross-sectional area of ​​copper or aluminum conductors. Therefore, the current threshold at which the connection is made is 20% higher than that of a typical cable with equivalent cross-sectional area of ​​copper conductors.

[0056] Typically, capacitive cables, as described in International Publication No. 2019 / 234449, comprise several layers of conductive load and power strands that are capacitively related by alternating within or between layers. Protected by embodiments of the present invention are the load and power strands and / or the dielectric between their layers. The choice of dielectric is not part of the fundamental invention. Typically, the dielectric is a lacquer as a non-conductive polymer material between layers of so-called magnet wire or un-enameled wire. At each end of the cable, the strands of each conductor can be bundled and guided to a protective device. However, it is preferable to bundle them and connect them to the above portion of a conventional cable guided to the protective device. The power and load cables are likely to be of the same type as conventional cables. Preferably, these cables or portions have a grounding sheath within their range from the protective device.

[0057] In installations where the connection and protection device is used with a short capacitive cable or two cables with a negligible difference in capacitance, the device may have internal capacitance that provides the capacitive cable advantages to the capacitive cable or the two cables. Alternatively, the connection and protection device may be installed with external capacitance that provides these advantages.

[0058] Preferably, the protective device has a conductive case that encloses the connecting means and the junctions of the three conductors with the connecting means. Preferably, the connecting means and the three conductors are all electrically isolated from the conductive case, the latter providing, when in use, a facility for grounding which may be realized by a grounding cable sheath or a separate earth connection.

[0059] During use, the voltage applied to the power conductor induces a voltage in the load conductor of the capacitive cable. Under certain network conditions, such as low loads, the capacitiveness of the cable offers little advantage, and the switch can be closed to connect all terminals of the device to each other. For this reason, the device may conveniently be provided with a wired or wireless interface for remotely controlling the closing of the switch. Such an interface may be similar to one for communication with another similar device at the other end of a long circuit.

[0060] As the load and, consequently the current, increase, the voltage difference between the load conductor and the power conductor increases. All conductors conduct the cable's rated voltage relative to ground, but the relative voltage between conductors in a capacitive cable is at least an order of magnitude lower than the rated voltage. For this reason, the dielectric material between conductors in a capacitive cable may be rated at the relative voltage at full load.

[0061] For similar reasons, the connection means of protective devices are rated to react and make contact at a voltage an order of magnitude lower than the rated voltage. In fact, if the connection means were rated to react at the rated voltage, the dielectric would be destroyed before the connection means could react. In other words, it is preferable that the threshold be set approximately an order of magnitude lower than the rated voltage, or even lower.

[0062] The connection means preferably includes, as circuit elements, a separate voltage detection means, such as those found in a voltage measurement circuit, and an element such as a switch that closes when a voltage threshold is detected.

[0063] The voltage between conductors in a capacitive cable can be disturbed by various factors, and the connection means may have various devices to accommodate these disturbances.

[0064] The connection means may include detecting whether a voltage threshold has been exceeded, as seen in circuit elements such as spark gap devices that conduct at a voltage that can jump over the gap. Alternatively, it may include a separate voltage detection means, as seen in voltage measurement circuits, and the connection means may include a circuit element such as a switch that closes when the voltage threshold is reached.

[0065] The above description assumes the connection of two capacitively connected cables when the voltage between them exceeds a threshold. However, there is another scenario in which this connection is desirable, specifically when the current demand for the cables is low. In such cases, the advantage of the cables being capacitive tends to be minimal or even disadvantageous. Therefore, the device may include means for connecting the two conductors when the current is below such a threshold. Typically, the connection means is the same as that used when the voltage between the conductors exceeds a threshold, i.e., preferably an active control component such as a switch. Alternatively, a separate active control component may be provided.

[0066] The above device preferably defaults to having the cable conductors connected to each other at startup. In this case, one component is normally closed and controlled to open when a current threshold is reached, while the other is controlled to close in the event of an overvoltage.

[0067] According to another aspect of the present invention, a connection and protection device is provided that is combined with a power transmission cable having two capacitively connected conductors, which are connected to a power cable at one end and a load cable at the other end, respectively, when in use, the connection and protection device is • Power / load connection terminals for connecting to either the power cable or the load cable mentioned above, • A pair of cable terminals for connecting to each capacitively connected conductor, or the interconnection portion of the cables from said terminals to each conductor, • A direct connection within the device between the power / load connection terminal and one of the pair of cable terminals, wherein the other of the pair of cable terminals is not normally connected to the power / load connection terminal. The following means are provided for connecting the other of the pair of cable terminals to the power / load connection terminal in order to protect the capacitive connection of the two conductors: • If the voltage between the pair of cable terminals exceeds the threshold, • If the current in the direct connection described above exceeds the threshold.

[0068] Typically, a power transmission cable with two capacitively connected conductors is combined with two similar connection and protection devices, one at one end and the other at the other.

[0069] The connection and protection device may incorporate a capacitor to improve the capacitive connection of the conductors.

[0070] In embodiments of the present invention, two or more relays are used, thereby simplifying control. In these embodiments, the apparatus or system is A normally closed relay that enables nighttime use, which opens when the current exceeds a threshold, It includes a normally open relay that closes when the differential voltage exceeds a threshold.

[0071] Optionally, this can be done completely automatically without the need for a control circuit. For example, if the coil of an NC relay is energized by an inductive loop around the main busbar, the NO relay is energized by an ohm wire between the busbars.

[0072] To aid in understanding the present invention, specific embodiments thereof will be described below, by example, with reference to the accompanying drawings. [Brief explanation of the drawing]

[0073] [Figure 1]Figure 1 is a diagram of the basic connection and protection device of the present invention. [Figure 2] Figure 2 is a diagram of a three-phase power supply including the connection and protection devices of the present invention. [Figure 3] Figure 3 is a block diagram showing the arrangement of components of the protective and connecting device of the present invention. [Figure 4] Figure 4 is a schematic diagram of an exemplary connection and protection device of the present invention. [Modes for carrying out the invention]

[0074] Referring to Figure 1 of the drawings, a first embodiment is shown in which two active control components are present, one component 1 being normally closed and controlled to open when a current threshold is reached, and the other component 2 being controlled to close when an overvoltage occurs. The device has a conductive housing 3, with three terminals 4, 5, and 6 provided in isolation inside the wall 7 of the housing. Inside the housing, a busbar 8 extends between terminals 4 and 5. A further busbar extends from terminal 6 to an isolated receptacle 9 on the other side of the housing.

[0075] An induction current sensing coil 11 is provided around the busbar 8 in series with the coil 12 of a normally closed (NC) relay 14, which has contacts connected to each busbar. During startup, when no current is flowing to the device via the busbar 8, terminals 5 and 6 are connected to each other by the normally closed relay. When the current reaches the current threshold, the relay opens, and sufficient current flows through coils 11 and 12 to enable capacitive operation of the capacitive cable whose conductors are connected to terminals 5 and 6.

[0076] A voltage sensing line 21, having a high-resistance series resistor 22 (sized to allow sufficient current to flow only for the following purpose), is connected in series with the coil 23 of a normally open (NO) relay 24. Its contacts are each connected to a busbar. Normally, during startup and normal operation, the voltage between the busbar and the conductor is within the capacity of the dielectric between the conductors, and the relay 24 remains open. If the voltage between busbars 6,8 / terminals 5,6 / cable conductor (not shown in Figure 1) exceeds a threshold that puts the dielectric in a potentially dangerous state, sufficient current flows through line 21, resistor 22, and coil 23 to close the NO relay, and the conductors connect to each other as during startup, but by relay 24 instead of relay 14.

[0077] As described above, in this embodiment, it is anticipated that the relay will need to be specially tuned so that the current in its coil operates at desired current and voltage thresholds. For this reason, the relay is preferably controlled by a control circuit, and in fact, it is preferable to use a single relay, as described below in the second embodiment.

[0078] However, it should be noted that in the simplest embodiment of the present invention, only one NO relay or other electronic switches configured to close when the voltage between conductors exceeds a threshold are required.

[0079] A second embodiment will be described with reference to Figures 2 to 4 of the drawings. A boosted transmission voltage (typically 33kV) distribution network 101 is provided between a power source 102 and a load 103. These and other features of the distribution network are shown in the drawings. 2 This is schematically shown in [reference]. This is a three-phase network where each phase is denoted by R, G, and B, and therefore, some of the above features are provided in three quantities. However, when the features of the present invention are provided in each phase, i.e., in the three phases as their respective features, these features have a common reference numeral.

[0080] The main cable of the power distribution network is a capacitive cable 104 having a plate 105 connected to the power source and a plate 106 connected to the load, with a dielectric 107 in between. The plates and dielectric are shown schematically. One end of the plate is connected, and the other end is connected. The unconnected end is usually simply cut.

[0081] A connection and protection device 108 is provided between the power cable 109 and the load cable 110 in each phase, with a short length of conventional cable 111 interposed between the device 108 and the capacitive cable 104. The connection between cable 104 and cable 111 is made by a connector 112, schematically shown. These may be as described in the applicant's International Publication No. 2019 / 234449, specifically in Figures 6 to 10.

[0082] All connection and protection devices 108 are identical, and only one representative example will be described with reference to Figure 4. These are voltage boosters using voltage components, some of which are operated by much lower electronic voltage control circuits. This is intended to ensure that the device has adequate grounding isolation for the power grid. For example, this boost is typically 33kV. As described above, the instantaneous voltage across the plates of a capacitor is an order of magnitude lower than this boost. As a result, the capacitive plates of a cable, which is practically composed of multiple strands and is a capacitive conductor, may be isolated by a dielectric with a much lower rated voltage. In other words, the breakdown voltage of the dielectric may be about one-third of the cable's rated voltage. Similarly, the connection and protection device may have a rated voltage that protects the dielectric in response to an abnormal voltage of 15% to 20% of the rated voltage. This is the low voltage mentioned above. The associated circuitry for at least some operation on the low-voltage components may operate at an electronic circuit voltage, typically 12 volts. This voltage relationship is shown in Figure 3.

[0083] As shown in Figures 2 and 4, the connection and protection device is, schematically, power / load cable 109, 110 From capacitive cable104 The cable has a straight connecting rail 121 to one of the plates 105, 106 and an isolation rail 122 for the other plate 106, 105. Since the cable 104 is capacitive, at the power supply end, plate 105 is straight connected by rail 121 with plate 106 connected to isolation rail 122, while at the load end of the capacitive cable, plate 106 is straight connected by connecting rail 121 with plate 105 connected to isolation rail 122.

[0084] However, exemplary connection and protection devices are described below as standalone devices. These devices have a steel outer case 123 with an earth connection suitable for power distribution cable connections. The structural configuration of the case or cabinet can be determined by those skilled in the art according to the electrical features described below.

[0085] Two rails 121 and 122 are arranged throughout the case 123. The straight / direct connection rail 121 has two cable terminals, one at each end, as connectors 125 and 126. These may also be socket components of the Pfisterer MV-Connex cable connectors described at https: / / www.pfisterer.com / fileadmin / pfisterer / downloads en / CableSystemMV-CT-EN.pdf. The connected cable has the cable core connected to the rail and the cable sheath connected to the outer case. 123 A plug component for connection is provided. The isolation rail is mounted in an insulated manner at one end, and a cable terminal / connector 127 is provided at the other end. Various circuit elements are connected to the rails and between the rails.

[0086] As shown in Figure 3, the circuit described below is composed of three groups. That is, • High-voltage components of Group I, directly connected between rails 121 and 122 of the busbar, to allow current to flow from one rail to the other when the voltage between the rails exceeds a voltage threshold. A Group III low-voltage control circuit component that receives power from the rails and monitors the current flowing through the rails and their relative voltages. • A Group II switch 128, whose threshold voltage is set to the rated voltage, allows current to be conducted between rails as needed under the control of Group III components.

[0087] All of the above components are completely insulated by high-voltage insulation from the conductive case 123, which is grounded during use, preventing insulation failure from one group to the next. In other words, although the switch 128 and the group I components are connected to the rails by their terminals, the switch 128 and the group I components only receive the rail voltage, so the rail voltage can be the rated voltage. The internal insulation of the switch isolates the rail voltage from the low voltage on its control wires connected to the low-voltage control circuit.

[0088] All of the above components may be mounted on a single board, insulated by a line voltage whose rated voltage is equal to the voltage that insulates them from the case. However, the components of Group I may be mechanically and electrically connected between the rails. The same applies to the contacts of switch 128.

[0089] The low-voltage components mentioned above are mounted on a printed circuit board that is completely insulated from the case from the transmission line voltage.

[0090] One element between the rails is a normally open switch 128, for which a drive circuit 129 is provided. As shown in Figure 3, this switch is configured to receive a radio control signal. The purpose of this switch is to short-circuit the two rails so that no potential exists between them when the rail-to-rail voltage exceeds a threshold. Note in particular that the cable, connector and rails are rated at 33kV, but the switch operates at 4kV. The possibility arising from this apparent dichotomy is that, under normal operating conditions, the capacitive connection of the two plates 105,106 of the capacitive distribution cable 104 causes the voltage differential between the load plate and the power plate to depend on the cable current acting on the capacitance between the plate elements of the capacitor. Therefore, the instantaneous voltage between the plate and rail is lower than the nominal peak voltage of 33kV or other relevant voltages, and in fact, almost an order of magnitude lower. Dielectrics in cables, such as those shown in International Publication No. 2019 / 234449 of this application, have the instantaneous voltage between the plates as their rated voltage. This is why the rated voltage of the circuit components in the above-mentioned connection and protection device can be set to a low voltage.

[0091] In another mode, switch 128 is normally closed, and the necessary modifications are made to the above operations. In the normally closed state, this state allows the cable to "fail-safe" back into normal mode by short-circuiting the red and green wires if the system loses external DC power to the control circuit. Thus, in response to a command to enter capacitive mode, the relay switch is kept electromechanically open, and this trigger releases power to the relay, allowing the relay to return to the closed position.

[0092] Referring to Figure 4, the voltage between the rails is measured by the measurement circuit 130. If this voltage exceeds a threshold, typically 4kV, the circuit signals the drive circuit 129 for switch 128. The drive circuit closes the switch, and the two rails 121 and 122 are connected to each other by the switch, eliminating the voltage difference between them. Since this switch is an electromagnetic relay switch, it requires a discernible amount of time to close in the event of an event such as a lightning strike. In other words, this switch is too slow, so a thyristor switch 228 is provided in parallel with the circuit and operated by the same drive circuit 129. Other faster components are provided, as will be described below.

[0093] The device also includes a current transformer 132 that detects overcurrents in the rail 121 and sends a signal to the drive circuit 129 for closing the switch and sharing the overcurrents between the two capacitive conductors. The drive circuit is also configured to keep the switch closed after startup and at other times when the current in the rail 121 is below other lower thresholds.

[0094] In other words, the current transformer serves a further purpose in detecting when the current is below a low threshold, which is advantageous for the capacitive conductor to behave like a normal conductor. The switch is configured as a normally closed relay switch, so that it is closed by a normal network switch (not shown) when the capacitive cable is first switched to the operating state.

[0095] The other circuit components in the above device are as follows: • Includes rectifier and battery, switch drive cycle Road Low-voltage power supply 133, which supplies power to other components including • A voltage divider 134 between rails for supplying AC to the above power supply in the electronic circuit voltage, For example, a metal oxide surge arrester 135 to limit the transient voltage peak between the rails caused by an impulse. This is due to the semiconductor property of the surge arrester, which allows current to flow between the rails when the transient voltage rises to the surge arrester's breakdown voltage. Preferably, the surge arrester is specified to shut down at a voltage approximately half the voltage at which the switch is controlled to operate, i.e., 2kV in this embodiment. This ensures that the switch is not operated while the transient voltage is limited to 2kV by the surge arrester. If the power of the transient voltage, i.e., the power of the impulse, is too high, this may not be possible, and in particular if the surge arrester burns out, a spark gap 136 is provided to allow a steep-sided impulse to pass between the rails. The spark gap is provided so that a steep-sided spike conducts before the surge arrester conducts, just as the surge arrester is expected to operate faster than the switch and its drive circuit. Conveniently, the conduction voltage of the spark gap is the same as the conduction voltage of the surge arrester. A further device in parallel with the surge arrester and spark gap is a varistor 236, which more ensures that the dielectric of the capacitive cable is protected before the switch (in its electromagnetic and thyristor forms).

[0096] Note that the following surge arresters, spark gaps, varistors, and capacitor 139 are included in Group I with respect to insulation, in that they are fully exposed to line voltages relative to the grounded conductive case.

[0097] Power supply and monitoring circuits are included in Group III, and like Group I components, they operate at low voltages and are exposed to line voltages only to the extent that they protect the circuits from full line voltage or even interconductor voltage.

[0098] Switches are designated as Group II components because the voltage between their contacts to the rails and the control contacts between them must not exceed or fall by more or less than an order of magnitude the line voltage to ground.

[0099] When the switch is closed due to an exceedance of a voltage threshold or current threshold, it remains closed until the disturbance that caused the overvoltage or overcurrent disappears. The switch drive circuit reopens the switch and resumes normal operation only when the current measured by the current measuring device 132 falls below the high current threshold. The above monitoring and switching are managed by a controller 137, which is driven by a power supply and sends a "closed" or "opened" signal to the switch drive circuit as appropriate.

[0100] Each switch operation is expected to generate a capacitive discharge current within the switch. To protect against this, a current attenuator is included as part of the connection mechanism. 138 It exists in series with switch 128.

[0101] The above device also includes an optional capacitor 139. One or more of these may be mounted inside or outside the case 123. Its function is to increase the capacitance between capacitively connected conductors, especially when it is a normal cable capacitively connected only by the capacitor 139.

[0102] The present invention is not intended to be limited to the details of the embodiments described above. For example, the connection and distribution equipment may be mounted in a grounded cabinet inside a substation. In this case, the grounded external case 123 can be omitted. Also, if the connection and distribution equipment is installed in such a substation cabinet, it may be powered by the substation's own power supply. Further inputs may be provided to the switch drive circuit 129 from wired or wireless input ports, thereby allowing the switch 128 to be closed to a state indicated by the network condition. In fact, the measurement of network current and / or interconductor voltage may be provided without a grounded case, and / or, in fact, power for the grounded cabinet and the closing of control signals and / or relays may be provided in a case / cabinet for closing the interconductor switch in response to the measurement and / or external control. This is particularly true when the other end of a capacitive cable is closed by a measurement at one end, and it is desirable to also perform the closing of the other end.

[0103] Additional embodiments of the present invention are shown below:

[0104] 1. A power transmission cable protection and control configuration for a capacitive power transmission cable, wherein the configuration comprises, At one end of the cable, • Load terminals or power terminals for load cables or power cables, A pair of cable terminals for a pair of conductors of the capacitive power transmission cable, wherein the conductors are connected directly or via extension conductors of the terminals when in use. One of the pair of cable terminals is connected to the load terminal or power terminal by a rail or busbar, - The rail or busbar and the other of the pair of cable terminals are provided with an electromagnetic switch or electronic switch, At one end or the other end of the cable, • Means for measuring the differential voltage between the pair of cable terminals, i.e., between the capacitive cable conductors, during use. • Means for controlling the switch to close when the differential voltage exceeds a threshold below the dielectric breakdown of the capacitive cable. A power transmission cable protection and control configuration comprising:

[0105] 2. A power transmission cable protection and control configuration according to Embodiment 1, The switch control means is configured to control the switch in a second or third event, or alternatively, a separate switch control means is provided. The second event is that the current in the busbar or rail falls below a certain threshold. A power transmission cable protection and control configuration in which the third event is that the current in the busbar or rail exceeds a certain threshold.

[0106] 3. A power transmission cable protection and control configuration according to Embodiment 1, The second switch control means is configured to control the second switch between the rail or busbar and the other of the pair of cable terminals in the second or third configuration. The second event is that the current in the busbar or rail falls below a certain threshold. A power transmission cable protection and control configuration in which the third event is that the current in the busbar or rail exceeds a certain threshold.

[0107] 4. A power transmission cable protection and control configuration according to Embodiment 1, Embodiment 2, or Embodiment 3, comprising a capacitor that provides or increases the capacitance between the conductors of the capacitive cable.

[0108] 5. A power transmission cable protection and control configuration according to any of the preceding embodiments, comprising a connection and protection device housed in a grounded or groundable conductive case or conductive cabinet, wherein the terminals are isolated from the power transmission voltage, and the switch has a rated voltage of the differential breakdown voltage.

[0109] 6. The connection and protection device according to Embodiment 5, wherein the measuring means and control means are housed together with the terminals and the switch in a case or cabinet.

[0110] 7. The connection and protection device according to Embodiment 6, which is combined with a second such device for the opposite end of the capacitive cable, wherein the device is configured for wireless communication, wired communication, or optical fiber communication.

[0111] 8. The connection and protection device according to Embodiment 5, Embodiment 6, or Embodiment 7, which includes between the rail or busbar and the other of the pair of cable terminals an autonomous device configured to conduct and reduce the differential voltage faster than the switch can close, preferably at least one of a metal oxide surge arrester, spark gap, and varistor.

[0112] 9. A connection and protection device according to any one of embodiments 5 to 8, comprising both an electromagnetic switch and an electronic switch, wherein the electronic switch is configured to close earlier than the electromagnetic switch.

[0113] 10. A connection and protection device according to any one of embodiments 5 to 9, The aforementioned connecting means The rated voltage shall be 20% or less, preferably 15% or less, of the voltage transmitted by the capacitive cable, and • Configured to operate with lower voltage control, The event detection means includes means for detecting when the voltage between the pair of cables exceeds a threshold of 20%, preferably 15%, of the transmitted voltage. The aforementioned device, • Low-voltage power supply inside the case or cabinet, A connection and protection device comprising: a low-voltage controller in the housing for causing the connection means to make the connection when it detects that the voltage exceeds the threshold.

[0114] 11. A connection and protection device according to any one of embodiments 5 to 10, which is combined with one or more capacitors connected between the pair of cable terminals and located outside the device.

[0115] 12. A combination of a cable and a connection and protection device according to Embodiment 11, wherein the cable includes a pair of conductors that are capacitively related along its length.

[0116] 13. A connection and protection device according to any one of embodiments 5 to 12, combined with a power transmission cable having two capacitively connected conductors, which are connected to a power cable at one end and a load cable at the other end, respectively, when in use.

[0117] 14. The combination of connection and protection device and cable according to Embodiment 13, wherein the cable includes a pair of conventional boost power transmission cables, which are housed as circuit elements of the connection and protection device or are capacitively connected at one end or the other by one or more conventional capacitors housed separately.

[0118] 15. The combination of a connection and protection device and a cable according to Embodiment 13, wherein the cable includes a pair of conductors that are capacitively related along its length, and an additional capacitor is provided as a circuit element within the device.

[0119] 16. A connection and protection device for a power transmission cable having two capacitively connected conductors, which are connected to a power cable at one end and a load cable at the other end, respectively, when in use, • Groundable conductive housing, Each of the three connection terminals is rated to provide a termination point for voltage boosting isolation from the housing and an internal connection point within the housing, One of the connection terminals is for the insulated termination and internal connection of either the power cable or the load cable. The other cable terminals are either a pair for the insulated termination and internal connection of each of the capacitively connected conductors, or one of the interconnection portions of the cable from the terminal to each of the conductors, and the other three terminals are connected terminals. A direct connection between one of the connection terminals within the housing and one of the pair of cable terminals, wherein the other of the pair of cable terminals is not normally connected to the connection terminal. - In order to protect the capacitive connection of the two conductors when the voltage between the pair of cable terminals exceeds a threshold, means within the housing for connecting the other of the pair of cable terminals to the connection terminal and A connection and protection device comprising:

[0120] 17. The connection and protection device according to Embodiment 16, comprising event detection means including means for detecting that the voltage between the pair of cables exceeds a threshold.

[0121] 18. A connection and protection device in combination with a power transmission cable having two capacitively connected conductors, which are connected to a power cable at one end and a load cable at the other end, respectively, when in use, • Groundable conductive housing, Each of the three connection terminals is rated to provide a termination point for voltage boosting isolation from the housing and an internal connection point within the housing, One of the connection terminals is for the insulated termination and internal connection of either the power cable or the load cable. The other cable terminals are either a pair for the insulated termination and internal connection of each of the capacitively connected conductors, or one of the interconnection portions of the cable from the terminal to each of the conductors, and the other three terminals are connected terminals. A direct connection between one of the connection terminals within the housing and one of the pair of cable terminals, wherein the other of the pair of cable terminals is not normally connected to the connection terminal. - Means within the housing for connecting the other of the pair of cable terminals to the connection terminal in order to protect the capacitive connection of the two conductors when the voltage between the pair of cable terminals exceeds a threshold, The connection means is set to a rated voltage of 20% or less of the boosted voltage. The connection means is configured to operate by low-voltage control, • Event detection means including means for detecting when the voltage between the pair of cables exceeds a threshold of 20% of the boosted voltage, • Low-voltage power supply within the housing, - A low-voltage controller within the housing, which, when it detects that the voltage has exceeded the threshold, causes the connection means to make the connection. A connection and protection device comprising:

[0122] 19. Power grid, • Power supply connected to the first node, The first node is connected to the second node by two or more conductors separated by a dielectric, The second node and, A power supply network comprising a control system, The two or more conductors are capable of transmitting power between the first node and the second node via a galvanic connection in the first mode, or as a capacitive cable in the second mode. A power grid in which the control system is capable of switching the two or more conductors between the first node and the second mode.

[0123] 20. The power grid according to embodiment 19, wherein the switching between the two or more conductors can be performed manually by an operator.

[0124] 21. The power supply network according to embodiment 19 or 20, further comprising a dielectric device capable of switching between the two or more conductors in response to a trigger event.

[0125] 22. The power supply network according to Embodiment 21, wherein the trigger event includes an overvoltage between each conductor when operating as a capacitive cable.

[0126] 23. The power grid according to Embodiment 21, wherein the trigger event includes a safety warning indicating that the operating mode of the conductor in the current mode is inappropriate.

[0127] 24. The power grid according to Embodiment 21, wherein the trigger event includes a reduction in load, indicating that galvanic connection is preferred over capacitive mode.

[0128] 25. The two or more conductors include a first conductor and a second conductor, In the first mode, the first end of the first conductor is connected to the first node, the second end of the first conductor is connected to the second node, and / or the first end of the second conductor is connected to the first node, and the second end of the second conductor is connected to the second node, A power supply network according to any one of embodiments 19 to 24, wherein, in the second mode, the first conductor is connected to the first node at its first end but not to the second node at its second end, and the second conductor is not connected to the first node at its first end but is connected to the second node at its second end.

[0129] 26. The power grid according to any one of embodiments 19 to 25, wherein the control system includes control circuits at both the first node and the second node, and the switching between the first node and the second mode includes operating relays simultaneously at both nodes.

[0130] 27. A power supply network according to any one of embodiments 19 to 26, wherein the control system comprises the connection and protection devices described in any one of embodiments 1 to 17.

Claims

1. - Power supply connected to the first node, - The first node is connected to the second node by two or more conductors separated by a dielectric, - The second node and, A power supply network comprising a control system, The two or more conductors are capable of transmitting power between the first node and the second node via a galvanic connection in the first mode, or as a capacitive power transmission cable in the second mode. A power grid in which the control system is capable of switching the two or more conductors between the first mode and the second mode.

2. The power grid according to claim 1, wherein the switching between the two or more conductors can be performed manually by an operator.

3. The power supply network according to claim 1 or 2, further comprising a dielectric device capable of switching between the two or more conductors in response to a trigger event.

4. The power grid according to claim 3, wherein the trigger event includes an overvoltage between each conductor when operating as a capacitive power transmission cable.

5. The power grid according to claim 3, wherein the trigger event includes a safety warning indicating that the operating mode of the conductor in the current mode is inappropriate.

6. The power grid according to claim 3, wherein the trigger event includes a reduction in load, indicating that galvanic connection is preferable to capacitive mode.

7. The two or more conductors include a first conductor and a second conductor, In the first mode, the first end of the first conductor is connected to the first node, the second end of the first conductor is connected to the second node, and / or the first end of the second conductor is connected to the first node, the second end of the second conductor is connected to the second node, The power supply network according to any one of claims 1 to 6, wherein in the second mode, the first conductor is connected to the first node at its first end but not to the second node at its second end, and the second conductor is not connected to the first node at its first end but is connected to the second node at its second end.

8. The power grid according to any one of claims 1 to 7, wherein the control system includes control circuits at both the first node and the second node, and the switching between the first mode and the second mode includes operating relays simultaneously at both nodes.

9. The control system, At one end of the aforementioned capacitive power transmission cable, - Load terminals or power terminals for load cables or power cables, - A pair of cable terminals for a pair of conductors of the capacitive power transmission cable, wherein the conductors are connected directly or via extension conductors of the pair of cable terminals when in use. - One of the pair of cable terminals is connected to the load terminal or power terminal by a rail or busbar, - comprising an electromagnetic switch or electronic switch between the rail or busbar and the other of the pair of cable terminals, At one end or the other end of the capacitive power transmission cable, - Means for measuring the differential voltage between the pair of cable terminals, i.e., between the conductors of the capacitive power transmission cable, during use, - Means for controlling the electromagnetic switch or electronic switch to close when the differential voltage exceeds a threshold below the dielectric breakdown of the capacitive power transmission cable. A power grid according to any one of claims 1 to 8, comprising connection and protection devices.

10. In the aforementioned connection and protection device, - The means for controlling the electromagnetic switch or the electronic switch is configured to control the electromagnetic switch or the electronic switch in a second or third event, or alternatively, a separate switch control means is provided. - The second event is that the current in the busbar or rail falls below a certain threshold. The power grid according to claim 9, wherein the third event is that the current in the busbar or rail exceeds a certain threshold.

11. In the aforementioned connection and protection device, - The second switch control means is configured to control the second switch between the rail or busbar and the other of the pair of cable terminals in the second or third configuration. - The second event is that the current in the busbar or rail falls below a certain threshold. The power grid according to claim 9, wherein the third event is that the current in the busbar or rail exceeds a certain threshold.

Images