Disclosure of Invention
The invention aims to overcome the defects in the background technology and provide an all-solid-state breaking structure for an on-line uninterrupted ice melting device for split wires.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
An all-solid-state breaking structure for an on-line uninterrupted ice melting device for split conductors, comprising:
A series of multi-unit series-parallel structures, each multi-unit series-parallel structure is configured corresponding to one sub-conductor in the split conductor, each multi-unit series-parallel structure is formed by connecting a plurality of all-solid-state power units in series into a plurality of series branches, and the plurality of series branches are connected in parallel;
The all-solid-state power unit comprises an anti-parallel topology formed by a pair of insulated gate bipolar transistors and anti-parallel diodes which are connected by common emitters so as to realize bidirectional current conduction and blocking, a voltage limiting circuit, an overvoltage protection device, a voltage limiting circuit and a power supply, wherein the voltage limiting circuit comprises a resistor, a capacitor and diodes which form an RCD voltage limiting module and are connected in parallel at two ends of each insulated gate bipolar transistor;
The control driving unit is electrically connected to the grid electrode of each insulated gate bipolar transistor, and each all-solid-state power unit in the multi-unit serial-parallel structure is synchronously turned on and off under the control of the control driving unit;
The two ports of each multi-unit serial-parallel structure are respectively connected to two connection points of each sub-wire of the split wire and are fixed at the wire connection position of the transmission tower.
Further, in the multi-unit serial-parallel structure:
the number of the series branches is determined by the voltage difference born by the switch when the switch is opened, so as to ensure that the voltage of the single all-solid-state power unit is in a safe range;
The number of parallel branches is determined by the instantaneous maximum current in the ice melting state, so as to improve the through-flow capacity of the system.
Further, the voltage difference is calculated according to the following formula:
;
Wherein, theFor the short-circuit point and the distance from the short-circuit point on the through-current sub-conductorThe voltage difference at which,For the phase currents flowing through the subconductors,For the distance to the short-circuit point,Is the resistance per unit length of the sub-conductor,The inductance of the sub-conductor in the case of one through-current and one cut-off.
Further, the RCD voltage limiting module parameters satisfy the following formula:
;
Wherein, C is the capacitance value,Stray inductance in an IGBT turn-off loop;
the value of the resistor R should satisfy the following formula:
;
Wherein, theIs the maximum value of the collector current of the IGBT.
Further, the actual number of the series-parallel branches is 1.5 times the calculated number of redundant configurations.
Further, the multi-unit serial-parallel structure further includes:
and the buffer impedance element is connected with each all-solid-state power unit and is used for inhibiting circulation and oscillation between the units.
Further, the control driving unit satisfies:
The grid control signals output to the insulated gate bipolar transistors in the multi-unit serial-parallel structure are synchronous in time sequence, and the time difference is within a set acceptable error range;
the gate control signals of all insulated gate bipolar transistors on the same subconductor are the same.
In some embodiments, the all-solid-state switching structure for the split conductor on-line uninterrupted ice melting device comprises an all-solid-state power unit, a voltage limiting circuit, a multi-unit serial-parallel connection structure, a control driving unit and a control driving unit, wherein the all-solid-state power unit comprises an Insulated Gate Bipolar Transistor (IGBT) and an anti-parallel diode which are connected by a common emitter, the voltage limiting circuit comprises an RCD voltage limiting structure consisting of a resistor, a capacitor and a diode;
The series-parallel connection structure formed by the units is provided with two ports, the two ports are respectively connected to jumper wire joints of a tower, RCD modules of a voltage limiting circuit are connected in parallel to two ends of each unit, the number of the RCD modules is identical to that of anti-parallel power modules, a metal oxide piezoresistor overvoltage protection device is connected in parallel to two ends of each group of all-solid-state power units, output ports of a control driving unit are aligned to grid areas of the insulated gate bipolar transistors in the anti-parallel power modules, grid control signals of the same sub-wires are identical, time sequences are synchronous, the time difference from the control signals to the grid is required to be within an acceptable error range, and the series-parallel connection structure is completely arranged in an on-line uninterrupted ice melting device of the split wires, receives signals from a monitoring module and a total control module of the ice melting device, and is fixed at the joints of the two sections of wires of the power tower, so that ice melting current transfer on the sub-wires is realized.
The all-solid-state power unit comprises a first insulated gate bipolar transistor and a second insulated gate bipolar transistor, wherein an emitter of the first insulated gate bipolar transistor is connected to an emitter of the second insulated gate bipolar transistor, a cathode of the first diode is connected with a collector of the first insulated gate bipolar transistor, a cathode of the second diode is connected with a collector of the second insulated gate bipolar transistor to form an anti-parallel structure, grid electrodes of the first insulated gate bipolar transistor and the second insulated gate bipolar transistor are respectively connected to the control driving unit and used for independently receiving control signals with the same time sequence, and the anti-parallel structure can realize a bidirectional current conduction and blocking function and is suitable for the on-off operation of an alternating current circuit.
The voltage limiting circuit comprises an RCD voltage limiting circuit formed by a resistor, a capacitor and a diode, wherein the RCD voltage limiting circuit is connected with a corresponding insulated gate bipolar transistor in parallel, the resistor is connected with the diode in parallel, a parallel port on the cathode side of the diode is connected with the capacitor in a parallel structure formed by the resistor, namely the parallel structure formed by the resistor and the diode is connected with the capacitor in series to form a complete voltage limiting module, the resistor is used for limiting the overvoltage amplitude in the switching-on and switching-off process, the capacitor is used for absorbing transient energy in the switching-on and switching-off process and controlling the voltage rising rate, the diode is used for providing a unidirectional conduction path to ensure capacitor discharge, and the impedance parameter of the voltage limiting circuit is matched with the parasitic parameter of the insulated gate bipolar transistor so as to ensure uniform voltage distribution in a multi-unit structure and improve the voltage withstanding capability and reliability of the system.
The metal oxide piezoresistor is connected in parallel to two ends of each all-solid-state power unit, rated working voltage of the metal oxide piezoresistor is higher than normal working voltage of the all-solid-state power units and lower than the maximum withstand voltage value of the all-solid-state power units, and when transient overvoltage occurs in the system, the metal oxide piezoresistor is conducted to absorb excessive energy to limit voltage amplitude of the two ends of the all-solid-state power units.
The multi-unit serial-parallel structure comprises a plurality of all-solid-state power units connected in series to form a plurality of serial branches, wherein the serial branches are connected in parallel to form a complete switching-on unit, the number of all-solid-state power units in each serial branch is determined according to a voltage difference under a switching-off situation to ensure that the voltage born by each all-solid-state power unit is within a safe range, the number of parallel branches is determined according to the instantaneous maximum current which can pass through subconductors in a deicing state to improve the current carrying capacity of the system, redundancy is also needed to be considered in the serial-parallel structure, the number of actual serial-parallel branches which is 1.5 times the number of serial-parallel branches is needed to be calculated because the switching-off structure is applied to a main power transmission line with higher voltage level, each all-solid-state power unit in the multi-unit serial-parallel structure realizes synchronous switching-on and switching-off through the control driving unit to ensure uniform distribution of voltage and current, and the multi-unit serial-parallel structure also comprises a buffer impedance element connected with each unit to inhibit circulation and oscillation phenomena among the units.
The invention has the following beneficial effects:
The invention provides an all-solid-state switching-on and switching-off structure for an on-line uninterrupted ice melting device for split conductors, which adopts an all-solid-state IGBT as a core power electronic device, constructs a circuit breaker unit in an anti-parallel topology mode, and realizes a voltage limiting function by utilizing a passive RCD circuit. The invention designs a multi-unit serial-parallel configuration scheme, effectively improves the voltage-resistant capacity and the through-current capacity of the system, and is suitable for the voltage and current requirements of high-voltage lines. The switching-on and switching-off structure has the advantages of high response speed, high reliability, good electromagnetic compatibility and the like, can realize the ice melting operation of the high-voltage circuit under the condition of not interrupting power supply, and solves the technical problem that the traditional ice melting method needs power failure. The all-solid-state switching-on/off structure replaces a mechanical switch, eliminates the ageing and arc hidden trouble of mechanical parts, avoids the potential switching-on/off faults of the mechanical switch in extreme environments such as cold, damp and the like, and ensures the stable operation of the system in high-pressure environments by the optimized anti-parallel topology and the RCD voltage limiting circuit design. The invention realizes reliable breaking in the process of ice melting of the high-voltage line, and in the whole process, a power grid user cannot perceive power interruption, thereby realizing 'ice melting without power failure' in the true sense. The solution of the invention provides a key support for the online uninterrupted ice melting technology of the power transmission line, and has important significance for improving the operation reliability of the power grid under severe weather conditions.
Other advantages of embodiments of the present invention are further described below.
Detailed Description
The following describes embodiments of the present invention in detail. It should be emphasized that the following description is merely exemplary in nature and is in no way intended to limit the scope of the invention or its applications.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for both a fixing action and a coupling or communication action.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing embodiments of the invention and to simplify the description, and do not denote or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
The invention provides an all-solid-state breaking structure for an on-line uninterrupted ice melting device for split conductors, which realizes reliable breaking in the process of ice melting of a high-voltage line by anti-parallel IGBT topology, RCD voltage limiting circuits, multi-unit serial-parallel configuration and control of a driving unit and provides key support for the on-line uninterrupted ice melting technology of a power transmission line.
Referring to fig. 1 to 4, an embodiment of the present invention provides an all-solid-state breaking structure for an on-line uninterrupted ice melting device for split conductors, which includes a control driving unit and a series of multi-unit serial-parallel structures. Each multi-unit serial-parallel structure is configured corresponding to one subconductor in the split conductor, and a plurality of all-solid-state power units are connected in series to form a plurality of serial branches in each multi-unit serial-parallel structure, and the serial branches are connected in parallel. The all-solid-state power unit comprises an anti-parallel topology formed by a pair of Insulated Gate Bipolar Transistors (IGBT) and anti-parallel diodes which are connected through common emitters so as to realize bidirectional current conduction and blocking, a voltage limiting circuit, an RCD voltage limiting module formed by a resistor R, a capacitor C and a diode D, and an overvoltage protection device, wherein the RCD voltage limiting module is connected in parallel to two ends of each insulated gate bipolar transistor, and the overvoltage protection device is connected in parallel to two ends of each insulated gate bipolar transistor. The switching-on and switching-off structure is based on IGBT, and constructs a common-emission-stage circuit breaker topological unit and a passive RCD buffer circuit. The multi-unit serial-parallel configuration promotes withstand voltage and current capacity. The control driving unit is electrically connected to the grid electrode of each insulated gate bipolar transistor, and each all-solid-state power unit in the multi-unit serial-parallel structure is synchronously turned on and off under the control of the control driving unit. Two ports of each multi-unit serial-parallel structure are respectively connected to two sections of split conductors and are positioned at jumper strings of the transmission tower.
In some embodiments, the control driving unit outputs the same gate control signal to all the insulated gate bipolar transistors in the multi-unit serial-parallel structure, and the time difference is within a set acceptable error range.
In some embodiments, the all-solid-state power unit comprises a first insulated gate bipolar transistor IGBT1, a second insulated gate bipolar transistor IGBT2, a first diode D1 and a second diode D2, wherein the first insulated gate bipolar transistor IGBT1 and an emitter of the second insulated gate bipolar transistor IGBT2 are commonly connected, a cathode of the first diode D1 is connected with a collector of the first insulated gate bipolar transistor IGBT1, a cathode of the second diode D2 is connected with a collector of the second insulated gate bipolar transistor IGBT2 to form an anti-parallel bi-directional conduction structure, and gates of the first insulated gate bipolar transistor IGBT1 and the second insulated gate bipolar transistor IGBT2 are respectively and independently connected to the control driving unit.
In some embodiments, the RCD voltage limiting module is characterized in that a resistor R is connected with a diode D in parallel to form a parallel structure, a diode cathode side port of the parallel structure is connected with a capacitor C in series, the resistor is used for limiting the overvoltage amplitude, the capacitor is used for absorbing transient energy and controlling the voltage rising rate, and the diode provides a capacitor discharging path.
In some embodiments, the overvoltage protection device is a Metal Oxide Varistor (MOV) whose rated operating voltage is above the normal operating voltage of the all-solid-state power unit and below its maximum withstand voltage value for absorbing transient overvoltage energy.
In some embodiments, the multi-unit serial-parallel structure is characterized in that the number of serial branches is determined by the voltage difference born by the switch when the switch is opened so as to ensure that the voltage of a single all-solid-state power unit is in a safe range, and the number of parallel branches is determined by the instantaneous maximum current in the ice melting state so as to improve the through-current capacity of the system.
In a preferred embodiment, the calculation of the voltage difference is according to the following formula:
;
Wherein, theFor the short-circuit point and the distance from the short-circuit point on the through-current sub-conductorThe voltage difference at which,For the phase currents flowing through the subconductors,For the distance to the short-circuit point,Is the resistance per unit length of the sub-conductor,The inductance of the sub-conductor in the case of one through-current and one cut-off.
In a preferred embodiment, the RCD voltage limiting module parameters satisfy the following equation:
;
Wherein, C is the capacitance value,Stray inductance in an IGBT turn-off loop;
the value of the resistor R should satisfy the following formula:
;
Wherein, theIs the maximum value of the collector current of the IGBT.
In a preferred embodiment, the actual number of the series-parallel branches is 1.5 times the calculated number of redundant configurations.
In some embodiments, the multi-cell series-parallel structure further includes a snubber impedance element connecting each all-solid-state power cell for suppressing inter-cell circulation and oscillation.
Specific embodiments of the present invention are described further below.
An all-solid-state breaking structure for an on-line uninterrupted ice melting device for split conductors comprises a multi-unit serial-parallel structure formed by a plurality of all-solid-state power units and a control driving unit.
As shown in fig. 1, the all-solid-state power unit comprises a common emitter connected Insulated Gate Bipolar Transistor (IGBT) and an anti-parallel diode, wherein the common emitter insulated gate bipolar transistor has a bidirectional conduction function, and a serial-parallel structure formed by the unit is provided with two ports which are respectively connected to the jumper connection parts of two split conductors positioned on a pole tower.
The dual-current-conducting and blocking device comprises a first insulated gate bipolar transistor IGBT1, a second insulated gate bipolar transistor IGBT2, a first diode D1 and a second diode D2, wherein an emitter of the first insulated gate bipolar transistor IGBT1 is connected to an emitter of the second insulated gate bipolar transistor IGBT2, a cathode of the first diode D1 is connected with a collector of the first insulated gate bipolar transistor IGBT1, a cathode of the second diode D2 is connected with a collector of the second insulated gate bipolar transistor IGBT2 to form an anti-parallel structure, grids of the first insulated gate bipolar transistor and the second insulated gate bipolar transistor are respectively connected to a control driving unit and used for independently receiving control signals with the same time sequence, and the anti-parallel structure can realize a dual-current-conducting and blocking function and is suitable for the on-off operation of an alternating current circuit.
In this embodiment, the voltage difference at the switch is greatly affected by the high-voltage transmission line and the corresponding rated subconductor current, so as to help determine the parameters and the selection type of the insulated gate bipolar transistor IGBT.
Taking two split wires as an example, one of the two sub wires is disconnected, and the voltage difference between the wires and the voltage difference between the break points of the disconnected wires are calculated under the condition that the other one of the two sub wires is disconnected, and the position voltage difference from the short circuit point to the x position of the short circuit point on the through-current sub wire is calculated according to ohm's lawAnd (3) performing calculation:
Wherein, theFor the short-circuit point and the distance from the short-circuit point on the through-current sub-conductorThe voltage difference at which,For the phase currents flowing through the subconductors,For the distance to the short-circuit point,Is the resistance per unit length of the sub-conductor,The inductance of the sub-conductor in the case of one through-current and one cut-off.
Further, the grid frequency is 50Hz, and it can be determined that:
Wherein, the。
Furthermore, the high-voltage transmission line adopts steel-cored aluminum stranded wires, and the corresponding resistance per unit length can be obtained according to the type of the steel-cored aluminum stranded wiresAnd inductorParameters, the current of the transmission line is judged according to actual conditions, if 110kV is taken as an example, the current level of the transmission line can be 600-1200A, if the common steel-cored aluminum stranded wire resistance and inductance parameters of the 110kV line are adopted, the distance from the current to a short circuit point is reducedCalculating 10km to 20km, and obtaining the position voltage difference from the short circuit point to the short circuit point x on the current sub-conductorCan reach 3kV-10 kV.
Further, when the voltage difference between two ends of the fracture of the sub-conductor of the high-voltage transmission line is calculated, the method is the same as the method, and for the through-current sub-conductor, the voltage at the short-circuit point isThe voltage at the position x from the short circuit point isAnd for the broken sub-wires, the voltage at one side is the same as the short-circuit point, and the voltage at the other side is the same as the voltage at the position x from the short-circuit point (because the ice melting device is provided with the short-circuit point), so the voltage difference at the two ends of the wire ports is the same as the voltage difference between the split wiresIn the same range of 3kV-10kV, the insulated gate bipolar transistor IGBT disclosed in the patent can bear larger voltage and larger current, so that the number of devices is reduced, and the mechanical and electrical complexity of the whole switch structure is reduced.
The RCD voltage limiting circuit comprises a resistor R, a capacitor C and a diode D, wherein the RCD voltage limiting circuit is connected with a corresponding insulated gate bipolar transistor in parallel, the resistor R is connected with the diode D in parallel, a parallel port on the cathode side of the diode D is connected with the capacitor C in a parallel structure, namely the parallel structure formed by the resistor R and the diode D is connected with the capacitor C in series to form a complete voltage limiting module, the resistor R is used for limiting overvoltage amplitude in the switching-on and switching-off process, the capacitor C is used for absorbing transient energy in the switching-on and switching-off process and controlling voltage rising rate, the diode D is used for providing a unidirectional conduction path to ensure capacitor discharge, the impedance parameter of the voltage limiting circuit is matched with the parasitic parameter of the insulated gate bipolar transistor to ensure uniform distribution of voltage in a multi-unit structure, the voltage withstand capacity and reliability of the system are improved, and the number of RCD modules is identical to the number of power modules in parallel connection with two ends of each unit.
The resistor R and the capacitor C of the voltage limiting RCD module are selected in the following parameter selection mode:
the energy on the stray inductance at the moment of switching off needs to be completely transferred to the capacitor C, with:
Wherein the method comprises the steps ofThe stray inductance in the IGBT circuit breaker is obtained by the arrangement of an empirical formula:
In the embodiment, the breaking structure is in a normally open or normally off state, the influence of C discharge through R is not required to be considered, so that the larger capacitance C value can be properly taken, the breaking structure also fully considers the heat dissipation condition of the online ice melting device, the larger capacitance discharges to enable the current amplitude born by the resistor R to be smaller, the power of R is reduced, the size of the integral structure and the heat generation condition of the current are further reduced, the heat dissipation pressure of the integral device is effectively reduced, and the discharge current of the capacitance C is limited to be 25% of the maximum value of the IGBT collector currentIn this case, the resistor R should satisfy the following formula:
Further, the metal oxide piezoresistor (MOV) overvoltage protection device is connected to two ends of each all-solid-state power unit in parallel, rated working voltage of the metal oxide piezoresistor is higher than normal working voltage of the all-solid-state power units and lower than the maximum withstand voltage value of the all-solid-state power units, and when transient overvoltage occurs to the system, the metal oxide piezoresistor is conducted to absorb surplus energy to limit voltage amplitude of the two ends of the all-solid-state power units.
The multi-unit serial-parallel structure comprises a plurality of all-solid-state power units connected in series to form a plurality of serial branches, wherein the serial branches are connected in parallel to form a complete breaking unit, the number of all-solid-state power units in each serial branch is determined according to a voltage difference under a switch breaking situation so as to ensure that the voltage born by each all-solid-state power unit is within a safety range, and the number of parallel branches is determined according to the instantaneous maximum current which can pass through a subconductor in an ice melting state so as to improve the current carrying capacity of the system;
Considering that the on-state loss of the IGBT is high when the current is high, the IGBT with high withstand voltage and high maximum collector current should be selected as much as possible, so as to reduce the number of series branches and further reduce the overall heat dissipation pressure of the ice melting device.
In this embodiment, redundancy needs to be considered in the serial-parallel structure, and because the circuit breaking structure is applied to a main transmission line with higher voltage level, the actual serial-parallel branch number 1.5 times of the serial-parallel branch number needs to be calculated, and each all-solid-state power unit in the multi-unit serial-parallel structure realizes synchronous on and off through the control driving unit, so that uniform distribution of voltage and current is ensured.
As shown in fig. 4, the all-solid state break-up structure of the present invention can be applied to a four-split conductor system. In this embodiment, the all-solid-state breaking device is mounted on one of the four split conductors. When the ice melting operation is needed, the control system sends out an instruction, the all-solid-state breaking structure executes the breaking operation according to a preset program, the ice melting current is led into other appointed wires, and meanwhile, the normal power supply function of the other wires is kept, so that the aim of uninterrupted ice melting is fulfilled.
In this embodiment, the all-solid-state breaking structure applied to the split conductor on-line uninterrupted ice melting device should be placed in the ice melting device as a breaking module, and the ideal installation position of the ice melting device is located at the conductor connecting part of the transmission tower. In the installation position, the control unit of the all-solid-state switching structure adopts a sealing waterproof design, and can adapt to various severe weather conditions. The control unit maintains real-time data exchange with the ground monitoring center through the optical fiber communication system, and can remotely monitor the running state of the device and receive control instructions. When the meteorological monitoring system detects the icing risk, the control center sends out an ice melting instruction, and the all-solid-state switching-off structure firstly executes the operation of switching off the appointed subconductors, and then ice melting current flows into the rest subconductors. In the whole process, a power grid user cannot sense power interruption, and the uninterrupted ice melting is realized in a true sense.
In summary, the invention provides an all-solid-state breaking structure for an on-line uninterrupted ice melting device for split conductors, which adopts an all-solid-state IGBT as a core power electronic device, constructs a breaker unit in an anti-parallel topology mode, and realizes a voltage limiting function by utilizing a passive RCD circuit. The invention designs a multi-unit serial-parallel configuration scheme, effectively improves the voltage-resistant capacity and the through-current capacity of the system, and is suitable for the voltage and current requirements of high-voltage lines. The switching-on and switching-off structure has the advantages of high response speed, high reliability, good electromagnetic compatibility and the like, can realize the ice melting operation of the high-voltage circuit under the condition of not interrupting power supply, and solves the technical problem that the traditional ice melting method needs power failure. The all-solid-state switching-on/off structure replaces a mechanical switch, eliminates the ageing and arc hidden trouble of mechanical parts, avoids the potential switching-on/off faults of the mechanical switch in extreme environments such as cold, damp and the like, and ensures the stable operation of the system in high-pressure environments by the optimized anti-parallel topology and the RCD voltage limiting circuit design. The solution of the invention has important significance for improving the operation reliability of the power grid under severe weather conditions.
The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the invention, and these alternatives or modifications should be considered to be within the scope of the invention. In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Those skilled in the art may combine and combine the features of the different embodiments or examples described in this specification and of the different embodiments or examples without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the invention as defined by the appended claims.