DE19716826A1 - Power supply network, in particular ship's electrical system - Google Patents

Abstract

The present invention pertains to a power supply network, especially an on-board power supply network, comprising main distribution lines (11, 12) and secondary distribution lines (13, 14) powered by generators (17), current services (18 to 20) that capable of being connected to such lines, current switches inserted between the distribution lines (11 to 14), on the one hand, and the distribution lines (11 to 14) and the generators (17) and the current services (18 to 20), on the other hand, as well as protective devices (22) combined with the current switches (15) and connected to a protective meter (26). In order to effect a very quick switching-off of the network areas affected by a short-circuit on the on-board power supply network with loopings and meshings, the current pick-up shoes contained in the protective devices (22) are designed so as to measure in amount and phase the current flowing through the current switches (15) for comparison with a virtual network voltage. The protective meter (26) continuously compiles for the groups of current switches (15) which delimit predetermined network areas the current vectors measured by the current pick-up shoes and, when the result significantly deviates from null, generates a switching signal to the current switches belonging to the group concerned (15).

Description

The invention relates to a power supply network, in particular a ship's electrical system, which in the preamble of Claim 1 defined genus.

For the permanent availability of Power supply networks, in particular shipboard networks, It is essential that short circuits occur quickly switched off and the short-circuit locations for troubleshooting be recognized quickly.

Ship electrical systems are still based on the principles of Current and time selectivity protected. This is everyone Circuit breaker between the main and Sub-distribution lines as well as between the Sub-distribution lines and important electricity consumers equipped with protective devices that when a Short circuit with different delay times Trip circuit breakers with trip times from Electricity consumers to the main distribution lines and the generators feeding the main distribution lines increase. So every circuit breaker gives that subordinate switch time to switch off a short circuit, before it in turn triggers. The is realized Time-selective disconnection of the circuit breakers in the Way that when a short circuit occurs in the vehicle electrical system a time counter is activated for all protective devices and each the protection device that first its individual Time limit reached, the assigned circuit breaker  opens.

So that the time selectivity works smoothly, we have to the circuit breakers in every conceivable short-circuit path, this is the way between the fault location and the generators, always in the order of the protection devices set delay times. Regroupings are therefore only limited and only with high technical effort possible, and a ring and Mesh formation of the electrical system is omitted. With the principle the time selectivity, it is also disadvantageous that Short circuits are switched off the later, the closer they are are due to the generators. This is the most serious and most powerful faults the longest in the vehicle electrical system.

It has already been proposed (DE 196 34 094.2-32) integrated digital network protection To maintain shipboard networks in that all Protection devices next to their switching relays to trigger the assigned circuit breaker receive a current sensor, the current flowing through the circuit breaker Height and direction recorded. All protective devices communicate with a protection computer to which the address of each Protection devices is known. The protection computer recognizes on the basis of the measured values supplied by the current sensors Occurrence of a short circuit and the location of the Short circuit on the closest circuit breaker and gives a trigger or release command for this Circuit breaker off, so that the short circuit area of the Electrical system is disconnected. To achieve full selectivity each outlet from the vehicle electrical system must be reached with a Current sensor to be fitted to the network computer is to be connected.  

The invention is based on the object Power supply network of the type mentioned with a to provide integrated, digital network protection that also in networks with difficult network configurations, such as ring and Mesh formation, can be applied and an extreme rapid shutdown of the network area of the vehicle electrical system, in short circuit occurs.

The task is in a power supply network in the Preamble of claim 1 specified genus According to the invention by the features in the characterizing part of the Claim 1 solved.

The power supply network according to the invention has the advantage that by the continuous addition of those of the Current sensors supplied current vectors in the event of a short circuit it is immediately recognized whether the short-circuit current is one of a Group of circuit breakers limited network area flows through or has a depression in the network area. in the the latter case is the short circuit due to network faults within causes this network area, and the protection computer switches the boundaries of this network area Circuit breaker by controlling the Circuit breakers associated with switching devices in the associated protective devices free, so that this network area is very quickly disconnected from the rest of the network and the Maintain the function of the remaining power supply remains. In contrast to the one described at the beginning time-selective switch-off principle is that of the short circuit affected network area switched off regardless of whether it distant or very close to the generators located. This makes even the most powerful Short-circuit faults eliminated immediately, which may Consequential damage can be prevented. Because all current vectors are on  which are related to the virtual mains voltage, also prepare the transformers in the network and those of them generated swivel angle with respect to their input and Output voltages no problems.

Because with today's power supply networks, in particular Shipboard networks, usually for other reasons data traffic between the protective devices at the Circuit breakers and a central operator station is installed is the technical effort for the Integration of digital network protection relatively low.

In the power supply network according to the invention can additionally the usual differential protection of the Transformers easily moved to the protection computer and thereby commissioning and engineering costs be saved. With differential protection the Transformers are the amplitudes and phase positions of primary and secondary currents of the transformers compared, to be able to recognize special faults in the transformer. With conventional differential protection, that the transformers have a non-zero Swivel angle between primary and secondary voltages own the currents before comparison by means of Auxiliary transformers can also be pivoted. Here but the current sensors according to the invention the phase position of the Currents in the circuit breakers automatically correct can record without these auxiliary measures in the protection computer an error, e.g. B. a short circuit in the transformer immediately recognized and the corresponding transformer switched off will.

Appropriate embodiments of the invention Power supply network with advantageous developments  and embodiments of the invention result from the further claims.

The invention is based on one in the drawing illustrated embodiment in the following described. Show it:

Fig. 1 is a block diagram of a ship-board network,

Fig. 2 is a block diagram of a protection device for a circuit breaker in the electrical system of FIG. 1.

The three-phase ship electrical system shown in the block diagram in FIG. 1 as an example of a power supply network is divided into main distribution lines 11 , 12 and sub-distribution lines 13 , 14 . The number of main and sub-distribution lines 11 to 14 is arbitrary, and the network can also be split into third and fourth levels of sub-distributions. The main distribution lines 11 , 12 and the sub-distribution lines 13 , 14 are coupled to one another via circuit breakers 15 . In the illustrated embodiment of the on-board electrical system, the sub-distribution lines 13 , 14 are operated with a lower mains voltage than the main distribution lines 11 , 12 , so that between the main distribution lines 11 , 12 and the sub-distribution lines 13 , 14, transformer transformers 16 are arranged, which are both on the main distribution lines 11 , 12 and also to the sub-distribution lines 13 , 14 are connected by means of circuit breakers 15 . If the sub-distribution lines 13 , 14 are operated with the same mains voltage as the main distribution lines 11 , 12 , the main distribution lines 11 , 12 and the sub-distribution lines 13 , 14 are directly coupled to one another by circuit breakers 15 .

The main distribution lines 11 , 12 are fed by vehicle electrical system generators 17 , which in turn are connected to the main distribution lines 11 , 12 via circuit breakers 15 . Large current consumers, such as supply transformers 18 and asynchronous motors 19 , are connected to the main distribution lines 11 , 12 via circuit breakers 15 , and further arbitrary current consumers 20 are connected to the sub-distribution lines 13 , 14 and can be switched on and off via mains switches 20 .

A protection device 22 is assigned to each circuit breaker 15 , as is shown in detail in FIG. 2 in the block diagram. Each protection device 22 has a switching device 23 for actuating the circuit breaker 15 and a current sensor 24 which detects the current flowing through the circuit breaker 15 . The protective devices 22 communicate via data lines 25 with a protective computer 26 , the protective devices 22 of the same distribution level each being connected to one of a plurality of data concentrators 27 to 29 , which in turn are connected to the protective computer 26 . In the exemplary embodiment in FIG. 1, the protective devices 22 , which are assigned to the circuit breakers 15 for connecting the vehicle electrical system generators 17 to the main distribution lines 11 , 12 , to the data concentrator 27 , the protective devices 22 which are connected to the circuit breakers 15 for connecting the transformers 16 , 18 and Asynchronous motors 19 are assigned to the main distribution lines 11 , 12 , to the data concentrator 28, and the protective devices 22 , which are assigned to the circuit breakers 15 between the sub-distribution lines 13 , 14 and the circuit breakers 15 for connecting the transformers 16 to the sub-distribution lines 13 , 14 , to the data concentrator 29 guided. The corresponding data lines 25 are shown in broken lines, dash-dotted lines and dotted lines in FIG. 1.

The switching device 23 comprises a switching relay 30 for actuating the circuit breakers 15 , an amplifier 31 and a decoder 32 which decodes a switching command coming from the protective computer 26 and controls the switching relay 30 . The switching relay 30 operates according to the open-circuit principle, ie it opens the circuit breaker 15 when charging with excitation current.

The current sensor 24 is designed to measure the current and current flowing through the circuit breaker 15 according to magnitude and phase. The phase measurement is based on a virtual line voltage U _vir , the phase position of which corresponds to the phase position of the line voltage immediately before the short-circuit occurs. This virtual mains voltage U _vir is obtained by means of a follow-up synchronization, by means of a so-called PLL (phase locked loop) circuit 33 , which is connected to a line voltage of the three-phase distribution line in which the circuit breaker 15 is located. Such a PLL is known for an application of communications technology from Tietze / Schenk, semiconductor technology 9th edition, Springer Verlag Berlin 1989, page 954 ff. And is implemented there in analog technology. Here it is preferably implemented as a program that can be implemented in the protection computer 26 . In the exemplary embodiment shown in FIG. 2, the circuit breaker 15 connects the sub-distribution lines 13 and 14 to one another, so that the PLL circuit 33 is connected to a line voltage of either the sub-distribution line 14 or the sub-distribution line 13 . The virtual mains voltage U _vir generated by the PLL circuit 33 is at the input of an evaluation unit 34 to which a current measuring device 35 for measuring the phase currents in the three-phase distribution line (in FIG. 2 in the sub-distribution line 14 ) is connected. The evaluation unit 34 determines the amount of the three phase currents i ₁ , i ₂ , i ₃ and their phase position in relation to the virtual mains voltage U _vir , that is to say the quantities describing the vector of the phase currents i ₁ , i ₂ and i ₃ , which are supplied to a coding unit 36 . The output of the encoding unit 36 is via the data line 25 and the corresponding data concentrator 27 is connected to the protection of computers 26 to 28. The coded data transmission to the protection computer 26 takes place once per mains voltage period.

In the protection computer 26 , the incoming data are assigned to groups of circuit breakers 15 , which limit predetermined network areas. For example, in FIG. 1, the circuit 37 denotes a network area which is delimited by four circuit breakers 15 . In the same way, the other circuit breakers 15 in the network are grouped together to define predetermined network areas. During network operation, the protection computer 26 continuously adds the current vectors of the phase currents i ₁ , the phase currents i ₂ and the phase currents i ₃ measured by the current sensors 24 and transmitted via the data lines 25 for each group of circuit breakers 15 . As long as the vectorial addition of all currents i ₁ or i ₂ or i ₃ supplied by the current sensors 24 of the group of circuit breakers 15 to the protective computer 26 is approximately zero, this network area is error-free. A short-circuit current occurring in the vehicle electrical system flows through this network area, but is not caused by an error in this network area. If, on the other hand, the result of the vectorial addition differs substantially from zero, this is an indication that the short-circuit current does not flow through the network area but has a sink within the network area, that is to say the short-circuit current is caused by an error in this network area. In this case, the protection computer 26 generates a switching command for all the circuit breakers 15 delimiting this network area, which switches to the switching devices 23 of the protection devices 22 of these circuit breakers 15 via the data lines 25 . The corresponding switching relays 30 of the circuit breakers 15 are energized and the circuit breakers 15 are opened. The faulty network area is thus activated, while the undisturbed operation of the remaining network areas is ensured.

The invention is not restricted to the exemplary embodiment described above. Thus, instead of the direct measurement of the phase currents i ₁ , i ₂ , i ₃ by amount and phase, the amount and phase of a co-system, a counter system and a zero system can also be determined, which is calculated from the phase currents i ₁ , i ₂ , i ₃ will. For a ship's electrical system, it is sufficient if only the co-system is taken into account. If the co-systems (or the counter systems and the zero systems) are then vectorially added for all circuit breakers 15 by a group of circuit breakers 15 delimiting a network area, the same statement about a fault location inside or outside this network area is obtained. This conversion into the co-systems simplifies the mathematical calculation. In addition, the usual differential protection for the transformer transformers 16 present in the power supply network can be implemented very easily by a computing routine in the protective computer 26 , so that considerable savings are achieved compared to the conventional differential protection. In differential protection, the primary and secondary currents are compared with one another to identify faults in the transformer. Since, as a rule, the primary and secondary voltages of transformers are shifted by a multiple of 30 ° relative to each other, a direct comparison of the primary and secondary currents is not possible; rather, this shift or swivel must be reversed beforehand, which is usually the case with current transformers and output converters can be used. The comparison then no longer takes place between the primary and secondary currents, but between appropriately pivoted images of the currents. This is very difficult to interpret and offers plenty of opportunities for confusion. However, if a current monitoring system is calculated from the phase currents at the input and output of the transformer, the current monitoring system of the secondary windings has approximately the same angle to the secondary voltage as the current monitoring system of the primary windings to the primary voltage, regardless of the pivoting angle of the transformer. By simply comparing the co-systems on the primary and secondary sides of the transformer, the differential protection can then be taken over by the protection computer 26 without any additional effort.

However, the same also applies if the conversion of the phase currents i ₁ , i ₂ , i ₃ into the co-systems is dispensed with and the vector addition of the phase currents relating to the virtual voltage U _vir in their phase position is carried out. Since the phase angles of the currents in each case relate to the virtual mains voltage obtained on the distribution line, the swiveling angles caused by the transformer transformer 16 between the conductor voltages on the primary-side distribution line 11 and 12 and on the secondary-side distribution line 13 and 14 are automatically compensated for.

The determination of the vectorial current sum is relative complex. An equivalent statement about the location of one Short-circuit source can be simplified according to a Implement embodiment of the invention in that only the short-circuiting switches are evaluated, d. H. it is checked whether the phase angle of the Short-circuit currents at all allow the vectorial Current sum can be zero. Have z. B. all Short-circuit currents in a limited network area approximately the same phase angle, then the vectorial sum does not become zero, and the error must be in this network area.

Claims (7)

1. Power supply network, in particular ship's electrical system, with main distribution lines ( 11 , 12 ) fed by generators ( 17 ) and with sub-distribution lines ( 13 , 14 ) and with current consumers ( 18 , 19 , 20 ) that can be connected to them, with between the distribution lines ( 11 to 14 ) on the one hand and the distribution lines ( 13 to 14 ) and the generators ( 17 ) and the current consumers ( 18 , 19 , 20 ) on the other hand arranged circuit breakers ( 15 ) with the circuit breakers ( 15 ) assigned protective devices ( 22 ), each one assigned to the Circuit breakers ( 15 ) actuating switching devices ( 23 ) and a current sensor ( 24 ) detecting the current flowing through the assigned circuit breakers ( 15 ), and with a protective computer ( 26 ) communicating with the protective devices ( 22 ), characterized in that the current sensors ( 24 ) for measuring the current (i ₁ to i ₃ ) according to amount and phase, which is based on a virtue ll line voltage (U _vir ), the phase position of which corresponds to that of the line voltage before the short circuit occurs, and that the protective computer ( 26 ) for groups of circuit breakers ( 15 ), which delimit predetermined network areas ( 37 ), continuously measure those measured by the current sensors ( 24 ) Current vectors are added and, if the addition result deviates significantly from zero, a switch-off command is generated for the circuit breakers ( 15 ) belonging to the group. 2. Network according to claim 1, characterized in that instead of a complete vector addition, only one Check the phase positions of the phase currents accordingly takes place whether this is a vectorial current sum of zero allow or not. 3. Network according to claim 1 or 2, characterized in that the measured values of the current sensors ( 24 ) are transmitted coded to the protective computer ( 26 ). 4. Network according to claim 3, characterized in that the Coding and transmission once per Mains voltage period takes place. 5. Network according to one of claims 1 to 4, characterized in that for obtaining the virtual network voltage (U _vir ) each current sensor has a PLL circuit ( 33 ) connected to a line voltage of the three-phase distribution line ( 11 to 14 ), which occurs with a short circuit records the immediately preceding phase position of the mains voltage. 6. Network according to claim 5, characterized in that each current sensor ( 24 ) has a current measuring device ( 35 ) for measuring the phase currents (i ₁ to i ₃ ) in the three-phase distribution branches ( 11 to 14 ), an evaluation unit ( 34 ) for calculating the amount and phase of the phase currents (i ₁ to i ₃ ) and a coding unit ( 36 ) for coding the magnitude and phase values, which is connected to the protective computer ( 26 ) via a data line ( 25 ). 7. Network according to one of claims 1 to 6, characterized in that instead of the vector addition of the phase currents within a group of circuit breakers ( 15 ), which delimit predetermined network areas, a vector addition of at least the co-systems calculated from the phase currents (i ₁ to i ₃ ) he follows.