DE10008185A1 - Method of selective protection during short-circuits in steady-state load circuits, esp. for railway power supply equipment, national grid and motor vehicles, requires evaluating - Google Patents

Abstract

Selective protection against short-circuits, particularly in steady-state load circuits aims at providing economically acceptable and reliable protection in circuits and parts of circuits connected to current-regulated power sources, and short-circuit detection takes place in or at the current-regulated power source and/or at one or more protective switches which join the current-regulated source to the network or parts of the network. The change-with-time of the power (energy) consumption capacity of the network or a network section is then determined and evaluated.

Description

The invention relates to a method for selective protection in the event of short circuits stationary consumer circuits when using energy sources with current control characteristic, especially in operational and municipal energy supply directions, rail energy supply facilities and state networks.

Known energy supply systems represent a business chip for consumers with a specified tolerance. According to the current The load results in the amount of current. In the event of short circuits or Overloads, this current rises above the operationally permissible value. Through the Application of short-circuit protection devices becomes the faulty circuit switched off as selectively as possible.

Energy supply systems based on current regulation are also known can deliver electrical energy such. B. energy storage systems in the form of Rotary mass energy storage, batteries or high-performance capacitors. task Such a store is to absorb energy at certain times and to close it to deliver at other times. To do this, the one flowing through the energy store Electricity can be regulated. Due to this principle of action, short-circuit protection is required Not possible according to the overcurrent principle, since the current control does not provide an overcurrent Allows error detection. The consequence of this is that a current regulated In the event of a short circuit, the energy source is separated from the circuit in another way must be prevented in order to prevent permanent supply of a short circuit.

Short-circuit protection is required at the beginning of each circuit and at all points where the short-circuit current capacity can be reduced, provided an upstream protective device cannot ensure the required protection in the event of a short circuit (DIN VDE 0100 Part 430 ). An additional problem is that a current controlled energy source can affect or nullify the effectiveness of the short circuit protection for other non current controlled energy sources. The causes of this are described below and are shown in FIGS . 1 and 2 in schematic form.

A possible solution to this problem would be that the tension in the protective network measured at local short distances and when falling short the current-controlled energy source is disconnected from the grid under operational values. This variant would have an unacceptable economic outlay for a larger number of measuring devices.

The known prior art in the field of short-circuit protection primarily includes overcurrent protection devices. These have been used for years and must meet the requirements of DIN VDE 0100 Part 430 in the Federal Republic of Germany. The overcurrent protection devices can be designed as a fuse or circuit breaker, depending on the permissible current and the required shutdown speed. The switch-off criterion is either the level of the current flowing through or the I ² t value. These protective devices are ruled out for current-controlled energy sources due to the physical conditions described above.

EP 0 662 615 B1 describes a method for short-circuit protection on regenerative power known to DC vehicles. In the event of a short circuit, the network brake switched off and the braking locomotive was disconnected from the circuit. A Transfer of this known method to the short-circuit protection in the energy supplier power networks with current-controlled energy sources is not possible. It also allows Method according to EP 0 662 615 B1 no selective shutdown of individual errors power supplies.

DE 196 46 279 C1 describes a method and a circuit arrangement for Range increase of motor vehicles presented. That is the interaction various energy storage such. B. Batteries and flywheel storage described, some of which can be viewed as current-controlled energy sources. The task is to control the interaction of different types of Energy storage with the goal of better energy management and thus one Range increase of the vehicle. In DE 198 26 551 C1 a control for  one consisting of at least one energy store and one energy source Hybrid system described. The use of such a hybrid system as a current controlled Energy source is basically possible. The proposed control system serves however, to control the regular operation and does not take into account the critical Short circuit case.

The object of the invention is a method and an arrangement for selective protection in the event of short circuits in stationary consumer circuits in which Energy sources with current control characteristics are available. Doing so with simple Means and without additional information transmission facilities Reliable, selective and economically justifiable protection in the event of short circuits in electrical networks or parts thereof using current-controlled energy sources connected.

The task is carried out according to the process by the characteristic features of the main claim solved. Advantageous embodiments of the method are in the dependent Subclaims described.

The detection of short circuits in electrical networks, the at least one have current-controlled energy source, takes place in that the temporal change the energy absorption capacity of the network or network section under consideration determined continuously or in intervals and the respective current values with be compared with a setpoint that is to be regarded as permissible. When over or Falling below a permissible threshold for the change in time Energy absorption capacity of the network or network section is achieved using known means the connection between the current regulated energy source (s) and the considered network or network section separately.

While known energy supply systems in the event of a short circuit, an adequate one Short-circuit protection is lacking in the case of current-controlled energy sources effective devices. Likewise, there is no possibility of electricity-controlled energy sources  in the event of a short circuit, selectively disconnect from the circuit to persons effective against touch voltages and the affected devices before the danger to protect against thermal destruction. For this, criteria are necessary, the one Ensure selective shutdown in the event of a fault and the fault-free operation Do not impair the function of the system.

In order to be able to detect a short circuit, in a preferred embodiment of the method, the change in time of electrical quantities at the current control ( 2 ) of the energy source ( 3 ) or its circuit breakers ( 8 ) and ( 9 ) is applied to a sudden change caused by a short circuit Change in the energy absorption capacity of the network or a network section closed.

Thus, in a first preferred embodiment, parameters on the Current control used for short-circuit detection and when detecting a Short circuit all circuit breakers of the energy source disconnected at the same time.

In a second, likewise preferred embodiment, sizes on the Circuit breakers included in the detection and the faulty circuit selectively switched off.

According to the first embodiment, the first derivatives of the following variables are preferably used as parameters for the short-circuit detection:

• - the current flowing through the energy source,
• - the voltage present at the energy source,
• - the electrical power delivered by the energy source,
• - the equivalent conductance of the electrical network connected to the energy source.

According to the second embodiment, the first derivatives of the following variables are preferably used as detection variables for the short-circuit detection:

• - the currents flowing through the individual circuit breakers,
• - the voltage present at the energy source,
• - The electrical power output via the individual circuit breakers  
• - The equivalent conductance of that connected to the individual circuit breakers electrical network or network section.

The first derivatives of the aforementioned variables are advantageously determined in a microcomputer or controller through the mathematical transition to the difference quotient. For this purpose, the physical quantities are preferably continuously recorded at intervals and stored in a memory. The difference between the current measured value and a measured value older by a time interval t _V ( 32 ) is proportional to the difference quotient and can be used as a detection variable with little computing effort.

The first derivative of the aforementioned parameters is advantageously determined in periodic, equally large cycles. This reduces the effort for the determination, Storage and evaluation of the measured variables for determining the temporal Change in the energy absorption capacity of the network or network section reduced. In a further preferred embodiment of the method, the determination is made of the relevant parameters alternating at shorter intervals as soon as the current energy absorption capacity in the network or network section under consideration Value within a predeterminable tolerance to the threshold value.

In the event that a critical situation is incorrectly detected as a short circuit and one The current-regulated energy source has been disconnected from the grid, this is shown Method according to the invention in a preferred further development the possibility before that the separation of the connection between current controlled energy source and the network or the faulty part of the network according to a specifiable Time interval is canceled again, if after this time interval the Voltage at the current-controlled energy source or the associated circuit breakers is back in a standardized area. In the case of a incorrect selection, the separated network areas are returned to the network at short notice get connected.  

It is also advantageous that when using this method only a selective one The network section disturbed by a short circuit is switched off and all other network areas can continue to operate without any problems.

Another advantage is that by using the inventive Procedure for the first time a problem-free feeding of a route section through more than two stationary energy sources is made possible.

Flywheel or rotating masses are preferred as current-controlled energy sources memory used, the even feeding of the temporarily stored Enable energy in the network or network area. They are also preferred Use batteries or high performance capacitors that are short term Enable energy feed-in, especially in peak load situations. In a further advantageous embodiment of the method, the separation of the current controlled. Power source from the network or the faulty network area too then when the operating voltage at the current-controlled energy source is below one permissible value drops. The shortfall of those to be regarded as admissible Operating voltage is detected as a signal for a possible short circuit and evaluated.

There is an arrangement for realizing the method for short-circuit detection advantageously from a data processing device in which the parameters are voltage and current at the current controlled energy source in differentially small intervals be recorded and processed. The temporal change in the energy absorption capacity of the network or network section is determined by the cyclical comparison of the determined parameters Δi / Δt or Δu / Δt. The results are compared with the network spec permissible threshold values compared. When the threshold is exceeded all circuit breakers are opened, via which the current-controlled energy source with the Network or connected to the endangered network area. After a Predeterminable time interval is the instantaneous voltage at the mains connection  of all affected circuit breakers. Provided at all at this time affected circuit breakers are back to the normalized operating voltage, so the relevant switches closed again and the connection of the current-controlled Energy source with the network or network area restored.

In a preferred arrangement, the parameters are determined for the Short circuit directly at the energy store or in close proximity. In another, Likewise preferred training is the determination of the parameters for the Short circuit directly at the circuit breakers or in close proximity.

With these preferred arrangements, there is the possibility of the detection device to integrate directly into the relevant assemblies (memory, switches). This significantly reduces manufacturing costs and reliability and Reliability of the short-circuit detection device compared to one spatially separated arrangement improved in a separate assembly.

The invention is described below in several exemplary embodiments and in Drawings shown:

Show it:

Fig. 1: a counting to the prior art circuit arrangement state of a current regulated power source in a power supply system in operation,

FIG. 2 shows the circuit arrangement of Figure 1 with a short circuit in a network portion.

FIG. 3 shows a basic circuit arrangement for performing the process,

FIG. 4 shows a further circuit arrangement wherein the evaluation unit is integrated with the circuit breaker in an assembly,

FIG. 5 shows a further circuit arrangement wherein the evaluation unit is integrated with the power source in an assembly,

FIG. 6 shows a circuit arrangement for carrying out the method when using a rotating mass memory in a railway network,

Fig. 7: the waveforms of characteristic metrics, at the detection of a short circuit in a stationary network with eingebundener current-controlled source of energy

FIG. 8 shows the waveforms of characteristic metrics in the detection of a short circuit, which takes place the determination of the rele vant characteristics in time intervals shorter when it reaches a tolerance limit of the threshold value of the energy absorption capacity.

Fig. 1 shows a highly schematic representation of a known circuit arrangement of an energy store that works as a current-controlled energy source. Two consumers ( 4 ) and ( 5 ) are supplied with energy from a voltage source ( 1 ). Energy producers and consumers are each protected against possible overload by a fuse ( 6 , 7 , 10 , 11 ). Fuses ( 6 ) and ( 7 ) simultaneously take over short-circuit protection. The two consumers ( 4 ) and ( 5 ) represent a time-fluctuating load. With a correspondingly high resistance of the supply lines, the voltage at the consumers will fluctuate over a wide range depending on the load.

The energy store, consisting of the control electronics ( 2 ) and the motor generator ( 3 ), is capable of absorbing energy from the energy supply network when the load is low, and of releasing it again when the load is heavily removed. In this way, both the load peaks of the energy supply network and the voltage drops at the consumer are reduced.

The circuit breakers ( 8 ) and ( 9 ) can selectively disconnect the energy store from the circuit.

Fig. 2 shows a short circuit ( 12 ) on one of the two consumers.

If the energy store ( 3 ) is largely filled at this point in time, energy is released to the consumers and the voltage at its connection point is increased. As a result, only a small current is drawn from the voltage source ( 1 ). As a result, fuses ( 6 ) and ( 7 ) can no longer fulfill their protective function. The short circuit remains and is fed by both the energy store and the voltage source. Since the energy store ( 3 ) has a current control ( 2 ), the short-circuit current cannot be switched off by a fuse assigned to the energy store, since its height does not differ from the operating current.

If, on the other hand, the energy store ( 3 ) is not very full, the fuse ( 7 ) fulfills its protective function and the voltage source ( 1 ) supplying the circuit is selectively switched off by the faulty circuit. However, the energy store itself will initially be discharged via the short circuit, so that a short circuit current continues to flow for a time dependent on the fill level of the energy store. If the consumer ( 4 ) not affected can feed energy back into the circuit, the energy store could even be recharged.

Fig. 3 shows a highly schematic representation of a circuit arrangement for performing the method. The parameters are determined directly at the energy source. Current and voltage at the current-controlled energy source ( 2 ) are recorded at intervals Δt ( 34 ) via measuring transducers ( 13 , 14 ) and downstream analog-to-digital converters ( 15 ) and the measured values are transferred to a microprocessor ( 16 ).

From this, he calculates the other quantities power p and equivalent conductance q using the known formulas

p = u. i

and

q = i / u

The sizes are stored in a ring memory ( 19 ). In the subsequent calculation step, the new detection variables are determined by forming the difference with the values older by a time t _V ( 32 ) and it is checked whether the specified threshold value has been exceeded. In the event of a threshold value being exceeded, a pulse ( 17 ) is output which leads to the circuit breaker ( 8 ) being switched off.

Fig. 4 shows a further embodiment of a circuit arrangement in which the evaluation unit is integrated with the circuit breaker in an assembly.

Since the quantities to be processed are all measured at the relevant switch, each switch has its own control unit ( 20 ), ( 21 ), which is combined with the switch to form a structural unit. The currents and voltages are measured separately for each circuit breaker and the measured values are transferred to the respective microcomputer or controller. The microcomputer or controller carries out the same arithmetic operations for each circuit breaker as in exemplary embodiment 1. In the event of a short circuit, the shutdown takes place selectively only for the network section concerned.

FIG. 5 shows a second exemplary embodiment of a circuit arrangement in which the processing of the measured variables takes place at all switches as in the previously described exemplary embodiment (see FIG. 4), but with the difference that a single microprocessor or controller takes over the processing of all signals and the results of the current-controlled energy source can be assigned directly. In this case, the signal processing can also be carried out by the control device of the energy source.

Fig. 6 shows a further embodiment of a circuit arrangement for carrying out the method when using a rotating mass memory in a railway network.

An energy store ( 2 , 3 ) is used to improve the energy quality between two substations ( 23 , 24 ) of a rail network that are relatively far apart. A two-track line is to be supplied, consisting of contact lines ( 25 , 26 ) to be fed separately in each direction and the tracks ( 27 , 28 ) used for the return line.

Each circuit breaker ( 8 , 9 ) is assigned its own protective device ( 20 , 21 ) with a microprocessor or controller ( 16 ). If a short circuit ( 12 ) occurs on the route, substation 1 ( 23 ) can no longer detect the short circuit when the energy store is emitting energy, since the short circuit current component of the substation is not sufficient to detect the short circuit.

The energy store in turn cannot switch off the short circuit using the known means according to the prior art. By using the arrangement according to the invention, in the event of a short circuit, the direction of travel concerned is selectively switched off by the corresponding circuit breaker ( 8 ), thereby also enabling the substations to be switched off safely. The direction of travel not affected by the error remains in operation, so that driving on the route is affected as little as possible.

Another advantage is that by using the inventive Process for the first time a problem-free feeding of a route section by more as two stationary energy sources.

During switching operations in the network, sudden changes in the energy absorption capacity are possible if there is no short circuit. In order not to permanently switch off the current-controlled energy source in this case, a check is carried out in a preferred embodiment after an adjustable return time interval t _WK to determine whether the operating voltage is still present on the network side of the circuit breaker. In the event of a short circuit, the protective devices of the network are activated after the return time interval t _WK , so that there is no longer any mains voltage. However, if there is still mains voltage, the fault is tripped and the current-controlled energy source can be connected to the mains again. This results in a selective shutdown of the faulty network sections by detection at the current-controlled energy source.

Fig. 7 shows the waveforms of exemplary charkteristischer metrics in the detection of a short circuit in a stationary network with eingebundener stromgere elapsed-energy source. The short circuit is detected with the help of the change in the current over time. The upper diagram shows the course of current ( 30 ) and voltage ( 29 ) of the current-controlled energy source. Both variables are recorded periodically in a time interval Δt ( 34 ) and stored in the ring memory of the microprocessor or controller. After the measurement, the microprocessor calculates the values for the current change Δi ( 31 ) and Δu ( 33 ) within the time period t _V ( 32 ). The result is shown in the middle diagram. If the threshold value ( 37 ) is exceeded, the microprocessor or controller sets the trigger signal ( 17 ) as shown in the diagram below. This opens the corresponding circuit breaker. After the time t _WK ( 38 ), the value of the voltage ( 29 ) is measured and stored in the memory as a return voltage U _WK ( 35 ). In the example in FIG. 7, the voltage has dropped to such a low value that it must be assumed that there is a short circuit. Therefore the trigger signal ( 17 ) remains set. If the voltage were still in the operational area, the signal ( 17 ) would be withdrawn and the corresponding circuit breaker or switches would be closed again.

If the short circuit in the electrical vicinity of the current controlled energy source occurs, the level of the voltage at the energy source decreases significantly. Therefore, the protection shown can be advantageous by an undervoltage protection will be added who will separate the current-controlled energy source if the voltage drops below a certain threshold.  

Fig. 8 shows the waveforms in more diagrams of characteristic metrics in the detection of a short circuit, wherein the energy absorption capacity is carried out on reaching a tolerance limit of the threshold value (37) the determination of the relevant parameters in a time shorter intervals. As soon as the characteristic variable .DELTA.i / tv reaches the switchover value ( 42 ), the sampling interval of the measurements is reduced in order to promptly detect the point in time of a possible short circuit.

Overview of reference symbols used

1

Power source for energy supply

2

Current control of the energy source

3rd

Energy storage

4

consumer

1

5

consumer

2

6

Fuse circuit

1

7

Fuse circuit

2

8th

Circuit breaker

1

for current controlled energy source

9

Circuit breaker

2

for current controlled energy source

10th

Consumer protection

1

11

Consumer protection

2

12th

Short circuit

13

Voltage converter

14

Power converter

15

Analog-to-digital converter

16

Microcomputer or controller

17th

Trigger

1

18th

Trigger

2

19th

Ring buffer

20th

Unit from circuit breaker and protective device according to the invention

1

21

Unit from circuit breaker and protective device according to the invention

2

22

Unit from current-controlled energy source and protective device according to the invention

23

Substation

1

24th

Substation

2

25th

Catenary direction of travel

1

26

Catenary direction of travel

2

27

Track direction of travel

1

28

Track direction of travel

2

29

Time course of the voltage at the current-controlled energy source

30th

Time course of the current at the current-controlled energy source

31

Current difference Δi

32

Time t _V

33

Voltage difference Δu

34

Measuring interval Δt

35

Return voltage U _WK

36

Time t

37

Threshold

38

Return time interval t _WK

39

electricity

40

tension

41

Detection quantity Δi / t _V

42

Switchover value for reduced sampling interval

43

Reduced sampling interval

Claims (10)

1. Procedure for selective protection in the event of short circuits in stationary consumers circuits when using at least one energy source with electricity control characteristics, especially in operational and municipal energy supply facilities and rail energy supply facilities, the detection of the short circuit in or on the current-controlled energy source and / or on one or more circuit breakers, the current Connect the regulated energy source to the network or power supplies by changing the energy absorption capacity of the network over time or of a network section determined and evaluated and when crossing or Un exceeding a predetermined permissible threshold value for the temporal changes change in the energy absorption capacity of the network or of the network section Connection between current-controlled energy source and network or network cut is separated. 2. The method according to claim 1, characterized in that the temporal change in the energy absorption capacity of the network or network section is determined by continuously determining the first derivative according to time or by determining the difference quotient of one or more of the following parameters at the current-controlled energy source:

• - the current flowing through the current regulated energy source,
• - the voltage present at the current-controlled energy source,
• - the electrical power delivered by the current regulated energy source,
• - The equivalent conductance of the electrical network or network section connected to the current-controlled energy source.

3. The method according to claim 1, characterized in that the change over time in the energy absorption capacity of the network or network section is determined by the continuous determination of the first derivative based on the time or the difference quotient of one or more of the following parameters at the circuit breakers:

• - the currents flowing through the individual circuit breakers,
• - the voltage present between the circuit breaker and the opposite polarity,
• - the electrical power output via the individual circuit breakers,
• - The equivalent conductance of the electrical network section connected to the individual circuit breakers.

4. The method according to any one of claims 1 to 3, characterized, that the temporal change in the energy absorption capacity of the network due to mathematical linking of the parameters and continuous determination of the first derivative or the difference quotient is determined. 5. The method according to any one of claims 1 to 4, characterized in that for determining the first derivative, the measured variables to be evaluated are determined and stored in an interval-like manner, subtracted from the value recorded at time t and the value recorded at time t - t _V the result is compared with a threshold value ( 37 ). 6. The method according to any one of claims 1 to 5, characterized in that the disconnection of the connection between the current-controlled energy source and the network or faulty power supply is canceled after a time interval t _WK ( 38 ) as if after the time interval t _WK ( 38 ) the voltage at the current-controlled energy source or at the associated circuit breaker (s) is in a defined range, where t _WK corresponds to the minimum time required for a safe shutdown of all non-current-controlled energy sources in the network. 7. The method according to any one of claims 1 to 6, characterized, that the current-controlled energy source as a flywheel or rotating mass feed cher, battery or high-performance capacitor is formed. 8. The method according to any one of claims 1 to 7, characterized, that the circuit is disconnected even if independent of The characteristic of the voltage at the current-controlled energy source falls below an operationally permissible value.   9. Circuit arrangement for performing the method according to one of claims 1, 2 or 4 to 7, characterized in that
that a microprocessor or controller ( 16 ) via an analog-digital converter ( 15 ) with a current-voltage converter ( 14 ) and via a further ren analog-digital converter ( 15 ) with a voltage converter ( 13 ) and with a Ring memory ( 19 ) is connected,
that the microprocessor or controller ( 16 ) detects voltage and current at the current-controlled energy source at intervals Δt ( 34 ) and stores the digitized values in the ring memory ( 19 ),
after the measured values for current and voltage have been stored, the power and equivalent conductance of the network or power pack are calculated therefrom by the microprocessor or controller ( 16 ) and stored as calculated values in the ring memory ( 19 )
that after the measured values have been stored, the measured and calculated values older by a time interval t _V ( 32 ) are read out of the ring memory ( 19 ) and subtracted from the determined measured and calculated values,
that the microprocessor or controller ( 16 ) compares the calculated differences with permissible threshold values ( 37 ),
that when at least one of the threshold values is exceeded, a signal ( 17 ) is triggered, which opens all circuit breakers that connect the current-controlled energy source to the network,
that the microprocessor or controller ( 16 ) determines the voltage at the line-side connection of the circuit breakers after a time interval t _WK ( 38 ), the time interval t _{WK being} so large that all non-current-controlled energy sources in the network or power supply unit have been switched off in the event of a short circuit ,
that the microprocessor or controller ( 16 ) then resets the trigger signal ( 17 ) for all switches to which the operating voltage is applied, so that the switches are closed again. 10. Circuit arrangement for performing the method according to one of claims 1, 3 to 7, characterized in that
that a microprocessor or controller ( 16 ) via an analog-digital converter ( 15 ) with a current-voltage converter ( 14 ) and via a further ren analog-digital converter ( 15 ) with a voltage converter ( 13 ) and with a Ring memory ( 19 ) is connected,
that the microprocessor or controller ( 16 ) at intervals Δt ( 34 ) detects voltage and current at a circuit breaker associated with a current-controlled energy source and stores the digitized values in the ring memory ( 19 ),
after the measured values for current and voltage have been stored, the power and equivalent conductance of the network or power pack are calculated therefrom by the microprocessor or controller ( 16 ) and stored as calculated values in the ring memory ( 19 )
that after the measured values have been stored, the measured and calculated values older by a time interval t _V ( 32 ) are read out of the ring memory ( 19 ) and subtracted from the measured and calculated values determined,
that the microprocessor or controller ( 16 ) compares the calculated differences with permissible threshold values ( 37 ),
that when at least one of the threshold values is exceeded, a signal ( 17 ) is triggered which opens the circuit breaker,
that the microprocessor or controller ( 16 ) determines the voltage at the line-side connection of the circuit breakers after a time interval t _WK ( 38 ), the time interval t _{WK being} such that all non-current-controlled energy sources in the network or in the event of a short circuit have been switched off,
that the microprocessor or controller ( 16 ) resets the trigger signal ( 17 ) for all switches to which the operating voltage is applied, so that the switches are closed again.