NL1036389C2

NL1036389C2 - Adaptive circuit breaker and method.

Info

Publication number: NL1036389C2
Application number: NL1036389A
Authority: NL
Inventors: Hendrik Antonie Hoeflake; Johannes Hermanus Maria Kuil
Original assignee: H A Hoeflake Electrotechniek B V
Priority date: 2009-01-08
Filing date: 2009-01-08
Publication date: 2010-07-12

Description

Adaptive circuit breaker and method

The present invention is related to a circuit breaker and method for breaking an electrical connection in an 5 electrical network.

Such a circuit breaker and method are known from WO 2006/009672 A1. This known circuit breaker measures current flowing from a power source to a load device. It compares the measured current with at least one programmable limit.

10 Should the limit be exceeded, the current flow between the power source and load device is interrupted. Additionally, it can be determined if a current limit is exceeded for a predetermined amount of time. By interrupting the current flow after this predetermined amount of time, current 15 glitches or spikes do not result in switching off the device.

A drawback of this circuit breaker is that it is not able to differentiate between changes in current levels that are caused by regular phenomena, such as aging, and changes 20 that are a result of an electrical failure. Consequently, current levels must be set relatively broad to prevent unnecessary current interruption and or a user must regularly reset or adjust the limits to be set.

It is therefore an objective of the present invention 25 to provide a solution to this problem that allows more accurate and narrow limits.

This objective is achieved by the circuit breaker as defined in claim 1 and the method as defined in claim 16.

The circuit breaker according to the invention 30 comprises measuring means for determining electrical connection data. The electrical connection data comprises at least one measured and or derived value for at least one electrical parameter corresponding to the electrical 1036389 2 connection, such as a voltage and or current. Breaking means are provided for breaking the electrical connection. Processing means are provided and arranged to control the breaking means in dependence of the electrical connection 5 data. The circuit breaker is characterized by a memory for storing at least part of the electrical connection data for forming an electrical history and in that the processing means are arranged to adjust the control of the breaking means based on this electrical history.

10 It is important to note that the adjustment of the control can be carried out without user intervention. An adaptive protecting scheme is thereby obtained.

The measuring means can be arranged to determine, e.g. by measurement, a value for an electrical parameter such as 15 voltage and or current and or a value for a derived parameter, such as delivered power to a load, using the aforementioned measured value(s). Additionally or alternatively, multiple measurements can be carried out to determine a single parameter. For example, the current and 20 or voltage can be sampled at a sufficiently high frequency to accurately capture the waveform of these parameters.

Using this waveform, parameters such as phase, amplitude, and spectral composition can be determined. Each of these parameters by itself or taken in combination can be part of 25 the electrical connection data and can be used by the processing means for determining whether or not to activate the breaking means. If for instance the circuit breaker is used for protecting a power line, the current amplitude can be used to determine whether the connection must be 30 interrupted. However, the adjustment of this control, for instance adjustment of the current limit that is used, is based on the electrical history for the power line. This history is at least partly based on the electrical 3 connection data. It is therefore possible that other electrical parameters are used for forming the electrical history than the current used for the comparison to the current limit. For example, the electrical connection data 5 may comprise voltage amplitude and phase, and current amplitude. The current amplitude is subsequently used for comparison with a current limit. An electrical history is formed by storing the voltage amplitude and phase in a memory. The adjustment to the control of the breaking means, 10 in this case the adjustment of the current limit, is based on this voltage based electrical history and therefore does not comprise any current data.

The electrical history is preferably based on a plurality of electrical connection data measured at 15 different times. In the context of the present application, electrical connection data is the collection of electrical parameters determined and or measured directly or indirectly, by derivation, by the measuring means at a given measurement interval or moment. By using electrical 20 connection data measured at multiple intervals or moments a better insight in the electrical behaviour of the electrical connection can be obtained.

The processing means preferably comprise comparing means for comparing at least part of the electrical 25 connection data to a first breaking profile. This first breaking profile determines and or describes a moment of activating the breaking means in dependence of an electrical parameter corresponding to the at least part of the electrical connection data. In this case, the adjustment of 30 the control of the breaking means comprises adjusting the first breaking profile. It is important to note that the part of the electrical connection data for comparing with the first breaking profile could relate to a current and or 4 subsequent measured and or determined value. For instance, the current measured value is the most recently measured value. In this case, a measured value is compared to a corresponding limit. Should the limit be exceeded, the 5 breaking means are activated and the electrical connection is interrupted. If subsequent measured values are also taken into account, measurements at different times can be used to decide whether or not to interrupt the connection. For instance, the electrical connection is only interrupted if a 10 certain current limit is exceeded for a certain time period.

An example of a breaking profile is the time between detection of a given current magnitude and activation of the breaking means as a function of this current magnitude. Normally, a higher current magnitude will result in a faster 15 activation of the breaking means.

Preferably, more than one breaking profile can be selected by the user depending on the application or the type of electrical connection. It is advantageous if these profiles are pre-installed in the circuit breaker although 20 it might also be possible to upload or otherwise incorporate these profiles into the circuit breaker. Switching between breaking profiles can be achieved by user input or it can be achieved automatically. An example of the latter is that the historical data is used to adaptively switch, without user 25 intervention, between breaking profiles. For instance, the processing means could determine that due to aging it is more appropriate to use a breaking profile based on current amplitude than a breaking profile based on the current amplitude squared multiplied by time (I2T profile). Hence, in 30 this situation the breaking profile is changed instead of the settings or parameters, such as limits, that are changed as discussed previously.

5

It is advantageous if the circuit breaker is arranged to work with more than one breaking profile. For instance, one breaking profile could be directed towards long term behaviour, e.g. aging phenomena, whereas another profile 5 could be directed towards short term effects, such as spikes. To this end, it is convenient if the comparing means are further arranged for comparing at least part of the electrical connection data to a second breaking profile.

This second breaking profile determines a moment of 10 operating the breaking means in dependence of an electrical parameter corresponding to the at least part of the electrical connection data. In this case, the comparing means are arranged for simultaneous comparison to the fist and second breaking profile. Adjustment of the control 15 comprises adjusting at least one of the first and second breaking profile.

Simultaneous in this context means that both breaking profiles are active, meaning that both profiles are used during the comparison stage.

20 It should be noted that the first and second breaking profiles do not necessarily relate to the same part of the electrical connection data. Furthermore, the breaking profile could be a function of a plurality of electrical parameters. Hence, in one breaking profile it is for 25 instance possible to monitor both current and voltage.

Apart from simultaneous comparison, breaking profiles can also be used sequentially wherein for instance exceeding a limit of one breaking profile will activate a further breaking profile. As such, a shift between breaking profiles 30 is established. Preferably, only comparison with the latter breaking profile will result in activation of the breaking means.

6

To this end, it is convenient if the comparing means are arranged for comparing at least part of the electrical connection data to a second breaking profile, wherein the comparing means are arranged for sequential comparison to 5 the first and second breaking profile, starting with the second breaking profile. The second breaking profile determines a starting moment of comparison to the first breaking profile in dependence of an electrical parameter corresponding to the at least part of the electrical 10 connection data. Adjustment of the control comprises adjusting at least one of the first and second breaking profile.

The processing means preferably comprise triggering means for comparing at least part of the electrical 15 connection data to a trigger level. The triggering means provide a trigger to the comparing means when the trigger level is exceeded. The comparing means, being responsive to this trigger, will switch accordingly between a non-activated state, in which the comparing means are not able 20 to control the breaking means, to an activated state, in which the comparing means are able to control the breaking means.

By including triggering means, the sensitivity of the circuit breaker for current spikes can for instance be 25 reduced. First, the current spike will be detected by the triggering means, which will trigger the comparing means. If the comparing means are arranged to compare the breaking profile to subsequent measurements only, it is likely that these measurements do not show the influence of the current 30 spike. As such, the current spike will not result in unnecessary interruption of the electrical connection.

The comparing means can be arranged to switch from the activated state to the non-activated state after a 7 predetermined amount of time. This ensures that sudden glitches or spikes do not result in a continuous activated state of the comparing means. Also the breaking profile itself can accommodate this switch. For instance, the 5 breaking profile can be provided with a reset condition, for instance if a parameter does not exceed a predetermined limit for a predetermined time. This will reset the comparing means back to the non-activated state.

It is also advantageous if the circuit breaker further 10 comprises delay means to delay the triggering of the comparing means by the trigger by a predetermined delay time. As mentioned, this helps to reduce the sensitivity of the circuit breaker against current spikes for instance.

It is advantageous if the processing means are arranged 15 to adjust at least one of the delay time, the trigger level, and the predetermined delay time based on the electrical history of the electrical connection.

In general, adjustment based on the electrical history will involve a computation of a new limit, level, or time, 20 given the corresponding old limit, level, or time and the electrical history. A computation algorithm to compute the adjustments based on the electrical history can be provided in the processing means.

It is advantageous if the electrical connection data 25 further comprises at least one measured and or derived value for a harmonic level for at least one electrical parameter corresponding to the electrical connection. More preferably, the measuring means are arranged to measure or determine a plurality of harmonic levels for the at least one electrical 30 parameter. Consequently, the processing means can control the breaking means based on at least one of the measured or determined harmonic levels. Additionally, at least one of the measured harmonic levels can be used to construct the δ electrical history. A high harmonic level could indicate electrical failure although this level as such might not be clearly visible by looking at the magnitude or the root means square of the corresponding parameter.

5 The electrical network can comprise at least one phase conductor and a neutral conductor. In this case, it is advantageous if at least one conductor, preferably a phase conductor, is provided with breaking means, and if each of the conductors is provided with measuring means specific to 10 those conductors. The electrical connection data measured and or determined by the measuring means comprises at least one measured and or derived value for at least one electrical parameter for each of the at least one phase conductor and neutral conductor.

15 In this case, the electrical connection data preferably comprises an amplitude and phase for a current in each of the at least one phase conductor and neutral conductor. In addition, the processing means are arranged to calculate a vector sum of currents in each of the at least one phase 20 conductor and neutral conductor, and to control the breaking means in dependence of the vector sum.

In a symmetrically loaded three-phase system, a vector sum of the currents in the three phase conductors and the neutral conductor is zero. Should leakage occur in one of 25 the loads connected to the phase conductors, the return current in the neutral conductor is no longer zero. By comparing the vector sum to a given or set limit, and by activating the breaking means should this limit be exceeded, electrical failures such as earth faults can be detected.

30 The vector sum can be part of the electrical connection data as it is a derived electrical parameter for the electrical connection. Hence, a breaking profile can be construed allowing the various protection schemes discussed above.

9

Preferably, each phase conductor is provided with breaking means. Furthermore, the processing means are preferably arranged to determine the phase conductor of which a phase of the measured current therein corresponds to 5 the phase of the vector sum, and to control the breaking means of that phase conductor specifically in dependence of the vector sum.

If each of the phase conductors is provided with breaking means, the phase connected to the failing load can 10 be switched off without having to interrupt the other phase conductors.

The electrical connection data preferably comprises harmonic levels for the vector sum. The processing means then preferably control the breaking means in dependence of 15 a harmonic level for the vector sum. This enables detection of frequency dependent leakage failures.

The above mentioned measures allow for a better detection of electrical failures. As such, the circuit breaker is better equipped to distinguish between harmless 20 and potentially harmful electrical failures. Consequently, the current limits, or any other limit for an electrical parameter, can be set more stringent.

The present invention further provides a method for breaking an electrical connection in an electrical network. 25 According to the invention, this method comprises the step of determining electrical connection data corresponding to the electrical connection. The electrical connection data comprises at least one measured and or derived value for at least one electrical parameter corresponding to said 30 electrical connection. The method further comprises controlling breaking means for breaking said electrical connection in dependence of said electrical connection data. The method is characterized by storing at least part of the 10 electrical connection data for forming an electrical history and by adjusting the control of the breaking means based on this electrical history.

It is advantageous if the determining of electrical 5 connection data comprises measuring a harmonic level for said at least one electrical parameter.

If the electrical network comprises at least one phase conductor and a neutral conductor, it is advantageous if each of these conductors is provided with measuring means 10 specific to those conductors and if at least one of the conductors is provided with breaking means. In this case determining of electrical connection data comprises determining a value for at least one electrical parameter for each of the at least one phase conductor and neutral 15 conductor.

Preferably, the above stated determining a value for at least one electrical parameter for each of the at least one phase conductor and neutral conductor comprises measuring a magnitude and phase for a current in each of the at least 20 one phase conductor and neutral conductor. The method then further comprises calculating a vector sum of currents in each of the at least one phase conductor and neutral conductor, and controlling said breaking means in dependence of said vector sum.

25 It is advantageous if each phase conductor is provided with breaking means. The method then further comprises determining the phase conductor of which a phase of the measured current therein corresponds to a phase of the vector sum and controlling the breaking means of that phase 30 conductor specifically in dependence of the vector sum.

If each of the phase conductors is provided with breaking means, the phase connected to the failing load can 11 be switched off without having to interrupt the other phase conductors.

Preferably, the electrical connection data comprises harmonic levels for the vector sum. The method then further 5 comprises controlling the breaking means in dependence of a harmonic level for the vector sum.

In the following, embodiments of the present invention will be described in more detail with reference to the accompanying drawings in which: 10 Figure 1 illustrates shows the general concept of the present invention wherein a circuit breaker is coupled to an electrical connection between a power source and a load.

Figure 2 depicts an example of electrical history;

Figure 3 illustrates a preferred embodiment of the 15 processing means of figure 1;

Figure 4 shows a possible current curve for the electrical connection in figure 1;

Figure 5 illustrates the breaking profile used for the current curve in figure 4; 20 Figure 6 illustrates the computation of a vector sum for a three-phase network according to the present invention.

Figure 1 shows the general concept of the present invention. A power source 1 is connected to a load 2 by 25 means of an electrical connection 3. In this example, electrical connection 3 comprises a phase conductor 4 and a neutral conductor 4'. A circuit breaker 5 is coupled to electrical connection 3. It comprises breaking means 6, which in figure 1 are schematically illustrated as a switch 30 connected to phase conductor 4, although the switch could have been connected to neutral conductor 4' or even to both. Breaking means 6 are controlled by processing means 7. Furthermore, measuring means 8 are arranged to determine 12 electrical connection data corresponding to electrical connection 3. This data is at least partly stored in a memory 9 thereby forming an electrical history. Processing means 7 are arranged to adjust the control of the breaking 5 means based on this electrical history.

In figure 1, measuring means 8 determine, e.g. by measurement, at least one electrical parameter for conductor 4, 4' or even for both. The measuring means can be arranged to determine continuously in time or at discrete times. In 10 addition, a measurement and or determination of a given electrical parameter can in fact comprise multiple measurements and or determinations. For instance, to determine the phase of a current or voltage, multiple measurements might be necessary to extract an associated 15 waveform.

Figure 2 depicts an example of electrical history in the form of a graph. The electrical history comprises information about the values for current amplitude ( 111) and voltage amplitude (|v|) measured by the measuring means at a 20 number of discrete points in time. In this example, the current amplitude is used by processing means 7 to control breaking means 6. Processing means 7 use the electrical history to adjust the control of breaking means 8. In this example, historical data for the voltage amplitude and 25 current amplitude are used by processing means 7 to reduce the current amplitude limit 10 at A. Hence, if a current amplitude is detected after A that exceeds that limit, which in this case means that the current amplitude is larger than the limit, breaking means 6 are activated and electrical 30 conduction through conductor 4 is interrupted.

It should be noted that it is also possible to have identical electrical parameters for the construction of the electrical history and the control of breaking means 6. For 13 example, the current amplitude limit can be adjusted based on historical data for the current amplitudes that occurred in the electrical connection. In this way, the limit can be set more accurately, which improves the sensitivity of the 5 system for electrical failures in load 2 and or power source 1.

Figure 3 illustrates a preferred embodiment of processing means 7 of figure 1. Triggering means 11 are provided that compare at least part of the electrical 10 connection data comprising at least one measured and or derived value for at least one electrical parameter to a trigger level. It should be noted that more than one value for a given parameter can be used for this comparison, for instance values determined at different time points. It is 15 also possible that several different parameters are used, or a combination of different parameters and multiple values. The trigger level can therefore comprise more than one value.

If it has been determined that a trigger level is 20 exceeded, a trigger is sent to the comparing means 12. This process can be delayed by delay means 13. Comparing means 12 compare at least part of the electrical connection data to a breaking profile. This breaking profile determines a moment of activating breaking means 8 in dependence of an 25 electrical parameter corresponding to the at least part of the electrical connection data. The most simple configuration of the breaking profile is that the breaking means are activated directly regardless the measured value. In this case, the trigger level acts as a limit, exceeding 30 of which will result in a delayed activation of breaking means 8.

Comparing means 12 are able to switch, in response to the trigger, between an activated state, in which they are 14 able to control the breaking means, to an non-activated state in which they cannot. It can also be possible that comparing means 12 only compare in the activated state.

Preferably, measuring means 8 measure and or determine 5 continuously. Comparing means 12 then compare the most recent electrical connection data to the breaking profile. However, it might also be possible to use multiple measurements for the comparison. For instance, the breaking profile can indicate that breaking means 6 should be 10 activated if the current amplitude exceeds a given limit at two distinct time points. For this comparison, one needs the current and a previous current amplitude measurement.

If comparing means 12 determine that breaking means 6 should be activated based on the measurements and the 15 breaking profile, an activation signal is sent to breaking means 6.

Figure 4 shows a possible current curve for the electrical connection in figure 1. At to an electrical failure occurs in load 2. As a consequence, the current 20 amplitude in phase conductor 4 increases between time points to and t2. At time point tl, the current amplitude exceeds the trigger limit 14. Consequently, after a given delay Δχ, comparing means 12 switch to the activated state in which they compare the measured values (indicated by dots), to the 25 breaking profile indicated in figure 5. This breaking profile determines the moment of activation of breaking means 6 for different current magnitudes. Below |l0| no activation is needed. However, as indicated, for the measured current amplitude |li|, breaking means 6 will be 30 activated after a delay of Δ2 seconds. Consequently, the electrical conduction of phase conductor 4 will be interrupted at time point tl+hx+h2. After this, comparing means 12 can switch back to the non-activated state after a 15 predetermined amount of time. According to the present invention, the breaking profile, the delay time and the predetermined amount of time can also be adjusted based on the electrical history. In figure 5 adjusting of the 5 electrical history could involve changing the value 1101 or the slope of the curve.

In a preferred embodiment, different breaking profiles can be used. These different profiles can be pre-installed in the circuit breaker or can be uploaded. Typically, these 10 breaking profiles are defined parametrically, e.g.

111 =c0 (1 /1)2 with c0 being a parameter. Adjusting the breaking profile then involves changing the relevant parameters, such as c0 in this example.

Examples of possible breaking profiles are: 15 RMS current profile: In this profile measured root means square (RMS) values of voltage and/or current measurements are compared with the profile. This profile is a time related sequence of limiting values; each value is used as a limit at a specific moment in time since the 20 comparing means were activated. An activation signal is sent to the breaking means when the measured RMS value exceeds the momentary profile value. Additionally or alternatively, an envelope may be defined in which the RMS value should fall to prevent activation of the breaking means.

25 Constant I2T current profile: Once the breaking means have been activated, it will sequentially compare the integrated values of the square of the RMS current measurements with a programmable limit. This limit represents the amount of energy that is allowed to be 30 consumed by the load during a limited time.

Phase checks: Using the phase checks profile, the measured RMS values of voltage and or current are continuously checked with each other. The breaking means 16 will be activated once one or more of the measured values deviate by more than a programmed difference. Instead of interrupting the electrical connection, a warning could be dispatched to the user. This profile also allows detection 5 of a change in behavior of the load. For instance, if the phase difference changes by more than 90 degrees, the load will change between generator and load behavior.

Figure 6 illustrates the computation of a vector sum for a three-phase network according to the present 10 invention. In such a network, power is transferred using three phase conductors of which the voltage is 120 degrees out of phase and a common neutral conductor. In this embodiment, breaking means are provided such that at least each phase conductor can be interrupted. Measuring means 15 determine a value for at least one electrical parameter for each phase conductor and the neutral conductor yielding a total of at least four values.

In the example in figure 6, the current amplitude and phase are determined for each phase conductor and the 20 neutral conductor. In a balanced system, in which each phase conductor is similarly loaded, the error computed as the vector sum of all currents would be zero. Due to an asymmetry, for instance caused by earth leakage, the current in phase conductor pi is enlarged. The corresponding vector 25 sum E reflects this. In fact, the phase of the vector sum E corresponds to the phase of the phase conductor pi to which the failure can be attributed. In this embodiment, the processing means are arranged to selectively control the breaking means to only switch off phase conductor pi.

30 Failures related to one phase conductor do therefore not require a complete interruption of the electrical connection.

17

The measuring means can also be arranged to determine harmonic levels for the at least one electrical parameter. For instance, in addition the current magnitude at a given time point, the spectral composition is determined 5 comprising the amplitude and phase for each spectral component. This information can be included in the electrical connection data used for controlling the breaking means. For instance, the processing means can monitor the second harmonic of the current in phase conductor 4. A load, 10 which is sensitive for an electrical failure that shows itself by a change in second harmonic current levels, can thus be monitored more efficiently. It should be noted that unacceptable high harmonic content cannot always be deduced from the current momentary magnitude or root mean square.

15 The analysis of harmonic levels can be applied to the three-phase system as well. In this case, the error signal is computed for each harmonic level. Should at least one of these harmonic error signals indicate a problem, the corresponding phase conductor can be interrupted. It should 20 be noted that the harmonic levels can also be included in the electrical history, even without being part of the electrical connection data used for controlling the breaking means.

Switching off a phase conductor, or more particularly 25 multiple phase conductors, generally involves large transients. The breaking means and or processing means can therefore be adapted to time these interruptions such that the impact on the power source is minimal. The same applies to the switching on of the phase conductors.

30 In the above, embodiments of the present invention have been described in detail. However, it should be obvious to the skilled person in the art that various modifications to 18 these embodiments are possible without deviating from the scope of the invention as defined by the appended claims.

It should be noted further that the aspect of measuring harmonic levels is useful even without adjusting the control 5 of the breaking means based on electrical history.

1036389

Claims

Circuit breaker for interrupting an electrical connection in an electrical network, said circuit breaker comprising: measuring means for determining electrical connection data, the electrical connection data comprising at least one measured and / or derived value for at least one electrical parameter corresponding to said electrical connection; interrupting means for interrupting said electrical connection; processing means adapted to control said interrupting means in dependence on said electrical connection data; characterized by a memory for storing at least a portion of said electrical connection data for forming an electrical history and in that the processing means are adapted to adjust the control of the interrupt means based on said electrical history.

2. Circuit breaker according to claim 1, wherein said electrical history is based on a plurality of electrical connection data measured at different times.

3. Circuit breaker as claimed in claim 1 or 2, wherein said processing means comprise comparison means for comparing at least a part of said electrical connection data with a first interrupt profile, said first interrupt profile defining a moment for operating 1036389 said interrupt means in dependence on an electrical parameter corresponding to said at least a portion of said electrical connection data, said adaptation of said control comprising adapting said first interrupt profile.

4. Circuit breaker according to claim 3, comprising a plurality of interrupt profiles which are selectable by a user.

5. Circuit breaker according to claim 3 or 4, wherein said comparing means are further adapted to compare at least a part of said electrical connection data with a second interrupt profile, wherein said second interrupt profile determines a moment for operating the said interrupt means in dependence on an electrical parameter corresponding to said at least a portion of said electrical connection data, the comparing means being arranged for simultaneous comparison with said first and second interrupt profile, and wherein said adaptation of said control adjusting at least one of said first and second interrupt profile.

6. Circuit breaker according to claim 3 or 4, wherein said comparing means are further arranged for comparing at least a portion of said electrical connection data with a second interrupt profile, wherein the comparing means are arranged for sequential comparison with said first and second interrupt profile, starting with said second interrupt profile, wherein said second interrupt profile determines a start time of comparison with said first interrupt profile depending on an electrical parameter corresponding to said at least a portion of said electrical connection data, and said adaptation of said control comprising adapting at least one of said first and second interrupt profile.

7. Circuit breaker as claimed in any of the claims 3-6, wherein said processing means comprise trigger means for comparing at least a portion of said electrical connection data with a trigger level, said trigger means providing a trigger to said comparison means when said trigger level is exceeded, said comparator means being switchable between a non-activated state, in which the comparator means is unable to control the interrupting means, to an activated state, in which the comparator means is capable of controlling the interrupting means by the said trigger. 25

8. Circuit breaker according to claim 7, wherein said comparing means are adapted to switch from said activated state to said non-activated state after a predetermined amount of time.

The Ciruic breaker according to claim 7 or 8, further comprising delay means for delaying the triggering of said comparison means by said trigger with a delay time.

The circuit interrupter of any one of claims 7-9, wherein said processing means is adapted to adjust at least one of said delay time, said trigger level, and the predetermined amount of time based on said electrical history of said electrical connection.

11. Circuit breaker according to any of claims 1-10, wherein the electrical connection data further comprises at least one measured and / or derived value for a harmonic level for at least one electrical parameter corresponding to said electrical connection.

12. Circuit breaker according to any of claims 1-11, wherein said electrical network comprises at least one phase conductor and a neutral conductor, at least one of which is provided with interrupting means, wherein each conductor is provided with measuring means specific for those conductors wherein the electrical connection data measured by said measuring means comprises at least one measured and / or derived value for at least one electrical parameter for each of the at least one phase conductor and neutral conductor.

13. Circuit breaker according to claim 12, wherein the electrical connection data comprises an amplitude and phase for a current in each of the at least one phase conductor and neutral conductor, and wherein the processing means are arranged to calculate a vector sum of currents in each of the at least one phase conductor and neutral conductor, and wherein the processing means are further adapted to control the interrupting means in dependence on the vector sum.

14. Circuit breaker as claimed in claim 13, wherein each phase conductor is provided with interrupting means, and wherein said processing means are further adapted to determine the phase conductor of which a phase of the measured current therein corresponds to a phase of the vector sum and wherein the processing means are further adapted to control the interrupting means of specifically that phase conductor in dependence on the vector sum.

15. Circuit breaker as claimed in any of the claims 12-14, insofar as dependent on claim 11, wherein electrical connection data comprises harmonic levels for the vector sum, and wherein the processing means are adapted to control the interrupting means in dependence on a harmonic level for the vector sum.

16. Method for interrupting an electrical connection in an electrical network comprising the steps of: determining electrical connection data corresponding to said electrical connection, said electrical connection data comprising at least one measured and / or derived value for at least one electrical parameter corresponding to said electrical connection; controlling the interrupting means for interrupting said electrical connection in dependence on said electrical connection data; 5 characterized by storing at least a portion of said electrical connection data to form an electrical history and by adjusting the control of said interrupt means based on said electrical history. 10

The method of claim 16, wherein said determining electrical connection data comprises measuring a harmonic level for said at least one electrical parameter. 15

18. Method as claimed in claim 16 or 17, wherein said electrical network comprises at least one phase conductor and a neutral conductor, at least one of which is provided with interrupting means, wherein each conductor is provided with measuring means specific for said conductors, said said determining electrical connection data determining a value for at least one electrical parameter comprises for each of the at least one phase conductor and neutral conductor. 25

19. Method according to claim 18, wherein said determining a value for at least one electrical parameter for each of the at least one phase conductor and neutral conductor comprises measuring a magnitude and phase for a current in each of the at least one one phase conductor and neutral conductor, said method further comprising calculating a vector sum of currents in each of the at least one phase conductor and neutral conductor and controlling said interrupting means in dependence on said vector sum.

The method of claim 19, wherein each phase 5 conductor is provided with interrupting means, the method further comprising: determining the phase conductor whose phase of the measured current therein corresponds to a phase of said vector sum; 10. controlling the interrupting means of specifically that phase conductor in dependence on the vector sum.

21. Method according to any of claims 18-20, insofar as dependent on claim 17, wherein electrical connection data comprises harmonic levels for the vector sum, further comprising controlling the interrupt means in dependence on a harmonic level for the vector sum. 1 0 36 3 89