Method for avoiding blocking of intelligent electronic unit (IED) function

Abstract

The invention relates to a method for avoiding a blocking of the function of intelligent electronic units, i.e. IEDs (2, 4), which are connected to one another as part of a local area network (1) and via the local area network (1), the local area network (1) having at least two time setting units (3).

Description

Technical Field

[0001] In order to synchronize the time settings of devices that are networked together via a communication network, a time protocol has been introduced which is also called the Precision Time Protocol in English and is referred to below as PTP. Background Art

[0002] Local area networks are implemented, for example, in transformer substations for power supply. Such transformer substations are used to step down and step up the network voltage in the power supply network by means of transformers, and their operation is known. In addition to the transformer, the transformer substation also has a switching unit, such as a power switch, which disconnects the conductor outlet of the transformer substation from the rest of the power supply network after receiving a switching signal.

[0003] The switching signals are generated by protection and automation devices, which monitor the current and voltage curves in the conductors of the substation to determine whether a fault condition exists. If a fault condition exists, a switching signal is generated and sent to one or more selected switching units, so that the switching units are switched to their interruption positions. In the interruption position, the contacts of the selected switching units are separated from each other, so that the current through the switching units is prevented from being conducted. The conductor line connected to this contact of the switching unit is disconnected from the rest of the power supply network connected to other contacts of the switching unit.

[0004] In order for the protection devices and automation devices to be able to monitor the current and voltage curves in the conductors of the substation to determine whether a fault condition exists, the protection devices and automation devices must be continuously provided with current and voltage values ​​that change over time. To provide the current and voltage values, current and voltage transformers are provided, which detect the current and voltage in the conductors at the measuring points of the substation and provide calibrated measurement signals from the secondary side, which are scanned at a fixed scanning rate to obtain scanning values. The scanning values ​​are then digitized. In addition, a fixed matching time stamp is applied to the scanning values. This is achieved with the help of so-called "merging units" or with the help of other intelligent electronic devices (IEDs) in the substation. In order to be able to compare the measured values ​​with each other, the time detection of the IEDs must be synchronized, which time detections are linked to each other via a process bus. For this purpose, the so-called PTP is used.

[0005] Therefore, PTP is used in the power supply of digital substations to synchronize intelligent electronic devices (IEDs), for example the so-called IEC61850 process bus.

[0006] The comparison of measured values ​​originating from different IEDs is particularly critical. If the time synchronization between these devices is lost or insufficient, this can lead to blocking of protection functions in protection and automation equipment or to erroneous triggering of switch units, resulting in unplanned interruptions of the power supply.

[0007] A digital process bus environment is usually formed in a digital substation. In order to measure the current and voltage in the high-voltage conductor, for example, current and voltage transformers are used, which provide analog measurement values ​​on the output side. The analog measurement values ​​are separated from the protection devices on the digital side by a special device, which is also called a merging unit (MU) by professionals. The merging unit provides a digital stream of scanned values. The data stream has a data message that complies with the IEC 61850-9-2 standard. The protection device that plays the role of a data message receiver (also called Sampled Value Subscriber (SV-SUB) in the digital network records a large number of data streams from different MUs, converts the data streams through digital filters, evaluates the quality and synchronization properties of the data, and provides the converted data to protection or other functional algorithms.

[0008] In addition to the data streams transmitted by the device in the same digital network, the protection device can also receive other digital data streams, for example, digital data streams originating from other, more distant substations. This approach is necessary, for example, in line differential protection. Data streams from different sources can be combined almost freely as inputs to multiple protection devices. However, the algorithms of the protection functions place high demands on the accuracy of the scanning synchronization at their inputs, because inaccurate scanning of analog measured values ​​can lead to malfunctions of the protection function.

[0009] Thus, differential protection checks, for example, that the sum of the currents of the fully measured protected object is equal to zero in the fault-free state. False synchronization can lead to phase differences between the measured data streams and thus to significant differential currents. This can lead to fault triggering. In teleprotection, too, erroneous synchronization of the measured value detection between current and voltage can lead to erroneous impedances.

[0010] When the synchronization accuracy of the incoming data stream is questionable, the IED's functioning may fail. The protection device may, for example, lose its protection function. Typically, the IED's functioning may be due to the recognition of a sudden change in the synchronization time base. And the identification of the synchronization source may yield the same result.

[0011] In order to ensure the necessary synchronization accuracy, the same synchronization source is used for all participating devices. The preferred synchronization method described in the IEC61850 standard is the IEEE 1588 Precision Timing Protocol (PTP). In order to maintain the protection functionality unchanged when the synchronization source fails, multiple redundant synchronization sources are usually used, such as the PTP Grand Master Clock (GMC) or the Grand Master Time Unit (Grandmaster-Zeiteinheit). According to the protocol IEEE 1588, the so-called Best Master Clock Algorithm (BMCA) is responsible for setting one of the time setting units to play the role of the active PTP Grandmaster (PTP-Grandmaster) and using it as a synchronization source. The time setting unit will also be referred to as the super master time setting unit below. The selection of the super master time setting unit is decentralized based on the properties of the PTP data set within the time setting unit.

[0012] Failure of the IED functionality is undesirable and should therefore be avoided as much as possible. Summary of the invention

[0013] Therefore, the technical problem to be solved by the present invention is to provide a method of the above-mentioned type, in which the occurrence of malfunctions in the IED function can be reduced or even completely avoided.

[0014] This object is achieved according to the invention by the features of claims 1 and 12 .

[0015] Solutions of the invention are the subject matter of the dependent claims.

[0016] It has been recognized within the scope of the invention that this function need not be blocked when the synchronization source changes. This occurs when the super-master role changes between mutually synchronized time setting units.

[0017] The invention provides a method for avoiding functional failure of an intelligent electronic unit IED, which is interconnected via a local area network as part of a local network. The local area network has a plurality of and therefore at least two time setting units. One of the time setting units is used as a synchronization source and plays the role of an active super master. All other time setting units then maintain their slave state and are synchronized with the time setting unit in the super master role. When one of the time setting units in the slave state changes to the role of the super master time setting unit, a pre-synchronization report is sent to all IEDs in the local area network. The pre-synchronization report reports to the IED whether the current super master time setting unit and, if necessary, with which previous super master time setting unit has been synchronized. That is, if the IED is to process a data stream synchronized with a previous synchronization source or a current synchronization source, there is no need to hinder the function of the IED, because the data is synchronized with each other despite the time stamps of different sources. Therefore, blocking the function of the IED can be avoided within the scope of the invention.

[0018] In addition, the present invention also relates to a device for avoiding functional obstruction of an intelligent electronic unit (IED), the device comprising a local area network, which has an IED and at least two time setting units and a communication network, using the communication network to associate the IED and the time setting unit with each other, wherein the time setting unit is designed to take a super-master role or a slave state, in which the time setting unit is used as a synchronization source for the IED, and in the slave state the time setting unit is synchronized with the time setting unit in the super-master role, wherein the time setting unit is designed so that when one of the time setting units in the slave state changes to the role of the super-master time setting unit, the time setting unit informs all IEDs in the local network through the network of a pre-synchronization report: whether the current super-master time setting unit and, if necessary, with which previous super-master time setting unit has been synchronized, thereby avoiding functional obstruction of the IED, and the scan value of the data stream processed by the IED is detected synchronously with the previous super-master time setting unit.

[0019] The time setting unit can in principle be implemented arbitrarily within the scope of the present invention. Within the scope of the present invention, the time setting unit can be any unit that is able to generate a time standard. The unit can exist as a separate device or as a component or member of other devices, such as IEDs, in particular protection or automation devices. The time setting unit can have its own oscillator. Such an oscillator has, for example, a quartz crystal, whose oscillations are converted into a time standard. However, oscillators are known to those skilled in the art, so their exact working method will not be described in detail here. Within the scope of the present invention, the oscillator used in the time setting unit is synchronized with other oscillators.

[0020] Advantageously, within the scope of the invention, BMCA is implemented in a network. Depending on the result of the detection, one of the time setting units changes to the super-master role or remains in the slave state.

[0021] If a time setting unit fails, the BMCA determines this and triggers a change in the super-master role. Advantageously within the scope of the invention, the restored or reconnected time setting unit with super-master capabilities is forced to remain in its slave state until its own internal oscillator is synchronized with the current PTP super-master time setting unit (if any). The forced slave state can then be stopped. The BMCA then determines whether the restored and synchronized time setting unit assumes the super-master role. In this way, time mutations are avoided.

[0022] The forcing of the slave state can be achieved by setting the priority of the time setting unit. If the priority of a time setting unit with super master performance is set to, for example, 254 or 255, the time setting unit remains in its slave state when passing the BMCA check. In the present invention, the method can be implemented in addition to sending a pre-synchronization report.

[0023] A local area network ("LAN"), abbreviated as "LAN", is to be understood within the scope of the present invention as a network limited in space. The local area network is, for example, a network specified in the IEC standard IEC 61850. Advantageously, the local area network has structured lines. According to a preferred embodiment, the network is a process bus communication network. The network limited in space comprises intelligent electronic devices (IEDs), which are connected to each other, for example, via wired communication lines or radio, such as a 5G network. However, the use of Ethernet technology is preferred within the scope of the present invention. Other local area networks are also feasible in principle within the scope of the present invention.

[0024] The abbreviation IED is to be understood within the scope of the present invention as intelligent electronic device. IEDs are, for example, protection or automation devices, relays or field control devices used in substations, for example in the field of protection and control technology. IEDs are often also referred to as processor-based controllers.

[0025] Within the scope of the present invention, a blocked function is understood to mean that, when an obstacle exists, an IED designed for a function cannot be implemented in the presence of the obstacle. If the IED is, for example, a protection device, the protection function of the protection device is blocked. This protection function includes a protection algorithm of the protection device, which is applied in the protection device. Within the scope of the present invention, all protection functions of the protection device may also be blocked. Other IEDs may have other functions or be used for other purposes. An automation device is also an IED within the scope of the present invention. In the case of a blocked function of an automation device, for example, a job that should be automatically performed by the automation device cannot be used smoothly during the blocked period.

[0026] Advantageously, PTP is used within the scope of the present invention.

[0027] According to another expedient embodiment, the local area network is a radio network. It is particularly advantageous if the radio network is a 5G radio network.

[0028] In a preferred design of the present invention, the local area network includes a process bus communication network of the substation, and Ethernet technology is preferably used in the process bus communication network.

[0029] Within the scope of the present invention, the number of time setting units is not limited to two time setting units. For example, five or more time setting units can communicate with each other in the network.

[0030] Expediently, at least one time setting unit is integrated or in other words installed in the IED. That is to say, the time setting unit is a component of the IED and is arranged in a housing of the IED.

[0031] It is further advantageous if at least one IED is a protection or automation device of an electrical energy supply network. Furthermore, within the scope of the invention, an MU can be an IED.

[0032] In one design of the present invention, the pre-synchronization report is a binary pre-synchronization report. "Binary pre-synchronization report" should be understood as: the pre-synchronization report sends information about the pre-synchronization status in the design of binary information. The binary pre-synchronization report only indicates whether the pre-synchronization has been successfully completed. The identity of the synchronization source is not indicated in this case. In this simple and therefore low-cost design of the present invention, it is assumed that there are only two synchronization sources (PTP-GMC) in the network. In other words, it indicates whether the current super-master time setting unit is synchronized with the previous super-master time setting unit. If the binary pre-synchronization information is true, the originally designed check on the synchronization identity will be temporarily invalid. Otherwise, the check on the synchronization identity remains activated.

[0033] Functional impairments can also be avoided in this way.

[0034] Within the scope of the invention, in principle any unit can send the pre-synchronization report to the IED of the local network. Advantageously, however, this is done by the IED or the time setting unit which determines the change of the super-master role due to the check of the synchronization identity. Such a time unit can be a time setting unit which changes to the super-master role. However, it is also possible within the scope of the invention for the sending to be done by other time setting units which have not changed to the super-master role. A further advantage is that the time setting unit sends the pre-synchronization report at the moment when it changes to the role of the super-master time setting unit. Delays in sending the pre-synchronization report are avoided by this design.

[0035] Advantageously, the pre-synchronization report comprises the identity of the current super-master time setting unit, the identity of the previous super-master time setting unit and an indication whether the current super-master time setting unit and the previous super-master time setting unit have been synchronized. In this case, the synchronization source that has been successfully pre-synchronized, in other words the current super-master time setting unit, can inform the IED of its own synchronization identity and the synchronization identity of the synchronization source that has been synchronized with it. The IED can use two values ​​in order to check the synchronization identity of the incoming data streams, because the data streams are based on the same time base. When the super-master identity transmitted by the MU in the data message respectively corresponds to the super-master identity transmitted in the pre-synchronization report and has been successfully pre-synchronized, obstruction of the protection function can be prevented.

[0036] In another embodiment of the invention, each pre-synchronization report is sent as a GOOSE report. GOOSE reports are known to the skilled person from the standard IEC 61850-8-1. GOOSE stands for Generic Object Oriented Substation Events. GOOSE reports can be sent by a supermaster time setting unit (IED implemented as MU) or by a protection device with an embedded GMC function.

[0037] In the thus-converted design, when the super-master time unit assumes the super-master role, each pre-synchronization report is sent by the super-master time unit, wherein the super-master time unit is connected to the local area network as an independent unit.

[0038] In the context of the present invention, it is provided that the current super master time unit is a functional module integrated in the IED. If the super master time unit is implemented as a functional module and is installed in the IED as a functional module and it is also designed to send a pre-synchronization report, the transmission of the pre-synchronization report is preferably carried out in the form of a GOOSE message. The GOOSE mechanism is usually already used for other purposes in the IED, in which the super master time setting unit is installed.

[0039] According to a relevant improvement scheme that meets the purpose, the pre-synchronization report includes a type-length-value (TLV) field. TLV is used in the above-mentioned PTP protocol and is known to those skilled in the art. Further description of this can also be omitted here.

[0040] Advantageously, the IED comprises a plurality of merging units (MU) and at least one protection device.

[0041] The pre-synchronization report advantageously expires after a predefined time.

[0042] According to another design, the first time setting unit is forced to be in a slave state when it has been identified that other time setting units are in a super master role in the local area network, wherein the first time setting unit is synchronized with the time setting unit in the super master role, and after synchronization, the slave state forcing of the first time setting unit is stopped, and the first time setting unit is transformed into the role of the super master time setting unit when it is more suitable for the super master role, or when other time setting units in the network are more suitable for the super master role, the first time setting unit remains in its slave state. In this way, the function of the IED can be avoided from being blocked, because the time setting units that alternate the super master role are always synchronized with each other.

[0043] According to the purpose-oriented improvement scheme related thereto, the time setting unit with super master performance that is available again or reconnected to the network remains in a slave state and continuously synchronizes with the current super master time setting unit. Only when the super master time setting unit is cancelled does it change to the super master role.

[0044] Advantageously, the method according to the invention is a computer-implemented method or in other words a method implemented by a computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention is explained in more detail below with reference to exemplary embodiments, wherein identical reference numerals designate identically acting components and wherein:

[0046] Figure 1 shows an embodiment of a process bus communication network,

[0047] Figure 2 A flow chart is shown for explaining an exemplary embodiment of the method according to the invention. DETAILED DESCRIPTION

[0048] Figure 1A local area network 1 is shown as an example. The network 1 has protection devices 2a, 2b and 2c as IEDs. In addition, the IEDs also include so-called merging units (MU) 4a, 4b and 4c. The time setting units are marked with reference numerals 3a, 3b and 3c. As mentioned above, the BMCA is responsible for making the time setting unit 3a assume the role of super master. The time setting units 3b and 3c are in the slave state.

[0049] In the embodiment, the time setting unit 3a can send PTP synchronization messages according to the predetermined structures of "notification", "synchronization", and "follow-up" through the communication process bus 6 to the IEDs that are also connected to the process bus communication network 6, namely the protection devices 2a, 2b and 2c and MU4a, 4b and 4c.

[0050] The time setting unit 3 can in principle be connected to a reference reference clock source, a so-called reference reference clock (PRC), such as a global navigation satellite system (GNSS). However, since it can be affected by jamming transmitters (jamming) or other means (such as camouflage), such satellite-supported global reference clocks are risky and often not allowed to be used depending on their application area. In this case, an oscillator internal to the device can be used, which is installed in the time setting unit 3, wherein the time setting unit independently gives a relative time reference with respect to the outside, which is expressed in the form of a time value in the process bus communication network 6.

[0051] When the process bus communication network 6 is used in a substation of an electrical energy supply network, relative time values ​​provided by the local oscillators in the time setting units 2 , 3 are sufficient for synchronization, since absolute time values ​​are not required.

[0052] Multiple time setting units are used for redundancy, i.e. availability purposes. Under fault-free conditions, a single time setting unit 3a is selected as the active super master by means of the Best Master Clock Algorithm (BMCA). Only this time setting unit 3a sends PTP synchronization messages 5 via the network 6. The other time setting units 3b and 3c do not send PTP synchronization messages, but are in a slave state. They receive PTP synchronization messages 5 from the super master time setting unit 3a like IEDs 2 and 4, and their own internal oscillators are synchronized with the oscillator of the time setting unit 3a, so that the internal oscillators of the time setting units 3b, 3c oscillate at almost the same speed as the internal oscillator of the time setting unit 3a. However, the time setting units 3b and 3c are ready to switch to the active super master role.

[0053] In addition, Figure 1As shown, the protection device 2 obtains a data message stream or in other words a data stream 7. Each data stream 7 is provided from the output side by MU4. Mu4 receives the measured values ​​of a current or voltage measuring device on the input side, and the current or voltage measuring device detects the current or voltage of a component in a high-voltage conductor or an electrical energy supply network. For this purpose, the MU is connected to the current or voltage measuring device. For the sake of simplicity of the diagram, the current or voltage measuring device is not shown. If the measured value is in analog form at the input of the MU, each MU scans the analog signal to obtain a scanned value. The scanned value is digitized with the aid of a digital-to-analog converter to obtain a digital measured value. To form a data message, the digital measured value is provided with a timestamp t x , where the x as a subscript represents a consecutive integer. In order to be able to compare the digital measured values ​​of MU4a with the digital measured values ​​of MU4b or 4c, the MUs must be synchronized with each other. This is achieved via PTP synchronization messages.

[0054] When the super-master time setting unit 3a fails, the super-master role is transferred to the time setting unit 3c, for example. This is determined by the BMCA. Since the time setting unit 3c is already synchronized with the time setting unit 3a, this does not result in a loss of synchronization. If the time setting unit 3a becomes functional again or is reconnected to the network 1, the previously executed algorithm prevents the super-master role from being directly taken over by the time setting unit 3a. The time setting unit remains in the slave state and is synchronized with the super-master time setting unit 3c. If synchronization is achieved, the slave state enforcement is stopped again by the algorithm. The BMCA then determines the situation of the time setting unit 3a.

[0055] If the time setting unit 3a is abolished or disconnected from the network, its absence will be recognized by the time setting units 3b and 3c due to the lack of PTP notification messages from the time setting unit 3a. According to BMCA, for example, the time setting unit 3c changes to the super master role. If the time setting unit 3c has recognized this change, it directly or in other words immediately sends a pre-synchronization report to the protection device 2, including the effective content that it has completed synchronization with the time setting unit 3a before changing to the super master role.

[0056] Based on the PTP message, the IEDs 2 and 4 recognize the change of the super master role from the time setting unit 3a to the time setting unit 3c. Here, if the internal oscillator of the time setting unit 3c has been synchronized with the oscillator of the time setting unit 3a before the switch, the time synchronization of the IED is not disturbed. The synchronization of the time detection in the IED continues smoothly. No time jump occurs during or after the super master switch.

[0057] After the transfer, the IED 2, 4 does not recognize the time jump, and its internal oscillator does not need to be synchronized with the new local oscillator of the new super master time setting unit 3c. This resynchronization process can last no longer than 20 seconds. During this time, the protection function of the protection device 2 is blocked, thereby avoiding possible false triggering of the power switch.

[0058] Figure 2 A flow chart showing an embodiment of a method according to the present invention is shown. Figure 1 The protection device 2 shown is implemented in the protection device 2. All data streams inputted to the protection device 2 are compared separately. For this purpose, the method according to the invention always compares two data streams, which may originate from different MUs, with each other at a certain moment. The method is repeated frequently until all data streams inputted to the respective protection devices are compared with each other. Thus, Figure 2 2 shows two data streams 9a and 9b, which originate from MU4a and 4b. The method is implemented to determine whether MU4a and 4b are synchronized with each other. If this is the case, the protection function of the protection device 2 is continuously executed, otherwise the protection function must be blocked.

[0059] The protection device 2 receives the pre-synchronization report 8 and the two data streams 9a and 9b of MUs 4a and 4b. According to the standard IEC 61850-9-2, the data messages of the data streams 9a and 9b contain information about the source of the synchronization time (global, local or internal to the IED) and the identity of the super-master time setting unit. Said information is transmitted via the characteristics "smpSynch" and "gmIdentity". The pre-synchronization report 8 contains an indication whether the current super-master time setting unit has been successfully synchronized with the previous super-master time setting unit before the super-master role change. In addition, the pre-synchronization report includes the identity of the current super-master time setting unit and the identity of the previous super-master time setting unit.

[0060] In a first step 10, it is checked whether MU4a and 4b are globally or locally synchronized. If one of the MUs is globally synchronized and the other is locally synchronized or at least one MU is synchronized internally in the IED, then the MUs 4a and 4b use different time bases. They should therefore not be synchronized with each other. This corresponds to the result 11b "out of synchronization". In other words, the result 11a "synchronized" of the check process is that the data streams of the two MUs 4a and 4b are synchronized with each other. However, in order to be able to confirm the existing synchronization, an additional check step must be performed.

[0061] In the check step 12 it is checked whether both MUs 4a and 4b are globally synchronized. If this is the case, the MUs use the same global time base and the check ends with the result 11a "synchronized". If the two data streams are not globally synchronized, then in conjunction with this result of the check step 10, the two data streams must be locally synchronized.

[0062] In a check step 13 it is checked whether MUs 4a and 4b are synchronized with the same PTP grandmaster clock. If this is the case, the MUs use the same time base and are synchronized with each other. The result of this check is 11a "synchronized". If, however, it is determined that MUs 4a and 4b are synchronized with different grandmaster time setting units, another final check step must be carried out.

[0063] In the fourth check step 14, it is checked whether the different super-master time setting units are the current and previous super-master time setting units. If so and pre-synchronization has been successfully completed, the two use the same time base. MU4a and 4b are synchronized with each other in this case. Check step 14 is performed with the aid of pre-synchronization report 8. If the current super-master time setting unit, for example 3c, has completed synchronization (pre-synchronization) with the previous super-master time setting unit 3a before the super-master role change, and the two MU4a and 4b are synchronized with the current super-master time setting unit or with the previous super-master time setting unit, then the two MU4a and 4b are synchronized with each other. The result is 11a "synchronized", otherwise it is 11b "unsynchronized".

[0064] This means that, by means of this checking step 14 , it is possible to reliably avoid a hindrance to the protective function of the respective protective device, which would result in a hindrance to the function in the known method.

Claims

1. A method for preventing functional impairment of intelligent electronic units, also known as IEDs (2, 4), which are part of a local area network (1) and are interconnected via the local area network (1), wherein: A local area network (1) has at least two time setting units (3), wherein: - one of the time setting units (3a) assumes the active super-master role as a synchronization source, while all other time setting units (3b, 3c) remain in their slave state and synchronize with the time setting unit (3a) in the super-master role; - when the time setting unit (3b, 3c) in the slave state changes to the role of the super-master time setting unit, the local area network (1) is used to inform all intelligent electronic units (2, 4) in the local area network (1) through a pre-synchronization report (8): whether the current super-master time setting unit (3c) is synchronized with and, if necessary, with which previous super-master time setting unit (3a), thereby avoiding obstruction of the function of the intelligent electronic unit (2, 4) which processes a data stream whose scan values ​​are detected synchronously with the previous super-master time setting unit.

2. The method according to claim 1, characterized in that The pre-synchronization report (8) is a binary pre-synchronization report.

3. The method according to claim 1 or 2, characterized in that: The pre-synchronization report (8) is issued by the super master time setting unit (3) or the intelligent electronic unit (2, 4).

4. The method according to any one of the preceding claims, characterized in that The pre-synchronization report (8) includes the identity of the current super master time setting unit (3c), the identity of the previous super master time setting unit (3a) and a description indicating whether the current super master time setting unit and the previous super master time setting unit have been synchronized with each other.

5. The method according to any one of claims 1 to 3, characterized in that The pre-synchronization report (8) is sent as a GOOSE message.

6. The method according to any one of claims 1 to 3, characterized in that The pre-synchronization report (8) is sent in the form of a PTP message and includes a type-length-value field.

7. The method according to any one of the preceding claims, characterized in that The pre-synchronization report (8) is sent by the super master time setting unit (3c) when it assumes the super master role, wherein the super master time setting unit (3c) is connected to the local area network (1) as an independent unit.

8. The method according to any one of the preceding claims, characterized in that The present super master time setting unit (3c) is a functional module integrated in the intelligent electronic unit (2, 4).

9. The method according to any one of the preceding claims, characterized in that The intelligent electronic unit (2, 4) comprises a plurality of merging units (3) and at least one protection device (2).

10. The method according to any one of the preceding claims, It is characterized in that - the first time setting unit (2) is forced into its slave state when it has been identified that another time setting unit is in a super-master role in the local area network (1), wherein the first time setting unit (2) is synchronized with the time setting unit (3) in the super-master role, - after successful synchronization, stopping the slave state forcing of the first time setting unit (2), - The first time setting unit (2) changes to the role of the super master time setting unit when it is more suitable for the super master role, or when other time setting units (3) in the local area network (1) are more suitable for the super master role, the first time setting unit remains in its slave state.

11. The method according to any one of the preceding claims, characterized in that A time setting unit with super master capability that becomes available again or rejoins the network remains in a slave state and continuously synchronizes with the current super master time setting unit, and changes to the super master role only when the super master time setting unit becomes obsolete.

12. A device for preventing the function of an intelligent electronic unit, that is, an IED, from being blocked, the device comprising - A local area network (1) having intelligent electronic units (2, 4) and at least two time setting units (3) and a communication network (6) by means of which the intelligent electronic units and the time setting units are connected to one another, wherein: - the time setting unit (3) is designed to assume a super-master role or a slave state, in which it serves as a synchronization source for the intelligent electronic units (2, 4) and in which it is synchronized with the time setting unit (3a) in the super-master role, - Wherein, at least one intelligent electronic unit (2, 4) or the time setting unit (3) is designed so that when one of the time setting units (3b, 3c) in a slave state changes to the role of a super master time setting unit, the time setting unit informs all intelligent electronic units (2, 4) in the local area network (1) through the communication network (6) with the help of a pre-synchronization report (8): whether the current super master time setting unit (3c) has been synchronized with the previous super master time setting unit, thereby avoiding the function of the intelligent electronic unit (2, 4) being blocked. The intelligent electronic unit processes a data stream whose scan value is detected synchronously with the previous super master time setting unit.

13. A computer program product comprising instructions which, when said program is executed by a computer, cause the computer to implement the method according to any one of claims 1 to 11.

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