METHOD FOR SYNCHRONIZING INTELLIGENT ELECTRONIC UNITS IN A LOCALLY RESTRICTED NETWORK, AND A TIMING UNIT FOR A LOCALLY RESTRICTED NETWORK

Description

/ 14 METHOD FOR SYNCHRONIZING INTELLIGENT ELECTRONIC UNITS IN A LOCALLY RESTRICTED NETWORK, AND A TIMING UNIT FOR A LOCALLY RESTRICTED NETWORK

[001] To synchronize the timing of devices connected to each other via a network, a Network Time Protocol was created, which is abbreviated as NTP below. In addition, a timing protocol called Precision Time Protocol, referred to as PTP below, was introduced. Compared to NTP, PTP has greater accuracy in recording the time of devices connected to each other via a network.

[002] For example, a locally restricted network is implemented in electrical power supply substations. These substations are used to decrease or increase the prevailing network voltages in the supply network by means of a transformer whose operating mode is known. In addition to a transformer, substations have switching units, such as circuit breakers, which, after receiving a switching signal, disconnect the substation's output conductors from the rest of the supply network.

[003] These switching signals are generated by protection and automation devices that are used to monitor the current and voltage characteristics in the substation conductors for the presence of fault conditions. If a fault condition exists, a switching signal is generated and transmitted to one or more selected switching units so that the switching units are moved to their switching position. In the switching position, the contacts of the selected switching units are separated from each other, preventing the flow of current through the switching units. A conductor connected to a contact of said switching unit is then disconnected from the rest of the network. Petition 870250090353, of 03 / 10 / 2025, page 11 / 30 / 14 power supply, which is connected to the other contact of said switching unit.

[004] In order for protection and automation devices to monitor the current and voltage characteristics in the substation conductors for the presence of fault conditions, they must be continuously supplied with time-dependent current and voltage values. To provide these current and voltage values, provision is made for current and voltage transformers that record the current and voltage in the conductors at a measurement point in the substation and provide a calibrated measurement signal on the secondary side, which signal is sampled at a specified sampling rate to obtain samples. The samples are then digitized. In addition, a date and time stamp is permanently assigned to the samples. This is done by means of so-called fusion units or using other intelligent electronic devices (IEDs) in the substation.In order to compare the measured values ​​with each other, the time records of the IEDs connected to each other via a process bus must be synchronized. This is done using PTP.

[005] The PTP is then used in digital power supply substations to synchronize intelligent electronic devices (IEDs), for example, on the so-called IEC 61850 process bus.

[006] The comparability of measured values ​​originating from different IEDs is fundamental. Lost or insufficient time synchronization between these devices causes the protection functions in the protection and automation devices to be disabled or a switching unit to be tripped erroneously, resulting in unintentional power interruption.

[007] Figures 1a and 1b illustrate the time recording process according to PTP within a process bus communication network 1, in which two timing units 2 and 3 are provided and transmit PTP synchronization messages, according to the structure Petition 870250090353, dated 03 / 10 / 2025, page 12 / 30 / 14 predefined “Announce”, “Sync” and “Follow_Up”, via an Ethernet switch 4 to IEDs 5, for example, protection devices, which are also connected to the process bus communication network 1. In Figures 1a and 1b, a dashed arrow corresponds to a PTP Announce message, and a solid arrow represents a Synchronization or Follow-Up message. The IEDs 5 are in the subordinate state provided in the PTP protocol. They therefore have a passive behavior with respect to the recording of time values ​​and adopt the time specified to them by a timing unit that is in the so-called grandmaster role.

[008] Timing units 2, 3 can be connected to a primary reference clock source – the so-called Primary Reference Clock (PRC) – for example, the Global Navigation Satellite System (GNSS). However, due to the possibility of being influenced by interfering transmitters (interference) or other means (e.g., spoofing), such satellite-based global reference clock sources constitute a risk and often cannot be used depending on their field of application. In this case, it is possible to use an oscillator internal to the device that is installed in one of the timing units 2, 3, wherein these specify a relative time reference in the form of time values ​​on the process bus communication network 1, independently of the outside.

[009] The relative time values ​​provided by the local oscillator in timing units 2, 3 are sufficient for synchronization when a process bus communication network 1 is used in a substation, since absolute time values ​​are not required.

[0010] The use of two timing units is for redundancy purposes, i.e., availability. Under fault-free conditions, a single timing unit 2 is selected to be the active grandmaster with the aid of the so-called best master clock algorithm. This unit Petition 870250090353, dated 10 / 03 / 2025, page 13 / 30 / 14 transmits PTP synchronization messages via Ethernet switch 4. The other timing unit 3 does not transmit any PTP synchronization messages and is in a subordinate state. It receives PTP synchronization messages from the grandmaster timing unit 2 and synchronizes its own internal oscillator according to the oscillator of timing unit 2, with the result that the internal oscillator of timing unit 3 oscillates at virtually the same speed as the internal oscillator of timing unit 2. However, timing unit 3 is ready to switch to an active role.

[0011] Figure 1b illustrates a situation where timing unit 2 has failed or been disconnected from the network. The absence of timing unit 2 is detected by timing unit 3 due to the absence of PTP Advertisement messages from timing unit 2. Timing unit 3 switches to the role of grandmaster.

[0012] The IEDs detect the grandmaster change from timing unit 2 to timing unit 3 based on PTP messages. The timing synchronization of the IEDs is not interrupted because the internal oscillator of timing unit 3 was synchronized with the oscillator of timing unit 2 before the switch. The timing register synchronization between the IEDs continues without problems. There is no time jump during or after the grandmaster switch.

[0013] If the malfunction of timing unit 2 has ended or the decoupled timing unit 2 has been reconnected to the process bus communication network 1, the BMCA according to the invention immediately decides that timing unit 2 assumes the role of grandmaster. As the grandmaster timing unit 2, it starts transmitting PTP synchronization messages again.

[0014] During the absence of timing unit 2, the oscillator Petition 870250090353, dated 03 / 10 / 2025, page 14 / 30 / 14 The local oscillator of timing unit 3 operates at its own speed and distances itself, in terms of time, from the local oscillator of timing unit 2. The time and frequency difference between the local oscillators of timing units 2 and 3 can be considerable at the moment when timing unit 2, which is functional or reconnected, takes over. After taking over, the IEDs detect a time jump and resynchronize their internal oscillator again with the new local oscillator of the new grandmaster timing unit 2. This resynchronization process can take up to 20 seconds.

[0015] The IEDs disable their protection functions during this resynchronization to prevent possible false trips of the circuit breakers. This is a considerable disadvantage.

[0016] Figure 2 illustrates the facts described above with the aid of a two-dimensional graph, on the abscissa of which time is illustrated and on the ordinate 6 of which the time displacement of timing unit 3 relative to timing unit 2 according to Figure 1 is illustrated, in each case in arbitrary units. The distance 20 between the dashed lines is the degree of time displacement between timing units 2 and 3 that is permitted for IED protection applications. The solid curve therefore represents said time displacement based on time. If the curve is between the dashed lines, it is an acceptable time displacement.

[0017] In the time slot referenced with 7, timing unit 2 operates in a fault-free manner and is connected to the process bus communication network 1. It operates in this time slot 7 as grandmaster timing unit 2. At time 8, the grandmaster role is assumed by timing unit 3, since the PTP Announcement messages from timing unit 2 are absent and this is detected by timing unit 3. In time slot 9, the unit of Petition 870250090353, dated 03 / 10 / 2025, page 15 / 30 / 14 timing unit 3 then operates as the timing unit for grandmaster 3. At time 10, the role of grandmaster is returned to timing unit 2. Because the oscillators of timing units 2 and 3 were no longer synchronized in time track 9, the timing values ​​of timing unit 3 deviated from those of timing unit 2. In time track 11, this deviation is greater than allowed. The IEDs detect this time jump and synchronize their internal oscillator again until, at time 12, the IEDs are synchronized with the returning timing unit of grandmaster 2. The previous method has the disadvantage that the IED protection algorithms are disabled in the dashed time track 11.

[0018] The objective of the invention is to specify a method of the type mentioned at the beginning, in which the disabling of IED protection algorithms can be reduced in terms of time or even completely avoided.

[0019] This objective is achieved according to the invention by the means of patent claim 1.

[0020] Dependent patent claims refer to variants of this invention.

[0021] Within the scope of the invention, it was recognized that the disadvantage of the previously described technique is caused by the fact that a PTP timing unit with grandmaster capability assumes the role of grandmaster as soon as it determines that it is the best PTP timing unit in the network according to the BMCA (Best Master Clock Algorithm). A timing unit with grandmaster capability according to the PTP is a timing unit that can assume the role of grandmaster based on the BMCA and can simultaneously become the sole synchronization source, the grandmaster, in a network. The problem recognized by the inventors of mutually non-resolved local oscillators Petition 870250090353, dated 03 / 10 / 2025, page 16 / 30 / 14 synchronized upon returning the grandmaster role is not taken into account in the BMCA and the PTP port state machine. This results in the described time jump and the deactivation of protection functions (protection algorithms).

[0022] The present invention proposes that a locally synchronized timing unit with grandmaster capability that has been restored or reconnected does not immediately assume the role of grandmaster, but rather that the following steps are performed first:

[0023] First, a check is performed to determine if there is currently an active PTP grandmaster for the dedicated PTP domain, which is defined by its domain number. This check is performed by waiting for a PTP Advertisement message to be received. If the timing unit with grandmaster capability does not receive a PTP Advertisement message from another timing unit within a predefined time period, it is assumed that there is no active grandmaster in the domain. If no other grandmaster is detected on the network, the BMCA will be executed by the timing unit. It switches to the grandmaster role.

[0024] However, if a grandmaster timing unit is detected on the network, the timing unit switches to its subordinate state and begins synchronizing its own internal oscillator with that of the current grandmaster.

[0025] After the timing unit synchronizes its own internal oscillator with the grandmaster with the required precision, the implementation of its subordinate state is canceled. The BMCA is executed and, depending on the result of this check, said timing unit will switch to the role of grandmaster or remain in the subordinate state.

[0026] The crucial point is therefore that the timing unit with grandmaster capability that has been restored or reconnected Petition 870250090353, dated 10 / 03 / 2025, page 17 / 30 / 14 initially synchronize your own internal oscillator with that of the current PTP grandmaster timing unit, if available, before assuming the role of grandmaster. This prevents a time jump.

[0027] For the purposes of the invention, a locally restricted network, which is referred to as a “local area network” and as a “LAN” for short, shall be understood to mean a spatially restricted network. For example, the locally restricted network is a network defined in the IEC 61850 standard. Advantageously, the locally restricted network has structured cabling. According to a preferred variant, the network is a process bus communication network. The spatially restricted network comprises intelligent electrical devices (IEDs) that are connected to each other, for example, by wired or radio communication lines, for example, 5G radio networks. However, the use of Ethernet technology is preferred within the scope of the invention. In principle, however, other locally restricted networks are also possible within the scope of the invention.

[0028] The abbreviation IED should be understood within the scope of the invention as meaning an intelligent electronic device. An IED is, for example, a protection or automation device, a relay, or a field control device that is used, for example, in the field of protection and control engineering in substations. An IED is also frequently called a processor-based controller.

[0029] PTP is advantageously used within the scope of the invention, where the subordinate state is enforced by defining the priority of said timing unit. If the priority of a timing unit with grandmaster capability is set to 254 or 255, for example, it will remain in its subordinate state during a check by the BMCA.

[0030] Checking which timing unit is more Petition 870250090353, dated 03 / 10 / 2025, page 18 / 30 / 14 suitable for the role of active grandmaster is advantageously performed according to the best master clock algorithm of the IEEE 1588 protocol.

[0031] Other advantages arise if each timing unit has its own oscillator. Such an oscillator has, for example, a quartz crystal, whose oscillations are converted into a time pattern. However, oscillators are known to one skilled in the art and therefore their exact method of operation need not be discussed in more detail at this time. However, within the scope of the invention, the oscillator used in a timing unit can be synchronized with another oscillator.

[0032] According to a convenient additional variant, the locally restricted network is a radio network. In particular, advantages arise if the radio network is a 5G radio network.

[0033] According to a preferred embodiment of the invention, the locally restricted network is a substation process bus communication network. Ethernet technology is preferably used in the process bus communication network.

[0034] Within the scope of the invention, the number of timing units is not restricted to two timing units. For example, five or more timing units can also communicate with each other on the network.

[0035] At least one timing unit is conveniently integrated, or in other words, installed, in an IED. Therefore, it is a component of the IED and is arranged in its housing.

[0036] Other advantages arise if at least one IED is a protection or automation device for an electrical power supply network.

[0037] Another variant of the method according to the invention involves the timing unit with grandmaster capability which is Petition 870250090353, dated 03 / 10 / 2025, page 19 / 30 / 14 available again or is connected to the network again, not immediately assuming the role of grandmaster again after having synchronized with the current grandmaster. Instead, it remains in the subordinate state and continues to synchronize continuously with the current grandmaster timing unit. Only when the absence of a grandmaster timing unit is detected does said timing unit switch to the grandmaster role based on the BMCA. This reduces the number of grandmaster switches on the network. This is advantageous in terms of PTP synchronization stability.

[0038] The present invention also relates to a timing unit for a locally restricted network, whereby intelligent electronic units (IEDs) are connected to each other. According to the invention, at least this timing unit is configured to perform one of the methods mentioned above.

[0039] For the purposes of the invention, a timing unit may be understood as any unit that is capable of generating a time pattern. This unit may be present as a separate device or may be a component or component part of another device, for example, a protection or automation device.

[0040] The invention is explained in more detail below using exemplary embodiments, wherein identical reference signals refer to identical acting components, and Figure 1a schematically illustrates an exemplary embodiment of a process bus communication network having two functional timing units, Figure 1b schematically illustrates an exemplary embodiment of a process bus communication network having a timing unit that has failed or been disconnected from the network, Figure 2 schematically illustrates a two-dimensional diagram. Petition 870250090353, dated 03 / 10 / 2025, page 20 / 30 / 14 to illustrate a method for assuming the role of grandmaster according to the prior art, Figure 3 schematically illustrates a two-dimensional diagram to illustrate a method for assuming the role of grandmaster according to the invention, and Figure 4 schematically illustrates an exemplary embodiment of the method according to the invention based on a flowchart.

[0041] Figures 1a, 1b and 2 have already been discussed in connection with prior art recognition.

[0042] Figure 3 illustrates an exemplary embodiment of the method according to the invention. It schematically shows the timing progression, which is specified in a local area network according to Figure 1 and to which the IEDs in network 1 synchronize, based on a two-dimensional graph, on the abscissa of which the time is illustrated and on the ordinate 6 of which the time offset of timing unit 3 relative to timing unit 2 according to Figure 1 is illustrated, in each case in arbitrary units.

[0043] The distance 20 between the dashed lines is again the degree of time offset between timing units 2 and 3, which is permitted by the IED protection applications. The solid curve therefore represents the progression of the time offset between the timing units based on time. If the curve is between the dashed lines, it is an acceptable time offset.

[0044] In the time slot referenced with 13, timing unit 2 operates in a fault-free manner and is connected to the process bus communication network 1. It operates as grandmaster timing unit 2 in this slot 13. At time 14, the role of grandmaster is assumed by timing unit 3. In the time slot Petition 870250090353, dated 03 / 10 / 2025, page 21 / 30 / 14 At time 15, timing unit 3 then operates as grandmaster timing unit 3. At time 16, timing unit 2 regained its full functionality. In another example, it was disconnected from the network and reconnected to network 1 again at time 16.

[0045] In contrast to the previous technique, it does not immediately assume the role of grandmaster again, but synchronizes, or in other words, synchronizes its oscillator with that of the grandmaster timing unit 3. This synchronization is achieved at time 17. The BMCA is used to determine if timing unit 2 is more suitable for the role of grandmaster. There is a switching in the role of grandmaster at time 17. In time range 18, timing unit 2 again performs the role of grandmaster.

[0046] Within the scope of the invention, the permitted limits regarding the time shift of the IEDs are not exceeded at any time. The deactivation of the IED protection algorithms is avoided within the scope of the invention.

[0047] To avoid the immediate assumption of the grandmaster role within the scope of the invention, that is, in other words, forcing the subordinate state of the respective timing unit, the work is carried out with the so-called priorities within the scope of this exemplary embodiment of the invention which is based on PTP. However, it is important to emphasize that the subordinate state can also be forced by other means, without departing from the scope of the invention.

[0048] Priorities are parameters defined in the IEEE 1588 standard and evaluated by the BMCA. Thus, priority 1 and priority 2 can, in principle, be assigned to each timing unit 2. After failure of timing unit 2, its priority 1 is limited to 255 and 254. The priority value of timing unit 3 remains fully configurable by the user. Priority 2 remains, Petition 870250090353, dated 03 / 10 / 2025, page 22 / 30 / 14 therefore, at the value previously predefined by the network user.

[0049] Under normal and undisturbed conditions, the user-configured priority parameter is used. At time 16, the priority value 1 of timing unit 2 is set to the highest possible value 255; this corresponds to the lowest priority for assuming the role of grandmaster. During the execution of BMCA, timing unit 2 therefore reliably remains in its subordinate state.

[0050] At time 17, the internal oscillator of timing unit 2 is synchronized with the current PTP grandmaster, specifically the oscillator of timing unit 3, with the required precision. At time 17, the priority value 1 of timing unit 2 is reset to its previously user-defined value. The sleep state implementation is therefore canceled. Timing unit 2 resumes the role of grandmaster when executing BMCA.

[0051] Figure 4 illustrates the method according to the invention by means of a flowchart. For reasons of space, instead of a timing unit in the role of grandmaster, reference is made in Figure 4 to a control clock.

[0052] If a timing unit – for example, timing unit 2 – becomes functional again or is reconnected to the network, a first step determines whether the network contains a timing unit in the role of grandmaster, i.e., a control clock. If there is no control clock, timing unit 2 switches to its normal operation. A BMCA will determine that timing unit 2 will assume the role of grandmaster. This is then implemented.

[0053] However, if it is determined that the network contains a control clock, the priority 1 of timing unit 2 is set to 255. This forces timing unit 2 into a subordinate state. The control clock is then sought in a cycle and timing unit 2 Petition 870250090353, dated 03 / 10 / 2025, page 23 / 30 / 14 synchronizes with the control clock, i.e., with timing unit 3 here. This cycle runs until the time offset between the control clock and timing unit 2 is greater than the predefined limit value and the control clock is still available. Priority value 1 is then reset to its pre-configured value. Petition 870250090353, dated 03 / 10 / 2025, page 24 / 30

Claims

1 / 2 CLAIMS 1. Method for synchronizing intelligent electronic units, LEDs, (5) in a locally restricted network (1), wherein the locally restricted network (1) has at least two timing units (2, 3), characterized in that - for a timing unit (2) that is again functional or is again connected to the network, a check is performed to determine if the network contains an additional timing unit (3) that assumes an active grandmaster role (1), - the first timing unit (2) is forced into its subordinate state if another timing unit in the grandmaster role is detected in the locally restricted network (1), wherein the first timing unit (2) synchronizes with the timing unit (3) in the grandmaster role, - after synchronization, the implementation of the subordinate state is canceled for the first timing unit (2),- the first timing unit (2) changes to the role of grandmaster timing unit if it is more suitable for the grandmaster role, or remains in its subordinate state if another timing unit (3) in the network (1) is more suitable for the grandmaster role.

2. Method according to claim 1, characterized in that the subordinate state is forced using the PTP defining the priority of said timing unit (2).

3. Method according to claim 1 or 2, characterized in that the verification of which timing unit (2, 3) is most suitable for the role of active grandmaster is performed according to the best master clock algorithm of the IEEE 1588 protocol.

4. Method according to claim 3, characterized in that each timing unit (2, 3) in the network (1) has an oscillator. Petition 870250090353, dated 03 / 10 / 2025, page 25 / 30 2 / 2 5. Method according to any of the preceding claims, characterized in that the locally restricted network (1) is a domain.

6. Method according to any of the preceding claims, characterized in that the locally restricted network is a process bus communication network (1) of a substation.

7. Method according to any of the preceding claims, characterized in that at least one IED (5) is a protection or automation device.

8. A method according to any of the preceding claims, characterized in that at least one timing unit is installed in an IED.

9. A method according to any of the preceding claims, characterized in that a timing unit with grandmaster capability that is available again or is reconnected to the network remains in the subordinate state and continuously synchronizes with the current grandmaster timing unit and changes to the grandmaster role only when the grandmaster timing unit is removed.

10. Timing unit (2, 3) for a locally restricted network (1), whereby intelligent electronic units, IEDs, (5) are connected to each other, characterized in that it is configured to perform a method as defined in any of the preceding claims. Petition 870250090353, dated 03 / 10 / 2025, p. 26 / 30

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