Harmonic monitoring device and method for a direct current converter station

Abstract

The present application belongs to the field of fault monitoring of DC converter station, and particularly relates to a harmonic monitoring device and method for DC converter station. The device does not contain an independent hardware acquisition unit for sampling analog quantity to obtain analog quantity data; the device comprises a communication module, which is used to establish communication connection with an AC station control system and a converter control system of the DC converter station respectively, so as to obtain AC analog quantity data sampling values collected by the AC station control system and DC analog quantity data sampling values collected by the converter control system respectively; the device performs harmonic monitoring of the DC converter station according to the AC and DC analog quantity data sampling values obtained by the communication module. The device indirectly collects signal data required for harmonic monitoring through data sharing between the device and the control and protection system of the converter station and the converter control system, thereby avoiding the problems of increasing field wiring complexity and improving secondary circuit fault risk caused by independent acquisition of signal data.

Description

Technical Field

[0001] This invention belongs to the field of fault monitoring of DC converter stations, and specifically relates to a harmonic monitoring device and method for DC converter stations. Background Technology

[0002] Currently, harmonic monitoring devices in DC converter stations generally adopt an independent architecture, which has certain limitations. For example, because the harmonic monitoring device is an independent unit, it is usually equipped with a separate analog signal acquisition board to acquire analog signals such as AC voltage, AC current, DC voltage, and DC current. The acquisition of these analog signals typically increases the complexity of on-site wiring and raises the risk of secondary circuit faults. Furthermore, since existing harmonic monitoring devices generally lack fault diagnosis capabilities, they cannot trigger the control and protection system to promptly determine the cause and location of harmonic faults when harmonic anomalies are detected.

[0003] Chinese invention patent application CN116488339A discloses a power data processing method and apparatus for multi-service integration, including acquiring data from a substation; calculating the amplitude and phase of the fundamental wave based on the acquired data to obtain dynamic measurement results; summarizing the acquired data according to a single-cycle time window to obtain the amplitude and phase of the fundamental wave and the 2nd to 13th harmonics, and integrating the amplitude and phase of the fundamental wave and the 2nd to 13th harmonics to obtain steady-state measurement results; organizing the acquired data according to a preset data time window TN to obtain the amplitude and phase of each interharmonic with a frequency resolution of 1 / TNHz, and correcting the amplitude and phase of each interharmonic using spectral interpolation to obtain interharmonic measurement results. This method effectively integrates the multi-service functions of PMU devices, measurement and control devices, and broadband measurement devices, effectively reducing the number of devices, simplifying the system architecture, and improving the overall intelligence level of the power grid. The power data processing device includes a sampling board for acquiring data from the substation. This board comprises analog and digital sampling boards. The analog sampling board acquires analog data in real time via an external cable connection. It is evident that existing devices for measuring or monitoring harmonics rely on separate analog acquisition boards to obtain analog signals, increasing the complexity of on-site wiring and raising the risk of secondary circuit failures. Summary of the Invention

[0004] The purpose of this invention is to provide a harmonic monitoring device and method for DC converter stations, which solves the problem that existing devices for measuring or monitoring harmonics all acquire analog signals through a separate analog acquisition board, leading to increased complexity of on-site wiring and increased risk of secondary circuit failure.

[0005] To achieve the above objectives, the first aspect of the present invention provides a harmonic monitoring device for a DC converter station, wherein the device does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data. The device includes a communication module for establishing communication connections with the AC station control system and the converter control system of the DC converter station, respectively, to acquire AC analog data sampling values ​​collected by the AC station control system and DC analog data sampling values ​​collected by the converter control system; the device performs harmonic monitoring of the DC converter station based on the AC and DC analog data sampling values ​​acquired by the communication module.

[0006] The first aspect of the present invention provides a harmonic monitoring device for a DC converter station. In one possible implementation, the communication module is further used to obtain converter operating status parameters from the converter control system in real time. The device also includes a fault diagnosis module, which is used to calculate the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog data sampling values ​​obtained by the communication module, and to detect whether there is a harmonic anomaly based on the calculated parameters. The fault diagnosis module is also used to identify the fault source when a harmonic anomaly is detected by using preset logic criteria and combining the converter operating status parameters of the same time section as the data with the harmonic anomaly.

[0007] The first aspect of the present invention provides a harmonic monitoring device for a DC converter station. In one possible implementation, the communication module is further used to send the result of the fault source identification to the monitoring backend so that the monitoring backend can display the fault diagnosis conclusion.

[0008] The first aspect of the present invention provides a harmonic monitoring device for a DC converter station. In one possible implementation, the communication module establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, through the internal control bus of the control and protection system of the DC converter station.

[0009] The first aspect of the present invention provides a harmonic monitoring device for a DC converter station. In one possible implementation, the communication module is further used to send the parameters required for harmonic fault diagnosis calculated in real time by the fault diagnosis module to the monitoring backend, so that the monitoring backend can display the trend of harmonic parameter changes.

[0010] The above-described technical solution of the present invention provides a novel harmonic monitoring device for DC converter stations. Its beneficial effects include: fully considering that the analog and digital signal data required for harmonic monitoring have usually already been collected in the control and protection system and the converter control system, resulting in duplicate collection, the device indirectly collects the signal data required for harmonic monitoring by sharing data with the converter station control and protection system and the converter control system respectively. This avoids the problem of the harmonic monitoring device independently collecting analog and digital signal data through its own hardware acquisition unit, which would increase the complexity of on-site wiring and increase the risk of secondary circuit failure.

[0011] The present invention also provides a harmonic monitoring method for a DC converter station, comprising: The communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, and acquires the AC analog data sample values ​​collected by the AC station control system and the DC analog data sample values ​​collected by the converter control system. Based on the AC and DC analog data sample values ​​acquired by the communication module, harmonic monitoring of the DC converter station is performed. The harmonic monitoring and diagnostic device does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data.

[0012] The second aspect of the present invention provides a harmonic monitoring method for a DC converter station, which, in one possible implementation, further includes: acquiring converter operating status parameters in real time from the converter control system through the communication module of the harmonic monitoring and diagnostic device; The fault diagnosis module of the harmonic monitoring and diagnostic device calculates the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog data sampling values ​​obtained by the communication module, and detects whether there is a harmonic anomaly based on the calculated parameters. When a harmonic anomaly is detected, the fault source is identified by using preset logical criteria and combining them with the converter operating status parameters of the same time section as the data with the harmonic anomaly.

[0013] The second aspect of the present invention provides a harmonic monitoring method for a DC converter station, which, in one possible implementation, further includes: sending the result of fault source identification to the monitoring backend through the communication module of the harmonic monitoring and diagnostic device, so that the monitoring backend can display the fault diagnosis conclusion.

[0014] The second aspect of the present invention provides a harmonic monitoring method for a DC converter station. In one possible implementation, the communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, through the internal control bus of the control and protection system of the DC converter station.

[0015] The second aspect of the present invention provides a harmonic monitoring method for a DC converter station, which, in one possible implementation, further includes: The communication module of the harmonic monitoring and diagnostic device sends the parameters required for harmonic fault diagnosis, which are calculated in real time by the fault diagnosis module, to the monitoring backend so that the monitoring backend can display the trend of harmonic parameter changes.

[0016] The technical solution of the harmonic monitoring method for DC converter stations described above can achieve the same beneficial effects as the harmonic monitoring device for DC converter stations described above. Attached Figure Description

[0017] Figure 1 This is a block diagram illustrating the connection structure of the harmonic monitoring device in the DC converter station of the present invention, showing how the device performs harmonic monitoring in the DC converter station. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] Implementation of Harmonic Monitoring Device for DC Converter Stations This embodiment provides a technical solution for a harmonic monitoring device for a DC converter station. By reusing analog data collected by the control and protection system, it avoids redundant data collection and resource waste, and significantly reduces system complexity and failure risk.

[0020] The harmonic monitoring device of the DC converter station does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data. The device includes a communication module for establishing communication connections with the AC station control system and the converter control system of the DC converter station, respectively, to acquire AC analog data sampling values ​​collected by the AC station control system and DC analog data sampling values ​​collected by the converter control system; the device performs harmonic monitoring of the DC converter station based on the AC and DC analog data sampling values ​​acquired by the communication module.

[0021] This device takes into account that the analog and digital signal data required for harmonic monitoring have usually already been collected in the control and protection system (including the AC station control system and the converter control system), resulting in duplicate data collection. Therefore, by sharing data with the converter station control and protection system and the converter control system respectively, the device indirectly collects the signal data required for harmonic monitoring. This avoids the problem of the harmonic monitoring device independently collecting analog and digital signal data through its own hardware acquisition unit, which would increase the complexity of field wiring and the risk of secondary circuit failure.

[0022] Furthermore, in order to make full use of the existing communication connection architecture of the DC converter station, avoid additional wiring of the control and protection system and the converter control system, and further reduce the complexity of field wiring, in this embodiment, the communication connection established between the communication module and the AC station control system and the converter control system of the DC converter station is realized through the internal control bus of the control and protection system of the DC converter station.

[0023] In other embodiments, the communication module establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively. This can also be achieved through additional communication lines that are connected to the AC station control system and the converter control system of the DC converter station, respectively.

[0024] In one specific embodiment, the harmonic monitoring device no longer has a separate analog signal acquisition board. Instead, it establishes a communication connection with the AC station control system (ASC) through the internal high-speed control bus of the converter station control and protection system. The ASC collects and preprocesses the AC voltage and AC current sample values ​​and sends them to the harmonic monitoring device in real time through the control bus. The harmonic monitoring device establishes a communication connection with the converter control system (CCP). The CCP collects and preprocesses the DC voltage and DC current sample values ​​and sends them to the harmonic monitoring device in real time through the control bus.

[0025] Considering that existing harmonic monitoring devices typically lack fault diagnosis capabilities and cannot link with the control and protection system when harmonic anomalies are detected to accurately determine the cause and location of harmonic faults, this embodiment also uses a communication module to obtain converter operating status parameters from the converter control system in real time. The device also includes a fault diagnosis module, which calculates the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog data sampled by the communication module, and detects the presence of harmonic anomalies based on the calculated parameters. When a harmonic anomaly is detected, the fault diagnosis module uses preset logical criteria, combined with converter operating status parameters at the same time segment as the data showing the anomaly, to identify the fault source. Thus, at the functional implementation level, harmonic data and the internal status data of the control and protection system can be comprehensively analyzed at the same time segment. When a harmonic anomaly is detected, the device can automatically identify the root cause of the fault based on built-in logical criteria, giving the harmonic monitoring device fault diagnosis capabilities and achieving a leap from "data monitoring" to "intelligent analysis."

[0026] In one specific embodiment, refer to Figure 1 Harmonic monitoring device (i.e.) Figure 1The integrated harmonic monitoring device (ICD) establishes real-time communication with the converter control unit (CCP) via a control bus. On one hand, the ICD obtains real-time converter operating status parameters from the CCP, including but not limited to firing angle, arc extinction angle, commutation failure signal, and AC low voltage signal. On the other hand, the ICD performs correlation analysis on parameters such as the 2nd to 50th harmonic content rate and total harmonic distortion rate calculated in real time with the status parameters sent by the CCP at the same time cross section. When a harmonic anomaly is detected, the ICD automatically identifies the fault source based on internally preset logic criteria. For example, if the harmonic anomaly is accompanied by commutation failure or AC low voltage signal, it is determined to be a harmonic anomaly caused by AC system disturbance. If the harmonic anomaly is present but the CCP parameters are stable, it is determined to be a filter bank detuning or equipment failure, thus achieving rapid location and cause identification of harmonic faults.

[0027] In other embodiments, the function of the fault diagnosis module may not be integrated into the harmonic monitoring device. Instead, it may be transmitted through the communication module of the harmonic monitoring device to other devices or cloud platforms that have the function of "real-time calculation of parameters required for harmonic fault diagnosis and detection of harmonic anomalies based on the calculated parameters". Fault diagnosis is achieved based on the AC and DC analog data sampling values ​​obtained by the harmonic monitoring device with low wiring complexity and low risk of secondary circuit faults.

[0028] In addition, considering that existing harmonic monitoring devices are usually located in the secondary equipment room and use independent LCD screens to display the data of each harmonic locally, there are still problems such as inconvenience for operation and maintenance personnel to monitor the panel, and it is also impossible to integrate and analyze the data with the monitoring backend, thus failing to realize other advanced applications of the converter station; therefore, in this embodiment, the communication module is also used to send the result of the fault source identification to the monitoring backend so that the monitoring backend can display the fault diagnosis conclusion.

[0029] Furthermore, in this embodiment, the communication module is also used to send the parameters required for harmonic fault diagnosis calculated in real time by the fault diagnosis module to the monitoring backend, so that the monitoring backend can display the trend of harmonic parameter changes.

[0030] This setup at the system integration level breaks down information silos between harmonic monitoring devices. By sending harmonic parameters and fault diagnosis conclusions to the monitoring backend in a timely manner, it facilitates monitoring by operation and maintenance personnel and lays a data foundation for the subsequent development of advanced applications in converter stations.

[0031] In a preferred embodiment, the harmonic monitoring device is equipped with an IEC 61850 communication interface and directly connects to the converter station monitoring backend network. The harmonic monitoring device sends the calculated harmonic data, total harmonic distortion rate, and fault diagnosis conclusions obtained through collaborative diagnosis to the monitoring backend via the IEC 61850 protocol. After receiving the data, the backend system can intuitively display the trend of harmonic parameter changes in a graphical manner and directly present the fault diagnosis conclusions. This eliminates the need for maintenance personnel to manually analyze massive amounts of raw data, achieving deep integration of harmonic monitoring data and station-wide monitoring information.

[0032] Implementation of Harmonic Monitoring Methods for DC Converter Stations This embodiment provides a technical solution for a harmonic monitoring method for a DC converter station, the method comprising: The communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, and acquires the AC analog data sampling values ​​collected by the AC station control system and the DC analog data sampling values ​​collected by the converter control system. Based on the AC and DC analog data sampling values ​​acquired by the communication module, harmonic monitoring of the DC converter station is performed.

[0033] The harmonic monitoring and diagnostic device does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data.

[0034] This method takes into account that the analog and digital signal data required for harmonic monitoring have usually already been collected in the control and protection system (including AC station control system and converter control system), resulting in duplicate collection. Therefore, by sharing data with the converter station control and protection system and the converter control system respectively, the signal data required for harmonic monitoring is indirectly collected. This avoids the problem of the harmonic monitoring device independently collecting analog and digital signal data through its own hardware acquisition unit, which would increase the complexity of field wiring and increase the risk of secondary circuit failure.

[0035] Furthermore, in order to make full use of the existing communication connection architecture of the DC converter station, avoid additional wiring of the control and protection system and the converter control system, and further reduce the complexity of field wiring, in this embodiment, the communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station respectively, which are realized through the internal control bus of the control and protection system of the DC converter station.

[0036] In other embodiments, the communication module establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively. This can also be achieved through additional communication lines that are connected to the AC station control system and the converter control system of the DC converter station, respectively.

[0037] In one specific embodiment, the harmonic monitoring device used in the harmonic monitoring method no longer has a separate analog signal acquisition board. Instead, it establishes a communication connection with the AC station control system (ASC) through the internal high-speed control bus of the converter station control and protection system. The ASC collects and preprocesses the AC voltage and AC current sample values ​​and sends them to the harmonic monitoring device in real time through the control bus. The harmonic monitoring device establishes a communication connection with the converter control system (CCP). The CCP collects and preprocesses the DC voltage and DC current sample values ​​and sends them to the harmonic monitoring device in real time through the control bus.

[0038] Considering that existing harmonic monitoring devices typically lack fault diagnosis capabilities and cannot link with control and protection systems to accurately determine the cause and location of harmonic faults when harmonic anomalies are detected, this embodiment of the harmonic monitoring method further includes: The communication module of the harmonic monitoring and diagnostic device obtains the converter operating status parameters from the converter control system in real time. The fault diagnosis module of the harmonic monitoring and diagnostic device calculates the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog data sampling values ​​obtained by the communication module, and detects whether there is a harmonic anomaly based on the calculated parameters. When a harmonic anomaly is detected, the fault source is identified by using preset logical criteria and combining them with the converter operating status parameters of the same time section as the data with the harmonic anomaly.

[0039] Therefore, at the functional implementation level, harmonic data and the internal status data of the control and protection system can be comprehensively analyzed at the same time section. When a harmonic anomaly is detected, the device can automatically identify the root cause of the fault based on the built-in logic criteria, giving the harmonic monitoring device fault diagnosis capability and realizing the leap from "data monitoring" to "intelligent analysis".

[0040] In one specific embodiment, the harmonic monitoring device establishes real-time communication with the converter control unit (CCP) via a control bus. On one hand, the harmonic monitoring device obtains real-time converter operating status parameters from the CCP, including but not limited to firing angle, arc extinction angle, commutation failure signal, and AC low voltage signal. On the other hand, the harmonic monitoring device performs correlation analysis on parameters such as the 2nd to 50th harmonic content rate and total harmonic distortion rate calculated in real time with the status parameters sent by the CCP at the same time cross section. When a harmonic anomaly is detected, the harmonic monitoring device automatically identifies the fault source based on internally preset logical criteria. For example, if the harmonic anomaly is accompanied by commutation failure or AC low voltage signal, it is determined to be a harmonic anomaly caused by AC system disturbance. If the harmonic anomaly is present but the CCP parameters are stable, it is determined to be a filter bank detuning or equipment failure, thus achieving rapid location and cause identification of harmonic faults.

[0041] In other embodiments, the function of the fault diagnosis module may not be integrated into the harmonic monitoring device. Instead, it may be transmitted through the communication module of the harmonic monitoring device to other devices or cloud platforms that have the function of "real-time calculation of parameters required for harmonic fault diagnosis and detection of harmonic anomalies based on the calculated parameters". Fault diagnosis is achieved based on the AC and DC analog data sampling values ​​obtained by the harmonic monitoring device with low wiring complexity and low risk of secondary circuit faults.

[0042] In addition, considering that existing harmonic monitoring devices are usually located in the secondary equipment room and use independent LCD screens to display the harmonic data locally, there are still problems such as inconvenience for operation and maintenance personnel to monitor the panel, and the inability to integrate and analyze the data with the monitoring backend, thus failing to realize other advanced applications of the converter station; therefore, in this embodiment, the harmonic monitoring method also includes: sending the result of the fault source identification to the monitoring backend through the communication module of the harmonic monitoring and diagnostic device, so that the monitoring backend can display the fault diagnosis conclusion.

[0043] Furthermore, in this embodiment, the harmonic monitoring method also includes: The communication module of the harmonic monitoring and diagnostic device sends the parameters required for harmonic fault diagnosis, which are calculated in real time by the fault diagnosis module, to the monitoring backend so that the monitoring backend can display the trend of harmonic parameter changes.

[0044] This setup at the system integration level breaks down information silos between harmonic monitoring devices. By sending harmonic parameters and fault diagnosis conclusions to the monitoring backend in a timely manner, it facilitates monitoring by operation and maintenance personnel and lays a data foundation for the subsequent development of advanced applications in converter stations.

[0045] In a preferred embodiment, the harmonic monitoring device can be directly connected to the converter station monitoring backend network via the IEC 61850 communication interface configured on it. The harmonic monitoring device sends the calculated harmonic data, total harmonic distortion rate, and fault diagnosis conclusions obtained through collaborative diagnosis to the monitoring backend via the IEC 61850 protocol. After receiving the data, the backend system can intuitively display the trend of harmonic parameter changes in a graphical manner and directly present the fault diagnosis conclusions. This eliminates the need for maintenance personnel to manually analyze massive amounts of raw data, achieving deep integration of harmonic monitoring data and station-wide monitoring information.

[0046] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or explanatory of the principles of the present invention, and do not constitute a limitation thereof.

Claims

1. A harmonic monitoring device for a DC converter station, characterized in that, The device does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data; The device includes a communication module for establishing communication connections with the AC station control system and the converter control system of the DC converter station, respectively, to acquire AC analog data sampling values ​​collected by the AC station control system and DC analog data sampling values ​​collected by the converter control system; the device performs harmonic monitoring of the DC converter station based on the AC and DC analog data sampling values ​​acquired by the communication module.

2. The harmonic monitoring device for a DC converter station according to claim 1, characterized in that, The communication module is also used to obtain converter operating status parameters from the converter control system in real time; The device also includes a fault diagnosis module, which is used to calculate the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog signal data sampling values ​​obtained by the communication module, and to detect whether there is a harmonic anomaly based on the calculated parameters. The fault diagnosis module is also used to identify the fault source when a harmonic anomaly is detected, by using preset logical criteria and combining the converter operating status parameters of the same time section as the data with the harmonic anomaly.

3. The harmonic monitoring device for a DC converter station according to claim 1 or 2, characterized in that, The communication module is also used to send the results of fault source identification to the monitoring backend so that the monitoring backend can display the fault diagnosis conclusion.

4. The harmonic monitoring device for a DC converter station according to claim 1 or 2, characterized in that, The communication module establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, through the internal control bus of the DC converter station's control and protection system.

5. The harmonic monitoring device for a DC converter station according to claim 3, characterized in that, The communication module is also used to send the parameters required for harmonic fault diagnosis calculated in real time by the fault diagnosis module to the monitoring backend, so that the monitoring backend can display the trend of harmonic parameter changes.

6. A harmonic monitoring method for a DC converter station, characterized in that, include: The communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, and acquires the AC analog data sample values ​​collected by the AC station control system and the DC analog data sample values ​​collected by the converter control system. Based on the AC and DC analog data sample values ​​acquired by the communication module, harmonic monitoring of the DC converter station is performed. The harmonic monitoring and diagnostic device does not contain a separate hardware acquisition unit for sampling analog quantities to obtain analog data.

7. The harmonic monitoring method for a DC converter station according to claim 6, characterized in that, Also includes: The communication module of the harmonic monitoring and diagnostic device obtains the converter operating status parameters from the converter control system in real time. The fault diagnosis module of the harmonic monitoring and diagnostic device calculates the parameters required for harmonic fault diagnosis in real time based on the AC and DC analog data sampling values ​​obtained by the communication module, and detects whether there are harmonic anomalies based on the calculated parameters. When a harmonic anomaly is detected, the source of the fault is identified by using preset logical criteria and combining them with the converter operating status parameters of the same time section as the data containing the harmonic anomaly.

8. The harmonic monitoring method for a DC converter station according to claim 6 or 7, characterized in that, Also includes: The communication module of the harmonic monitoring and diagnostic device sends the results of fault source identification to the monitoring backend for display of fault diagnosis conclusions.

9. The harmonic monitoring method for a DC converter station according to claim 6 or 7, characterized in that, The communication module of the harmonic monitoring and diagnostic device establishes communication connections with the AC station control system and the converter control system of the DC converter station, respectively, through the internal control bus of the control and protection system of the DC converter station.

10. The harmonic monitoring method for a DC converter station according to claim 8, characterized in that, Also includes: The communication module of the harmonic monitoring and diagnostic device sends the parameters required for harmonic fault diagnosis, which are calculated in real time by the fault diagnosis module, to the monitoring backend so that the monitoring backend can display the trend of harmonic parameter changes.

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