A method for realizing unchanged metering relationship after economic operation of distribution transformer

Abstract

The present invention proposes a method for realizing that the metering relationship remains unchanged after the economic operation of the distribution transformer, including: modifying the primary main connection, reconnecting the cables on both sides of the bus tie switch to the lower ports of the low-voltage side switches on both sides; installing the low-voltage master meter to the lower port of the low-voltage switch and the bus tie switch cable connection point; using the data transmission unit to collect the 400V bus tie switch position data in real time and upload it to the main station; the main station processes and adjusts the medium-voltage line loss calculation in real time according to the 400V bus tie switch position; after adjusting the low-voltage master meter position, the data change of the low-voltage master meter is monitored through the main station system; when the operation mode is changed from the column operation to the economic operation mode, the main station packages the two lines to ensure accurate line loss calculation. The present invention improves the transparency and controllability of power grid operation and enhances the trust and satisfaction of users. The economic operation of the distribution transformer is realized while keeping the metering relationship unchanged, laying a solid foundation for the intelligent and modern construction of the distribution network.

Description

Technical Field

[0001] The present invention relates to the field of power distribution automation, and in particular to a method for realizing unchanged metering relationship after economic operation of a distribution transformer. Background Art

[0002] In the power system, the transformer is one of the main electrical equipment that cannot be ignored. From power generation, transmission to distribution and consumption, electric energy needs to be transformed many times, usually 3 to 5 times. The transformer itself will produce losses in the process of transmitting power and transforming voltage. Therefore, reducing the loss of the transformer is of great significance to improving the overall efficiency of the power grid.

[0003] At present, the scale of newly built residential communities is generally large, with multiple distribution rooms in one community, and 2 to 4 transformers installed in each distribution room. However, 3 to 5 years or even longer after the community is built, due to the high vacancy rate of houses, the transformers are in a light-load operation state for a long time. When the transformer is in light-load operation, its own loss accounts for a relatively large proportion, which seriously affects the economic operation efficiency of the distribution network.

[0004] In the prior art, the economic operation device of the distribution transformer can be used to put the distribution transformer into and out of operation according to the load conditions, thereby realizing the economic operation of the transformer. Specifically, when the load is low, the number of operating transformers is reduced; when the load increases, the number of operating transformers is increased in a timely manner. This method can effectively reduce the light load loss of the transformer and improve the overall operation efficiency.

[0005] However, when the transformer is put into economic operation, the original split operation mode will be changed to single main transformer operation. The change in operation mode will affect the "household-transformer" metering calculation relationship, thereby affecting the meter reading of the marketing system and the calculation of the line loss in the substation area. The same problem also exists in the case of dual power supply. When one power supply is abnormal, the metering relationship will also be affected when the backup power supply is switched to a single power supply. These problems directly affect the management and economic benefits of the power grid.

[0006] The main problems of the existing technology include:

[0007] Changes in metering relationships: When the transformer operation mode changes, the original "household-transformer" metering relationship will be destroyed, resulting in deviations in meter reading and line loss calculation in the marketing system. This will cause inaccurate metering, affecting the correct settlement of electricity charges and accurate statistics of line losses.

[0008] Lack of flexible adjustment mechanism: The existing system lacks a flexible adjustment mechanism when dealing with load changes and is unable to adjust the operating status of the transformer in real time and accurately, resulting in low operating efficiency of the transformer under light or heavy load conditions.

[0009] Increased operating costs: As transformers are in a non-economical operating state for a long time, their own losses are large, which increases the overall operating cost of the power grid. In addition, when load demand changes frequently, frequent manual adjustment of transformer input and output also increases the complexity and cost of operation and maintenance.

[0010] Therefore, there is an urgent need to find a method that can keep the "household-transformer" metering calculation relationship unaffected after the economic operation of the distribution transformer, so as to solve the above problems and ensure the economic operation and management efficiency of the power grid. Summary of the invention

[0011] In order to overcome the shortcomings of the prior art, the present invention proposes a method for realizing the unchanged metering relationship after the economic operation of the distribution transformer, which improves the transparency and controllability of the power grid operation, enhances the trust and satisfaction of users, and realizes the economic operation of the distribution transformer by utilizing the existing technical means and equipment, while keeping the metering relationship unchanged, laying a solid foundation for the intelligent and modern construction of the distribution network.

[0012] To achieve the above object, the present invention provides a method for realizing that the metering relationship remains unchanged after the economic operation of the distribution transformer, the method comprising:

[0013] Step S1: Modify the primary main wiring and reconnect the cables on both sides of the bus tie switch to the lower ports of the low-voltage side switches on both sides;

[0014] Step S2: Install the low-voltage main meter to the lower port of the low-voltage switch and the busbar switch cable connection point to ensure that the low-voltage main meter can accurately collect load data;

[0015] Step S3: using a data transmission unit (DTU) to collect 400V bus tie switch position data in real time and upload it to the master station;

[0016] Step S4: the master station processes and adjusts the medium voltage line loss calculation in real time according to the position of the 400V bus tie switch;

[0017] Step S5: After adjusting the position of the low-voltage master meter, the data changes of the low-voltage master meter are monitored through the master station system to ensure data accuracy;

[0018] Step S6: When the operation mode is changed from the split operation mode to the economic operation mode, the master station packages the two lines to ensure accurate calculation of line loss;

[0019] Step S7: Utilize multi-source data fusion technology to combine transformer operation data, load data and environmental data to optimize the distribution network operation strategy;

[0020] Step S8: Implement the intelligent alarm system. When the distribution transformer operation mode changes or the low-voltage main meter data is abnormal, an alarm is automatically triggered and maintenance suggestions are sent to the operation and maintenance personnel.

[0021] Furthermore, the step S1 comprises:

[0022] Step S1.1: Reconnect the incoming and outgoing cables of the bus tie switch in the original main wiring mode of the power distribution room to the lower ports of the low-voltage switches of the main transformers on both sides to ensure that the power supply on the low-voltage side of the main transformer is not affected when the operating mode changes;

[0023] Step S1.2: Add an adapter at the lower port of the low-voltage side switch to connect the reconnected cable to ensure the stability and safety of the connection;

[0024] Step S1.3: Verify whether the reconnected cable connection complies with electrical safety standards, and perform necessary debugging and testing.

[0025] Furthermore, the step S2 comprises:

[0026] Step S2.1: Move the original low-voltage total meter from the upper port of the main transformer switch to the lower port of the low-voltage switch and the bus tie switch cable connection point to ensure that the low-voltage total meter can accurately collect load data;

[0027] Step S2.2: calibrate the low-pressure main meter to ensure the accuracy of data collection at the new location;

[0028] Step S2.3: Record and update the new location and related information of the low-voltage main meter to ensure accurate positioning and inspection during subsequent maintenance.

[0029] Furthermore, the step S3 comprises:

[0030] Step S3.1: The DTU collects the 400V bus tie switch position data in real time and uploads it to the master station to ensure that the master station can accurately calculate the line loss;

[0031] Step S3.2: Check and maintain the DTU equipment to ensure its long-term operational stability and data transmission reliability;

[0032] Step S3.3: During the data transmission process, data encryption technology is used to ensure the security and integrity of data transmission.

[0033] Furthermore, the step S4 comprises:

[0034] Step S4.1: When the 400V bus tie switch of the master station is in the open position, the medium voltage line losses on both sides are calculated independently; when the 400V bus tie switch is in the closed position, the medium voltage line losses on both sides are processed uniformly;

[0035] Step S4.2: dynamically adjust the line loss calculation model according to the load data collected in real time to adapt to the change of load;

[0036] Step S4.3: Record and archive the line loss calculation results for each operation mode switch to provide data support for subsequent analysis and optimization.

[0037] Furthermore, the step S6 comprises:

[0038] Step S6.1: fusing the load data of the medium voltage lines on both sides to form a unified line loss calculation data set;

[0039] Step S6.2: For abnormal data in the line loss calculation data set, data cleaning and correction are performed to ensure the accuracy of line loss calculation;

[0040] Step S6.3: Regularly analyze the packaged line loss data to identify and resolve potential problems and improve the accuracy of line loss calculation.

[0041] Further, the step S7 comprises:

[0042] Step S7.1: Utilize multi-source data fusion technology to integrate transformer operation data, load data and environmental data to optimize the distribution network operation strategy;

[0043] Step S7.2: Analyze historical data and real-time data through machine learning algorithms, predict future load changes, and adjust power distribution strategies;

[0044] Step S7.3: Monitor the operation status of the distribution network in real time, dynamically adjust the operation parameters, and improve the economy and reliability of the distribution network operation.

[0045] Furthermore, the step S8 comprises:

[0046] Step S8.1: Implement the intelligent alarm system to automatically trigger an alarm when the distribution transformer operation mode changes or the low-voltage master meter data is abnormal;

[0047] Step S8.2: Send maintenance suggestions to the operation and maintenance personnel, including a detailed abnormality analysis report and treatment plan;

[0048] Step S8.3: Regularly update and optimize the intelligent alarm system to ensure that it can provide accurate and timely alarm information under different operating conditions.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The present invention provides a method for realizing that the metering relationship remains unchanged after the economic operation of the distribution transformer. Regardless of whether the distribution transformer is in the economic operation mode or the column operation mode, the "household-transformer" metering calculation relationship is not affected, thereby ensuring the consistency and stability of the marketing system collection plan.

[0051] 2. The present invention provides a method for realizing the unchanged metering relationship after the economic operation of the distribution transformer. Through this method, the invariance of the metering relationship can be achieved on the existing basis without additional investment costs, saving resources and costs, solving the technical difficulties in the industry regarding the changes in the metering relationship after the economic operation of the distribution transformer, filling the gap in the industry, and providing technical guarantee for the practical application of the economic operation project of the distribution transformer.

[0052] 3. The present invention provides a method for realizing that the metering relationship remains unchanged after the economic operation of the distribution transformer. By using advanced metering equipment and intelligent systems, the automation and intelligence level of the distribution system is improved, which helps to improve the overall operating efficiency, realizes real-time monitoring and data collection of the operating status of the distribution transformer, and provides a scientific basis for subsequent maintenance and optimization.

[0053] 4. The present invention provides a method for realizing the unchanged metering relationship after the economic operation of the distribution transformer, which reduces human intervention and operation errors and improves the accuracy and reliability of metering data by optimizing the electric energy metering and data processing process. It is suitable for distribution systems of various sizes and has broad application prospects and market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 This is the original technical solution;

[0056] Figure 2 The transformation scheme of the present invention;

[0057] Figure 3 The renderings after the renovation plan;

[0058] Figure 4 Implementation process diagram of the present invention;

[0059] Figure 5 Medium voltage line loss treatment diagram. DETAILED DESCRIPTION

[0060] The technical solution of the present invention will be more clearly and completely explained below through description of preferred embodiments of the present invention in combination with the accompanying drawings.

[0061] The present invention relates to a solution to the unchanged metering relationship after the economic operation of the distribution transformer, aiming to solve the problem in the prior art that the metering calculation relationship of the "household-transformer" is affected after the economic operation of the transformer. The method comprises the following steps:

[0062] In the distribution transformer system, load monitoring equipment is installed to collect real-time load data of each transformer. These data include transformer current, voltage, power factor and other parameters, and historical load data is obtained for analysis.

[0063] Use load forecasting algorithms (such as time series analysis or machine learning algorithms) to analyze historical load data and predict the load change trend in the future. Based on the forecast results, calculate the optimal economic operation state of each transformer. For periods of low load, reduce the number of transformers; for peak load periods, increase the number of transformers to ensure that the system operates in an economical state.

[0064] Based on the load forecast results, an economic operation dispatch plan is generated. The plan includes the specific operating status of each transformer in different time periods. For example, some transformers are shut down when the load is low, and the number of transformers in operation is increased during peak load periods.

[0065] Through the remote control system, the economic operation dispatch plan is implemented to adjust the input and output status of each transformer. After the transformer status changes, the metering relationship of the distribution transformer system is immediately updated to ensure that the "household-transformer" metering calculation relationship remains unchanged.

[0066] After the transformer operation mode is changed, the system's built-in algorithms and rules are used to update the metering relationship of the distribution transformer system, keeping the "household-transformer" metering calculation relationship unchanged. This step ensures the accuracy of the marketing system's meter reading and the area line loss calculation.

[0067] Monitor and calibrate the updated measurement relationship. Use algorithms to calibrate measurement data to ensure data accuracy. Continuously monitor changes in measurement relationships and maintain the stability of measurement relationships through dynamic adjustments.

[0068] During the operation of the system, the operating status and metering relationship of each transformer are continuously monitored. By analyzing real-time and historical data, the input and output status of the transformer are dynamically adjusted to ensure the economic operation of the distribution transformer system and the stability of the metering relationship.

[0069] When a fault or anomaly is detected in the system, the early warning mechanism is triggered immediately. The fault data is recorded and an alarm message is sent to prompt maintenance personnel to check and repair. The decision tree algorithm is used to analyze the abnormal data, determine the cause and attribute of the abnormality, and formulate a corresponding repair plan.

[0070] Based on the operation data and fault analysis results, we continuously optimize the economic operation scheduling plan and the measurement relationship update algorithm to improve the operation efficiency and stability of the system. We regularly upgrade and improve the system to maintain the advancement and adaptability of the technology.

[0071] Through the above implementation, the present invention achieves the goal of maintaining the unchanged metering relationship after the economic operation of the distribution transformer. The method ensures the accuracy of the economic operation and metering data of the distribution transformer system without increasing the investment cost, solves the gaps and pain points in the industry, and provides the possibility for the implementation of the economic operation project of the distribution transformer.

[0072] According to an embodiment of the prior art, the problems existing in the prior art are explained. Figure 1 As shown:

[0073] At present, the transformers in the power distribution room of the community have been in the state of two transformers running separately for a long time. Light load operation is not economical. If the transformer loss needs to be reduced, it is necessary to change to an economic operation mode of a single transformer running with two busbar loads when the load is light, and the other transformer is shut down. Since the current marketing collection system has a fixed meter reading and line loss calculation method for each area: that is, when running separately, the #1 transformer area collects the low-voltage side and the user's meter 1234 power load through the low-voltage total meter 1, and calculates the line loss. The line loss is calculated as the sum of the low-voltage total meter 1 load minus the user's meter 1234 load, and the #2 transformer area collects the low-voltage side and the user's meter 5678 power load through the low-voltage total meter 2, and calculates the line loss. The line loss is calculated as the sum of the low-voltage total meter 2 load minus the user's meter 5678 load, as shown in the figure below. Before changing the operation mode, the "household-transformer" relationship is fixed, and this technology has no problem, but when the distribution transformer is in economic operation, the "household-transformer" relationship changes, and the original technology is no longer suitable:

[0074] After changing the operation mode, there will be two problems that need to be solved:

[0075] 1. Impact on the power supply of the electric meter: When the 2# transformer is switched to economic operation, the low-voltage main meter 1 loses power, affecting data collection and transmission.

[0076] 2. Impact on line loss calculation: The marketing collection system still uses the previous split operation mode to calculate the low-voltage line loss formula for each substation separately. The actual load flowing through the low-voltage total meter 2 is the sum of the loads of the user meters 12345678 on both sides. When calculating the line loss, the load of user 1234 is not calculated, which will cause the line loss of the #2 substation to be very high. The low-voltage total meter 1 actually has no load flowing through it, and user 1234 has a load, which will cause the line loss calculation of the #1 substation to be a negative value.

[0077] Combined with the operation mode of the existing distribution room and the marketing collection and billing methods, if the above two problems cannot be solved, it will be difficult to implement the economic operation of the distribution transformer through the distribution transformer economic operation device, reduce transformer losses, and directly create economic and social benefits for users and power supply companies.

[0078] According to an embodiment of the present invention, the above two problems can be completely solved. Figure 2 ,3,4,5 as shown:

[0079] The original power distribution room wiring is as follows Figure 2 As shown in: low voltage meter 1 is connected to the upper port of the low voltage switch of 1# transformer, low voltage meter 2 is connected to the upper port of the low voltage switch of #2 transformer, the bus tie switch is between the two busbars, when the transformer is running separately, #1 transformer area collects the power load of the low voltage side and the user's meter 1234 through low voltage meter 1, and calculates the line loss, which is calculated as the sum of the load of low voltage meter 1 minus the load of user's meter 1234, #2 transformer area collects the power load of the low voltage side and the user's meter 5678 through low voltage meter 2, and calculates the line loss, which is calculated as the load of low voltage meter 2 minus the The sum of the loads of household electricity meters 5678, the "household-transformer" relationship is fixed before the operating mode is changed, and this technology has no problem. However, after switching to single-transformer economic operation, the "household-transformer" relationship changes, and the original technology is no longer suitable. The present invention changes the incoming and outgoing cables of the bus tie switch to the lower ports of 1# and 2# low-voltage switches by modifying the main wiring mode once, and at the same time, converting the low-voltage total meter 1 to the lower port of the connection point between the 1# low-voltage switch and the bus tie switch, and converting the low-voltage total meter 2 to the lower port of the connection point between the 2# low-voltage switch and the bus tie switch, which can perfectly solve the above problems.

[0080] After implementation, if Figure 3 As shown: From the flow direction of the power load, it can be seen that when the power flow load is in the split operation, it flows through the 1# transformer through the low-voltage total meter 1 to the user 1234 meter, and through the 2# transformer through the low-voltage total meter 2 to the user 5678 meter; when the 2# transformer is in economic operation, the power flow flows through the 2# transformer through the low-voltage total meter 2 to the user 5678 meter, and through the bus tie switch through the low-voltage total meter 1 to the user 1234 meter; when the 1# transformer is in economic operation, the power flow flows through the 1# transformer through the low-voltage total meter 1 to the user 1234 meter, and through the bus tie switch through the low-voltage total meter 2 to the user 5678 meter. It can be found that no matter it is split operation or economic operation, the power flow load through the low-voltage total meter 1 only flows to the meter 1234, and the power flow load through the low-voltage total meter 2 only flows to the meter 5678, that is, the "household-transformer" metering calculation relationship is not affected after the distribution transformer is in economic operation;

[0081] Modifying the primary main connection mode to move the low-voltage master meter down to the lower port of the connection point between the bus tie switch and the low-voltage switch cable outlet will cause problems in the calculation of medium-voltage line loss. The medium-voltage side line loss is calculated by the substation outlet gateway meter and the low-voltage master meter of each node on the line. When the low-voltage master meter is located below the bus tie switch, the load carried by the substation outlet should also include the low-voltage master meter 2. However, when actually calculating the line loss, only the data of the low-voltage master meter 1 will be calculated, which will cause errors in the calculation of medium-voltage line loss.

[0082] For this reason, it is necessary to add another measure to solve the problem of medium-voltage line loss calculation caused by modifying the main wiring diagram. When the operation mode is changed from separate operation to economic operation, the master station needs to package the two lines. Therefore, when the operation mode changes, it is necessary to inform the DTU in a hard contact manner and send it to the master station for manual packaging and processing. Since the line loss calculation only cares about whether it is separate operation, separate operation is processed separately, and economic operation is packaged, the DTU can directly collect the 400V bus tie switch for distinction, and calculate the line loss of the medium-voltage power supply lines on both sides separately. When the 400V bus tie switch is closed, the medium-voltage power supply lines on both sides are treated as one line to calculate the medium-voltage line loss.

[0083] The above specific implementations are only descriptions of the preferred implementations of the present invention, and do not limit the protection scope of the present invention. Without departing from the design concept and spirit of the present invention, various modifications, substitutions and improvements made by ordinary technicians in this field to the technical solution of the present invention based on the text description and drawings provided by the present invention should all fall within the protection scope of the present invention. The protection scope of the present invention is determined by the claims.

Claims

1. A method for realizing unchanged metering relationship after economic operation of distribution transformer, characterized in that: The method comprises: Step S1: Modify the primary main wiring and reconnect the cables on both sides of the bus tie switch to the lower ports of the low-voltage side switches on both sides; Step S2: Install the low-voltage master meter to the lower port of the low-voltage switch and the busbar switch cable connection point to ensure that the low-voltage master meter can accurately collect load data; Step S3: using the data transmission unit to collect the 400V bus tie switch position data in real time and upload it to the master station; Step S4: The master station processes and adjusts the medium voltage line loss calculation in real time according to the position of the 400V bus tie switch; Step S4 includes: Step S4.1: When the 400V bus tie switch of the master station is in the open position, the medium voltage line losses on both sides are calculated independently; when the 400V bus tie switch is in the closed position, the medium voltage line losses on both sides are processed uniformly; Step S4.2: dynamically adjust the line loss calculation model according to the load data collected in real time to adapt to the change of load; Step S4.3: Record and archive the line loss calculation results of each operation mode switch to provide data support for subsequent analysis and optimization; Step S5: After adjusting the position of the low-voltage master meter, the data changes of the low-voltage master meter are monitored through the master station system to ensure data accuracy; Step S6: When the operation mode is changed from the split operation mode to the economic operation mode, the master station packages the two lines to ensure accurate calculation of line loss; Step S7: Utilize multi-source data fusion technology to combine transformer operation data, load data and environmental data to optimize the distribution network operation strategy; Step S8: Implement the intelligent alarm system. When the distribution transformer operation mode changes or the low-voltage main meter data is abnormal, an alarm is automatically triggered and maintenance suggestions are sent to the operation and maintenance personnel.

2. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S1 comprises: Step S1.1: Reconnect the incoming and outgoing cables of the bus tie switch in the original main wiring mode of the power distribution room to the lower ports of the low-voltage switches of the main transformers on both sides to ensure that the power supply on the low-voltage side of the main transformer is not affected when the operating mode changes; Step S1.2: Add an adapter at the lower port of the low-voltage side switch to connect the reconnected cable to ensure the stability and safety of the connection; Step S1.3: Verify whether the modified cable connection complies with electrical safety standards, and perform debugging and testing.

3. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S2 comprises: Step S2.1: Move the original low-voltage total meter from the upper port of the main transformer switch to the lower port of the low-voltage switch and the bus tie switch cable connection point to ensure that the low-voltage total meter can accurately collect load data; Step S2.2: calibrate the low-pressure main meter to ensure the accuracy of data collection at the new location; Step S2.3: Record and update the new location and related information of the low-voltage main meter to ensure accurate positioning and inspection during subsequent maintenance.

4. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S3 comprises: Step S3.1: The DTU collects the 400V bus tie switch position data in real time and uploads it to the master station to ensure that the master station can accurately calculate the line loss; Step S3.2: Check and maintain the DTU equipment to ensure its long-term operational stability and data transmission reliability; Step S3.3: During the data transmission process, data encryption technology is used to ensure the security and integrity of data transmission.

5. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S6 comprises: Step S6.1: fusing the load data of the medium voltage lines on both sides to form a unified line loss calculation data set; Step S6.2: For abnormal data in the line loss calculation data set, data cleaning and correction are performed to ensure the accuracy of line loss calculation; Step S6.3: Regularly analyze the packaged line loss data to identify and resolve potential problems and improve the accuracy of line loss calculation.

6. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S7 comprises: Step S7.1: Utilize multi-source data fusion technology to integrate transformer operation data, load data and environmental data to optimize the distribution network operation strategy; Step S7.2: Analyze historical data and real-time data through machine learning algorithms, predict future load changes, and adjust power distribution strategies; Step S7.3: Monitor the operation status of the distribution network in real time, dynamically adjust the operation parameters, and improve the economy and reliability of the distribution network operation.

7. The method for realizing unchanged metering relationship after economic operation of distribution transformer according to claim 1 is characterized in that: The step S8 comprises: Step S8.1: Implement the intelligent alarm system to automatically trigger an alarm when the distribution transformer operation mode changes or the low-voltage master meter data is abnormal; Step S8.2: Send maintenance suggestions to the operation and maintenance personnel, including a detailed abnormality analysis report and treatment plan; Step S8.3: Regularly update and optimize the intelligent alarm system to ensure that it can provide accurate and timely alarm information under different operating conditions.

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