1.1 Fixed value calculation requires a large amount of upfront data
The calculation of the fixed value should have accurate calculation data, which is the premise of the calculation of the fixed value. It includes: first and second drawings; nameplate data and manufacturer's instructions for transformers, capacitors, arc suppression coils, reactors, etc.; voltage transformers, current transformer ratios and test reports; measured line parameters or theoretical calculation parameters; protection Device technical specification, on-site protection device print list, etc.
1.2 Problems encountered in actual calculation
The drawings or materials do not conform to the actual situation; for example, the ratio of TA to the actual does not match, the length of the line does not match the actual length, the short-circuit impedance of the transformer does not match the actual one, and the parameters that should be measured have no measured values, drawings errors, and so on.
The data required for the calculation of the fixed value is incomplete: the internal wiring form of the capacitor is not provided; there is no printed list of the field protection device.
The information provided is unclear: the overhead line is not marked with the length and model number; the cable line does not indicate the user or the double cable in the scheme.
1.3TA ratio is not consistent with the actual value, making the calculation of the fixed value wrong.
Example: A substation 10kV outlet with two capacity SN is 1000kVA transformer, the short-circuit impedance UK is 6%, the data supply TA ratio N is 600/5, and the actual transformation ratio N is 1000/1.
Protection setting calculation:
The ratio of TA to 600 is 600/5, and the overcurrent protection is set to avoid the maximum load current:
I≥1.5×2SN×3 1/2UeN=1.37A
The general setting is the minimum value: 600/5, 2A.
The actual situation:
TA ratio N is taken as 1000/1, substituted
I≥0.16A
Optional: 1000/1 1A.
The quick-break is set to avoid the short-circuit of the low-voltage side of the transformer:
The value of the short-circuit impedance is: (take the reference capacity SB = 100MVA, the reference voltage UB = 10.5kV, the reference current IB = 5500A) when UB = UN
X*=UK%×SB/(100×SN)=6
I≥1.3×5500/(X*×N)=9.93A (N takes 600/5)
Generally the minimum is desirable: 600/5, 10A.
Actual situation: N=1000/1,
1.3×5500/(X*×N)=1.19A
Can be selected: 1000/1, 2A.
Conclusion: It can be seen that the actual TA of 1000/1 is calculated according to 600/5, and the selected values ​​will be very different.
1.4 solutions
The equipment operation and maintenance unit is set up by the equipment operation and maintenance unit, and the database needs to be updated, accurate, and shared.
As the data unit, the correctness of the information required for the fixed value should be paid enough attention. This is the basic work for the calculation of the fixed value. The wrong or inaccurate data will directly cause the relay protection device to fail to operate correctly, causing serious consequences.
Complicated fixed value calculation units should be calculated for different engineering contents and different fixed value calculations, and provide a list of required data for calculation so that the engineering organization unit can provide all the information as soon as possible.
2 fixed value calculation work
The fixed value calculation is the key to determining the correct operation of the protection device. The value calculation personnel should have a high degree of responsibility for work and establish a global concept and overall concept. The setting calculation work should strictly abide by the basic principles of setting calculation: partial obedience to the whole; subordinate obeying the superior; local problems to be digested by themselves; taking care of the needs of the regional power grid and the next-level power grid as much as possible; and ensuring the power supply of important political users. It meets the requirements of reliability, selectivity, sensitivity and quick action of relay protection and safety automatic devices, and should be reasonably traded when it is not satisfied.
The protection device is suitable for on-site needs to be continuously updated, especially the version of the microcomputer protection device is continuously upgraded. The setting calculator has to spend a lot of time and energy to learn new content word by word, repeatedly communicate with the technical personnel of the protection device manufacturer, master the principle and action logic, and it is easy to make mistakes when adopting the new microcomputer protection device.
Since the protection devices come from different manufacturers, sometimes the same protection definition is different and the names are different, which is easy to cause confusion. Some protection manufacturers' instructions are not detailed enough, such as the lack of a logic circuit diagram, making it difficult for the setting calculator to determine whether the protection is active. There are also manufacturers of value menus that are too cumbersome, such as setting up many control words and throwing back and forth.
The drawings changed by the secondary wiring are not timely.
The setting calculation personnel are unclear about the content, meaning and secondary circuit of the new device, and do not have a good grasp, so that the contents of the fixed value are wrong.
The protection device is inherently insufficient. For example, some old models have large step-by-step units and cannot be eliminated after the decimal point, which affects the accuracy of the fixed value list and even affects the coordination relationship between the upper and lower levels.
The setting personnel did not participate in the work of relay protection configuration, design review and equipment selection. When the calculation value was calculated, the problem was discovered. Especially when the design itself had design defects, it was difficult to be modified, and the protection configuration was inherently insufficient.
The lower level fixed value does not interface with the higher level fixed value. The upper level changes the line setting value and the lower level replaces the transformer. The lower and upper level units are not notified in time to make the protection setting lose the matching relationship.
After the line is cut or replaced, the system impedance is not modified in time, so that the calculation of the fixed value is deviated.
Example of fixed value calculation error:
Example 1: A 35kV/10kV substation, transformer backup overcurrent protection 1s disconnect 10kV bus-coupled circuit breaker, 1.5s disconnect 10kV main circuit breaker, when calculating 10kV outlet protection setting, the fixed value calculation personnel will routinely set 10kV outgoing line The value is set to 0.5s for quick disconnection and 1s for overcurrent, causing the 10kV out-of-line short-circuit to disconnect the 10kV bus-coupled circuit breaker.
Example 2: The wiring mode of a substation transformer is Yyd11 line. Due to the protection of the setting personnel, the meaning of the transformer connection control word of a certain device is not deeply understood. The error of 0002H is 0001H, which causes the transformer differential protection to trip when the 35kV line is short-circuited.
The solution should generally standardize the software version of the relay protection device, standardize the name of the pressure plate on the same protection and the same function, and standardize the manufacturer's technical specification and its necessary contents. In short, the standardization work is of great significance to the relay protection calculation and operation and maintenance work.
The setting calculation personnel should improve the quality of the business, strengthen the study of the new device, and actively participate in the configuration, selection and improvement of the protection device.
Strengthen the communication and learning between the setting calculation personnel at all levels and between the technical personnel of the manufacturer and the relay protection personnel on the site. Take advantage of each other's strengths and complement each other.
The dynamic training of the new microcomputer protection device has become the top priority of the new device. As a user of the microcomputer protection device, the setting calculator first contacts the new device, and unexpected problems may occur. And in the initial stage of the use of the new device, it is inevitable that there will be some problems. Therefore, it is very important for the fixed value calculation personnel and the on-site commissioning and maintenance personnel to grasp the performance of the microcomputer protection device as soon as possible. The intensity of dynamic training should be increased to improve the overall business technology level of relay protection personnel as soon as possible.
3 implementation of the fixed value list
The generation and execution of a fixed value list must be carried out by the organization unit to provide information, determine the operation mode, fixed value calculation, fixed value review, determine the power outage time, protection and debugging, and dispatch personnel check, etc., each of which may cause There is a problem with the valuation list during execution.
The relay protection of the operation must have a formal fixed value sheet as the certificate. Before the protection input, the dispatcher must check with the on-site personnel. After the confirmation is correct, the dispatching department fills in the execution date and stamps it, and returns the value within one week. The calculation department archives.
In the actual problems encountered, the executed fixed value list cannot be returned to the fixed value calculation department in time, so that the saved fixed value list and the on-site fixed value are deviated.
The fixed value list is lost during the execution of the flow or the execution is completed, causing the set value to be wrong.
Solution: The closed-loop management measures for the relay protection fixed value list should be established, and the fixed value single execution sign-off system should be established. Personnel in each department involved in the execution of the fixed value list shall strictly perform the work of the value list. It cannot be considered that the execution and protection of the fixed value list is only the responsibility of the relay protection personnel.
4 fixed value management work
The management of fixed value sheets should be meticulous and careful. It is very important to manage the fixed value list, fixed value draft and data plan for the calculation and maintenance of relay protection. The saved values ​​and their data must be consistent with the actual situation to ensure The calculation of the fixed value is correct and the execution is correct.
The actual problems encountered, such as the calculation of the final value of the work and the data in the work were not filed in time, the data was incomplete when recalculated, and a calculation error occurred. The annual fixed-point check-up workflow is in the form of no specific management measures.
The line of the outage and the line of the changed name did not inform the setting calculator.
Generally, the measures to be solved are to protect the operation and maintenance unit and establish the operation management library of the relay protection device. The relay protection and the file construction of the secondary equipment should be accurate and timely. The protection device is a basic work. Each device should establish a file, including the manufacturer, equipment specifications, software version, running performance, calibration date, defect problem, outage and commission date, replacement date, etc. Update from time to time, resource sharing.
We will conscientiously do a good job of checking the annual value of a single value, and establish a fixed value check and deposit management system. Establish an electronic version of the fixed value depository and check it regularly.
The management of the fixed value list is the basic work of the relay protection profession. Only when the basic work is started can the relay protection work be carried out in an orderly manner.
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