Beijing Tianyihongda Science & Technology Development Co., LTD
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| Length of cable at switch load side (m) | 50 | 100 | 150 | 200 | 250 | 300 | 350 | 400 | 450 | |
| Length of overhead line at switch load side (m) | <1000 | <4000 | ||||||||
| Fixed value (A) | 0.2 | 0.4 | 0.6 | 0.8 | 1.0 | 1.2 | 1.4 | 1.6 | 1.8 | 2.0 |
| Length of cable at switch load side (m) | 480 | 500 | 550 | 600 | 650 | 700 | 750 | 800 | 850 | 900 |
| Fixed value (A) | 2.2 | 2.4 | 2.6 | 2.8 | 3.0 | 3.2 | 3.4 | 3.6 | 3.8 | 4.0 |
Calculation formula for fixed values: Fixed value of current =1.5×3×(S1×L1+S2×L2)
L1 is the total length of overhead line at boundary switch load side. S1 is the empirical value of capacitive current of overhead line per km per phase. The recommended value is 0.02A/km.
L2 is the total length of cable at boundary switch load side. S2 is the empirical value of capacitive current of cable per km per phase. The recommended value is 1A/km.
Choose 1S when the neutral point is not earthed or earthed by arc suppression coil. Choose OS or lower when the neutral point is earthed by low resistance.
The calculation of fixed values for zero-sequence protection current only depends on the direct earth capacitance of cable or overhead line at switch load side. The table above is the results of approximate amount multiplied by safety factor. Users can calculate personally according to the actual condition of the line at switch load side. If there are both cable and overhead line at switch load side, add their direct earth capacitances together. The safety factor shall be chosen between 1.5~3 (It is recommended that a larger safety factor shall be chosen when the fixed value is relatively small, while a smaller one shall be chosen when the fixed value is relatively large.)
Enter Main Menu
When the system is idle, press “VIEW” to enter the main menu
After entering the main menu, press “ESC” to exit to idle status.
Switching of Menu Content
After entering the main menu, press “ENT” to select the content, press “” or “” to switch the content, and press “VIEW” to enter corresponding menu.
Press “ESC” to exit to idle status.
Modifying Fixed Value
After entering fixed value interface, press “ENT” to confirm the fixed value item and press “ENT” again to confirm the modification of fixed value. Press number buttons “0” to “9” to input the fixed value parameters. Press “” or “” to change the data position and press “SET” to save the fixed value (Press “ESC” to give up the modification and the fixed value after modification will not be saved).
After entering fixed value interface, press “” or “” to switch the fixed value interfaces.
After entering fixed value interface, press “ESC” to exit to the main menu.