When the power system is in various possible operating conditions, the sudden loss of active power occurs, resulting in a decrease in the system frequency. Therefore, it is necessary to remove a relatively unimportant part of the load in time so that the part of the system that is retained for operation can be quickly restored. Continue to operate near the rated power. The frequency in low-cycle load-shedding protection is obtained by sampling calculation of voltage and time. By using the counter of the CPU to measure the average time between two zero-crossing points of the voltage waveform, the frequency value of the system voltage can be calculated.
Our 900 high-end microcomputer protection device can realize low cycle load shedding protection function. This protection can realize distributed frequency control. When the system frequency is lower than the set value, the action can be protected by the set delay time. Protection can independently push and drop voltage blocking, slip blocking and undercurrent blocking. Voltage blocking Lockout protection when the system voltage is lower than the set value. Slip lock When the system fails, the frequency drops too fast and exceeds the slip frequency setting. Undercurrent blocking is blocked when the system current is too small (less than 0.5A).
[Operating conditions]
1) Low-cycle load shedding protection input;
2) The circuit breaker is in position;
3) The line frequency is less than the low frequency setting Fset (must be reduced from 49.5 to 50.5 Hz);
4) The delay exceeds the set time setting value Tset;
5) The three line voltages are greater than the voltage setting value Uset (if the voltage blocking function is input);
6) The frequency slip is smaller than the slip value Df/dt (if the slip lock function is input);
7) Any phase current is greater than 0.5A (if the undercurrent blocking function is input);
8) PT is not broken.
Our 900 high-end microcomputer protection device can realize low cycle load shedding protection function. This protection can realize distributed frequency control. When the system frequency is lower than the set value, the action can be protected by the set delay time. Protection can independently push and drop voltage blocking, slip blocking and undercurrent blocking. Voltage blocking Lockout protection when the system voltage is lower than the set value. Slip lock When the system fails, the frequency drops too fast and exceeds the slip frequency setting. Undercurrent blocking is blocked when the system current is too small (less than 0.5A).
[Operating conditions]
1) Low-cycle load shedding protection input;
2) The circuit breaker is in position;
3) The line frequency is less than the low frequency setting Fset (must be reduced from 49.5 to 50.5 Hz);
4) The delay exceeds the set time setting value Tset;
5) The three line voltages are greater than the voltage setting value Uset (if the voltage blocking function is input);
6) The frequency slip is smaller than the slip value Df/dt (if the slip lock function is input);
7) Any phase current is greater than 0.5A (if the undercurrent blocking function is input);
8) PT is not broken.
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