Purpose:
BFY-11、 12. The 13 negative sequence voltage relay is used in the relay protection circuit of generators and transformers as a voltage blocking element to reflect the negative sequence component of voltage during asymmetric short circuits.

Working Principle:
2.1 The block diagram is shown in Figure 1.
2.2 Action principle
2.2.1 Negative sequence voltage filter: C3, RA (R10, R12), C4, RB (R9, R13) form a resistive capacitive filter. The schematic diagram is shown in Figure 2. Choosing RA=3 XC3, RB=XC4 3 can result in no output (only a small unbalanced voltage) from the filter when a positive sequence voltage is applied to the input, while when a negative sequence voltage is applied to the input, the output voltage Umn=1.5 3U2Aej30o=1.5U2ABej60o. The vector diagram is shown in Figure 3 because negative sequence filters are generally connected to the phase to phase voltage of the system, that is, the zero sequence component is equal to zero.
2.2.2 The output voltage of the filter is rectified by voltage transformer YH and then applied to the trigger. Under normal circumstances, BG1 is conductive, BG2 is turned off, and the execution element CJ does not operate; When an asymmetric short circuit occurs in the system, the output voltage of the filter causes the trigger to flip, BG1 to turn off, BG2 to turn on, and the CJ action is executed. Adjusting potentiometer R13 can change the setting value of the relay.

Main technical parameters:
3.1 AC rated values: 110V, 173V, 50Hz.
3.2 DC rated voltage: 220V, 110V, 48V.
3.3 Negative sequence action line voltage setting range is 6-12V, with a variation not exceeding 6%.
3.4 Relays are allowed to apply 1.1 times the rated positive sequence current of AC for a long time.
3.5 Allowable range of DC voltage variation: 220V and 110V are allowed to vary within the range of 80-110%, and for 48V, it is allowed to vary within the range of 90-110%. The relay should work normally.
3.6 At rated voltage, the total power consumption of the AC circuit shall not exceed 5VA at 100V, 8VA at 173V, 8W at 220V, 4W at 110V, and 2W at 48V.
3.7 The relay has one dynamic contact (BFY-11A) and one dynamic contact (BFY-12A), or one dynamic contact and one dynamic contact (BFY-13).
3.8 Contact breaking capacity: In DC inductive load circuits with voltage not exceeding 220V and current not exceeding 0.2A (time constant not exceeding 5 × 10-3s), the breaking capacity is 25W. In AC circuits, it is 300VA.
3.9 Temperature Influence: When the ambient temperature changes within the range of -10 ℃ to+50 ℃, the difference between the operating line voltage at any set point of the relay and the operating line voltage at temperature+20 ℃ shall not exceed ± 10% of the latter.
3.10 Weight: Approximately 11kg. 3.11 Electrical lifespan: 5000 cycles.

Wiring diagram behind the relay:
BFY-11、 12. The 13 negative sequence voltage relay has a protruding plug-in structure (T-shaped).
BFY-11、 12. The principle wiring diagram of the 13 negative sequence voltage relay is shown in Figure 4.
BFY-11、 The back view terminal diagram of the 12 negative sequence voltage relay is shown in Figure 5.
The back view terminal diagram of BFY-13 negative sequence voltage relay is shown in Figure 6.

Relay external dimensions and opening dimensions:
BFY-11、 12. The appearance and installation dimensions of the 13 negative sequence voltage relay are shown in Figure 4 of the universal structural system.

Ordering instructions:
4.1 Relay name, model, and quantity.
4.2 AC and DC rated voltage values.