Distributed power supply access through switch station (power distribution room, box-type transformer)
Figure 1 shows the typical wiring diagram of the distributed power supply connecting to the 10(6)kV~35kV distribution network through the switch station (power distribution room, box transformer, etc., hereinafter referred to as the switch station). The user’s high-voltage main line switch (3DL in Figure 1) should be equipped with staged (directional) overcurrent protection and fault decoupling. The distributed power feeder circuit breaker (4DL in Figure 1) of the user’s high-voltage bus can be configured with staged (directional) overcurrent protection and reclosing.
When the overcurrent protection configured at the user’s high-voltage bus incoming circuit breaker (3DL in Figure 1) points to the line in the positive direction, the distributed power feeder circuit breaker that can act on the user’s high-voltage busbar according to the user’s choice is 4DL or 3DL in Figure 4.5. When the positive direction points to the user’s high-voltage bus, the action is to jump the 3DL circuit breaker. The fault decoupling configured at the user’s high-voltage bus incoming circuit breaker (3DL in Figure 1) acts on the distributed power feeder circuit breaker (4DL in Figure 1) that trips the user’s high-voltage bus.
The protections configured at the distributed power feeder circuit breaker (4DL in Figure 1) of the user’s high-voltage bus all act on tripping the circuit breaker.
The protection configured at the user’s high-voltage mains incoming circuit breaker (3DL in Figure 1) should meet the following requirements:
(1) When the current protection direction points to the line, in addition to setting according to the conventional principles, it is necessary to ensure that the 10kV busbar fault of the public substation has sufficient sensitivity, and the inverter type distributed power supply can be set according to 110%~120% of the rated current of the distributed power supply. When the direction of the current protection points to the user bus, the priority should be set according to the coordination requirements of the protection configuration at the switch station distributed power feeder circuit breaker (2DL in Figure 1). If it cannot be matched or the protection at the 4DL circuit breaker or the user’s internal load switch is difficult to set after the cooperation, it can be set according to the matching requirements of the protection configured directly with the public substation feeder circuit breaker (1DL in Figure 1).
(2) Requirements that should be met for fault decoupling:
① The action time should be less than the action time of the public substation fault disconnection, and there is a certain time difference;
② The action time setting should avoid the other interval fault clearance time on the system and the user bus, and consider the coordination with the system reclosing;
③The setting value of overvoltage and the setting value of low/overfrequency are set according to the requirements of DL/T584.
The protection configured at the distributed power feeder circuit breaker (4DL in Figure 1) of the user’s high-voltage bus shall meet the following requirements:
(1) The current protection should meet the coordination requirements of the configuration protection at the user’s high-voltage main incoming circuit breaker (3DL in Figure 1).
(2) Whether the 4DL circuit breaker is reclosed after tripping can be determined according to user needs. If reclosing is used, it can be checked for no-voltage or synchronous reclosing. It is preferred to set according to the coordination requirements of the recloser at the switch station distributed power feeder circuit breaker (2DL in Figure 1). If it cannot be matched, it can be set according to the coordination requirements of the recloser directly connected to the feeder circuit breaker of the public substation (1DL in Figure 1), and it should have the post-acceleration function.