Figure 1 shows the typical wiring diagram of the distributed power supply T connection to the 10 (6) kV~35 kV distribution network. The user’s high-voltage main line switch (2DL in Figure 1) should be equipped with staged (directional) overcurrent protection and fault decoupling. The distributed power feeder circuit breaker diagram of the high-voltage bus (3DL in Figure 1) can be configured with staged (directional) overcurrent protection and reclosing.
When the positive direction of the overcurrent protection configured at the user’s high-voltage bus incoming circuit breaker (2DL in Figure 1) points to the user’s high-voltage bus, the action will be to trip the 2DL. circuit breaker. If the line is pointed in the positive direction, the distributed power feeder circuit breaker (3DL in Figure 1) or 2DL can be jumped according to the user’s choice. When there are multiple distributed power lines, each distributed power feeder circuit breaker can be jumped at the same time.
The protection configured at the distributed power feeder circuit breaker (3DL in Figure 1) of the user’s high-voltage busbar acts on tripping the circuit breaker.
The relay protection and safety automatic device configured at the user’s high-voltage mains incoming circuit breaker (2DL in Figure 1) shall meet the following requirements:
(1) When the rated current of the distributed power source is greater than the current protection setting value of the end stage of the protection device installed at the feeder circuit breaker of the public substation (1DL in Figure 1), the current protection configured at the user’s high-voltage main incoming circuit breaker (2DL in Figure 1) is set in the direction of the user’s busbar, and cooperates with the protection configured at the public substation feeder circuit breaker (1DL in Figure 1). In order to improve the reliability of 2DL to remove line faults, a section of overcurrent protection directed to the line can also be set.
(2) The 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 extreme difference;
② The setting value of the action time should avoid the fault clearance time of other intervals on the system and the user bus, and at the same time consider meeting the coordination requirements of the system reclosing;
③ The overvoltage setting and the low/over frequency setting are set according to the requirements of DL/T584.
(3) The reclosing function should be disabled.
The protection configured at the distributed power feeder circuit breaker (3DL 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 (2DL in Figure 1).
(2) Whether the 3DL circuit breaker is reclosed after tripping can be determined according to user needs. If reclosing is used, it can check no-voltage or synchronous reclosing, and its delay should be coordinated with the reclosing at the feeder circuit breaker of the public substation, and should have the function of post-acceleration.