GB/T 38953-2020Technical requirements for relay protection of microgrid (English PDF)

4.2 Fix-value setting

4.2.1 The microgrid relay protection fix-value shall be set according to the microgrid working conditions and protection requirements such as the microgrid topological structure, the way of connecting and disconnecting from the grid, the type and status of internal distributed resources.

4.2.2 The microgrid relay protection fix-value shall be coordinated with the fault ride-through capability of microgrid. The setting of the grid-connected microgrid relay protection fix value shall be coordinated with the relay protection of the public grid.

4.3 Fault recording function

generator shall act reliably during out-of-step oscillation; it shall not malfunction during system short-circuit and stable oscillation.

7.1 General requirements

The protection of the microgrid 10(6) kV ~ 35kV voltage level transformer shall meet the relevant requirements of GB/T 14285.

7.2 Differential protection

The configuration principle of transformer differential protection shall meet the relevant requirements of GB/T 14285, and shall reliably trip the corresponding circuit breaker.

7.3 Non-electricity protection

7.3.1 Oil-immersed transformer shall be equipped with gas protection, heavy gas trip, light gas alarm.

7.3.2 Dry-type transformer shall be equipped with temperature over-limit protection, over-temperature alarm or trip.

7.4 Directional overcurrent protection and overload protection

7.4.1 Transformers without differential protection shall be equipped with current quick-break protection.

7.4.2 The transformer shall be equipped with over-current protection as a backup protection for phase-to-phase short circuit. When the selectivity does not meet the requirements, the overcurrent protection can add directional components.

7.4.3 The transformer shall be equipped with overload protection with constant time-lag or inverse time lag operation characteristics.

8.1 General requirements

8.5 Simultaneous closing

For the 380(220) V voltage level microgrid, the point of connection shall be equipped with the synchronous closing function.

8.6 Anti-islanding protection

The point of connection of microgrid shall be equipped with anti-islanding protection. When running in grid-connected mode, the anti-islanding protection shall be used; otherwise, the anti-islanding protection shall be exited. Anti-islanding protection shall be reliable action to trip the grid connection point switch.

9.1 General requirements

9.1.1 The 10(6) kV ~ 35 kV line protection inside the microgrid shall meet the relevant requirements of GB/T 14285.

9.1.2 The line protection of the microgrid shall be set according to the line type, length and load characteristics; the influence of the operation mode of the microgrid and the characteristics of distributed resources shall be considered comprehensively.

9.2 Differential protection

The internal cable line of the microgrid or the 10(6) kV ~ 35 kV line with difficulty in setting shall be equipped with the longitudinal current differential protection.

9.3 Overcurrent or directional overcurrent protection

9.3.1 The 10(6) kV ~ 35 kV voltage level lines inside the microgrid shall be equipped with overcurrent protection; when the selectivity does not meet the requirements, the overcurrent protection can add directional components.

9.3.2 The 380 (220) V voltage level lines inside the microgrid shall be equipped with instantaneous short-circuit protection, and should be installed with long-time short-circuit protection.

9.4 Ground fault protection

9.4.1 For microgrids that use neutral effective grounding, the 10(6) kV ~ 35 kV voltage level lines shall be equipped with ground fault protection. […]