Buried Box-Type Substation Principle (1)
1. (6-15) kV bus section by the single connection.
2. High Voltage Connection Mode:
- High voltage part: the load switch + current-limiting fuse as main protection of transformer, two groups of inserting fuse scope of protection and backup protection fuse series section.Tandem jump three-phase load switch, lack of phase operation does not occur.
- Line parts: load switch using dc power electric operation mechanism, since the launch of external ac power condition.
- Loop: configuration detection fault current with current transformers or sensors.
- High voltage switch: compressed air type load switch, vacuum load switch.
3. Power Supply Unit:
- 3 interval: The two cables in and out of the interval and a transformer loop interval.
- Load switch: In isolation fault line segment, the timely recovery loop continuous power supply;Connected to the fuse when born internal fault protection, isolation and grounding of fuse and the transformer.
- Load switch fuse combination:
♦ Protection of transformer, ON/OFF load current switching device, alternative circuit breaker, as the protection of transformer switch equipment.
♦ With ON/OFF short circuit current capacity, can’t open circuit short circuit current.
♦ Used alone away from the power center, and smaller terminal capacity, for reactive power compensation circuit, shunt reactor and motor, etc.
- Current limiting fuse type:
♦ Rely on filling in the melt quartz sand cooling around the arc, to achieve effective extinguishing arc, strong cooling in the process of the arc established above the working voltage of the electric arc voltage, strong current limiting capability.
♦ Short circuit after the start of the current rise, melt fever, temperature rise, current up to a point, melting, melt stop electricity flow rise, began to drop along the ab line and in point b current drop to zero, at this time to complete the arc.
♦ The process action takes place in an airtight porcelain tube, in extinguishing arc, turbulence not rushed out of the tube.
♦ Biggest cut-off current of fuse open circuit, current and expected steady state party, the relationship between root from the current value of the current limiting characteristics can be estimated by the current-limiting fuse protection when fault occurs in the electrical equipment of the mechanical and thermal effect.
♦ The structure is simple, cheap and convenient maintenance.Fuse is a major component of fuse body, when the fuse body through the current more than fixed value, the fuse body itself produce joule heat, temperature, make itself reaches melting point, the fuse body to fuse to cut off the overload or short circuit current.
4. High Voltage Room:
- Three working load switch, fuse, transformer, lightning arreste
5. Low Roltage Room:
- GGD type fixed low-voltage distribution panel, including the main switchgear, metering tank, multi-channel outlet ark, coupling capacitor.