What are the connection modes of power system? What are their advantages and disadvantages?

Power system wiring is mainly divided into power grid wiring, power plant main wiring and substation main wiring.

There are two main connection modes of power grid: standby connection and non-standby connection (single loop).

Non-standby connection modes (single loop) can be divided into radial, relay and chain. Advantages are simple and convenient, less investment, and disadvantages are low reliability, which is suitable for ordinary loads.

There are standby connection modes, which are divided into: double-loop line, single-power single-loop network, double-power double-loop network and double-ended power supply without standby mode. The advantages of double-ring network are simplicity, convenience and high reliability, but the disadvantage is poor economy. The advantages of ring network power supply are reliability and economy, but the disadvantages are complicated operation and poor voltage quality when fault occurs.

The main connection modes of power plants and substations are divided into busbar and non-busbar.

Bus bars are divided into single bus configuration, double bus connection, single bus with bypass bus connection and double bus connection. The advantages of single bus configuration are simple structure and good economy, but the disadvantages are poor reliability and flexibility. The advantage of double bus connection is good reliability and flexibility, but the disadvantage is poor economy.

Non-bus connection modes are divided into unit connection, bridge connection and polygon connection. The advantage of unit connection is that it reduces the cost and the possibility of failure. The disadvantage is that any component fails and the whole unit stops working, which is mainly suitable for large and medium-sized power plants without generator terminal voltage load. Bridge connection is divided into inner bridge and outer bridge. The inner bridge is suitable for thermal power systems with long lines and infrequent removal of main transformers, while the outer bridge is suitable for hydropower systems with short lines and crossing function and frequent removal of main transformers. The advantages of angle connection are high reliability and good economy, but the disadvantages are that it is not easy to expand, open-loop operation during maintenance or failure, and it is difficult to select equipment and set relay protection.