Microwave Tech - What is radial wiring?

Radial wiring refers to that special lines are led out from the substation bus to each user to directly supply power to the user, and other electrical equipment is not connected to the line. The advantage of radial wiring is that the power supply lines are independent of each other, and the line operation does not affect each other. When any line fails, it does not affect the normal operation of other lines, and the operation and maintenance are convenient; Relay protection is simple and easy to realize automation. The disadvantage is that there are many power outgoing circuits, large equipment consumption and large investment. Radial type can be divided into single circuit radial type and double circuit radial type, as shown in Figure 1. Single circuit radial wiring has only one power supply, and the power supply reliability is low; The double circuit radial wiring has two power supplies with high power supply reliability. The bus section disconnector QS in the double circuit radial wiring can also be replaced with a circuit breaker to realize automatic switching and improve the reliability of power supply.

Trunk line wiring refers to that one circuit of power supply trunk line is led out from the bus of the substation, and generally no more than 5 users are tapped along the trunk line. The advantages of trunk line wiring are less power outgoing circuits, short total length of power supply lines, less consumption of non-ferrous metals and distribution equipment and less investment. The disadvantage is that the reliability of power supply is not high, and the failure or maintenance of trunk line will lead to power failure of all users. Trunk line type can be divided into single circuit trunk line type and double circuit trunk line type, as shown in Figure 2. Double circuit trunk type has two power supplies for mutual standby, and its reliability is higher than that of single circuit trunk type.

Ring wiring means that two or more users are powered by two power supplies after contacting each other, as shown in Figure 3. Ring wiring is actually an improvement of trunk wiring. Two trunk lines are connected to form a ring line. The advantages of ring wiring are less equipment consumption and less investment; Each power line has different ways, which is not easy to fail and has high power supply reliability; Flexible operation. The disadvantage is that after line switching in case of fault, the power supply line of some users becomes longer and the voltage loss increases; The conductor section of the two circuit lines shall be considered as bearing the full load of the ring network in case of fault, and the consumption of non-ferrous metals is large.

Loop wiring has two operation modes: open-loop operation and closed-loop operation. Open loop operation is to disconnect the connecting line between users in the loop, and the two power supplies operate with part of the load. Closed loop operation is to connect the connecting line between users in the loop, and each user is jointly powered by the two power supplies. The relay protection device in closed-loop operation is more complex, and generally adopts open-loop operation mode. The selection principle of open-loop point is: during normal operation, the capacity borne by the two trunk lines shall be as close as possible, and the cross-section of the conductor used shall be the same; Alternatively, the open-loop point shall be set at the more important load, and the open-loop circuit breaker shall be equipped with automatic device.

According to the requirements of power supply reliability, the wiring mode of power supply system can also be divided into two categories: no standby system wiring and standby system wiring. Single circuit radial type and single circuit trunk type belong to non standby system wiring; Double circuit radial type, double circuit trunk type and ring type all belong to standby system wiring. The general characteristics of wiring without standby system are simple wiring, convenient operation and low power supply reliability. It is mainly used for power supply of class III loads and some secondary class II loads. The general characteristics of wiring with standby system are many equipment, large investment and high power supply reliability. It is mainly used for power supply of class I loads and important class II loads.