1. Representation of electrical connection lines
Electrical connecting wires, referred to as wires, are used to connect electrical components and equipment, and their function is to transmit electrical energy or transmit electrical signals.
1.1 General representation of wires
① Symbols of conductors Symbols of conductors are shown in Figure 11-14. General symbols can represent any form of conductors, and busbars refer to thick conductors used in power supply and distribution systems.
② Representation of multiple wires When representing multiple wires, multiple single wire symbols can be combined to represent multiple wires, or a single line can be used to represent multiple wires, as shown in Figure 11-15. If the number of wires is small, you can directly draw multiple 45° dashes on the single line; if there are many wires, usually draw a dash on the single line, and mark the number of wires beside it.
③ Indication of conductor characteristics The characteristics of the conductor mainly include the conductor material, cross-sectional area, voltage, frequency, etc. The characteristics of the conductor are generally marked directly next to the conductor, or a 45° dash line can be drawn on the conductor to specify the characteristic of the conductor, as shown in Figure 11-16. In Figure 11-16(a), 3N-50Hz380V means that there are 3 phase wires, 1 neutral wire, and the power supply frequency and voltage of the wires are 50Hz and 380V respectively. 3×10 + 1×4 means that the cross-sectional area of the three phase wires is 10mm2, and the cross-sectional area of the neutral wire is 4mm2. In Figure 11-16(b), BLV-3×6-PC25-FC indicates that there are 3 aluminum-core plastic insulated conductors with a cross-sectional area of 6mm2, and they are buried and concealed (FC) with a plastic conduit (PC) with a pipe diameter of 25mm.
④ The representation of wire transposition requires wire phase sequence transformation, polarity reversal and wire exchange in some cases, which can be represented by the method shown in Figure 11-17. The figure shows that L1 and L3 phase wires are interchanged.
2. Representation of wire connection points
There are T-shaped and ten-shaped wire connection points. For T-shaped connection points, black dots can be added or not, as shown in Figure 11-18(a); for ten-shaped connection points, if the cross wires are not electrically connected, no black dots will be added at the intersection, as shown in Figure 11-18(b). If the cross wires are electrically connected, black dots should be added at the intersection, as shown in Figure 11-18(c).
3. Wire connection relationship representation
There are continuous representation and interrupt representation for the connection relationship of wires.
① The continuous representation of wire connection means that when multiple wires are connected, either multi-wire or single-wire can be used, as shown in Figure 11-19. Representing wire connections as single lines keeps electrical diagrams simple and clear. Common single-wire connections are shown in Figure 11-20.
② The interruption of wire connection indicates that if the wire needs to pass through many graphic symbols, or the wire on one drawing is to be connected to another drawing, in these cases, the interruption method can be used to represent the wire connection. The interruption representation of wire connection is shown in Figure 11-21. Figure 11-21(a) uses the same mark at the wire interruption to indicate the wire connection relationship, and Figure 11-21(b) uses the connection target mark at the wire interruption to indicate the wire connection relationship.
