The symbols on the primary system diagram of the distribution cabinet represent meanings

The primary system diagram of the distribution cabinet contains a variety of symbols. The following are some common symbols and their representative meanings:

Power Supply and Busbars

- **Three-phase Alternating Current Power Supply**: It is usually represented by three diagonal lines inside a circle, or by a rectangle with three incoming lines, representing the input of the three-phase alternating current power supply.

- **Busbars**: Represented by thick solid lines, usually marked with the specifications and numbers of the busbars. For example, "TMY - 3[2(125×10)] + 1(125×10)" indicates a copper busbar, three phases, each phase consisting of two copper bars of 125×10, and the neutral line is a copper bar of 125×10.

Switching Electrical Appliances

- **Circuit Breaker**: Generally represented by a rectangle with one or more vertical lines in the middle. Different types of circuit breakers may have different detailed markings. For example, the symbol of a frame circuit breaker may have some additional lines outside the rectangle to represent its operating mechanism, etc.; the symbol of a molded case circuit breaker is relatively simple, which is just a rectangle plus vertical lines.

- **Isolating Switch**: Usually represented by a vertical line with one or more breakpoints in the middle. There are symbols similar to knife switches at the breakpoints, vividly indicating that it can disconnect the circuit and make the circuit have obvious breakpoints.

- **Load Switch**: The symbol is somewhat similar to that of the isolating switch, but there are usually some other markings on or beside the vertical line, such as a small circle or a diagonal line, indicating that it can connect and disconnect the load current under normal conditions.

 Protective Electrical Appliances

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- **Fuse**: Generally represented by a rectangle or a circle with one or more diagonal lines in the middle, and the diagonal lines represent the fuse element. The symbols of high-voltage fuses and low-voltage fuses may be different in details. The symbol of a high-voltage fuse may have some special markings to indicate its voltage level and other information.

- **Lightning Arrester**: Usually represented by a symbol similar to a lightning bolt, indicating that it is used to protect electrical equipment from the damage of lightning overvoltage and switching overvoltage.

- **Residual Current Device (RCD)**: The symbol is generally a circle or a rectangle with an arrow, and the arrow indicates the direction of the leakage current. Some symbols will also be marked with words such as "RCD" beside it.

Measuring Electrical Appliances

- **Current Transformer**: Represented by a circle or a rectangle with one or more diagonal lines in the middle, and the diagonal lines represent the iron core. The transformation ratio is usually marked beside it. For example, "1000/5A" means that when the primary side current is 1000A, the secondary side current is 5A.

- **Voltage Transformer**: The symbol is similar to that of the current transformer, but there are usually some different markings inside the circle or rectangle, such as using a dotted line to represent the iron core, etc. The transformation ratio and voltage level and other information will also be marked beside it.

- **Ammeter, Voltmeter**: The symbol of the ammeter is a circle with the letter "A" inside, and the symbol of the voltmeter is a circle with the letter "V" inside.

 Other Components

- **Capacitor**: Represented by a parallelogram, and sometimes information such as capacitance value and withstand voltage value will be marked beside it.

- **Reactor**: Usually represented by the symbol of a coil, that is, one or more circular or rectangular coils, and information such as inductance value may be marked beside it.

- **Cable**: Represented by a line with an arrow, and the arrow indicates the direction of the cable. Information such as the cable model, specifications and length may be marked on the line. For example, "YJV - 3×185 + 1×95 - 100m" indicates a cross-linked polyethylene insulated polyvinyl chloride sheathed copper core cable, three phases, each phase 185 square millimeters, the neutral line 95 square millimeters, and the length is 100 meters.