1. Switching Device Symbols (8 items)
| Symbol | Meaning | Symbol | Meaning |
|---|---|---|---|
| QS | Isolating switch | QF | Circuit breaker |
| QL | Load-break switch | QA | Field-discharge switch |
| KM | Contactor | KA | Relay |
| KT | Time relay | FR | Thermal overload relay |
2. Protection and Measurement Symbols (8 items)
| Symbol | Meaning | Symbol | Meaning |
|---|---|---|---|
| FU | Fuse | SPD | Surge protective device |
| RCD/RC | Ground fault protection | TA | Current transformer |
| TV | Voltage transformer | PA | Ammeter |
| PV | Voltmeter | PJ | Electricity meter |
3. Busbar and Conductor Symbols (8 items)
| Symbol | Meaning | Symbol | Meaning |
|---|---|---|---|
| WB | Busbar | WL | Line |
| L1/L2/L3 | Three-phase | N | Neutral conductor |
| PE | Protective ground | PEN | Protective neutral |
| +/- | DC | ~ | AC |
4. Control and Signal Symbols (8 items)
| Symbol | Meaning | Symbol | Meaning |
|---|---|---|---|
| SB | Pushbutton | SA | Selector switch |
| HL | Indicator light | HA | Audible alarm |
| HG | Green light | HR | Red light |
| HY | Yellow light | HW | White light |
5. Symbol Mnemonics (3 sentences)
Q-prefixed devices are all switches(QS/QF/QM);K-prefixed devices are all controls(KM/KA/KT);T-prefixed devices are all transformers(TA/TV/T). Memorize these three rules and you have covered more than half of the symbols.
FAQ FAQ
Do I have to memorize the symbol table?
The 32 high-frequency ones are worth memorizing; look up the rest in GB/T 6988.
What is the difference between QS and QF?
QS = disconnector (isolation only, cannot be operated under load); QF = circuit breaker (switching under load + protection).
How do I read the TA ratio?
For example, 600/5 means 600A primary and 5A secondary; multiply the meter reading by 120 to get the actual current.
What is SPD?
Surge Protective Device — protects against lightning-induced overvoltage and must be installed on the incoming side of a distribution box.
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