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SLDResources / SLD symbolsUpdated 29 Oct 2026

Relay, arrester and meter symbols

Protection and metering devices watch the system rather than carry its power: relays that trip breakers, surge arresters that clamp overvoltages, grounding and the meters that measure current, voltage and energy.

SymbolANSI / IEEEIEC 60617What it is
Protective relayS00327A protective relay measures current and voltage from the CTs and VTs and trips the breaker when it sees a fault.
Surge arresterS00373A surge arrester conducts to earth when the voltage rises above a set level, clamping lightning and switching surges to protect the insulation of equipment.
GroundS00200The ground or earth symbol shows a connection to the earthing system, for example a solidly earthed transformer neutral.
Neutral grounding resistorA resistor between a transformer or generator neutral and earth, which limits the current of an earth fault.
AmmeterS00910An ammeter shows the current in a circuit, usually fed from a current transformer.
VoltmeterS00910A voltmeter shows the voltage, usually fed from a voltage transformer.
Energy meterS00912An energy meter counts the energy that has passed, in kWh, for billing or monitoring.

Protection and metering: ANSI and IEC

Protection is where the standards differ most. ANSI one-lines show a relay as a circle with its device numbers, such as 50/51 or 87T. IEC drawings show a measuring relay as a box (S00327) with the quantity and its limit, such as I> or U<.

Grounds, ammeters and voltmeters are drawn the same way in both. Energy meters are a circle on ANSI drawings and a rectangle in IEC.

Frequently asked questions

Which protection and metering appear on a single line diagram?

This legend covers protective relay, surge arrester, ground, neutral grounding resistor, ammeter, voltmeter, energy meter. Project legends may add more.

Are these symbols different in IEC and ANSI?

4 of the 7 are drawn differently. Each symbol page shows both forms side by side.

Can I download these symbols?

Yes. Each symbol page has free SVG files, and the hub has printable PDF charts.

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