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IEC 60255-22-3: Protection Relay Radiated Immunity — Can a Walkie-Talkie Trip Your Protection?
A 5W Walkie-Talkie at 1m Generates ~30 V/m — Right at the Edge of Protection Relay Immunity
IEC 60255-22-3:2007 specifies radiated electromagnetic field immunity tests for measuring relays and protection equipment. A handheld radio (5W/430MHz) at 1m generates ~20–30 V/m — right at the limit of the most stringent Level 4 (30 V/m).
| Immunity Level | Test Field | Typical Environment |
|---|---|---|
| Level 2 | 3 V/m | Substation control room (shielded) |
| Level 3 | 10 V/m | Substation switchyard |
| Level 4 | 30 V/m | Inside GIS, close-proximity radio use |
The RF rectification mechanism: Protection device CT/VT input stages contain analog amplifiers and ADC inputs. These semiconductor devices can exhibit RF rectification under high-frequency electromagnetic fields — the RF signal is rectified by PN junctions, producing a DC offset voltage superimposed on real current/voltage measurements. Even though the RF carrier (430 MHz) is far above the relay bandwidth (typically <1 kHz), the rectified DC component enters the signal processing path.
TN Lab — Before keying that radio near a protection panel, confirm your relays passed Level 4 (30 V/m) radiated immunity.
