空间的辐射电磁场（EMI）主要是由电力网络、电气设备的暂态过程、雷电、无线电广播、电视、雷达、高频感应加热设备等产生的，通常称为辐射干扰，其分布极为复杂。若PLC系统置于所射频场内，就回收到辐射干扰，其影响主要通过两条路径：一是直接对PLC内部的辐射，由电路感应产生干扰；而是对PLC通信内网络的辐射，由通信线路的感应引入干扰。辐射干扰与现场设备布置及设备所产生的电磁场大小，特别是频率有关，一般通过设置屏蔽电缆和PLC局部屏蔽及高压泄放元件进行保护。
2.2.2来自系统外引线的干扰
主要通过电源和信号线引入，通常称为传导干扰。这种干扰在我国工业现场较严重。
（1）来自电源的干扰
Ingersoll Rand Centac 2C40M4 1973 Reb. 11,000 hrs
Allen Bradley AB 1336S-B250-AN-EN4-L6 250 HP VS Drive
Square D Transformer 2500/3333 kVA 12470/7200 480/277
Elliott Turbocharger Turbo Blower L-402 1L1 KVS Rebuilt
Allen Bradley AB 1336S-BX250-AX-EN4-L6 250/300 HP Drive
Square D 2500 Amp 2500A SED362500LSGES5D4 SED362500LSG
ABB MEGAMAX SACE F4S F4S3200 F4 3200 Amp 3200A 690V
Westinghouse Advantage W201KHCF Sz. 6 Reverse Contactor
Western Gear Increaser 4113-IHS High Speed Unit 9000 HP
General Electric DC Motor 250 HP 1750/1900 RPM CD504AT
Square D QED 4x NEF Breaker Panel 4000 Amp A 4W Ground
Square D NE NEF361200LSG 1200 Amp 1200A A LSIG
Square D NE NEF361200LSG 1200 Amp 1200A A LSIG
GE AKR-10D-125 5000 A Amp Breaker MVT Plus Trip 635 V
ASCO 1200 Amp G9623120097XC Transfer Switch 480/277 4W
Square D Enclosed 48 Soft Start Altistart 8839 400 HP H
Square D QED Breaker Panel 2x PEF361600LS 1600 Amp A 4W
Square D NE NEF36800LSG 800 Amp 800A A LSIG
Westinghouse Outside Outdoor Substation Walk-In for DSL
Square D 3000 Amp 3000A SED363000LIGES508 SED363000LIG
Custom Dual Shaft Unwind Stand Adjustable Tension 90″
Cutler-Hammer Magnum DS MDSC5N 5000 Amp Digitrip 520M
Square D QED BPO364 Bolt Loc Panel 4000 Amp A 4W Ground
Square D Masterpact Breaker MP25H1 2500 Amp 2500A A
Square D QED I-Line SwitchBoard 5000 Amp 5000A 480Y/277
Grate Wash Pump Control Panel Starter Helix 400A 480V
Cutler Hammer CH Advantage W240M6CFC Sz Size 6 MCCB
Square D New EZ Meter Pak EZM11600CB 3R Meter Center
Bell Gossett Plate Frame Heat Exchanger GPX 807 1057 sq
Square D QED BPO364 Bolt Loc Switch Panel 4000 Amp A 4W
Cutler Hammer CRD CRD320T33W 2000A 2000Amp 2000 A
Digitrip 310 TRIP UNIT RES2000LS W/AUX AND SHUNT TRIPS
Toshiba VFAS14132KPCA1 Inverter VF-AS1 VS Drive 200 HP
Square D QED 2x NEF Breaker Panel 4000 Amp A 4W Ground
General Electric A-425-13 Gear Increaser /Reducer 86 HP
NWL Transformer 260 kVA 460 500/24000 27000 260kVA oil
Fanuc A06B-6105-H002 6 Axis Servo Amplifier REM
GE Limitamp Multilin Starter 1250 HP 4160 V CR7160B118G
ITE GOULD BBC ABB K3000 K 3000 3000A Air Breaker LS
