In electrical engineering, low voltage is a relative term, the definition varying by context. Different definitions are used in electric power transmission and distribution compared with electronics design. Electrical safety codes define "low voltage" circuits that are exempt from the protection required at higher voltages. These definitions vary by country and specific codes or regulations.
a May depend on the applicable standard used.
The International Electrotechnical Commission (IEC) Standard IEC 61140:2016 defines Low voltage as 0 to 1000 V AC RMS or 0 to 1500 V DC[1] Other standards such as IEC 60038 defines supply system low voltage as voltage in the range 50 to 1000 V AC or 120 to 1500 V DC in IEC Standard Voltages[2] which defines power distribution system voltages around the world.
In electrical power systems low voltage most commonly refers to the mains voltages as used by domestic and light industrial and commercial consumers. "Low voltage" in this context still presents a risk of electric shock, but only a minor risk of electric arcs through the air.
exceeding 50 V ac or 120 V ripple-free dc. but not exceeding 1000 V ac or 1500 V dc between conductors, or 600 V ac or 900 V dc between conductors and earth.
The ripple-free direct current requirement only applies to 120 V dc, not to any dc voltage above that. For example, a direct current that is exceeding 1500 V dc during voltage fluctuations it is not categorized as low-voltage.
In electrical power distribution, the US National Electrical Code (NEC), NFPA 70, article 725 (2005), defines low distribution system voltage (LDSV) as 0 to 49 V..
El artículo 6.4.1.1 [4] de la norma NFPA 79 define la distribución de voltaje extra bajo protegido (PELV) como un voltaje nominal de 30 V rms o 60 V CC sin ondulaciones para ubicaciones secas, y 6 Vrms o 15 V CC en todos los demás casos. .
La norma NFPA 70E, artículo 130, edición 2021, [5] omite los conductores eléctricos energizados y las partes de circuitos que funcionan a menos de 50 V de sus requisitos de seguridad para trabajos que involucran riesgos eléctricos cuando no se puede establecer una condición de trabajo eléctricamente segura.
La norma UL 508A, artículo 43 (tabla 43.1) define de 0 a 20 V pico/5 A o de 20,1 a 42,4 V pico/100 VA como circuitos de energía limitada de bajo voltaje (LVLE).