or insulated as to the standard of the mains voltage. UK Reduced low voltage (RLV) The IET / BSI (BS 7671) also define Reduced Low Voltage (RLV) which can be either single-phase or three-phase AC This system has been used for many years on construction sites, in both single- and three-phase configurations. The single-phase voltage is 110V a.c. though having a "centre tapped Earth" reducing the voltage to earth to 55V AC. The three-phase system is 110V phase-to-phase and 63V to neutral / earth. This system voltage is slightly above the ELV limit, but is still very commonly used for cord-powered hand tools and temporary lighting in hazardous areas. As it is transformer-derived, the exposed voltage during an earth fault is depressed below the ELV level. Stand-alone power systems Cabling for ELV systems, such as in remote-area power systems (RAPS), is designed to minimise energy losses while maximising safety. Lower voltages require a higher current for the same power. The higher current results in greater resistive losses in the cabling. Cable sizing must therefore consider maximum demand, voltage drop over the cable, and current-carrying capacity. Voltage drop is usually the main factor considered, but current-carrying capacity is as important when considering short, high-current runs such as between a battery bank and inverter. Arcing is a risk in DC ELV systems, and some fuse types which can cause undesired arcing include semi-enclosed, rewireable and automotive fuse types. Instead high rupturing capacity fuses and appropriately rated circuit breakers are the recommended type for RAPS. Cable termination and connections must be done properly to avoid arcing also, and soldering is not recommended. Regulations Precise definitions of "extra low voltage" are given in applicable wiring regulations in a region. EU According to DIN EN 61140:2016 chapter 4.2 Table 1 (German version of EU standard EN 61140), Extra Low Voltage (≤ 50 V a.c. or ≤ 120 V d.c.) is defined as a sub-category of Low voltage (≤ 1000 V a.c. or ≤ 1500 V d.c.). This is similar to the definition provided in IEC 61140:2016. The European Union directives on the other hand do not define extra-low voltage. The nearest they get to this concept is in the Low Voltage Directive (2014/35/EU), which applies to the range between 50V AC / 75V DC and 1,000V AC / 1,500V DC. The General Product Safety Directive (2001/95/EC) covers consumer goods with a voltage below 50 V