AS 3015:2022 – Electrical installations – Extra-low voltagepower supplies and service earthing within telecommunications networks. Low voltage inverters in teleconimunicatlons facilities ConsideratIons
Low voltage inverters In telecommunications facilities are powered by the ELV power system, with an output voltage that is within the LV limits prescribed in AS/NZS 3000.
Inverters may have an a.c. bypass from the main switchboard supply (for maintenance or redundancy). The main risks with locating LV inverters in telecommunications facilities are —
(a) hazardous voltage exposure via LV a.c. faults circulating through the d.c. service earth system, or inelfective touch safeguards to prevent inadvertent contact with live power cunversi(rn equipment (PCE) terminals; and
(b) high current ELV faults circulating through the ac. protective earth system (via the a.c bypass, If installed). RequIrements
The installation of LV inverters shall conform to all of the following:
(a) LV inverters shall conform to the requirements of AS/NZS 3000.
(b) The LV inverter and associated loads shall be installed by an ES3-competent person if — (I) there is exposure to LV hazards when installing ELV cabling;
(ii) the LV inverter and associated loads are not designed as an appliance, refer to AS/NZS 62368.1; and
(iii) there is LV wiring that is hard-wired to the LV inverter or associated loads.
(c) LV inverrers shall include touch-guards regarding live LV terminals and conductors, to mitigate the risk of contact with energized parts to non-ES3 competent persons once the inverter Is Installed in a telecommunications facility.
(d) The following conductive material shall be electrically isolated with a minimum rating of I kV
a.c. from all surrounding building fabric, service earth•based equipment and conductors —
(I) the LV inverter (and rack in which it is mounted, if applicable);
(ii) associated LV output conductors and switchgear:
(iii) associated LV cable support structures; and
(Iv) associated LV powered equipment (and rack In which It is mounted, if applicable).
NOTE I Surrounding building fabric, service earth-based equipment and conductors may include walls, floor, building steel. adiacent equipment racks, and overhead cable trays
The Items below shall be earthed to the LV inverter’s protective earth in accordance with AS/NZS 3000:
(A) Low voltage conductors from the I.V inverter shall conform to the requirements of Clause 4.16.3 and AS/NZS 3000.
(B) The LV inverter’s output shall provide protective earth connections or terminals in accordance with AS/NZS 3000 and AS/NZS 62368.1.
(C) The LV inverter’s chassis and d.c. return terminals shall be bonded to the service earth system. The earth bonding wire shall conform to all of the following:
(I) The route length shall be as short as possible.
(II) The size of the earth bonding wire shall be sized to carry the maximum prospective d.c. fault current. ora minimum cross-sectional area of35 mm2. whichever is greater.
(ill) There shall be a dedicated earth bonding wire between the LV Inverter positive input and service earth bar (SEB) or single point connection (SPC).
(iv) The earth bonding wire shall be clearly and Indelibly labelled to identify its function as a dedicated LV inverter.
NOTE 2 the ELV d.c. side of the LV inverter Installation is considered Isolated d.c. return (DC-I). see Clause Si 2.2.2.
(D) LV inverters and their enclosures/racks shall be dearly labelled with hazardous voltage labels In accordance with AS/NZS 62368.1.
(E) Where there are conductive communications cables between LV-powered equipment (both the LV inverter and connected load) and ELV-powered equipment, the communications ports and communications cabling between devices shall be isolated.
NOTE 3 IEEE 802.3 conforming ethernet ports and CATS/6 cable or fibre optic cabling should meet this requirement.
NOTE 4 Ethernet cables are considered Isolated. RS232, RS4BS and RS422 use earth reference and should be avoided as they may carry currents.
Figure 2.2 illustrates an example of co-location of LV and ELV equipment.