IEC TS 62738-2018 pdf free download

IEC TS 62738-2018 pdf free download.Ground-mounted photovoltaic power plants – Design guidelines and recommendations.
This clause discusses PV array earthing. control, layout and mechanical configurations found in PV power plants.
5.2 Earthing configurations
5.2.1 General
Considerations for earthing a PV array are addressed in this clause. The requirements of manufacturers of PV modules and manufacturers of power conversion equipment (PCE) to which the PV array is connected shall be taken into account in determining the allowable or required system earthing arrangements.
5.2.2 Use of un-earthed d.c. circuits
When installed with a residual current monitoring system andlor with isolation resistance detection, PV systems with un-earthed d.c. arrays offer robust earth fault protection. A failure in any cable (positive or negative), causing a short circuit from the cable to an earthed surface results only in a shift of the array voltage reference from a floating state to an earth-referenced state. It does not create a closed circuit for fault current to flow, and therefore does not present a fire hazard. Un-earthed d.c. circuits are also a requirement where simple separation or isolation from an earthed a.c. system Is not provided by the inverter or a transformer.
5.2.3 Use of high-ohmic earthed d.c. circuits
High-ohmic earthed systems may be used in plants where operators want to achieve some of the benefits of an un-earthed or floating system while still maintaining an array voltage reference to ground to prevent potential induced degradation (PID). Resistance values are set to limit fault current to a target level (below 300 mA for example) in case of a hard fault occurring on the unreferenced d.c. circuit pole. This significantly reduces the arcing and fire causing currents that can occur with grounded systems, specifically those without supplemental high-sensitive ground fault detection.
5.2.4 Use of functionally earthed d.c. circuits
Protective earthing of any of the conductors of the PV array is not permitted. Earthing of one of the conductors of the PV array for functional reasons is allowed through internal connections inherent in the PCE or other earth fault protective device if designed and qualified for this configuration. Functionally earthed d.c. array based systems are sometimes used to prevent module PID.IEC TS 62738 pdf download.