http://www.iee.org/Publish/WireRegs/WiringMatters/Documents/Issue19/2006_19_summer_wiring_matters_understanding_rcds.pdf
http://www.iee.org/Publish/WireRegs/WiringMatters/Documents/Issue15/2005_15_summer_wiring_matters_inspection_and_testing_rcds.pdf
NtoEWhy RCDs trip on non ergised circuits with Neutral to Earth faults