16th Edition (reference only) – NOW superseded by the 17th Edition IEE Regulations.
 chapter 1 The IEE Regulations chapter 2 Installation Requirements and Characteristics chapter 3 Installation Control and Protection chapter 4 Cables, Conduits and Trunking chapter 5 Earthing chapter 6 Circuits chapter 7 Special Installations chapter 8 Testing and Inspection chapter 9 Data cabling and Networks
 Earthing
 5.1 - The earthing principle 5.6 - Protective multiple earthing (PME) 5.2 - Earthing Systems 5.7 - Earthed concentric wiring 5.3 - Earth fault loop impedance 5.8 - Other protection methods 5.4 - Protective conductors 5.9 - Residual current devices (RCDs) 5.10 - Combined functional and protective ---------earthing
 5.6.1 - What is protective multiple earthing? 5.6.2 - Increased fire risk 5.6.3 - Broken neutral conductor 5.6.4 - Special requirements PME-fed installations

5.6.2 - Increased fire risk

As with other systems of earth-fault protection, PME does not prevent a fault occurring, but will ensure that the fault protection device operates quickly when that fault appears. For example, if a fault of 2 Ohms resistance occurs in a 240 V circuit protected by a 20 A semi-enclosed fuse in a system with an earth-fault loop impedance of 6 Ohms, the fault current will be 240/(2 + 6) A = 240/8 A = 30 A. The fuse would not blow unless the circuit were already loaded, when load current would add to fault current. If the circuit were fully loaded with a load current of 20 A, total current would be 50 A and the fuse would blow after about 18 s. During this time, the power produced in the fault would be:

 P = I²R = 30²x6 = 5400W or 5.4kW

This could easily start a fire. If, however, the earth-fault loop impedance were I Ohm, current would be 80 A and the fuse would blow in about 1.6 s and limit the energy in the fault circuit.