24-08-2012, 04:07 PM
Electrical Protection and Earthing
Electrical Protection.pdf (Size: 161.19 KB / Downloads: 371)
Purpose
This Technical Reference is intended to provide a framework for DPI officers to assess coal
operation arrangements for electrical protection and earthing as part of the Electrical
Engineering Management Plan. It can also be used by coal operators as guidance material
for implementing, managing or reviewing their electrical protection and earthing
arrangements.
This Technical Reference describes acceptable arrangements that can be tailored to suit the
particular needs of an operation. It identifies some of the core hazards, risks and control
measures relevant to electrical circuitry. It is intended to protect the safety of workers, others
in the workplace and property.
Who is affected by this Technical Reference?
All operators of coal operations in New South Wales where there is an electrical installation
that is connected to the network of an electricity supply authority or where there is an
electrical installation with the source of electricity is a stand-alone power system such as
photovoltaic cells (solar panels), wind or water turbines, diesel or petrol generators.
All individuals, unincorporated businesses and corporations involved in utilizing electricity at
NSW coal operations including those who design, install and implement electrical safety
systems and those who commission, test, operate and maintain the systems
Electrical Protection
Although this statement relates to fuses it is obvious that it has some resonance for all types
of electrical protection and methods of opening circuits – without electrical protection
systems electricity would be far too dangerous for use in the work place.
All electrical circuits have a basic requirement that the conductors of the electric current be
of adequate size to carry normal and fault current loads without being damaged or degraded
by excessive heating. Furthermore all electric current conductors are required to be
insulated to prevent unwanted current flow from one conductor to another or from one or
more conductors to earth.
Philosophy
For a safe electrical distribution system the design of equipment (including cables) the
earthing system and the electrical protection must be integrated in a holistic manner.
Underground mines have unique challenges and the holistic design is underpinned by the
basic philosophy of the first fault must be a low energy earth fault. The basic philosophy of
the first fault being a low energy earth fault is worthy of applying to surface installations,
especially for mining machinery fed by flexible reeling, trailing or feeder cables. This has
implications for equipment design, especially cables, method of earthing and protection
devices.