1.0.1 This code is formulated with a view to implementing the national laws and regulations on safety in production, ensuring the electricity safety on construction site, preventing electric shock and electrical fire accidents, thus promoting the development of construction.
1.0.2 This code is applicable to the design, installation, use, maintenance and dismantling of 220/380V three-phase four-wire low voltage power system with directly grounded neutral-point in temporary electrification engineering of constructed, renovated and extended industrial and civil buildings and municipal infrastructure construction site.
1.0.3 The special 220/380V three-phase four-wire low voltage power system with directly grounded neutral-point in temporary electrification on construction site must meet the following requirements:
1 three-stage distribution system is adopted;
2 TN-S neutral protection system is adopted;
3 two-level leakage protection system is adopted.
1.0.4 In addition to this code, the temporary electrification on construction site shall also meet the requirements of the current relevant compulsory standards of the nation.
2 Terms and codes
2.1 Terms
2.1.1 low voltage
AC rated voltage of 1kV and below
2.1.2 high voltage
AC rated voltage above 1kV
2.1.3 external circuit
electric power circuit other than distribution circuit for temporary electrification on construction site
2.1.4 construction site with electrostatic field
construction site with electrostatic field harmful to human body and environment generated due to friction, extrusion, induction and poor ground connection
2.1.5 source of powerful electromagnetic wave
electromagnetic radiator with radiation wave generating hazardous voltage to ground by inducing on mechanical equipment on construction site
2.1.6 ground connection
connection between part of the equipment and the ground to form a conductive path
2.1.7 working ground connection
ground connection for circuit or equipment to meet the operation requirements, such as ground connection of low voltage neutral point of transformer and neutral point of generator
2.1.8 iterative ground connection
ground connection where the ground line of an equipment is connected to ground via grounding devices in one or more points
2.1.9 earth lead
metal conductor in direct contact with the ground by being buried in the ground
2.1.10 manual grounding
earth lead buried in the ground manually
2.1.11 natural grounding
various members buried in the ground before construction, which may be used as earth lead, such as steel bar structure for reinforced concrete foundation, metal shaft pipe, metal pipeline (non-gas), etc.
2.1.12 ground line
metal conductor (including connecting bolt) used to connect metal structure of equipment and earth lead
2.1.13 grounding device
assembly of earth lead and ground line
2.1.14 ground resistance
resistance of grounding device to ground, which is the sum of ground line resistance, earth lead resistance, contact resistance between earth lead and soil, and drift resistance of soil.
It may be approximately by calculation or measurement, which is equal to the ratio of the voltage of grounding device to ground to the current flowing into ground through grounding device
2.1.15 power frequency ground resistance
ground resistance calculated according to the power frequency current flowing into the ground through grounding device
2.1.16 shock ground resistance
ground resistance calculated according to the impulse current (simulated lightning current) flowing into the ground through grounding device
2.1.17 electric connect
conductor-to-conductor connection that provides electrical path directly (with contact resistance close to zero)
2.1.18 live-part
conductor or conductive part to be electrified for normal use, including neutral conductor (neutral line), excluding protective conductor (protective null line or guard line), and conventionally excluding wire (conductor) combining working null line with protective null line
2.1.19 exposed conductive part
accessible conductive part of electrical equipment, which is uncharged under normal conditions, but may be live under fault conditions
2.1.20 electric shock
current flowing through the human body or animal to cause pathophysiological effect
2.1.21 direct contact
contact of person or livestock with live-part
2.1.22 indirect contact
contact of person or livestock with exposed conductive part which has become live under fault conditions
2.1.23 distribution box
power distribution device specially used for distributing power, including general distribution box and sub distribution box, which are collectively called distribution box unless otherwise specified
2.1.24 switch box
general name of the final-stage distribution device which may also be used as the control device of electric equipment
2.1.25 isolating transformer
transformer with input winding and output winding electrically isolated from each other, so as to avoid the danger caused by accidentally touching live-part (or metal components which may be live due to insulation damage) and the ground at the same time
2.1.26 safety isolating transformer
isolating transformer for providing power supply for safety extra-low voltage circuit.
Its input winding and output winding are at least electrically isolated at a degree equivalent to double insulation or reinforced insulation.
It is specially designed to provide safety extra-low voltage for distribution circuits, tools or other equipment
