GB 50169-2016 English PDF

GB 50169-2016: Code for construction and acceptance of grounding connection electric equipment installation engineering
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GB 50169-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC
P GB 50169-2016
Code for construction and acceptance of grounding
connection electric equipment installation engineering
ISSUED ON. AUGUST 18, 2016
IMPLEMENTED ON. APRIL 1, 2017
Jointly issued by. Ministry of Housing and Urban-Rural Development of
the PRC;
General Administration of Quality Supervision,
Inspection and Quarantine of the PRC.
Table of Contents
1 General provisions ... 7 
2 Terms ... 8 
3 Basic requirements ... 10 
4 Grounding of electric equipment ... 12 
4.1 Selection of grounding connection ... 12 
4.2 Laying of grounding connection ... 15 
4.3 Join of grounding electrode (conductor) ... 19 
4.4 Reducing resistance of grounding connection ... 22 
4.5 Grounding of wind turbines and photovoltaic power station ... 23 
4.6 Grounding of air-termination system ... 25 
4.7 Grounding of transmission poles and towers ... 26 
4.8 Grounding of main control building, dispatching building and communication
station ... 28 
4.9 Grounding of relaying protection and security automatic equipment ... 30 
4.10 Grounding of metal jacket of power cable ... 32 
4.11 Grounding of distribution electric equipment ... 32 
4.12 Grounding of structures electric equipment ... 33 
4.13 Grounding of portable and mobile appliances ... 34 
4.14 Grounding against lightning induction and static electricity ... 35 
5 Engineering succession and acceptance ... 37 
Explanation of wording in this code ... 38 
Lists of quoted standards ... 39 
1 General provisions
1.0.1 To ensure the construction quality of grounding connection electric
equipment installation engineering, promote the improvement of technical level
of engineering construction, and to ensure the safe operation of grounding
connection, this Code is developed.
1.0.2 This Code is applicable to the construction and acceptance of grounding
connection electric equipment installation engineering, and not to the
construction and acceptance of high voltage DC power transmission grounding
electrode.
1.0.3 The construction and acceptance of grounding connection shall, in
addition to complying with this Code, comply with the current relevant national
standards.
2 Terms
2.0.1 Grounding electrode
Metal conductors buried in the ground and in direct contact with the earth are
called grounding electrodes. They are classified into horizontal grounding
electrodes and vertical grounding electrodes.
2.0.2 Natural grounding electrode
Various metal components, metal well pipes, foundations of reinforced concrete
buildings, metal pipelines and equipment in direct contact with the earth which
can be utilized for grounding.
2.0.3 Air-termination system
The generic term of devices for accepting lightning stroke, including lightning
rod, lightning belt, lightning conductor, lightning protection net, metal roofing,
and metal components, etc..
2.0.4 Grounding conductor
A metal conductor which is used to connect the grounding terminal of electric
equipment and air-termination system to the grounding electrode and does not
carry current under normal conditions.
2.0.5 Grounding connection
The sum of grounding electrode and grounding conductor.
2.0.6 Grounded
USE grounding conductor to connect the electric equipment, facilities,
overvoltage protective devices of power systems or structures to the grounding
electrode.
2.0.7 Grounding impedance
The impedance between a given point and a reference point of systems,
devices, or equipment at a given frequency.
2.0.8 Ground resistance
The resistive component of grounding impedance, which is power frequency
ground resistance at the power frequency.
2.0.9 Neutral line
3 Basic requirements
3.0.1 The installation of grounding connection shall be carried out by the
engineering construction organization in accordance with the approved design
documents.
3.0.2 When adopting new techniques, new technologies, and new materials,
they shall be tested and verified with national qualification.
3.0.3 The installation of grounding connection shall be in accordance with the
construction of the construction engineering. Before covering concealed
portions, related organizations shall make inspections and acceptances and
form records.
3.0.4 The following metal parts of electric equipment must be grounded.
1 Metal base, framework, shell, and transmission of electric equipment.
2 Metal base and shell for portable or mobile electric equipment.
3 Metal boxes of box-type substation.
4 Secondary winding of mutual inductor.
5 The panel (cabinet, box) for power distribution, control, and
protection, and the metal framework and base of console.
6 Metal jacket, connector box, terminals, and metal protection tube of
power cable, and shielding layer of secondary cable.
7 Cable bridges, bearers, and derricks.
8 Substation (converter station) framework, bracket.
9 Power line pole and tower with overhead ground wire or electric
equipment.
10 Metal barriers of power distribution equipment.
11 Metal shell for electric heating equipment.
3.0.5 The DC system grounding connection which needs to be grounded shall
meet the following requirements.
1 The grounding conductor which can form a closed loop with the ground
and often flows through current shall be laid along the insulating padding
plate; and shall not be metal-connected with metal pipelines, structures,
4 Grounding of electric equipment
4.1 Selection of grounding connection
4.1.1 Various grounding connections utilize natural grounding electrodes
directly buried in the ground or in the water. The following natural grounding
electrodes can be utilized.
1 Metal pipelines buried in the ground, but do not include pipelines which
transport combustible or explosive materials.
2 Metal well pipes.
3 The metal structure of a building which has a reliable join to the earth.
4 Metal pipes, piles, and foundation layer rebar meshes for hydraulic
structures and other structures located in water or moist soil environments.
4.1.2 The grounding conductor of the AC electric equipment can be grounded
using the following grounding electrodes.
1 Metal structure, beams, and columns of buildings.
2 The runway, corridors, platforms of production cranes, framework of cranes
and lifts, steel beams for transporting belt, framework of electric
precipitators, and other metal structures.
4.1.3 Grounding connections such as power plants and substations, in addition
to natural grounding electrodes, shall also be laid with a grounding grid which
consists mainly of horizontal artificial grounding electrodes. A measuring well
which separates the natural grounding electrode from the artificial grounding
electrode shall also be provided. For substations and power distribution stations
of 3kV ~ 10kV, when the rebar mesh in the structure foundation is used as the
grounding electrode and the ground resistance meets the specified value, no
artificial grounding is required.
4.1.4 The selection of grounding connection material shall meet the following
requirements.
1 Except for temporary grounding connections, the grounding connection,
when using steel, shall be hot dip galvanizing. The horizontally laid
connection shall be round steel and flat steel of hot dip galvanizing. The
vertically laid connection shall be angle steel, steel pipe, or round steel of
hot dip galvanizing.
2 When flat copper strip, copper stranded conductor, copper rod, copper
existing building (structure), steel pipes or other solid protective sheaths shall
be installed. Anti-corrosion measures shall be taken for chemically corroded
parts. At places where the grounding conductor passes through the newly-built
structure, it can bypass the foundation or pass underneath; and shall not be
broken or poured into the concrete.
4.2.4 When the grounding connection is composed of a plurality of sub-
grounding connection parts, according to the design requirements, the
disconnecting clip for easy separation shall be set. The joints of natural
grounding electrodes and artificial grounding electrodes, the grounding
conductor of incoming-outgoing line framework, etc. shall be provided with
disconnecting clips. The disconnecting clip shall be protected. When the
grounding grid is expanded, the join of the new and old grounding grids shall
be done through multiple points of grounding well.
4.2.5 The backfill of grounding connection shall meet the following requirements.
1 There shall be no stones and construction waste, etc. in the backfill. The
soil taken outside shall not be highly corrosive. When backfilling, it shall be
compacted in layers. For backfilling of outdoor grounding trench, an anti-
setting layer with a height of 100mm ~ 300mm shall be provided.
2 When laying grounding electrodes in mountainous rocky areas or in the
earth ditch of earthy sections with high resistivity, the backfill shall not be
less than 100mm thick pure soil cushion; and pure soil shall be compacted
in layers for backfilling.
4.2.6 The installation of exposed laying grounding conductor shall be in
accordance with the following requirements.
1 The installation position of the grounding conductor shall be reasonable,
easy to check, and shall not hinder equipment maintenance and operation
inspection.
2 The join of the grounding conductor shall be reliable. There shall be no
problems such as reduced cross section of grounding conductor,
weakened strength, or rust due to processing.
3 The distance between the grounding conductor supports shall be 0.5m ~
1.5m in horizontal straight-line part, 1.5m ~ 3m in vertical part, and 0.3m ~
0.5m in the turning part.
4 The grounding conductor shall be laid horizontally or vertically; or can be
laid in parallel with the inclined structure of building. In the straight-line
segment, there shall be no ups and downs and bending.
6) Grounding busbar and grounding terminal of gas-insulated metal
enclosed switchgear.
7) Grounding terminal of lightning arrester, lightning rod, and lightning
conductor.
2 When the electric equipment is not grounded by a specially laid grounding
conductor, the following provisions shall be complied with.
1) The grounding conductor of electric equipment shall utilize metal
components, steel bars of ordinary reinforced concrete components,
threaded steel pipes, etc.;
2) Grounding conductors for low voltage electric equipment for operation,
measurement, and signaling can utilize permanent metal pipelines, but
metal pipelines of combustible liquids, combustible or explosive gases
shall not be utilized;
3) When using the materials listed in Items 1) and 2) of this Clause as
grounding conductors, it shall ensure that the full length is an intact
electric pathway. When using the metal components in series as
grounding conductors, the metal components shall be welded with steel
with a cross-sectional area of not less than 100mm2.
3 The neutral point with a voltage class of 110kV and above and required for
direct grounding for operation shall have two grounding conductors
connected to different grounding points of grounding grid. The specification
for each of them shall meet the design requirements.
4 The iron core, clamp of transformer shall be reliably connected to the
grounding grid; and shall be easy to operate to monitor the circulation in
the grounding conductor.
5 Important electric equipment and equipment framework of 110kV and
above shall be provided with two grounding conductors. Each shall meet
the design requirements. The erection for connecting lead shall be
convenient for regular inspection and testing.
6 The basic steel of row-by-row installation plates and cabinets and the
grounding busbar of row-by-row switch cabinets shall have a clear and
reliable grounding of not less than two points.
7 The mechanism case, control cabinet (box), junction box, terminal box, etc.
of electric equipment, as well as the cable metal protection tube (tray),
shall be grounded clearly and reliably.
between them.
4.3.10 The grounding of GIS in power plants and substations shall comply with
the requirements of design and manufacturer, and shall comply with the
following provisions.
1 Each grounding busbar on the GIS base shall, by means of not less than
4 grounding conductors separately set at both ends thereof, be connected
to the grounding connection of the power plant or substation. The
grounding conductor shall be connected to the ring grounding busbar of
the GIS area. When the grounding busbar is long, another grounding
conductor shall be provided in the middle part and connected to the
grounding grid.
2 The grounding conductor and GIS grounding busbar shall be bolt-
connected.
3 When the GIS is installed in the open air or installed on the indoor ground
which is in direct contact with the soil, the joints between the grounding
switch, the special grounding terminal of metal oxide arrester and the GIS
grounding busbar shall be equipped with concentrated grounding
connection.
4 The ring grounding busbar shall be laid in the GIS room. The parts of the
indoor equipment to be grounded shall, in the shortest path, be connected
to the ring grounding busbar. When the GIS is placed on indoor floor, the
rebars in the reinforced concrete floor under its base shall be welded into
a net and connected to the ring grounding busbar.
5 Jumper connections shall be made between flange pieces; and a good
electric pathway shall be guaranteed. When the manufacturer uses basin-
type insulator and flange joint with metal grounding connection to ensure
electric conduction, there is no need for jumper connections between the
flange pieces.
4.3.11 The grounding of motor shall comply with the following requirements.
1 When the cross-sectional area of motor phase line is less than 25mm2, the
cross-sectional area of grounding conductor shall be equal to that of the
ph...