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This code is revised based on GB 50169-2006 Code for Construction and Acceptance of Grounding Connection - Electric Equipment Installation Engineering by China Electric Power Research Institute and the organizations concerned according to the requirements of Notice on Printing Development and Revision Plan for Engineering Construction Standards and Codes in 2013 (JIANBIAO [2013] No.6).
This code is finalized by the drafting group through review based on extensive investigation, careful summarization of practical experience, wide solicitation for opinions and multiple discussions and modifications during the revising process.
This code consists of 5 chapters, including General Provisions, Terms, Basic Requirements, Grounding of Electric Equipment and Engineering Succession and Acceptance.
The following contents are added with respect to the previous code:
1. General provisions;
2. Reducing resistance of grounding connection;
3. Grounding of wind turbines and photovoltaic power station;
4. Grounding of relaying protection and security automatic equipment;
5. Grounding against lightning induction and static electricity.
The provisions printed in bold type in this code are compulsory and must be implemented strictly.
The Ministry of Housing and Urban-Rural Development is in charge of the administration of this code and the explanation of the compulsory provisions; the China Electricity Council is responsible for routine management; the China Electric Power Research Institute is responsible for the explanation of specific technical contents. All relevant organizations are kindly requested to sum up experiences and accumulate information according to engineering practices during the process of implementing this code. The relevant opinions and advices, whenever necessary, can be posted to China Electric Power Research Institute (Address: No. 33, South Binhe Rd., Xicheng District, Beijing, 100055) for future reference in revision.
Contents
1 General Provisions 1
2 Terms 1
3 Basic Requirements 3
4 Grounding of Electric Equipment 4
4.1 Selection of Grounding Connection 4
4.2 Laying of Grounding Connection 7
4.3 Join of Grounding Electrode (Conductor) 11
4.4 Reducing Resistance of Grounding Connection 13
4.5 Grounding of Wind Turbines and Photovoltaic Power Station 15
4.6 Grounding of Air-termination System 17
4.7 Grounding of Transmission Poles and Towers 18
4.8 Grounding of Main Control Building, Dispatching Building and Communication Station 20
4.9 Grounding of Relaying Protection and Security Automatic Equipment 21
4.10 Grounding of Metal Jacket of Power Cable 23
4.11 Grounding of Distribution Electric Equipment 24
4.12 Grounding of Structures Electric Equipment 24
4.13 Grounding of Portable and Mobile Appliances 26
4.14 Grounding against Lightning Induction and Static Electricity 26
5 Engineering Succession and Acceptance 27
Explanation of Wording in This Code 29
Lists of Quoted Standards 30
1 General Provisions
1.0.1 This code is formulated with the view to ensuring the construction quality of grounding connection of electric equipment installation engineering, improving the engineering construction technical level and ensuring the safe operation of grounding connection.
1.0.2 This code is applicable to the construction and acceptance of grounding connection of electric equipment installation engineering, but not to the construction and acceptance of HVDC transmission grounding electrode.
1.0.3 In addition to the requirements stipulated in this code, the construction and acceptance of grounding connection shall also meet the requirements of current related standards of the nation.
2 Terms
2.0.1 grounding electrode
the metal conductor buried in the ground and contacting with the ground directly is named as the grounding electrode, which consists of horizontal grounding electrode and vertical grounding electrode
2.0.2 natural grounding electrode
various metal members, metal well casing, foundation of reinforced concrete building, metal pipe and equipment, etc. in direct contact with the ground and capable of being used for grounding
2.0.3 air-termination system
the generic term of devices receiving lighting strike, including lightning rod, lightning strip, lightning conductor, lightning network as well as metal roof and metal member, etc.
2.0.4 grounding conductor
metal conductor used for the connection of grounding terminal of electric equipment and air-termination system with grounding electrode and carrying no current under normal conditions
2.0.5 grounding connection
the generic name of grounding electrode and grounding conductor
2.0.6 grounded
connect the electric equipment, facility, overvoltage protection equipment of power system or building with grounding electrode by grounding conductor
2.0.7 grounding impedance
impedance between reference ground and designated point of system, device or equipment at a given frequency
2.0.8 ground resistance
the real part of ground impedance; which is power frequency ground resistance for power frequency
2.0.9 neutral line
conductor electrically connected to the neutral point and capable of distribution
2.0.10 protective ground
the grounding conducted to prevent from endangering the safety of human beings and equipment as the insulation of the metal enclosure of electric equipment and the frame and line pole tower of distribution equipment may be damaged and electrified
2.0.11 concentrated grounding connection
additional grounding connection installed for strengthening the distribution function for lightning current and reducing the potential to ground
2.0.12 grounding grid
network grounding connection composed of vertical and horizontal grounding electrodes with function like discharge and voltage sharing
2.0.13 exothermic welding
the welding method by heating workpiece directly or indirectly with the high temperature molten metal reduced by chemical reaction to fuse and taking chemical reaction heat of metal oxide and aluminum powder as heat source
2.0.14 equipotential grounding grid
the equipotential grounding grid of nodes formed by vertical and horizontal connection of horizontal conductors, which connects with grounding grid in soil finally
3 Basic Requirements
3.0.1 Grounding connection shall be installed by engineering construction organization according to approved design document.
3.0.2 The new technique, new process and new material while adopted shall be evaluated by test or national qualified verification.
3.0.3 The installation of grounding connection shall be carried out in combination with construction engineering. For concealed part, it shall be inspected, accepted and recorded by relevant organizations before being covered.
3.0.4 The following metal parts of electric equipment must be grounded:
1 The metal base, framework, enclosure and driving device of electric equipment.
2 Metal base and enclosure of portable or mobile appliance.
3 Metal box of box-type transformer substation.
4 Secondary winding of instrument transformer.
5 Metal framework and base of panel (cabinet and box) and operating table for power distribution, control and protection.
6 Metal jacket, connector box, terminal head and metal protective pipe of power cable and the shielding layer of secondary cable.
7 Cable bridge, support and well head frame.
8 Structure and support of transformer substation (convertor station).
9 Power line pole tower equipped with overhead ground wire or electric equipment.
10 Metal barrier of distribution equipment.
11 Metal enclosure of electric heating equipment.
3.0.5 The grounding connection of the to be grounded DC system shall meet the following requirements:
1 The grounding connector that can form closed loop with ground and has current flow frequently shall be laid along insulating padding plate and shall not have metal connection with members of metal pipe, building and equipment.
2 If there are places in soil where corrosive materials can be produced during electrolysis, grounding connection should not be laid; if necessary, external grounding connection or measure for improving soil may be adopted.
3 The positive DC grounding connector and grounding electrode shall not have metal connection with natural grounding electrode; where there is no insulated isolating equipment, the distance between each other shall not be less than 1m.
3.0.6 Various electric equipment shall be reliably connected with grounding grid; the grounding grid of extension project and the original grounding grid shall meet the design requirements and shall be connected in at least two points.
3.0.7 The acceptance test of grounding connection, including conduction test, shall be carried out after the construction of grounding connection and before the overhead ground wire is laid to the terminal pole tower and framework of the plant (station) incoming and outgoing lines; the ground resistance shall comply with the design requirements.
3.0.8 For the grounding connection in the region with high soil resistivity, when the ground resistance fails to meet the requirements, corresponding measures shall be taken according to the design and after ground resistance meets the requirements, the grounding connection may be put into operation.
3.0.9 The following metal parts affiliated to grounded electric equipment and production facilities may not be grounded:
1 Enclosure of electrical measuring instrument, relay and other low voltage apparatus installed on distribution panel, control panel and power distribution unit.
2 Enclosure of motor and electric appliance with reliable electric contact with machine tool and machine base.
3 Metal support in the battery room with nominal voltage of 220V and below.
3.0.10 Grounding conductor shall not be used for other purposes.
4 Grounding of Electric Equipment
4.1 Selection of Grounding Connection
4.1.1 Various grounding connections make use of the natural grounding electrode buried in ground or water directly and the following natural grounding electrodes may be used:
1 Metal pipe buried in ground, but excluding the pipe delivering combustible material or that containing explosive material.
2 Metal well casing.
3 Metal structure of building that is reliably connected to the ground.
4 Metal pipe, pile and foundation layer reinforcing mesh of hydraulic structure and other structures located in water or damp soil environment.
4.1.2 The grounding conductor of AC electric equipment may be grounded with the following grounding electrodes:
1 Metal structure, beam and post of building.
2 Metal structures such as the track, corridor and platform of crane for production, framework of crane and lifter, steel beam of conveyer belt and framework of electric precipitator.
4.1.3 For grounding connections in places such as power plant and transformer substation, in addition to utilizing natural grounding electrode, the grounding grid (largely horizontal artificial grounding electrode) shall also be laid and measuring well for separating natural grounding electrode and artificial grounding electrode shall be arranged. For 3~10kV transformer substation and distribution substation, when adopting the reinforcing mesh of building foundation as the grounding electrode and the ground resistance complying with the specified value, no other artificial grounding may be set additionally.
4.1.4 The selection of grounding connection material shall meet the following requirements:
1 Except for temporary grounding connection, when steel is adopted for grounding connection, it shall be hot galvanized; the horizontally laid steel shall be hot galvanized round steel and flat steel; and the vertically laid steel shall be hot galvanized angle steel, steel pipe or round steel.
2 Where materials such as flat copper strip, copper stranded wire, copper bar, copper coated steel (round wire, twisted wire) and zinc coated steel are adopted as grounding connection, their selection shall meet the design requirements.
3 Aluminum conductor shall not be adopted as grounding electrode or grounding conductor.
4.1.5 The artificial grounding electrode of grounding connection and sectional area of conductor shall meet the thermal stability, voltage-sharing, mechanical strength and corrosion-resistance requirements; the section of horizontal grounding electrode shall not be less than 75% of the section of grounding conductor connected to the grounding connection and the minimum specification of steel grounding electrode and grounding conductor shall not be less than those specified in Table 4.1.5-1 and Table 4.1.5-2; the sectional area of grounding electrode outgoing line of pole tower for power line shall not be less than 50mm2.
Table 4.1.5-1 Minimum Specification of Steel Grounding Electrode and Grounding Conductor
Type, specification and unit Aboveground Underground
Diameter of round steel (mm) 8 8/10
Flat steel Sectional area (mm2) 48 48
Thickness (mm) 4 4
Thickness of angle steel (mm) 2.5 4
Wall thickness of steel pipe(mm) 2.5 3.5/2.5
Notes:
1 For the diameter of the underground part of round steel, the values of the numerator and denominator shall be respectively corresponding to the overhead line and the grounding grid of power plant and transformer substation;
2 For the wall thickness of the underground part of steel pipe, the values of the numerator and denominator shall be respectively corresponding to those of the pipes buried in soil and buried in the indoor concrete ground.
Table 4.1.5-2 Minimum Specification of Grounding Electrode of Copper and Copper Coated Steel
Type, specification and unit Aboveground Underground
Diameter of copper bar (mm) 8 8 for horizontal grounding electrode
15 for vertical grounding electrode
Sectional area (mm2)/Thickness (mm) of copper bar 50/2 50/2
Wall thickness of copper pipe (mm) 2 3
Sectional area of copper stranded wire (mm2) 50 50
Diameter of copper coated round steel (mm) 8 10
Diameter of copper coated steel strand (mm) 8 10
Sectional area (mm2)/Thickness (mm) of copper coated flat steel 48/4 48/4
Notes:
1 Bare copper stranded wire should not be used as the grounding electrode of small grounding connection; when it is used as the grounding electrode of grounding grid, the sectional area shall meet the design requirements;
2 The diameter of single strand of copper stranded wire shall not be less than 1.7mm;
3 The specification of copper coated steel is the dimension of steel and the thickness of copper coating shall not be less than 0.25mm.
4.1.6 The zinc coating thickness of hot galvanized steel and zinc coated steel for grounding electrode shall meet the design requirements.
4.1.7 The minimum sectional area of aboveground exposed grounding conductor, which is connected to grounding electrode or protective conductor (PE), of low-voltage electric equipment shall meet those specified in Table 4.1.7.
1 General Provisions
2 Terms
3 Basic Requirements
4 Grounding of Electric Equipment
4.1 Selection of Grounding Connection
4.2 Laying of Grounding Connection
4.3 Join of Grounding Electrode (Conductor)
4.4 Reducing Resistance of Grounding Connection
4.5 Grounding of Wind Turbines and Photovoltaic Power Station
4.6 Grounding of Air-termination System
4.7 Grounding of Transmission Poles and Towers
4.8 Grounding of Main Control Building, Dispatching Building and Communication Station
4.9 Grounding of Relaying Protection and Security Automatic Equipment
4.10 Grounding of Metal Jacket of Power Cable
4.11 Grounding of Distribution Electric Equipment
4.12 Grounding of Structures Electric Equipment
4.13 Grounding of Portable and Mobile Appliances
4.14 Grounding against Lightning Induction and Static Electricity
5 Engineering Succession and Acceptance
Explanation of Wording in This Code
Lists of Quoted Standards
