HG/T 20513-2014 English PDF (HGT20513-2014)

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HG/T 20513-2014: Design code of instrument grounding
HG/T 20513-2014
HG
CHEMICAL INDUSTRY STANDARD
OF THE PEOPLE'S REPUBLIC OF CHINA
Filing number: J 1819-2014
Replacing HG/T 20513-2000
Design code of instrument grounding
ISSUED ON: MAY 6, 2014
IMPLEMENTED ON: OCTOBER 1, 2014
Issued by: Ministry of Industry and Information Technology of the People's
Republic of China.
Table of Contents
Foreword ... 4
1 General ... 6
2 Terms ... 6
3 Grounding categories ... 7
3.1 Safety grounding ... 7
3.2 Working grounding ... 8
3.3 Intrinsically safe grounding ... 8
3.4 Electrostatic protective earthing ... 9
4 Grounding system and grounding principles ... 9
5 Bonding methods ... 11
5.1 Field instrument bonding method ... 11
5.2 Fieldbus instrument cable shielding grounding method ... 14
5.3 Bonding method for instruments in the control room/field cabinet room ... 16
6 Grounding system bonding requirements ... 20
6.1 Bonding specifications ... 20
6.2 Bonding bar and bonding terminal bar specifications ... 20
6.3 Requirements for bonding structure ... 20
7 Grounding resistance ... 21
Explanation of words used in this standard ... 22
Design code of instrument grounding
1 General
1.0.1 This standard is formulated in order to unify the technical requirements for
instrument system grounding design in the chemical industry, promote the
standardization of instrument system grounding design, and achieve the goals of
technological advancement, economic rationality, safety, and applicability.
1.0.2 This standard is applicable to the design of grounding systems for instrument and
automatic control system engineering in the chemical industry.
1.0.3 In addition to complying with the requirements of this standard, the design of the
instrument grounding system shall also comply with the relevant current national
standards.
2 Terms
2.0.1 safety grounding
Grounding for the protection of instruments and personal safety, which is also called
safe grounding.
2.0.2 working grounding
Grounding required for the normal operation of instrument and control systems.
2.0.3 shielding grounding
Grounding is adopted to avoid electromagnetic field interference on instruments and
signals.
2.0.4 intrinsically safe grounding
Grounding required for proper operation of intrinsically safe instruments.
2.0.5 equipotential bonding
The connection by which the individual conductors are connected and equal to earth's
potential.
2.0.6 connecting resistance
The sum of the resistance of the conductors and connection points from the grounding
terminal of instruments and equipment to the grounding electrode.
2.0.7 grounding resistance
The sum of the grounding electrode's resistance to ground and the connecting resistance
is called grounding resistance.
2.0.8 grounding system
The general term for bonding wires, bonding bars, bonding trunk wires, bonding
terminal bars, and earthing electrodes.
3 Grounding categories
3.1 Safety grounding
3.1.1 The metal casing of electrical instruments and the normally non-energized metal
parts of automatic control equipment may carry dangerous voltage due to various
reasons (such as insulation damage). The safety grounding shall be implemented for the
following electrical instruments and automatic control equipment:
1 Instrument panels, instrument consoles, instrument cabinets, instrument frames
and instrument boxes;
2 Instrument control system cabinet and operating station;
3 Computer system cabinets and operating consoles;
4 Power supply panels, power supply boxes, electrical instrument casings, cable
trays, protective tubes, junction boxes and armor layer of armored cable.
3.1.2 When the metal casings of small low-voltage electrical appliances such as buttons,
signal lights, and relays installed on metal dials in non-explosion-proof situations have
good electrical contact with the metal dial frame that has safety grounding, separate
safety grounding may not be required.
3.1.3 For field instruments, transmitters and local switches with a power supply lower
than 36 V, safety grounding is not required unless there are special needs.
3.1.4 Automatic control equipment that has safety grounding can be considered to have
electrostatic grounding. When using an anti-static raised floor in the control room,
electrostatic grounding shall be done. Electrostatic grounding shall share the grounding
system with safety grounding.
3.2 Working grounding
3.2.1 Working grounding shall include signal loop grounding and shielding grounding.
3.2.2 The signal loop grounding shall meet the following requirements:
1 In electronic equipment such as automation systems and computers, non-isolated
signals need to establish a unified signal reference point, and the signal loop shall
be grounded (usually the negative pole of the DC power supply).
2 Isolated signals do not need to be grounded. Isolation shall be that each input
(output) signal is insulated from other input (output) signal circuits, insulated
from the ground, and the power supply is independent and isolated from each
other.
3.2.3 Shielding grounding shall meet the following requirements:
1 For components in the instrument system used to reduce electromagnetic
interference, such as cable shields, drain wires, and shielding grounding
terminals on the instrument, shielding grounding shall all be implemented.
2 The spare core of ordinary multi-core cables without shielding laid aerially
outdoors shall be grounded.
3 If the shielding layer of the shielded cable is grounded, the spare core does not
need to be grounded.
4 The spare core of a multi-core cable that wears a protective tube does not need
to be grounded.
3.3 Intrinsically safe grounding
3.3.1 For components of intrinsically safe instruments that need to be grounded for
safety functions, the intrinsically safe grounding shall be implemented according to the
requirements of the instrument manufacturer.
3.3.2 The bus bar of the Zener safety barrier shall be connected to the common terminal
of the DC power supply, and the bus bar (or guide rail) of the Zener safety barrier shall
be intrinsically safe grounded.
3.3.3 The isolation safety barrier does not need to be grounded.
6 Grounding system bonding requirements
6.1 Bonding specifications
6.1.1 The conductors of the grounding system shall be multi-stranded copper core
insulated wires or cables.
6.1.2 The cross-section of the grounding system connecting wire should be selected
according to the type of bonding and the following values:
Bonding wire: 1 mm2~2.5 mm2; grounding branch trunk wire: 4 mm2~16 mm2; bonding
trunk wire: 10 mm2~25 mm2; grounding main line: 16 mm2~50 mm2.
6.2 Bonding bar and bonding terminal bar specifications
6.2.1 The bonding bar should be made of 25 mm×6 mm copper strips, or it can be
formed by the combination of connecting terminals.
6.2.2 The bonding terminal bar and main grounding plate should be made of copper
plates. The thickness of the copper plate shall not be less than 6 mm, and the length and
width dimensions shall be determined as needed.
6.3 Requirements for bonding structure
6.3.1 All bonding wires shall be well insulated before being connected to the bonding
bar; all grounding branch trunk wires shall be well insulated before being connected to
the bonding terminal bar; all bonding trunk wires shall be well insulated before being
connected to the main grounding plate.
6.3.2 The bonding bar (bus bar), ...