Design specification for instrument system lightning surge protection in petrochemical industry
1 Scope
This specification specifies the design specification for lightning surge protection engineering of instrumentation.
This specification is applicable to the design of lightning surge protection for instrumentation used in explosive atmospheres and non-explosive atmospheres in petrochemical industry and for new construction, extension and renovation of factories using coal as raw materials to prepare fuel and chemical products.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 50057-2010 Code for design protection of structures against lightning
GB/T 18802.21 Low-voltage surge protective devices - Part 21: Surge protective devices connected to telecommunications and signaling networks - Performance requirements and testing methods
3 Terms and abbreviations
3.1 Terms
For the purposes of this specification, the following terms apply.
3.1.1
air-termination system
metal object and metal structure used for directly receiving or withstanding lightning strikes, such as air-termination rod (formerly known as "lightning conductor"), air-termination belt (line) and air-termination grid
3.1.2
down conductor system
conductor connecting the air-termination system to the earth termination system
3.1.3
earth termination system
set of bonding conductors between earthing electrodes
3.1.4
earth electrode
buried metal object forming conductive contact with the earth; various metal components, metal facilities, metal pipelines, metal equipment, etc., which are in direct contact with the earth, may be regarded as earth electrode, which is called natural earth electrode
3.1.5
bonding
connection of the equipment, instrument and bonding bar that need to be earthed into an earthing system with bonding wires and conductors
3.1.6
bonding conductor
conductor used for connecting various pieces of equipment and bonding bar that need to be earthed into an earthing system
3.1.7
direct lightning flash
lightning that directly strikes actual objects such as buildings, earth, facilities or equipment
3.1.8
lightning current
current in the lightning discharge path
3.1.9
thunderstorm day
number of days when one or more thunders are heard; the average annual thunderstorm day in a region is the average of annual thunderstorm day statistics for many years in this region, and it is one of the indicators to characterize the frequency of lightning activity in this region
3.1.10
lightning induction
electrostatic induction and lightning electromagnetic induction generated in the space surrounding lightning current
3.1.11
lightning electromagnetic induction
phenomenon that lightning current generates an electromagnetic field in the surrounding space and a conductor generates an induced electromotive force in this electromagnetic field
3.1.12
electromagnetic shielding
shield to the protected target with a material capable of reducing the passage of electromagnetic field
3.1.13
lightning surge
current and voltage in the form of pulses conducted along a circuit or conductor generated by lightning electromagnetic induction
3.1.14
equipotential bonding
conductive connection among various metal components, metal facilities, metal pipelines and metal equipment with conductors, so that the potentials of the objects are approximately equal
3.1.15
bonding strip
strip metal installed in the cabinet that collects and connects the bonding wires, which may be classified into working bonding strip, protective bonding strip, etc. based on the application
3.1.16
bonding bar
strip metal installed out of the cabinet, which has a large overall dimension and is used for collecting multiple bonding wires or composing earthing grid
3.1.17
surge protective device
device that uses gap discharge, bypass conduction and voltage limiting methods for shunting surge current and limiting instantaneous overvoltage to protect electrical or electronic devices
3.1.18
maximum continuous operating voltage
maximum voltage that is continuously applied to a surge protective device without affecting the signal transmission process and signal quality, also known as maximum operating voltage
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3.1.19
nominal discharge current
max. anti-surge current capacity of a surge protective device without being damaged, that is, the maximum discharge capacity of the surge protective device to surge current if it is subjected to the standard experimental waveform current and the specified number of experiments
3.1.20
voltage protection level
maximum voltage present at the rear end of a surge protective device when the surge protective device discharges the max. anti-surge current, that is, the residual voltage, also known as limited voltage
3.1.21
nominal voltage
long-term normal operating voltage of a surge protective device between wires or between wires and the earth under specified environmental conditions and limited leakage current
3.1.22
maximum leakage current
limited leakage current of a surge protective device at the nominal voltage
3.1.23
nominal current
long-term normal operating signal current of a surge protective device under specified environmental conditions and nominal voltage
3.1.24
instrumentation
general term for electric and electrical signal instruments and control systems in this specification
3.1.25
simple apparatus
electrical components whose electrical parameters conform to the intrinsic safety performance of the circuit, components and combinations of components such as capacitors, inductors and batteries without internal energy sources and with strictly limited energy storage parameters, that is, a specific term for intrinsic safe system
3.1.26
bonding terminal
bonding plate for connecting an instrumentation earthing grid with an electrical earth termination system
3.1.27
safety extra-low voltage
voltage for insulation and isolation between electrical system and other power supply systems that does not exceed the limit: ≤ AC 50 V, or ≤ DC 120 V, and exposed conductive part earthed, and that complies with the voltage specified in GB/T 16895.21-2020/IEC 60364-4-41:2017 on safety extra-low voltage
3.2 Abbreviations
For the purposes of this specification, the following abbreviations apply:
Abbreviation English name
SPD Surge protective device
Un Nominal voltage
Uc Maximum continuous operating voltage
Up Voltage protection level
In Nominal discharge current
Ic Maximum leakage current
IN Nominal current
SELV Safety extra-low voltage
4 General
4.1 In the design of lightning surge protection engineering, according to the specific situation of the protection target, an appropriate protection scope shall be determined and an appropriate protection scheme shall be adopted to reduce the risk of lightning strikes to a tolerable level, meet the investment conditions of disaster prevention and mitigation, effectively protect from lightning strikes, and reduce the losses caused by lightning strikes on instrumentation.
4.2 The lightning surge protection engineering for instrumentation shall adopt all of the following means:
a) Setting of the surge protective device;
b) Instrumentation earthing;
c) Shielding of instrumentation signal cables;
d) Shielding of instrumentation equipment.
4.3 The protective earthing, working earthing, intrinsic safe earthing, shielding earthing, static electricity protection earthing and surge protective device earthing of the instrumentation shall be finally connected to the electrical earth termination system, and the earthing resistance shall comply with the earthing resistance of the earth termination system.
4.4 The core twisted type shall be used in the instrumentation signal cables and communication cables.
4.5 The optical cables should be used in the communication network of outdoor instrumentation.
Foreword i
1 Scope
2 Normative references
3 Terms and abbreviations
3.1 Terms
3.2 Abbreviations
4 General
5 Decision of lightning surge protection engineering for instrumentation
6 Earthing system in lightning surge protection engineering for instrumentation
6.1 Instrumentation earthing system in control room
6.2 Cabinet and operating console earthing
6.3 Bonding conductor and wire
6.4 Laying of cables and wire
6.5 Bonding method
6.6 Earthing sign
7 Surge protective device
7.1 General
7.2 Type of surge protective device
7.3 Parameters of surge protective device for signal type
7.4 Surge protective device setting
7.5 Lightning surge protection in AC power supply
8 Lightning surge protection for instrumentation in control room
8.1 Shielding for instrumentation in control room
8.2 Installation for surge protective device
8.3 Earthing and bonding for surge protective device
9 Lightning surge protection for field instrumentation
9.1 Lightning protection for field instrumentation
9.2 Installation for surge protective device
9.3 Field instrumentation earthing
10 Lightning surge protection for cables
10.1 Shielding of cables
10.2 Earthing for cable shielding
10.3 Spare cable and spare core of cable
11 Lightning surge protection for intrinsic safety system
11.1 Surge protective device for intrinsic safety system
11.2 Installation for surge protective device
11.3 Bonding in intrinsic safety system
12 Lightning surge protection for fieldbus system
12.1 Surge protective device for fieldbus system
12.2 Surge protective device application
12.3 Fieldbus system earthing
13 Lightning protection for control building
Appendix B (Informative) Network type earthing referenced drawing
Appendix B (Normative) Shielding of cables earthing referenced drawing
Bibliography
Explanation of wording in this specification
