[2025 Grounding Systems] Are enclosure grounding and protective grounding the same thing?

The following responses are for reference only (not included in the attachments; the standard specifications in the text shall be based on the latest version). 1. HG/T 20513-2014 \"Code for Grounding Design of Instrument Systems\": 3.1.3 For field instruments, transmitters, local switches, etc. powered with voltages below 36V, protective grounding is not required unless there is a specific need for it. Explanation of the provisions: 3.1.3 The regulations regarding safe voltage levels vary from country to country. In our country, 36V and 12V are commonly used, while in some foreign countries 50V and 25V are specified ； Some companies in Japan stipulate that electrical meters with voltages below 60V do not require protective grounding. According to these specifications, field instruments, transmitters, local switches, etc. powered by voltages below 36V do not require protective grounding unless there are specific requirements. Due to the highly complex installation conditions on site, the metal enclosures of field instruments powered at less than 36V may also come into contact with other power sources at higher voltages than 36V; in such cases, the enclosures of these instruments should also be protected by grounding.

2. SH/T 3081-2019 \"Code for Design of Grounding of Instrumentation in Petrochemical Industries (under revision)\": 4.1.4 In non-explosive environments, the metal enclosures, metal protection boxes, and metal wiring boxes of field instruments with a supply voltage below 36V do not require protective grounding; however, those that may come into contact with equipment operating at voltages higher than 36V must be provided with protective grounding. 4.1.5 In explosive hazard environments, the metal enclosures, metal protection boxes, and metal wiring boxes of field instruments in non-intrinsically safe systems shall be provided with protective grounding, while those of field instruments in intrinsically safe systems need not have protective grounding. 4.1.6 The metal enclosures, metal protection boxes, and metal junction boxes of field instruments used for lightning protection shall be provided with protective grounding. Explanation of the provision: 4.1.4 This clause pertains to field equipment. Our country once specified that the safe voltage should not exceed 36V; later, different safe voltages were set for various working environments. The current Chinese standards specify the voltage levels that will not cause harm to humans under various environmental conditions and in different fault scenarios (see GB/T 3805-2008 (Limits for Extra-Low Voltage CELV)). To facilitate differentiation and implementation in engineering, this specification still limits it to 36V. 4.1.6 The field instruments referred to in this clause are those for which instrument lightning protection works are carried out in accordance with the provisions of SH/T 3164.

3. SH/T 3164-2021 \"Code for Design of Lightning Protection Engineering in Petrochemical Instrumentation Systems\": 9.3.1 The grounding of field instruments shall be protective grounding, and it shall comply with the provisions in Table 9.3.1; this can be achieved through the use of enclosure grounding terminals or by means of natural grounding during installation.

4. SH/T 3551-2024 \"Code for Construction and Acceptance of Petrochemical Instrumentation Projects\": 10.3.1 In explosive hazardous environments, the metal enclosures, metal protective boxes, and metal wiring boxes of field instruments in non-intrinsically safe systems shall be provided with protective grounding, while those of field instruments in intrinsically safe systems need not have protective grounding. 10.3.4 The metal enclosures, metal protection boxes, and metal junction boxes of field instruments used for lightning protection shall be provided with protective grounding.

5. GB 50093-2013 \"Code for Construction and Quality Acceptance of Automatic Instrumentation Projects\": 10.2.1 The enclosures of field instruments with a supply voltage higher than 36V, as well as all non-electrified metal parts such as instrument panels, cabinets, boxes, brackets, and bases, shall be provided with protective grounding. 10.2.2 For field instruments and switches with a supply voltage not exceeding 36V, protection grounding is not required unless specified otherwise in the design documents. Explanation of the provision: 10.2.1 This provision is mandatory; when the supply voltage exceeds 36V, it is considered a hazardous voltage. The normally non-electrified metal parts of electrical meters, such as their enclosures, dashboards, cabinets, boxes, trays, brackets, and bases, may acquire dangerous voltages due to unforeseen circumstances, posing a risk to people and equipment; therefore, protective grounding should be provided.

6. GB/T 50892-2013 \"Code for Design of Instrumentation and Control Systems in Oil and Gas Field and Pipeline Projects\": 11.3.1 The metal enclosures, metal frames, instrument cable trays, and cable protection tubes of all instrumentation equipment in explosive hazardous environments shall be reliably grounded. 11.3.2 Field instruments powered at 36V or below in non-explosion hazardous environments may not require protective grounding. Explanation of the provision: 11.3.1 For the metal protective conduit of buried cables, grounding is not required when the cable is buried throughout its length, such as across roads or at pipeline intersections. 11.3.2 This clause is formulated in accordance with the current standard **\"Grounding of AC Electrical Installations\" GB50065. Instruments based on microprocessors, integrated circuits, etc., usually require grounding when installed outdoors. For instrument devices with a relatively simple structure that are installed in non-explosive areas, such as alarm buttons, switch signals, and on-site alarms, no grounding requirement is applied.

7. GB 50160-2008 \"Code for Fire Protection Design of Petrochemical Enterprises\": 9.2.4 The measuring devices for the temperature and liquid level of flammable liquid storage tanks shall use armored cables or steel pipes for wiring; an electrical connection shall be established between the cable insulation or the wiring steel pipe and the tank body. Note: This clause falls under the 9.2 Lightning Protection section ； According to the text, it is explicitly required that the instruments be equipped with lightning protection grounding ； Even the instrumentation and its associated lightning protection grounding should not be connected to the tank.

8. GB 51283-2020 \"Fire Protection Code for Engineering Design of Fine Chemical Enterprises\" 11.4.3 In explosive hazardous environments, the metal enclosures of electrical equipment, metal pipelines, and the metal outer covers of armored cables must all be connected to ground reliably using specialized grounding wires; this applies as well to electrical equipment and metal pipelines that are installed on grounded metal structures. Explanation of the provision: 11.4.3 Grounding of metal objects is a key measure to prevent lightning induction. Note: This item is included in the Electrical section of Chapter 11.

9. AQ 3009-2007 \"Safety Code for Electrical Explosion Protection in Hazardous Areas\" 6.1.1.4.1 All non-live exposed metal parts of electrical equipment, such as its metal enclosures, metal frames, metal wiring ducts and their accessories, cable protection tubes, and the metal sheaths of cables, shall be grounded. Note: The definition of electrical equipment is given in Chapter 2. Instruments generally fall under the category of electrical devices, but with the exception of 220VAC four-wire instruments (which can barely be considered such), they cannot be regarded as electrical devices; therefore, it is not recommended to follow this guideline.

10. AQ 3036-2010 \"Code for the Installation of On-site Safety Monitoring Equipment in Tank Areas for Major Hazardous Sources of Hazardous Chemicals\" 6.3.6 Instrument installation, maintenance, and repair: Level sensors can be installed using flanges, threads, or mounting plates. Ensure that the sensor housing is properly grounded during installation. 11.4.1 The tank area shall be equipped with a grounding protection system to prevent lightning and static electricity; this grounding protection system shall meet the requirements of standards such as GB12158.