Quantity calculation for lightning-protection grounding devices and determination of the number of "groups": grounding electrodes counted by "piece", commissioning of independent grounding devices (up to 6 electrodes) counted by "group", grounding-grid testing counted by "system"

Topic Positioning

Quantity-calculation calibers for lightning-protection grounding devices of street lighting (and general electrical installation): what measurement units apply to grounding electrodes, grounding busbars, and grounding-device commissioning respectively, and how the "group" of "independent grounding device commissioning" is determined (the "up to 6 electrodes" caliber).

Core Conclusions

1. Grounding electrodes themselves (fabrication and installation) are counted by "piece", not by "group".

• Municipal street-lighting works: GB/T 50857-2024 Appendix H, Table H.6.1 "Lightning protection and grounding works" (code 040806) — the BOQ items, item characteristics, measurement units, and calculation rules for lightning-protection grounding works of street lighting shall follow that table; grounding electrodes are counted by "piece" per the quantity shown on the design drawings, and grounding busbars in "m" (plus the prescribed additional length).
• General installation works: GB/T 50856-2024 Table D.10.1 "Lightning protection and grounding devices" (code 0304010), grounding electrodes measured by "piece (block, set)".
• Where the design does not specify, the electrode length is taken as 2.5 m per electrode (SJG 181.7-2024 Clause 7.2.1: "Fabrication and installation of grounding electrodes shall be counted by piece per the quantity shown on the design drawings, the length per the design length; where the design does not specify, 2.5 m per electrode.")

2. "Group" appears only in electrical adjustment and testing — grounding-device commissioning rules (SJG 181.7-2024 Clause 8.2.6, verbatim):

1. Whether a grounding electrode assembly consists of one electrode or two or more, it is counted as one test; where the grounding resistance fails to meet requirements and another electrode is driven and tested again, one more test fee is counted.
2. For the main grid of a power plant or substation connected as one body, measurement of the grounding-grid resistance is counted as one system; an independent grounding grid that forms its own main grid and is not connected to the plant-area main grid has its grounding resistance measured and counted as another system.
3. Where each lightning rod has its own independent grounding grid, measurement of the lightning-rod grounding resistance is counted by one electrode (group) each.
4. Independent grounding devices shall be counted by the quantity shown on the design drawings, in electrodes (groups). For example, a pole-mounted transformer with one independent grounding device is counted as one electrode (group).
5. A grounding grid is composed of multiple grounding electrodes; the grounding-grid test sub-item includes the electrodes within it, and electrode tests may not be counted separately.

3. Key points for determining "group" (the <=6-electrode caliber):

• In the installation quota system (national unified quota and provincial adaptations), the "independent grounding device commissioning" sub-item has an applicability ceiling of "up to 6 grounding electrodes", counted by "group"; the "grounding-grid commissioning" sub-item is counted by "system".
• One independent grounding device (not networked with other grounding bodies) = 1 group: whether that location consists of 1, 3, or up to 6 electrodes, only 1 group is counted. "6 electrodes" is the sub-item's applicability ceiling, not "every 6 electrodes converted to 1 group".
• More than 6 electrodes, or already forming a grid (including grids welded from foundation rebar) -> the "independent grounding device commissioning" sub-item does not apply; count by "system" under "grounding-grid commissioning", and electrodes within the grid may not be counted again for electrode tests.
• The number of groups follows the number of "locations": as many independent grounding devices as the project has (e.g., each of several buildings or several light poles with its own device) is that many groups. Electrode fabrication/installation is counted by "piece", commissioning by "group" — the two are independent and priced separately.

4. Related listing calibers (GB/T 50856-2024 Table D.17.13 "Notes on issues in Table D.10.1", verbatim):

1. Where pile foundations serve as grounding electrodes, the number of piles under the pile cap shall be stated in the item characteristics, and the pile main bars are measured as column down-conductors. Where foundation rebar serves as grounding electrodes, list under the equipotential-ring code in this table.
2. Where column bars serve as down-conductors, the number of welded column bars shall be stated in the item characteristics.
3. Where ring-beam bars serve as equipotential rings, the number of welded ring-beam bars shall be stated in the item characteristics.
4. Where cables/wires serve as grounding conductors, list under the relevant items of Appendix D.9 cable installation and Appendix D.12 conduit and wiring of this standard.
5. Additional lengths of grounding busbars, lightning down-conductors, and lightning networks are given in Table D.17.3-6.
6. Grounding cross-connections refer to grounding-grid crossings, equipotential bonding, steel/aluminum window grounding, framework grounding, crossing between down-conductor main bars and ring-beam bars, and pile-cap pile grounding connections.
7. Intelligent lightning-protection monitoring systems include surge protective devices, SPD-dedicated backup protectors, SPD intelligent monitoring devices, intelligent lightning-protection monitoring and early-warning host equipment, grounding-performance monitoring devices, and other lightning-protection products.
8. Cathodic-protection grounding shall be listed under the relevant items of Appendix M painting, anti-corrosion, and thermal insulation works of this standard.
9. Earth and rock works for grounding electrodes, outdoor busbars, and resistance-reducing agents shall be listed under the relevant item codes of the current national standard GB/T 50854, Standard for Measurement of Building and Decoration Works.

5. Common practice for street lighting:

• Typical repeated-grounding design "3 electrodes per set, spacing about 5 m" + flat-steel grounding busbar: 3 electrodes counted, commissioning 1 group/location (per the design drawings).
• Where the pole foundation uses "flat steel embedded with the foundation, using foundation rebar", count by busbar length; the foundation rebar is listed under the "equipotential ring" code — here there is no independent "piece/group" to count.
• The BOQ/price assembly is best split into three items: grounding electrodes (piece) / grounding busbar (m) / grounding-device commissioning (group or system); commissioning groups are counted by "location", not by "electrode". Example: 3 pole foundations each with an independent grounding location of 3 electrodes -> 9 electrodes counted, 3 groups of commissioning.

6. Shenzhen additional caliber (SJG 181.7-2024 Clause 8.1.8): where a unit works has more than 5 groups of grounding-electrode testing, the sub-item for the portion above 5 groups is multiplied by 0.80.

Applicable Boundaries

• The "within 6 electrodes" ceiling applies only to "independent grounding devices" (not networked with other grounding bodies); those already forming a grid or connected to the plant main grid are counted by "system", and electrodes within the grid may not be tested again.
• Provincial quotas may differ in the naming and tiering of the "independent grounding device commissioning" sub-item; before submission and settlement, the current local quota volume and quota interpretations govern; "total electrodes / 6 = groups" is a common misuse that conflicts with the "one independent grounding device = one group" caliber.
• This card resolves measurement-unit and group-determination calibers; specific sub-item numbers and comprehensive unit prices follow the current local quota and price information.
• SJG 181.7-2024 is a Shenzhen local standard; its 2.5 m default length and 0.80 coefficient are Shenzhen calibers; other regions follow local standards.
• Quantities are primarily per the design drawings (shown quantities/lengths); default calibers (e.g., 2.5 m per electrode) apply only where the design is silent.

Further Reading

• GB/T 50857-2024 Standard for Measurement of Municipal Works, Appendix H street lighting, Table H.6.1 lightning-protection grounding works (code 040806).
• GB/T 50856-2024 Standard for Measurement of General Installation Works, Table D.10.1 lightning protection and grounding devices (code 0304010), Table D.17.3-6 (additional lengths of grounding busbars, down-conductors, lightning networks), Table D.17.13 (notes on related issues).
• SJG 181.7-2024 Consumption Standard for Municipal Works, Vol. 7: Power Ducts, Communication Conduits and Lighting Works, Clauses 7.2.1 (lightning protection and grounding works), 8.1.8 and 8.2.6 (electrical adjustment and testing).
• Related government-published pages for verifying local calibers (subject to the original texts):
  • https://zjj.jiujiang.gov.cn/zwgk_208/xzglyfw/ggfw/wyyzsgl/202302/t20230220_5940945.html
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3865233.html
  • http://zjt.gxzf.gov.cn/zfxxgk/fdzdgknr/wjtz/t27789614.shtml
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3845790.html
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3820668.html
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3829147.html
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3838695.html
  • https://zjj.zhuhai.gov.cn/zjj/gzhd/ywzsk/szl/content/post_3856791.html