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Renewable Energy · Power Systems · Published September 28, 2026
Grounding and Bonding a Solar-Plus-Storage Hybrid Plant: IEC 60364 and NEC 690 Together
A hybrid plant is not one electrical system with one earthing rule. The PV array follows IEC 62548 and IEC 60364-7-712 on one side of the fencing and NEC 690 Part V on the other; the battery containers add a third regime; and the shared trench underneath all of them is where the two philosophies actually collide. This article lays out what each code requires for equipment grounding, the single-point earthing of the array, the equipotential zone of a BESS enclosure, and the induced-loop problem that appears only when the circuits share a corridor.
01Why hybrid plants break single-standard thinking
The short answer
On a solar-plus-storage hybrid plant the DC array, the battery containers and the AC collection system are legally one installation but technically three. NEC 690.41(B) requires dc ground-fault protection on any PV circuit above 30 volts or 8 amperes, and NEC 690.43(C) requires the array's equipment grounding conductor to travel with the PV circuit conductors once they leave the array. IEC 62548-1 and IEC 60364-7-712 instead permit an array that is not earthed at all, provided the DC-side equipment carries Class II or equivalent insulation, and they require that where earthing is used the connection is made at a single point. Put those together on the same site and the layout question stops being "where is the ground rod" and becomes "which of these three zones is allowed to have its own reference point".
Most grounding guidance is written for one installation class at a time. A rooftop PV guide assumes the array sits on a building whose grounding electrode system already exists. A BESS guide assumes a container on a pad with its own earthing arrangement. A utility-scale guide assumes a substation with a mesh. The hybrid plant — the configuration now being built at scale for green direct-connect campuses, where wind and solar generation, grid-scale storage and a compute load share one fence line — is none of these individually and all of them collectively.
The structural reason is that a hybrid plant contains at least three different earthing philosophies inside one property boundary:
- The array, which under IEC practice may legitimately be unearthed on the DC side and specifies its earthing through IEC 62548-1 and IEC 60364-7-712.
- The battery containers, which are covered by the electrochemical-storage safety framework of IEC 62933-5-2 — a standard whose normative references explicitly include the IEC 60364 series.
- The AC collection and step-up system, which follows conventional installation practice and, in the United States, NEC Article 250.
Each of those three is internally consistent. The failure mode on a hybrid site is at the boundaries: an EGC that stops at the fence line of one zone, a functional earth that becomes a second connection to the same grounding electrode system, a trench that carries conductors from two of the three zones with a bonding arrangement designed for only one of them. This article is about those boundaries. For the building-side cable-side treatment of earthing and protective conductors we refer to our earthing and bonding cable sizing guide under IEC 60364; for the trench depth tables, the NEC 690 burial and conduit requirements guide. This page deliberately does not restate either.
Read this first if you are new to the siteThe campus-level walkthrough is in the green direct-connect campus cable chain, and the thermal duty that storage links see is in how load-following computing changes cable sizing and joint life. This article is the grounding layer underneath both.
02Array-side earthing under NEC 690 and IEC 62548
The two frameworks diverge at the first question. NEC 690.41(A) lists six acceptable PV system grounding configurations and then hands the DC-side protection burden to 690.41(B): any PV system dc circuit exceeding 30 volts or 8 amperes must be provided with dc ground-fault protection, meeting 690.41(B)(1) for detection, 690.41(B)(2) for the treatment of the faulted circuit, and 690.41(B)(3) for indication of the fault at a readily accessible location. The exception is narrow — solidly grounded PV source circuits with not more than two modules in parallel and not located on or in buildings may be installed without ground-fault protection.
The informational note attached to 690.41(B) is the practical sting: not all inverters, charge controllers and dc-to-dc converters include ground-fault protection, and equipment without it typically carries the manual warning "This unit is not provided with a GFDI device." On a hybrid plant, where the DC side is likely to include dc-to-dc conversion between the array bus and a storage bus, that note is the difference between a design that has ground-fault protection and a design that has a label admitting it does not.
IEC 62548-1 walks a different path. Its clause 7.3.2 provides a decision tree for earthing the exposed conductive parts of a PV array, and the principles that come out of it are stated consistently by the sources that summarise it:
- Protective earthing of the array's line conductors is not permitted. You cannot earth a live DC conductor for protection.
- Functional earthing of a live part on the DC side is permitted only where there is at least simple separation between the AC and DC sides — internally in the inverter, or externally via a separate transformer. IEC 60364-7-712 tightens this further: the functional earthing must be made at a single point near the converter's DC input, and the functional earthing cable must not be green-and-yellow, precisely so that nobody mistakes it for a protective conductor.
- Where the array is earthed, the connection is made at one point and taken to the main earthing terminal of the installation.
- The functional earthing conductor's current-carrying capacity must be not less than the rating of the ground-fault interrupting device, or the maximum fault current calculated from the series resistance of the circuit.
The contrast with the NEC is not a matter of severity but of direction. Under the NEC, exposed metal is bonded to an equipment grounding conductor — full stop, regardless of voltage, per 690.43. Under IEC practice, an array whose DC-side equipment is Class II or equivalent insulation (per IEC 60364-7-712 clause 712.412.101) may have frames that are not earthed by design, and plenty of European rooftop arrays do exactly that. A mounting system sold into both markets therefore has to support both arrangements, and a bill of materials written for one is not automatically compliant in the other.
Equipment grounding conductors: where the NEC is specific and the IEC is not
NEC 690.45 is unusually concrete, and two of its provisions are routinely violated in the field:
- Equipment grounding conductors for PV system circuits are sized in accordance with 250.122. Where no overcurrent protective device is used in the circuit, an assumed overcurrent device rated per 690.9(B) is used when applying Table 250.122.
- Increases in equipment grounding conductor size to address voltage drop considerations shall not be required. This is the opposite of the general Article 250 rule and it catches people who upsize the whole circuit for voltage drop on a long array run and then upsize the EGC along with it out of habit.
NEC 690.43(C) is the other provision that shapes hybrid layouts: the EGC for the array and its support structure must be contained within the same raceway or cable, or otherwise run with the PV system conductors when those circuit conductors leave the vicinity of the array. That single sentence is the reason a hybrid plant's cable corridor has to be designed as a grounding problem and not just a routing problem.
| Question | NEC 690 (2022 California Electrical Code, based on NFPA 70-2020) | IEC 62548-1 / 60364-7-712 |
|---|---|---|
| Must exposed module frames be earthed? | Yes — 690.43, regardless of voltage | Not if DC-side equipment is Class II or equivalent (712.412.101) |
| Is earthing a live DC conductor allowed? | Yes, in the permitted configurations of 690.41(A) | Protective earthing of array line conductors is not permitted; functional earthing only with at least simple AC/DC separation |
| Where is the earth connection made? | 690.42 — at the ground-fault protective device, or any single point on the PV output circuit for solidly grounded systems | Single point, taken to the main earthing terminal (712.444.5.5.101) |
| DC ground-fault protection trigger | 690.41(B) — above 30 V or 8 A | Insulation monitoring or residual-current monitoring, with the arrangement determined by the array's isolation method and earth reference |
| EGC sizing basis | 250.122 by OCPD rating, or assumed OCPD per 690.9(B); no upsizing for voltage drop (690.45) | Detail delegated to IEC 60364-5-54; functional earthing conductor rated not below the ground-fault interrupting device |
| Grounding conductor routing rule | 690.43(C) — EGC must run with the PV circuit conductors leaving the array | Equipotential bonding conductors laid as close as practicable to live conductors, to reduce induced loop area |
NEC column: 2022 California Electrical Code text of Article 690 Part V (lines 74866–75010 of our library copy) and Article 250.97; cross-checked against the EC&M and Mike Holt explanations of the same clauses. IEC column: IEC 62548-1:2023 clause 7.3.2 decision tree on earthing and bonding arrangements, and IEC 60364-7-712:2017 clauses 712.412.101 and 712.444.5.5.101. Where a standard's clause text is not held in our library, the comparison states the principle only, not a clause number. The NEC column follows the 2020-based text; jurisdictions that have adopted the 2023 edition should verify the clause numbering of Article 690 against their own copy.
03BESS enclosures: equipotential bonding zones
A battery container is not a big metal box that needs a ground rod. It is a bounded conductive volume inside which a battery rack, a DC bus, a power conversion system, a thermal management unit and a control system all sit within touching distance of one another — and inside which fault current has to be given a defined path that does not include the operator.
That framing comes from the electrochemical-storage safety framework rather than from Article 690. IEC 62933-5-2 covers grid-integrated electrochemical energy storage across its whole life cycle and organises its safety requirements around design, installation, operation, maintenance and end-of-service-life. Its protective scope is broken into categories — protection from electrical hazards, mechanical hazards, explosion, electric/magnetic/electromagnetic fields, fire, temperature, and chemical effects — and its normative reference list explicitly includes the IEC 60364 series. That reference is the important structural fact for a hybrid plant: the IEC system-safety standard for storage does not invent a separate earthing philosophy, it inherits one from the low-voltage installation standard. Note also that the current edition is Edition 2.0 (2025); sources still circulating that cite the 2020 first edition are describing an earlier text.
IEC 62933-5-2 also classifies systems along four axes — connection voltage (low / high), energy capacity (≤20 kWh / >20 kWh), site occupancy (occupied / unoccupied area), and electrochemical type — and the required protective measures differ by category. The practical consequence for grounding design is that a container's earthing arrangement cannot be copied from another project without checking which category that project fell into.
Why "equipotential zone" is the right mental model
An equipotential zone is a region where all accessible conductive parts are bonded together so that, during a fault, they rise and fall together. Within such a zone the touch voltage between any two accessible surfaces stays near zero even if the whole zone rises to a substantial potential above remote earth. That is a fundamentally different objective from "connect everything to a rod", and it is the objective a battery container needs, because a container provides an unusually large number of simultaneously accessible metal surfaces: door frames, rack rails, cable tray, containment, HVAC housings, and the enclosure shell itself.
What the NEC adds on the array side — and where the container sits instead
Where the NEC governs the site, 690.47 sets the array-side connection to the grounding electrode system: a building or structure supporting a PV system must use a grounding electrode system installed per Article 250 Part III, and the array's equipment grounding conductors must be connected to it per Article 250 Part VII — in addition to, not instead of, the 690.43(C) requirement that they run with the circuit conductors. For systems that are not solidly grounded, the EGC for the PV output may be the only connection to ground for the system where it connects to associated distribution equipment that is itself connected to a grounding electrode system (690.47(A)(1)). For solidly grounded systems, the grounded conductor is connected to the grounding electrode system by a grounding electrode conductor sized per 250.166 (690.47(A)(2)).
Note that Article 690 reaches the array, not the battery container. The NEC's own storage article is Article 706 (Energy Storage Systems), which applies to ESS above 1 kWh whether stand-alone or interactive; it governs installation, marking, ventilation, working space and circuit requirements for the container. It does not carry its own earthing clause — the container's equipment grounding and bonding are taken from Article 250, with Article 706 supplying the system-level requirements that surround them. A hybrid plant therefore sits under three code bodies at once: 690 for the array, 706 plus 250 for the storage container, and the IEC 62933-5-2 / 60364 family where the project is specified to IEC.
The informational note under 690.47 is worth reading twice, because it is the sentence that makes the hybrid plant tractable: most PV systems are functionally grounded systems rather than solidly grounded systems as defined in this Code, and for functionally grounded systems with an interactive inverter output, the AC equipment grounding conductor connected to the associated grounded AC distribution equipment is most often the connection to ground for both ground-fault protection and equipment grounding of the array. In other words, the array's earth reference in the overwhelmingly common case is not a rod at the array at all — it is the AC side's grounding electrode system, reached through the inverter. That is also precisely why the array and the AC system cannot be given two independent earth references and then expected to behave as one installation.
The two-rod trapAdding a local earth electrode at a container and connecting it to the site grounding electrode system is normal practice. Adding one and treating it as a second, independent reference is not. The relevant question is not "how many electrodes" but "how many points at which a conductor is connected to earth" — and for a functionally grounded system, 690.47(A)(1) permits a single such point. Additional electrodes are bonded to the same system; they are not a parallel reference.
If you are laying out the container interfacesSend us the container layout — rack pitch, PCS position, DC bus voltage and the trench cross-section — and we will return the cable schedule for the links that tie the container into the site earthing and DC collection system, with the standards basis for each construction: start a cable schedule.
04Shared trenches: induction, loops and separation
This is the section where IEC and NEC practice meet in a physical excavation, and it is the single most common source of late-stage redesign on hybrid projects, because the problem is invisible on a single-line diagram.
The underlying physics is not exotic. A cable's metallic screen, sheath or armour runs parallel to its own conductors for the whole route length, which makes it behave in part like the secondary winding of a 1:1 transformer. Alternating current in the conductor induces a longitudinal EMF along that parallel metallic path, proportional to the conductor current, the route length, and the mutual inductance between conductor and screen — which in turn depends on cable geometry and on the spacing between the phases. If that metallic path is earthed at both ends, the induced EMF has a closed circuit to drive, and a circulating current flows in it. If it is earthed at one end only, no circulating current flows, but a standing voltage appears at the open end.
The two consequences are quantified differently by different sources, and it is worth being explicit about that. Sources addressing long single-core HV circuits quote circulating sheath currents approaching 50–80% of conductor current and describe induced sheath voltages that reach tens of volts per kilometre at distribution-level currents — a figure consistent with the conductor-to-sheath mutual impedance of a single-core cable, but one for which we hold no independent second source, so treat it as illustrative of the order of magnitude rather than as a design value. Sources addressing general installations quote 30–40% of conductor current in some arrangements. The discrepancy reflects voltage level, cable construction, bonding scheme and route length rather than a disagreement about the mechanism. What all sources agree on is the direction: circulating current means I²R loss in the screen, additional heat, and a real reduction in the circuit's permissible current-carrying capacity — which is a sizing consequence, not merely an earthing curiosity.
| Scheme | Where the screen is earthed | Circulating current | Standing screen voltage | What it needs |
|---|---|---|---|---|
| Both-end (solid) | Both ends | Yes — a closed loop exists | Near zero (a few volts) | Nothing extra; safest to touch; derated circuit |
| Single-point | One end only | No | Highest at the open end; proportional to route length and load | Surge voltage limiters at the open end, plus a parallel earth-continuity conductor |
| Cross-bonding | Both ends of the major section, with the screen transposed at each intervening joint bay | Approximately cancelled over a full transposition cycle | Low, provided the three minor sections are electrically equal | Sectionalised joints, a cross-bonding link box at each transposition, and balanced section lengths |
| Split single-point | Interrupted at the midpoint, link boxes and SVLs at the isolation joints | No | Controlled by the SVLs | An earth-continuity conductor linking the earthing points of all link boxes |
Compiled from four independent cable-engineering sources (see Sources). The scheme definitions and their trade-offs are consistent across all four; the quantified circulating-current ranges are quoted in the text above with their spread, not as a design value.
The failure nobody notices
On a single-point-bonded or cross-bonded circuit the screen is deliberately held off earth along a minor section. That means a single sheath-to-earth fault — a jacket damaged during backfill, water ingress at a joint bay — silently converts the arrangement into a solidly bonded one. Nothing trips. The circuit simply begins circulating screen current, loses ampacity, and runs warmer than design for the rest of its life. On a cross-bonded system the same fault also unbalances the transposition, so the vector cancellation stops working. Keentel Engineering describes the sheath test at commissioning as the only test that detects this, and notes that nothing in the conductor test sequence will find it; we did not find the test required explicitly by a standard in our library, so treat it as established industry practice rather than a clause obligation.
That is the maintenance argument for documenting which bonding scheme applies to which circuit and where the link boxes are — and the reason a hybrid plant's trench drawing needs a bonding schedule alongside it.
Connecting it back to the array
IEC 62548-1 states the array-level version of the same principle directly: equipotential bonding conductors should be laid as close as practicable to the live conductors, to reduce the area of induced loops. NEC 690.43(C) reaches the same place from the other direction by requiring the EGC to be contained in the same raceway or cable, or run with the PV circuit conductors, once they leave the array. Both rules are loop-area rules, and both are the reason a hybrid plant's trench cannot be organised purely by "keep the power and the comms apart".
On a hybrid site the loop-area problem is compounded because the corridor carries conductors from more than one of the three zones. Where a BESS DC run and an MV collection circuit occupy the same trench, the bonding arrangement selected for one of them determines whether the other sees an additional parallel path. The practical rules that follow:
- Keep bonding conductors in the same trench as the circuit they serve, not in the nearest available duct. The induced EMF is a function of loop area; separating the bonding conductor from its circuit maximises it.
- Do not create an unintended parallel earth path between zones. Two separate single-point-bonded circuits with a shared earth-continuity conductor can form a loop that neither circuit's design accounted for.
- Treat the armour rule as construction-dependent, not site-dependent. Single-core aluminium wire armour is earthed at the supply end only, with the load end insulated, to prevent circulating currents; multi-core steel tape armour is earthed at both ends so that fault current has a low-impedance path; multi-core cable with a separate protective conductor is earthed at both ends with the protective conductor as the primary earth path. The same corridor can legitimately contain both.
- Remember that the armour is a conductive part regardless of whether it is used as the earthing conductor, and must be bonded either way. "Not used as the CPC" is not the same as "not connected".
For the trench geometry itself — depth tables, backfill, spacing, and the derating that spacing implies — the two prerequisite pages remain the references: solar cable burial and conduit requirements under NEC 690 and cable ampacity by installation method. The soil-side variable that decides whether a buried run keeps its rating is covered in soil thermal resistivity and cable ampacity; the layout comparison between tray, trench and direct burial is in cable management for utility-scale solar farms.
05One-page earthing layout checklist
The following is the checklist we would want completed before a hybrid plant's earthing drawing is issued for construction. It is written as questions, because most of the failures we see are unanswered questions rather than wrong answers.
| Zone | Question to close before issue for construction | Basis |
|---|---|---|
| A. Earth reference count | For each PV subsystem, is it solidly grounded, functionally grounded, or unearthed? | NEC 690.41(A) |
| How many points connect a current-carrying conductor to earth? Functionally grounded systems permit one; solidly grounded systems connect at a single point on the PV output circuit. | 690.42; 690.47(A)(1) — for functionally grounded systems with an interactive inverter, the AC EGC path is the single connection to ground | |
| Does the site have one grounding electrode system, or several bonded into one? They must not function as independent references. | Site design | |
| B. Array zone | Is the DC-side equipment Class II or equivalent, making the unearthed-frame route available? It must be a deliberate decision, not a default. | IEC 60364-7-712, 712.412.101 — under the NEC, 690.43 applies regardless |
| If functional earthing is used, is it at a single point near the converter DC input, and is the conductor correctly distinguished (not green-and-yellow)? | IEC 60364-7-712 — single point at the converter DC input and conductor identification; IEC 62548-1, 7.3.2 limits it to at least simple AC/DC separation | |
| Once the EGC leaves the array, is it contained in the same raceway or cable as the PV conductors, or run with them? | 690.43(C) | |
| Was the EGC sized from Table 250.122 against the OCPD rating — or the assumed device where there is no OCPD — and not upsized for voltage drop? | 690.45; 690.9(B) | |
| For solidly grounded PV circuits over 250 V to ground, does bonding follow the 250.97 requirements? The scope limit applies only to those circuits. | 690.43(D) | |
| C. BESS container zone | Are all simultaneously accessible conductive parts bonded into one equipotential zone — rack frames, PCS enclosure, HVAC housings, cable containment, door and shell? | IEC 60364-5-54; 690.43 |
| Is there exactly one deliberate link from that zone to the site grounding electrode system? | IEC 60364-5-54; site design — IEC 62548-1 covers PV arrays only and does not govern the container | |
| Has the container been classified against the IEC 62933-5-2 axes — connection voltage, energy capacity, site occupancy, electrochemical type — with protective measures selected for that category rather than inherited from another project? | IEC 62933-5-2, cl. 7.10 | |
| Where the NEC governs the site: is DC ground-fault protection present for the array DC circuits, with fault indication at a readily accessible location? (For the container's own DC circuits, the governing article is 706, not 690.) | 690.41(B) requires the protection; 690.41(B)(3) sets the indication. Container DC circuits: NEC Art. 706, with grounding and bonding from Art. 250 | |
| Have the DC-side cables between rack, container and PCS been specified for the container environment — see the PV cable versus BESS cable (TÜV 2PfG 2693) comparison and the UL 3932 style explainer? | Construction selection | |
| D. Shared trench | For every single-core circuit in the corridor, is the screen or armour bonding scheme stated explicitly — solid, single-point, cross-bonded or split single-point? | IEC 60364-5-54 |
| For every single-point or cross-bonded circuit, are surge voltage limiters specified at the correct locations, with a parallel earth-continuity conductor? | Link-box design | |
| Does any combination of bonding schemes create a loop that no individual circuit's design accounted for? | Section 04 | |
| Are equipotential bonding conductors laid with their own circuit, not routed along the nearest duct? | IEC 62548-1, 7.3.2 | |
| Is the protective-earthing and equipotential-bonding continuity test recorded as a mandatory initial-verification item? | IEC 62446-1, cl. 6.1 (Category 1) | |
| Is a sheath test in the commissioning scope? A sheath-to-earth fault silently converts a single-point bonding scheme into solid bonding, and no conductor test will reveal it. | Industry practice — described by Keentel Engineering; we did not find this test required by a standard in our library | |
| E. Documentation | Does the drawing set identify, for each zone, which standard governs its earthing? | Drawing control |
| Is protective earthing and equipotential bonding continuity recorded as a mandatory initial-verification item? | IEC 62446-1 Category 1 test | |
| Are as-built bonding arrangements and link-box locations recorded, so a future sheath fault can be diagnosed without dismantling the route? | As-built record |
Verify, do not assumeGrounding continuity is a commissioning measurement, not a drawing property. European practice quoted by racking suppliers runs to at least 6 mm² copper for equipotential bonding, rising where lightning current may be carried, and separation distances between an external lightning protection system and the array must be calculated rather than taken from a rule of thumb — sources that give typical calculated values in the 30–70 cm range explicitly warn that the empirical 50 cm figure cannot be used safely. Every one of those values is a project calculation.
06What this article covers, and what it deliberately does not
Three boundaries, stated so that you can tell whether this page answers your question:
- It covers the system-level earthing topology of an array-plus-storage plant and the boundary conditions where the NEC and IEC regimes meet. It does not cover building-side protective conductor sizing or the selection of earthing and bonding cable for commercial buildings — that is the subject of our IEC 60364 earthing and bonding cable guide.
- It covers trench-level induction and bonding-scheme selection. It does not restate burial depths, backfill requirements or the NEC 690 conduit tables — those are in the NEC 690 burial and conduit requirements guide, and the ampacity consequences of the same layout decisions are in cable ampacity by installation method.
- It is not a substitute for a design engineer. Grounding-system design, step-and-touch potential assessment and electrode sizing are the responsibility of the registered engineer of record for the installation and of the authority having jurisdiction. This page is written to help you ask the right questions at the layout stage and to recognise when a specification is silent on something it should not be.
What we do publish is the cable side: the DC-side constructions that carry the currents being bonded and earthed, in both the NEC and IEC regimes. On the array side, UL 4703 PV wire and EN 50618 / IEC 62930 H1Z2Z2-K constructions are compared in IEC 62930 versus EN 50618; the battery-side package is set out in the 1,500 V DC BESS cable selection whitepaper. Where a project needs to confirm that a purchased cable actually carries the certification it claims, the method is in how to verify TÜV and UL certification for solar cables, and the supplier-side questions are collected in the cable supplier audit checklist.
Laying out a hybrid plant's DC and earthing cable package?
Send the array DC voltage and string current, the container layout, the bonding scheme for each single-core circuit, and the trench cross-section. We will come back with the conductor options for the DC-side links and the standards basis for each construction — and flag where the specification is silent.
Sources checked
- NFPA 70, National Electrical Code, Article 690 Part V (System Grounding; Point of System Grounding Connection; Equipment Grounding and Bonding; Size of Equipment Grounding Conductors; Grounding Electrode System) and Article 250.97 — read in the 2022 California Electrical Code text held in our library. nfpa.org
- NFPA 70, Article 706 (Energy Storage Systems) — scope, system requirements and installation provisions for ESS above 1 kWh; read in the 2022 California Electrical Code text held in our library. Article 706 carries the container's system-level requirements but no earthing clause of its own, so equipment grounding and bonding are taken from Article 250. nfpa.org
- EC&M, Solar Photovoltaic Systems — Part 2 — independent explanation of the same Article 690 Part V clauses, including the 690.41 grounding configurations and 690.47 electrode-system conditions. ecmweb.com
- Mike Holt Enterprises, Introduction to Article 690 — Solar Photovoltaic (PV) Systems — second independent treatment of 690.43(A)–(D), 690.45 and 690.47. mikeholt.com
- IEC 62548-1:2023 (consolidated 2025), Photovoltaic (PV) arrays — Part 1: Design requirements, clause 7.3.2 and Annex B — array earthing and bonding arrangements, including the prohibition on protective earthing of array line conductors and the loop-area rule for bonding conductors. Summarised via Solaracks and the Brunei ESCOM solar guidelines. solaracks.com
- Government of Brunei, Department of Energy (ESCOM), Guidelines and Best Practices for Solar Photovoltaic Design, Installations and Maintenance — section 3.10 earthing requirements, citing IEC 62548 for array earthing and giving the 6 mm² minimum copper bonding conductor. shena.gov.bn
- IEC 60364-7-712:2017, Low-voltage electrical installations — Part 7-712: Requirements for special installations or locations — Solar photovoltaic (PV) power supply systems — Class II requirement for DC-side equipment, functional earthing conditions, and the single-point connection to the main earthing terminal. webstore.iec.ch
- IEC 62933-5-2, Electrical energy storage (EES) systems — Part 5-2: Safety requirements for grid-integrated EES systems — Electrochemical-based systems — current edition is Edition 2.0 (2025); the standard's normative references include the IEC 60364 series. webstore.iec.ch
- IEC 62446-1:2016, Photovoltaic (PV) systems — Requirements for testing, documentation and maintenance — Part 1 — continuity of protective earthing and equipotential bonding conductors as a Category 1 (mandatory initial verification) test, clause 6.1. Read from the clause summary published by Solaracks; we hold no copy of the standard text, so this is a single-source citation.
- Keentel Engineering, Cable Testing Before Energization — sheath bonding schemes, the sheath-to-earth fault that silently converts single-point bonding into solid bonding, and the commissioning test that detects it. keentelengineering.com
- PTE (Power Transmission Engineering), Link Boxes — single-point, split single-point and cross-bonding definitions, SVL function and earth-continuity conductor requirements. pte-sa.com
- QD Britop, Cable Sheath Circulating Current in High-Voltage Systems — induced sheath voltage mechanism and the 50–80% circulating-current magnitude quoted for long single-core circuits. qdbritop.com
- Power & Cables, HV Cable Sheath Bonding Methods — independent summary of solid, single-point and cross-bonding with their operating limits. powerandcables.com
- Industrial Monitor Direct, IEC Cable Armor Grounding Requirements — armour bonding ends by cable construction (single-core AWA supply end only; multi-core STA both ends; multi-core with separate CPC both ends) stated as IEC 60364 practice. Manufacturer-distributor technical note, used as engineering practice rather than as a clause citation. industrialmonitordirect.com
How this was written: every standard and code figure in this article is checked against the standard text or the published clause summary listed in Sources before publication. Where our library does not hold a standard's clause text we state the principle without a clause number, and where two sources give different magnitudes for the same quantity we print both rather than choosing one. Site-level design decisions remain with the engineer of record.
Related product · DC-side cable for the array and the battery link
ESS Energy Storage Cable (DC 1500V)
ApplicationBESS battery racks, battery containers, PCS connections in utility, C&I and residential storage
StandardsTÜV 2PfG 2693; EN/IEC 60228 Class 5; IEC 60332-1-2
ConductorTinned copper, Class 5 flexible stranded
InsulationXLPO insulation + LSZH sheath
Voltage Rating1,500 V DC
Ampacity—
TemperatureAmbient −40 °C; conductor +125 °C max
CertificationsTÜV 2PfG 2693
Cross Sections2.5–95 mm²
H1Z2Z2-K Solar Cable (EN 50618)
ApplicationPV string and harness wiring, 1.5 kV DC utility-scale arrays
StandardsEN 50618; IEC 62930
ConductorTinned copper, Class 5
InsulationXLPO, double-insulated, halogen-free
Voltage Rating1.5 kV DC
Ampacity—
TemperatureAmbient −40…+90 °C; conductor 90 °C continuous (120 °C up to 20,000 h per EN 50618)
CertificationsTÜV Rheinland per EN 50618
Cross Sections1.5–35 mm²
Bonding the array and the battery link? Send the DC voltage, string current and container layout and we will return the constructions that fit, with their certification basis. request a quote.
Q1Can a solar-plus-storage plant use both IEC 60364 and NEC 690 grounding rules?
Yes, and most hybrid plants do — but the two regimes must be resolved at the boundaries, not merged. The array may follow IEC 62548-1 and IEC 60364-7-712, which permit an unearthed array where DC-side equipment is Class II or equivalent; the AC collection system follows NEC Article 250; and both must resolve to a single grounding electrode system for the site. The design question is where, and how many times, a conductor is connected to earth.
Q2Does NEC 690 require a separate ground rod at the PV array?
No. NEC 690.47 requires the grounding electrode system to be installed per Article 250 Part III for the building or structure supporting the array, and the array's equipment grounding conductors to be connected to it per Article 250 Part VII. For functionally grounded systems — which the code's own informational note says describes most PV systems — 690.47(A)(1) permits the array's EGC to be the only connection to ground where it ties into associated distribution equipment already connected to a grounding electrode system.
Q3How is a BESS container grounded — one earth connection or several?
Treat the container as one equipotential zone: bond all simultaneously accessible conductive parts together — rack frames, PCS enclosure, HVAC housings, containment, door and shell — and take a single deliberate link from that zone to the site grounding electrode system. Additional electrodes bonded into the same system are normal practice; a second point at which a conductor connects to earth as an independent reference is not. IEC 62933-5-2 provides the safety framework and its normative references include the IEC 60364 series.
Q4Why does earthing a cable screen at both ends reduce its current rating?
Because a screen running parallel to its own conductor behaves in part as a transformer secondary. AC in the conductor induces a longitudinal EMF along the screen, proportional to current, route length and mutual inductance. If the screen is earthed at both ends that EMF drives a circulating current: sources quote magnitudes from roughly 30–40% up to 50–80% of conductor current depending on voltage level, construction and length. The screen loss is I²R — extra heat, and a lower permissible current for the circuit.
Q5What is the difference between single-point bonding and cross-bonding?
Single-point bonding earths the screen at one end only, so no circulating current flows — but a standing induced voltage appears at the open end, which limits the section length and requires surge voltage limiters plus a parallel earth-continuity conductor. Cross-bonding splits the route into three electrically equal minor sections and transposes the screens at each intermediate joint, so the three induced EMFs cancel over a full cycle; it needs sectionalised joints and link boxes, and unbalanced section lengths leave a residual current.
Q6How is the equipment grounding conductor sized for a PV circuit?
NEC 690.45 sizes it per Table 250.122 against the rating of the overcurrent protective device. Where the circuit has no OCPD, an assumed device rated in accordance with 690.9(B) is used when applying that table. One provision catches people out: increases in equipment grounding conductor size to address voltage drop considerations are explicitly not required — so an array feeder upsized for voltage drop does not carry the EGC up with it.