The hazard is the direct current
Most people assume the dangerous part of a solar installation is the high voltage. It is closer to the truth to say the dangerous part is the direct current, or DC — and the difference matters enormously for how you protect a system.
Alternating current, the kind that arrives from the grid, reverses direction a hundred times a second. Every time it passes through zero volts, an arc between two conductors loses its energy and goes out. Direct current does no such thing. A solar array produces a steady, one-directional current, so once an arc strikes across a loose terminal or a corroded connector, it keeps burning. And here is the awkward part: that arc draws no more current than the system normally carries, so a fuse or breaker sees nothing wrong. It will happily burn on a rooftop for hours.
This is why the international standard for PV array design, IEC 62548, is explicit that DC arrays can produce and sustain arcs at currents no greater than normal operating current, and that high-resistance connections — the kind created by a poorly crimped connector or a terminal loosened by years of thermal cycling — are the usual cause.
The four layers that keep a system safe
A safe solar-plus-storage site is not one device. It is four overlapping systems, each covering what the others miss.
Layer 1 — Earthing and bonding
Earthing gives fault current a deliberate, low-resistance path back to ground instead of through a person or a random piece of metalwork. In India the governing code of practice is IS 3043. For a solar installation the important idea is equipotential bonding: module frames, mounting rails, inverter enclosures, cable trays, the battery cabinet and the building’s earth must all be tied to a common earthing system, so that during a fault or a strike no two surfaces a person could touch sit at meaningfully different voltages.
The common failure here is a rooftop array bonded to its own separate earth pit, isolated from the building’s. That arrangement is worse than useless — it creates exactly the voltage difference between metal surfaces that bonding exists to prevent. Target earth resistance values depend on soil, system size and the standard being applied, so treat any single number you are quoted as something to check against IS 3043 and your consultant’s design rather than a universal rule.
Layer 2 — Lightning and surge protection
These are two different jobs, and conflating them is a frequent and expensive mistake.
- A lightning protection system (LPS), designed to IEC 62305, handles a direct strike to the structure — air terminals, down conductors and an earth termination that carry an enormous current safely around the building.
- Surge protection devices (SPDs) handle the far more common indirect event: a strike a few hundred metres away, or a grid switching operation, that induces a voltage spike travelling in along your cables. An SPD clamps that spike and diverts it to earth before it reaches an inverter.
A rooftop array is, unavoidably, a large metal structure in an exposed position with long cable runs — an efficient antenna for induced surges. SPDs belong on both sides: on the DC side between array and inverter, and on the AC side at the point of grid connection. Fitting only the AC side is common and leaves the inverter’s most vulnerable input unprotected. Both must be bonded to the same earthing system as layer 1, or the surge simply finds another route.
Layer 3 — Isolation and overcurrent protection
This is the layer IEC 62548 is mostly about: DC-rated isolators that can actually break a DC arc (an AC-rated switch used on DC is a genuine hazard), correctly rated string fuses, cable sized for the current and for rooftop temperatures, and residual current protection on the AC side. It also covers the ability to switch the array off safely for maintenance and for firefighters — a real concern when a roof stays energised in daylight no matter what you switch off downstairs.
On the equipment side, grid-connected inverters sold in India must hold IS 16221 certification, and modules carry fire-class ratings under IS 14286. These certifications are the baseline; they say the component was tested, not that it was installed correctly.
Layer 4 — Detection and fire protection
Because a sustained DC arc is invisible to conventional overcurrent protection, the final layer is about finding faults rather than interrupting them. Periodic thermal imaging of connectors, combiner boxes and terminals catches the high-resistance joints that precede arcs. Arc-fault detection devices, mandatory on rooftop systems in some jurisdictions, listen for the electrical signature of an arc. And where a battery is present, the detection requirement steps up considerably.
What changes when you add a battery
A battery introduces a category of hazard that solar alone does not have: stored energy that cannot be switched off. Open every isolator, disconnect the grid, wait for nightfall, and the battery is still fully live. Anyone working on the system has to treat it accordingly, and the installation needs its own clearly labelled isolation points and emergency shutdown.
The failure mode is different too. A battery fault can lead to thermal runaway — a self-sustaining reaction we cover in depth in BESS fire safety and thermal runaway. That is why storage systems carry a battery management system watching every cell, gas and heat detection, and suppression appropriate to the enclosure, rather than the smoke detector that might suffice for an inverter room. The certification framework is set out in BESS safety standards explained, and India’s CEA has notified dedicated battery safety rules taking effect in April 2027 for larger installations.
Questions worth asking your installer
Safety is largely invisible on a commissioned system — the difference between a good and a dangerous installation is inside the connectors. A few questions surface most of it:
| Ask this | What a good answer sounds like |
|---|---|
| How is the array earthed? | A single bonded system tying frames, rails, enclosures and building earth together, designed to IS 3043 |
| Where are the SPDs? | Both DC and AC sides, bonded to the same earth, with the type stated |
| Are the DC isolators DC-rated? | Yes, rated for the array’s full open-circuit voltage and current |
| Who crimped the DC connectors? | Named, trained technicians using the matched tool for that connector brand — never mixed brands |
| What is the inspection schedule? | Periodic thermography of connections, plus torque checks on terminals |
| How is the battery isolated and monitored? | Dedicated isolation, BMS with cell-level monitoring, gas/heat detection, labelled emergency shutdown |
The connector question is not a trivial one. Mixing connector brands that look identical but are not designed to mate is a well-known cause of high-resistance joints, and it is invisible once the array is up.
What this means for you
If you are commissioning solar or solar-plus-storage for a commercial site, the useful mental shift is this: most of your fire risk is decided during installation, not at purchase. Certified modules, a BIS-approved inverter and a good battery will not save a system whose connectors were crimped with the wrong tool or whose array earth is isolated from the building’s.
So specify the four layers explicitly in your tender rather than assuming they are included — earthing and bonding to IS 3043, an LPS to IEC 62305 with SPDs on both DC and AC sides, DC-rated isolation and protection to IEC 62548, and detection sized for whether a battery is present. Then budget for periodic thermography, which is inexpensive and catches the developing faults nothing else will see. If you are pairing storage with the array, treat the battery as its own system with its own isolation and detection, not as an add-on.
Standards and regulations here are updated by notification, so verify the current CEA regulations and applicable IS/IEC editions before finalising a design. To have a proposed solar-plus-storage design reviewed against these four layers before you sign, talk to our engineering team — or if you are still at the sizing stage, start with our savings calculator and bring us the shortlist.
Technical and regulatory snapshot as of August 2026. Indian Standards, IEC editions and CEA safety regulations are revised by notification; confirm current requirements and certifications with a licensed electrical consultant before design or financial decisions.