Best Fuses for Solar Farms

About this list

This list follows the power path of a typical utility-scale PV plant, from the modules through the DC collection system and inverter to the medium-voltage step-up transformer, and names the fuse type that normally protects each stage. Standards are cited from the IEC and UL Standards & Engagement pages that define them. It is a map of fuse types, not a ranking of suppliers.

1. 1. gPV string fuses in the combiner box

In short: Protecting individual PV strings and their cables against reverse current from parallel strings

When several strings are paralleled in a combiner box, a fault in one string can be fed by the others. String fuses sit in each string's conductors to interrupt that current. They must be in the gPV category: full-range fuses that can clear low overcurrents as well as short circuits in a DC circuit with no natural current zero.

IEC 60269-6 sets the requirements for fuse-links protecting PV strings and arrays in circuits up to 1500 V DC. In North America, UL 248-19 covers PV fuses protecting strings, arrays and their wiring. String fuses are usually cylindrical (for example 10 x 38 or 10 x 85 mm), sized by the array design.

• Category: gPV (full-range, photovoltaic)
• Standards: IEC 60269-6; UL 248-19 in North America
• Voltage class must cover open-circuit voltage at the lowest expected temperature

See the DENCO range

2. 2. gPV array fuses at recombiners and inverter DC inputs

In short: Protecting the larger cables that carry combined string current to the inverter

Downstream of the combiners, larger conductors carry the current from a group of strings to a recombiner or directly to the inverter's DC input. These positions use higher-current gPV fuses, commonly NH-style blade fuses in the 1XL, 2XL and 3L sizes built for 1500 VDC. Manufacturers describe them as protection in sub-arrays, arrays or at the DC input of inverters.

They are still gPV fuses under IEC 60269-6 or UL 248-19, but they are not interchangeable with string fuses: body size, holder and current class all differ.

• Common formats: NH1XL, NH2XL, NH3L at 1500 VDC
• Often available with a striker
• Specify with the recombiner or inverter maker's data

gPV array and main fuses website

3. 3. Fuse bases and holders rated for the DC voltage

In short: Making sure the whole fuse assembly, not just the fuse-link, suits a 1000 or 1500 VDC system

An assembly is rated only as high as its lowest-rated part: a 1500 VDC fuse in a 1000 VDC holder makes a 1000 VDC assembly. Holders and bases for PV duty are rated by body size and DC voltage, and many are sold only for particular fuse sizes. When you order, specify the fuse and base together, or confirm that the existing base carries the system voltage.

DENCO supplies gPV fuses with matching bases across 600 to 1500 VDC, which lets one quote cover both parts.

• Match holder DC rating to system voltage
• Match holder to fuse body size
• Quote fuse and base together where possible

See the DENCO range

4. 4. High-speed semiconductor fuses inside the inverter

In short: Protecting IGBT bridges and DC-link components that gPV fuses are not intended to protect

UL 248-19 states that PV fuses are not intended to protect downstream inverter components such as capacitors, or against those capacitors discharging back into the array. Inverter makers therefore use high-speed (semiconductor) fuses inside the inverter, chosen for low let-through energy (I²t) so a fault clears before the power semiconductors are destroyed.

IEC 60269-4 covers fuse-links protecting semiconductor devices in circuits up to 1000 V AC or 1500 V DC; UL 248-13 covers semiconductor fuses in North America. These fuses are specified by the inverter manufacturer and should be replaced like for like.

• Category: typically aR (short-circuit only) or gR
• Standards: IEC 60269-4; UL 248-13
• Replacement must match I²t and arc voltage, not only amperes

See the DENCO range

5. 5. Battery fuses for co-located energy storage

In short: Solar-plus-storage plants with battery racks and DC-coupled or AC-coupled storage

Where a solar farm includes battery energy storage, remember that battery short-circuit currents behave differently from PV currents: a battery can deliver a very high fault current with a fast rate of rise. Fuses for this duty belong to their own categories, gBat (full-range) and aBat (partial-range).

IEC 60269-7 sets the supplementary requirements for fuse-links protecting batteries and battery systems up to 1500 V DC. In North America, UL 248-21 (first edition October 2025) covers fuses protecting batteries and battery systems rated 2000 V DC or less. A gPV fuse is not a substitute for a battery fuse.

• Categories: gBat and aBat
• Standards: IEC 60269-7; UL 248-21
• Positions: rack, bank and module level

Battery fuses for co-located storage website

6. 6. Bay-O-Net and backup current-limiting fuses in the step-up transformer

In short: Oil-filled pad-mounted inverter step-up transformers on the medium-voltage collector system

Solar farms commonly step inverter output up to collector voltage with pad-mounted transformers, and transformer builders make dedicated solar inverter step-up (ISU) designs for this job. Pad-mounted transformers are usually self-protected by a bayonet-mounted fuse in the high-voltage compartment, in series with a backup current-limiting fuse.

The bayonet fuse clears secondary faults and transformer overloads and is field-replaceable. The backup current-limiting fuse operates only for a failure inside the transformer, so it is not a routine field replacement. DENCO's oil-immersed family covers Bay-O-Net holders and links plus oil-submersible current-limiting backup fuses.

• Bayonet (expulsion) fuse: field-replaceable, clears secondary faults and overload
• Backup current-limiting fuse: clears internal transformer faults
• Coordinate the pair using the transformer maker's fusing tables

See the DENCO range

7. 7. Loadbreak elbow fuses on underground collector circuits

In short: Plants whose medium-voltage collector cables terminate on dead-front equipment with loadbreak elbows

Pad-mounted equipment is typically fed by polymeric cable terminated in loadbreak elbows, which allow switching and isolation in the high-voltage compartment. Where a plant needs fusing at a cable termination, a loadbreak elbow fuse combines the elbow connection with a current-limiting fuse. DENCO's loadbreak elbow and load break disconnect fuses are 25 kV class for underground distribution.

• Fits dead-front, underground cable systems
• 25 kV class (DENCO family)
• Operate only with hot-stick procedures and PPE per NFPA 70E

See the DENCO range

8. 8. E-rated fuses for other medium-voltage transformers

In short: Medium-voltage transformer primaries elsewhere on site, such as those feeding station auxiliaries

Where a plant has medium-voltage transformers protected by fuses in switchgear or fused switches, E-rated current-limiting fuses are the usual choice. ANSI/IEEE C37.46 defines the E rating: a fuse rated 100 E or less melts in 300 seconds at 200 to 240% of its rating, and a fuse above 100 E melts in 600 seconds at 220% to 264%.

ANSI C37.40 classes current-limiting fuses as general-purpose, back-up or full-range, which tells you what range of fault current the fuse can clear. The class and rating must come from the transformer data and a coordination study.

• E-rating definition: ANSI/IEEE C37.46
• General-purpose, back-up and full-range classes: ANSI C37.40
• DENCO families include 9F60/EJ-1, 9F62/EJO-1 and Clip Lock 14 series

See the DENCO range

Why solar fuses are not interchangeable

Each fuse category in the IEC 60269 system is defined for a particular job. The first letter tells you the breaking range ("g" is full-range, "a" is short-circuit only) and the rest tells you the application: gPV for photovoltaic strings and arrays, aR or gR for semiconductors, gBat or aBat for batteries, gG for general cable protection. A gG or aR fuse of the same ampere rating is not a substitute for a gPV fuse, and a gPV fuse is not a substitute for a battery or semiconductor fuse.

Medium-voltage fuses on the AC side follow a different family of standards altogether, principally ANSI/IEEE C37 in North America and IEC 60282-1 internationally.

What to send when you request a solar fuse quote

Whichever supplier you use, a PV fuse quote goes faster when the request includes everything the supplier needs up front.

• Maximum system DC voltage, including open-circuit voltage at the lowest expected temperature
• String short-circuit current and the number of strings in parallel
• Required fuse ampere rating, if the design has already fixed it
• Fuse format (cylindrical size or NH size) and holder or base type
• Whether you need fuses only or fuses and bases together
• The standard or listing the installation must meet
• Ambient temperature range, enclosure type, quantity and required-by date

Frequently asked questions