Last Updated: July 17, 2026 | Version 1.1

TL;DR: IEC 62548 in Practical Engineering Terms

IEC 62548 is a key international reference for photovoltaic array design.

The current core publication is IEC 62548-1:2023, with Amendment 1 published in 2025.

In practical engineering terms, IEC 62548 addresses major PV array design topics including:

• DC array wiring
• Maximum system voltage
• Parallel string design
• Overcurrent protection
• Switching and isolation
• Earthing provisions
• Protection-device coordination

The most important principle is simple:

A PV array must be designed for its maximum possible electrical and environmental conditions, not only its normal operating values.

Engineers must consider cold-weather open-circuit voltage, reverse current from parallel strings, DC switching capability, cable conditions and protection coordination.

IEC 62548 should therefore be treated as a PV array design framework rather than a product checklist.

This guide explains the standard in practical engineering terms.

Table of Contents

1. What Is IEC 62548?
2. Current Version of IEC 62548
3. What Does IEC 62548 Cover?
4. Maximum PV Array Voltage
5. PV Strings and Parallel Array Design
6. Overcurrent Protection and gPV Fuses
7. PV DC Cable Design
8. Switching and DC Isolation
9. Earthing and Bonding
10. Surge Protection and IEC 61643
11. PV Combiner Box Design
12. Inverter Coordination
13. Inspection and Documentation
14. Common IEC 62548 Design Mistakes
15. Practical Design Workflow
16. IEC 62548 Engineering Checklist
17. Frequently Asked Questions
18. Final Engineering Recommendations

1. What Is IEC 62548?

IEC 62548 is commonly used when discussing the electrical design and safety of photovoltaic arrays.

The current publication is titled:

IEC 62548-1: Photovoltaic (PV) arrays – Part 1: Design requirements

The standard addresses design risks created by the specific characteristics of PV DC systems.

Photovoltaic arrays differ from conventional electrical circuits because they may:

• Generate voltage whenever sufficient sunlight is available
• Produce higher open-circuit voltage at low temperatures
• Include multiple parallel strings
• Use long outdoor DC cable routes
• Operate at 1000V or 1500V DC
• Remain energized after AC disconnection

These characteristics affect the selection of:

• Cables
• gPV fuses
• DC switches
• Isolators
• Surge protective devices
• Combiner boxes
• Inverter connections

IEC 62548 provides a system-level framework for addressing these issues.

Its value is not simply in identifying compliant products.

The standard helps engineers understand how the entire PV array should be designed within a coordinated Solar PV electrical protection system.

2. Current Version of IEC 62548

Many older technical articles still refer to IEC 62548:2016.

For current engineering work, the core publication is:

The current consolidated publication is IEC 62548-1:2023+AMD1:2025.

The general term IEC 62548 remains widely used in industry and online searches.

However, technical documentation should identify the actual edition used for a project.

This is especially important in:

• Tender specifications
• EPC technical documents
• Compliance statements
• Design reports
• Inspection records

Engineers should also verify whether the project uses a national or regional adoption of the IEC standard.

A generic statement such as:

Designed according to IEC 62548

may be less precise than identifying the relevant edition and adopted standard.

3. What Does IEC 62548 Cover?

IEC 62548-1 focuses primarily on photovoltaic array design.

Its scope includes major subjects such as:

• DC array wiring
• Electrical protection devices
• Switching
• Earthing provisions

In practical system terms, the standard follows the PV array toward the final power conversion equipment, normally the inverter.

It should not be assumed to cover every subsystem in a solar project.

For example, battery energy storage introduces separate issues such as:

• Battery fault current
• Battery management
• DC bus protection
• Thermal propagation

Broader PV installation requirements should also be coordinated with IEC 60364-7-712:2025 and the applicable national electrical rules.

This leads to an important engineering principle:

No single IEC standard should be expected to define every protection requirement for an entire solar power plant.

IEC 62548 primarily addresses the PV array design layer.

Other standards provide more detailed requirements for specific equipment or installation functions.

4. Maximum PV Array Voltage

Maximum PV voltage is one of the first design parameters that should be established.

Do Not Design Only from MPPT Voltage

The normal MPPT operating voltage of an inverter is not the same as the maximum voltage that a PV array can produce.

The maximum design voltage depends on factors including:

• Module open-circuit voltage
• Number of modules in series
• Module temperature coefficient
• Minimum expected temperature

Cold weather is particularly important.

As module temperature decreases, open-circuit voltage generally increases.

A string that appears acceptable under standard test conditions may exceed a device voltage limit under cold operating conditions.

Check the Complete DC Circuit

The maximum voltage assessment affects:

• PV modules
• Connectors
• DC cables
• gPV fuses
• Fuse holders
• SPDs
• DC isolators
• Circuit breakers
• Combiner boxes
• Inverter inputs

A system described as “1500V DC” is not automatically suitable for 1500V operation simply because the inverter or SPD carries a 1500V rating.

Every relevant component in the DC path must be suitable for the calculated conditions.

The complete electrical path must be reviewed, not only the main equipment.

5. PV Strings and Parallel Array Design

Series-connected modules primarily influence voltage.

Parallel-connected strings significantly affect current and fault conditions.

Normal String Current Is Not Enough

The engineer should review module data including:

• Maximum power current
• Short-circuit current
• Maximum system voltage
• Manufacturer protection limitations

However, normal operating current does not fully describe the fault condition.

Reverse Current from Parallel Strings

Consider one PV string operating independently.

Its available current is limited by the electrical characteristics of that string.

Now consider multiple strings connected in parallel.

If one string develops a fault, healthy strings may contribute reverse current toward the damaged circuit.

The designer should assess whether this current could exceed the safe limits of:

• PV modules
• String cables
• Connectors
• Other connected components

This analysis directly affects the need for string overcurrent protection.

More parallel strings do not simply mean that a larger fuse should be installed.

The fault architecture must be evaluated.

6. Overcurrent Protection and gPV Fuses

Overcurrent protection is one of the most important areas of PV array design.

What Is a gPV Fuse?

A gPV fuse is designed for photovoltaic DC circuit protection.

PV fuse-links for string and array protection are specifically addressed by IEC 60269-6.

PV circuits can involve:

• High DC voltage
• Continuous operating current
• Reverse current from parallel strings
• High enclosure temperatures
• Outdoor thermal cycling

These operating conditions differ from many conventional AC applications.

Understanding the difference between a gPV fuse and a standard fuse is important because ordinary AC fuses should not automatically be used as substitutes in PV DC circuits.

Does Every PV String Need a Fuse?

No.

The need for string protection depends on factors such as:

• Number of parallel strings
• Potential reverse current
• Module limitations
• Cable current-carrying capacity
• Equipment withstand capability

The correct process is:

Analyze the fault condition first. Select the protective device second.

Key gPV Fuse Selection Parameters

A gPV fuse review should include:

Rated DC Voltage

The fuse and fuse holder must be suitable for the maximum relevant DC voltage.

Rated Current

The fuse should carry normal PV operating current without nuisance operation while still protecting the circuit during abnormal overcurrent.

Module Limitations

The module manufacturer’s protection limits should be checked.

Breaking Capacity

The device must be capable of interrupting the applicable fault current.

Installation Temperature

Fuse behavior can be influenced by actual enclosure temperature.

A combiner box in direct sunlight may operate at a much higher internal temperature than the outdoor ambient temperature.

Protection Coordination

A fuse should not be selected independently from the protected circuit.

The protection relationship can be simplified as:

PV Source → Cable → Equipment Limit → Protective Device

The protective device should operate before an unacceptable current condition causes serious damage to the protected circuit.

This is why fuse selection is an engineering coordination problem rather than a simple current-rating comparison.

For common 1000V PV string applications, engineers can also review KUANGYA’s 10×38 gPV fuse link for solar systems.

7. PV DC Cable Design

PV cable design is directly related to protection.

A fuse or breaker cannot correct fundamentally incorrect conductor selection.

Current-Carrying Capacity

Cable sizing should consider:

• Design current
• Ambient temperature
• Cable grouping
• Installation method
• Enclosure temperature
• Solar exposure

The design should reflect realistic installation conditions.

Voltage Rating

Cable insulation must be suitable for the maximum PV circuit voltage.

This becomes increasingly important in 1500V DC systems.

Cable Routing

PV cable routing should consider:

• Mechanical protection
• Sharp edges
• UV exposure
• Water accumulation
• Connector strain
• Maintenance access

Positive and negative conductors should also be routed in a way that avoids unnecessarily large loop areas.

Cable management is not only an installation-quality issue.

It influences long-term electrical reliability.

Connector Compatibility

PV connectors are a common failure point.

Physically mating connectors should not automatically be assumed to be electrically compatible.

Differences in:

• Contact materials
• Contact geometry
• Mechanical tolerances

may increase contact resistance.

This can lead to:

• Local heating
• Insulation damage
• Arcing
• Long-term failure

Connector selection and installation should therefore form part of the PV electrical design review.

8. Switching and DC Isolation

Safe isolation is a major requirement in PV array design.

Purpose of a DC Isolator

A DC isolator provides a means of separating part of the PV DC circuit.

It may support:

• Maintenance
• Inspection
• Inverter replacement
• Combiner box servicing
• Emergency procedures

The device must be suitable for the actual PV DC application.

A DC Isolator Is Not Automatically a Circuit Breaker

The two devices perform different functions.

A DC isolator primarily provides an isolation function.

An overcurrent protection device responds to abnormal current conditions.

A circuit breaker may provide switching and protective functions according to its design.

Engineers should select the device according to the required function rather than using the terms interchangeably.

Verify DC Switching Capability

PV DC switching is technically demanding because DC current does not have the natural periodic zero crossing found in AC systems.

The designer should verify:

• DC voltage rating
• Current rating
• Pole configuration
• Wiring arrangement
• Switching duty
• Environmental suitability

Some multi-pole DC devices require a specific connection arrangement to achieve their intended rating.

Requirements for switches, disconnectors and switch-disconnectors are addressed by IEC 60947-3.

Incorrect wiring may reduce interruption capability.

Isolation Must Be Practical

A disconnect shown on a single-line diagram may still be poorly positioned in the actual installation.

Engineers should ask:

• Is the isolator safely accessible?
• Is the isolated circuit clearly identified?
• Can maintenance personnel control reconnection?
• Does the arrangement support real maintenance work?

These factors should be evaluated together during DC switch-disconnector selection, rather than checking voltage and current labels independently.

Safe isolation is both an electrical and operational design issue.

9. Earthing and Bonding

PV arrays may include extensive conductive structures such as:

• Module frames
• Mounting rails
• Electrical enclosures
• Cable management systems

The earthing and bonding strategy should be coordinated with:

• Electrical installation design
• Inverter requirements
• Lightning protection
• Applicable local regulations

Where protective bonding is required, the continuity of the bonding path should be maintained throughout the life of the installation.

Potential long-term problems include:

• Loose connections
• Corrosion
• Dissimilar metals
• Mechanical damage

Earthing Does Not Replace Surge Protection

A good earthing arrangement does not eliminate the need for correctly selected SPDs.

Similarly, an SPD does not correct a poor bonding system.

These functions interact but are not interchangeable.

10. Surge Protection and IEC 61643

PV arrays often include long outdoor conductors.

These conductors can be exposed to transient overvoltages caused by:

• Nearby lightning
• Direct lightning effects
• Electromagnetic coupling
• Switching events

IEC 62548 should be used together with more specific SPD standards where detailed surge protection design is required.

The IEC 61643 series includes:

• IEC 61643-31 for SPDs used on the DC side of PV installations
• IEC 61643-32 for PV SPD selection, installation and coordination

For a wider explanation of the standard family, SPD classifications and selection parameters, read our complete IEC 61643 surge protective device guide.

Key PV SPD Parameters

Important selection parameters may include:

• Maximum continuous operating voltage
• Voltage protection level
• Nominal discharge current
• Maximum discharge capability
• SPD type
• PV system topology

Selecting a product simply because it is described as a “solar SPD” is not sufficient.

Installation Location Matters

SPD performance depends partly on installation.

Long connection conductors can add additional voltage during a fast transient event.

Connection paths should therefore be kept appropriately short and direct.

Long cable distances between the PV array, combiner equipment and inverter may also require protection at more than one location.

Surge protection should be evaluated across the complete electrical path.

For 600V to 1500V photovoltaic applications, KUANGYA provides a Type 2 PV surge protective device for combiner boxes, inverter DC inputs and PV distribution cabinets.

11. PV Combiner Box Design

The PV combiner box is a major coordination point in multi-string systems.

It may include:

• gPV fuses
• Fuse holders
• DC SPDs
• DC switching devices
• Busbars
• Terminals
• Monitoring equipment

The combiner box should reflect the overall PV array protection strategy.

String Input Design

Review:

• Number of incoming strings
• String current
• Reverse-current conditions
• Fuse requirements
• Cable entry
• Polarity identification

Output Circuit

The combined output may carry significantly more current than one individual string.

The designer should verify:

• Busbar rating
• Output cable rating
• Terminal rating
• Switching-device rating

Internal Temperature

Heat can be produced by:

• Fuses
• Fuse holders
• Terminals
• Busbars
• Switching devices

Solar radiation can further increase enclosure temperature.

Component ratings and derating should reflect the actual internal operating environment.

IP Rating Is Not Enough

A high ingress-protection rating is important, but it does not prove that a combiner box has been correctly designed.

Electrical safety also depends on:

• Internal spacing
• Thermal management
• Component coordination
• Cable routing
• Connection quality

The complete assembly should be evaluated.

12. Inverter Coordination

Effective solar inverter protection requires the PV array voltage, current and external protection architecture to coordinate with the inverter or other power conversion equipment.

Important inverter parameters may include:

• Maximum DC input voltage
• MPPT voltage range
• Maximum input current
• Maximum short-circuit current
• Number of MPPT channels
• Number of inputs
• Internal DC protection

Do Not Confuse MPPT Voltage with Maximum Input Voltage

The MPPT range describes the inverter’s normal operating range.

It is not the same as the maximum permissible DC input voltage.

Cold-weather open-circuit voltage must be checked separately.

Check Current Limits

Modern PV modules may have relatively high operating and short-circuit currents.

A string arrangement can be acceptable from a voltage perspective while exceeding the inverter’s current limitations.

Both voltage and current must be reviewed.

Verify Internal Protection

Some inverters include:

• DC SPDs
• DC switches
• Fuse functions
• Insulation monitoring

These functions should be checked against actual manufacturer documentation.

Do not assume every inverter provides the same internal protection architecture.

13. Inspection and Documentation

Documentation, commissioning tests and inspection for grid-connected PV systems are addressed more specifically by IEC 62446-1.

Correct design does not eliminate installation errors.

Documentation, commissioning and inspection are therefore essential.

Important system documentation may include:

• Single-line diagrams
• String configuration
• Module data
• Inverter data
• Protection-device ratings
• Cable information
• Isolation points
• Earthing arrangements

Documentation should match the installed system.

Commissioning Inspection

Inspection should look for:

• Incorrect polarity
• Loose connections
• Damaged cables
• Incorrect protection ratings
• Incorrect switch wiring
• Poor cable support
• Water-entry risks

The objective is to verify both electrical design and installation quality.

Developing Failures

Many PV electrical failures develop gradually.

Examples include:

• Increasing connection resistance
• Terminal heating
• Connector deterioration
• SPD end-of-life
• Water ingress
• Corrosion

Preventive, corrective and performance-related maintenance practices are addressed by IEC 62446-2.

Periodic inspection can help identify problems before they become major failures.

14. Common IEC 62548 Design Mistakes

Mistake 1: Referring to IEC 62548 Without Checking the Edition

The project should identify the applicable publication and edition.

Mistake 2: Calculating Voltage Only from Normal Operating Conditions

Cold-weather open-circuit voltage must be evaluated.

Mistake 3: Assuming Every String Needs the Same Fuse Arrangement

String protection should reflect the actual fault architecture.

Mistake 4: Selecting a Fuse Only by Current Rating

Voltage, module limitations and installation conditions also matter.

Mistake 5: Using an AC Switch in a PV DC Circuit

The device must be suitable for the actual DC switching duty.

Mistake 6: Selecting Every Component Only by the Label “1500V”

Voltage rating alone does not define complete suitability.

Mistake 7: Ignoring Long Cable Routes

Cable length affects voltage drop, surge exposure and mechanical design.

Mistake 8: Assuming the Inverter Provides All Protection

Internal protection must be reviewed against the external array design.

Mistake 9: Choosing a Combiner Box Only by String Count

Current rating, thermal design and protection coordination also matter.

Mistake 10: Treating Compliance as a Product Certificate Exercise

Individually compliant components do not automatically create a correctly coordinated PV array.

15. Practical IEC 62548 Design Workflow

A practical PV array design workflow can be organized into eight steps.

Step 1: Collect Module Data

Record:

• Voc
• Isc
• Vmp
• Imp
• Temperature coefficients
• Maximum system voltage
• Relevant fuse limitations

Step 2: Define the Array Architecture

Determine:

• Modules per string
• Number of parallel strings
• MPPT allocation

Step 3: Calculate Maximum Voltage

Consider project temperature conditions and module characteristics.

Check all relevant DC equipment.

Step 4: Evaluate Current and Fault Conditions

Review:

• String current
• Short-circuit current
• Parallel current contribution
• Inverter current limits

Step 5: Define Overcurrent Protection

Assess whether string protection is required.

Select appropriately rated gPV fuses or other protective devices.

Step 6: Design Cabling and Isolation

Review:

• Cable rating
• Current capacity
• Routing
• Voltage drop
• DC isolation points

Step 7: Assess Surge and Combiner Protection

Coordinate:

• PV SPDs
• Combiner box design
• Fuse protection
• Switching devices

Correct DC fuse and DC SPD coordination is essential because overcurrent protection and transient overvoltage protection address different fault conditions.

Step 8: Verify the Complete DC Path

Review:

PV Module → String → Cable → Protection → Combiner → Isolation → Inverter

No component should be evaluated independently from the surrounding circuit.

16. IEC 62548 Engineering Checklist

PV Modules and Strings

• Module electrical data reviewed
• Modules per string confirmed
• Parallel string quantity confirmed
• Temperature coefficients checked
• Module protection limitations reviewed

Voltage Design

• Maximum open-circuit voltage calculated
• Minimum temperature considered
• Inverter maximum DC voltage verified
• All DC equipment voltage ratings checked

Current and Overcurrent Protection

• String current reviewed
• Short-circuit current reviewed
• Reverse current evaluated
• String fuse requirement assessed
• gPV fuse coordinated with the protected circuit

DC Cabling

• Cable voltage rating suitable
• Current capacity checked
• Installation temperature considered
• Cable routing reviewed
• Mechanical support reviewed

Switching and Isolation

• Isolation points identified
• DC voltage rating confirmed
• Current rating confirmed
• Pole configuration verified
• Device location supports maintenance

Surge Protection

• Surge risk assessed
• PV SPD type reviewed
• SPD voltage characteristics coordinated
• Installation location checked
• Connection path reviewed

Combiner Box

• String input quantity correct
• Fuse ratings coordinated
• SPD suitable for the system
• Output current verified
• Thermal design considered
• Environmental protection suitable

Inverter Coordination

• Maximum DC voltage checked
• MPPT range checked
• Input current checked
• Short-circuit input limits checked
• Internal protection functions verified

17. Frequently Asked Questions

What is IEC 62548?

IEC 62548 is commonly used to refer to the international design requirements for photovoltaic arrays.

The current core publication is IEC 62548-1.

What is the current version of IEC 62548?

The current core edition is IEC 62548-1:2023, with Amendment 1 published in 2025.

The applicable edition and national adoption should be verified for each project.

Does IEC 62548 cover battery energy storage?

The main scope focuses on PV array design.

Battery energy storage requires additional standards and system-specific protection assessment.

Does every PV string need a fuse?

No.

The need for string overcurrent protection depends on parallel-string configuration, reverse current and the electrical limits of the circuit.

What is the difference between IEC 62548 and IEC 60364-7-712?

IEC 62548-1 focuses on PV array design.

IEC 60364-7-712 addresses electrical installation requirements associated with PV power supply installations.

They are related but not interchangeable.

Does IEC 62548 cover surge protection?

It addresses PV electrical protection at the array design level.

Detailed PV SPD requirements and selection principles are addressed more specifically by IEC 61643-31 and IEC 61643-32.

Can an AC isolator be used in a PV DC circuit?

Only if the device is specifically suitable and rated for the actual DC voltage, current and switching duty.

An AC rating alone does not demonstrate suitability for PV DC use.

Is IEC 62548 only for 1500V systems?

No.

Its design principles apply to PV array design more broadly.

However, 1500V systems require particularly careful review of voltage ratings, insulation and DC switching.

Is a compliant fuse enough to make a combiner box compliant?

No.

The complete assembly must be reviewed for:

• Component ratings
• Thermal conditions
• Internal wiring
• Environmental protection
• Protection coordination

18. Final Engineering Recommendations

IEC 62548 should not be treated as a list of protection devices that must be installed in every photovoltaic system.

Its real engineering value is in system-level design.

Start with the PV module.

Define the string configuration.

Calculate the maximum voltage.

Evaluate current and reverse-current conditions.

Then coordinate:

• DC cables
• gPV fuses
• Surge protective devices
• DC isolators
• Combiner boxes
• Inverter inputs

Every protection device should address a specific electrical risk.

A gPV fuse should be selected because an overcurrent condition has been identified.

An SPD should be selected because surge risk has been evaluated.

A DC isolator should provide a clearly defined isolation function.

A combiner box should integrate multiple circuits without creating thermal or coordination problems.

The central engineering lesson is:

PV array safety depends on coordinated electrical design, not on selecting protective devices independently.

For modern photovoltaic systems, the complete DC path should always be reviewed:

PV Module → PV String → DC Cable → Overcurrent Protection → Combiner Box → Surge Protection → Isolation → Inverter

That is the practical purpose of IEC 62548.