What is H1Z2Z2-K voltage drop and how is it calculated?

Voltage drop is calculated as twice the one-way conductor resistance multiplied by the string current, because the current flows out and back. For a 6 mm2 tinned copper conductor the resistance is about 3.39 ohm per kilometre at 20 C. The practical check is to compare the resulting drop against the design allowance, commonly 2 percent of the string voltage, and increase the cross section if it is exceeded.

Solar PV Cable: H1Z2Z2-K, EN 50618 and IEC 62930

The DC side of a photovoltaic array is not an ordinary electrical installation. Cable runs in permanent sunlight, at up to 1.5 kV DC, on a circuit that cannot be switched off during daylight. This page sets out how PV cable is specified, what the designations actually mean, and how conductor size is chosen — the decisions that determine whether a string survives twenty-five years in the field.

EN 50618 / IEC 62930 1.0/1.0 kV AC · 1.5 kV DC 2.5 – 16 mm² Tinned copper, class 5 −40 °C to +90 °C

Why PV cable is a separate product

A PV array puts a cable in conditions that no building cable standard was written for. Four of them matter more than the rest.

1.5 kV DC, not 400 V AC

Utility-scale strings now operate at 1500 V DC, and IEC 62930 and EN 50618 set the reference rating at 1.5 kV DC. Standard 0.6/1 kV building cable is neither rated nor tested for that. Direct current also arcs differently from alternating current: it has no natural zero crossing, so a connector or cable fault that would self-extinguish on AC can sustain.

Permanent UV and ozone exposure

Most DC cable is clipped to the mounting structure in direct sunlight for the life of the plant. EN 50618 therefore specifies cross-linked halogen-free polyolefin insulation and sheath rather than PVC, and includes ozone and weathering tests. This is the single most common reason cheap non-PV cable fails early in the field.

The circuit stays live

A PV array cannot be switched off at the source. As long as there is light there is voltage on the string, so cable and connector work on the DC side is live work by definition. Cable that keeps its insulation properties and its joint resistance is what makes that tolerable.

Wide temperature cycling, every day

A conductor in full sun can sit far above ambient while carrying current, then cool overnight. The cycling repeats every day for decades. The class 5 fine-strand conductor and the cross-linked insulation are chosen to tolerate that movement without hardening or cracking.

Purchase note: the most expensive PV cable mistake is not paying too much — it is using ordinary cable on a 1500 V DC string because it looks the same on the drum. Ask for the designation (H1Z2Z2-K), the standard it is made to, and the rated voltage in writing before the cable reaches site.

H1Z2Z2-K and PV1-F: what the designations mean

Two designations appear on almost every PV cable datasheet. They come from different documents and should not be treated as synonyms.

Aspect	H1Z2Z2-K	PV1-F
Source document	EN 50618 (European standard for photovoltaic system cables)	TÜV Rheinland specification 2 PfG 1169
Rated voltage	1.0/1.0 kV AC, 1.5 kV DC	0.6/1.0 kV AC, 1.8 kV DC
Max. conductor temperature	90 °C continuous, 120 °C for 20,000 h	90 °C continuous
Conductor	Tinned copper, class 5 to EN 60228	Tinned copper, fine strand
Insulation and sheath	Cross-linked halogen-free polyolefin (XLPO)	Cross-linked halogen-free polyolefin
Where it is specified	European and international projects citing EN 50618 or IEC 62930	Projects where the specification names TÜV 2 PfG 1169

The two rating sets are not interchangeable. Quoting the PV1-F figure of 1.8 kV DC against an H1Z2Z2-K product, or the reverse, is a documentation error that a technical adviser will find. Treasol supplies both designations across the PV cable range from 2.5 to 16 mm², and states which standard each drum is manufactured to.

Construction and materials

Every item below exists for a reason that shows up in the field. This is the specification of the Treasol H1Z2Z2-K range.

Property	Value
Type designation	H1Z2Z2-K to EN 50618; PV1-F to TÜV 2 PfG 1169 also available
Rated voltage	1.0/1.0 kV AC, 1.5 kV DC
Max. system voltage	1500 V DC
Conductor	Tinned copper, class 5 to EN 60228 — flexible, and corrosion resistant at the strands
Insulation	Cross-linked halogen-free polyolefin
Sheath	Cross-linked halogen-free polyolefin, low smoke
Service temperature	−40 °C to +90 °C
Max. conductor temperature	+120 °C for 20,000 h
Flame retardant	EN 60332-1-2
Halogen free	EN 60754-1 / EN 60754-2
Ozone resistance	EN 60811-2-1
Cross section	2.5 / 4.0 / 6.0 / 10 / 16 mm²
Colours	Red and black

Ozone resistance is worth singling out. Ozone is produced around electrical equipment and in strong sunlight, and it attacks the double bonds in ordinary rubber and some polyolefin compounds, causing surface cracking that then propagates under bending. EN 60811-2-1 is the test that separates a genuine PV compound from a cable that merely looks black and flexible on delivery.

Choosing the cross section

Two requirements decide the conductor size, and on real projects the second one usually wins.

Cross section	Typical use	What decides it
2.5 mm²	Short module-to-module jumpers, low-current runs	Ampacity is rarely the limit; used where runs are short and mechanical handling favours a smaller cable
4 mm²	Common for residential and small commercial strings	Frequently the minimum that satisfies voltage drop on a typical roof run
6 mm²	The default for most commercial and utility-scale string wiring	The usual balance between voltage drop, ampacity and handling
10 mm²	Long string home runs, larger string currents	Chosen when voltage drop on a long run exceeds the allowance at 6 mm²
16 mm²	Long DC feeders, combiner-box to inverter runs	Voltage drop and, at higher currents, ampacity together

The rule of thumb that matters: ampacity is a check, voltage drop is the design driver. A 6 mm² PV cable carries far more current than a single string produces, but on a 120-metre run it will still be rejected if the drop exceeds the allowance. Size for drop first, then confirm ampacity — not the other way round.

Derating and voltage drop

A cable rating in a table is measured under stated conditions. Site conditions are not those conditions.

Voltage drop is a round trip

Current flows out along one conductor and back along the other, so the drop is twice the one-way figure. For a 6 mm² tinned copper conductor the resistance is roughly 3.39 Ω/km at 20 °C. At 10 A over 100 m of a 6 mm² string the drop is on the order of 6.8 V — a small fraction of a 1500 V system, which is why drop only becomes decisive on long runs or low-voltage strings.

The 2 percent design allowance

A common specification limit is about 2 percent total DC voltage drop between the array and the inverter. It is a design allowance rather than a standard requirement, and the project specification governs. The practical consequence is that the allowance is spent across the whole DC path, not per cable run, so leaving margin in the string cable matters.

Why ambient temperature derates

The conductor is rated to 90 °C continuous. If the surrounding air is already at 70 °C inside a rooftop conduit, the permissible temperature rise — and therefore the current — is smaller than the free-air table suggests. The same applies where several cables are bundled or run in a common conduit, because they heat each other.

Read the conditions, not the number

A current rating is only meaningful with its reference conditions attached: ambient temperature, installation method, number of loaded conductors. Two datasheets quoting different figures for the same cross section are usually quoting different conditions, not different quality.

Standards and compliance

Which document governs depends on where the array is built and what the project specification names.

Document	What it covers
EN 50618	Electric cables for photovoltaic systems. European standard; source of the H1Z2Z2-K designation. The reference document for PV DC cable in European projects.
IEC 62930	Electric cables for photovoltaic systems. The international counterpart, describing the same class of cross-linked halogen-free PV DC cable. A cable made to IEC 62930 may be designated H1Z2Z2-K where it also meets EN 50618.
UL 4703	North American standard for photovoltaic wire. Applies to US and Canadian projects in place of, or alongside, the EN and IEC documents.
EN 60228	Conductors of insulated cables. Defines class 5 flexible stranding, which is what makes PV cable handleable in the field.
IEC 62548-1 / IEC 60364-7-712	Installation standards for PV arrays and low-voltage PV power systems. They govern how the cable is installed, not how it is made.

Cable standards and connector standards are separate documents covering separate products. If you are qualifying a complete string assembly, the connector side is covered in the PV connector and cable standards reference, and the certification side in the PV connector certification hub.

In-depth guides

Each of these goes deeper on one part of the decision above. This page is the index; they are the detail.

Solar Panel Cable: Why H1Z2Z2-K Is the Standard How the designation is built up, what each character encodes, and why tinned class 5 copper replaced the earlier cable types. PV DC Cable Sizing: 4mm² vs 6mm² vs 10mm² Worked comparison of the three sizes most often specified, with the ampacity and voltage-drop checks that decide between them. PV Cable Installation: Crimping and Grounding Crimp tooling and dies, pull force acceptance, bending radius, strain relief and the grounding and bonding requirements. Custom PV Extension Cables at 1500 V When a factory-made extension assembly is the right answer, and how conductor size and connector rating have to be matched. Solar Wire Harness Assemblies Pre-assembled string harnesses: how they remove field crimping from the critical path, and what to specify. Solar PV Cable (H1Z2Z2-K) → The Treasol range: 2.5 to 16 mm², red and black, EN 50618 construction with full technical data. Solar PV Cable category → Browse the cable range with the mated connectors and accessories specified alongside it. PV Connector Manufacturer → The connector side of the same string circuit: MC4-compatible, branch, fuse and diode connectors.

Frequently asked questions about solar PV cable

The questions engineers and buyers ask most often. Product-specific questions are answered in our product FAQ.

What is H1Z2Z2-K solar cable?+

H1Z2Z2-K is the cable designation defined by EN 50618, the European standard for electric cables for photovoltaic systems. The letters encode the construction: 90 °C maximum conductor temperature, 1.0/1.0 kV AC rated voltage, cross-linked insulation, and halogen-free, low-smoke materials. PV1-F is a separate designation associated with the TÜV Rheinland specification 2 PfG 1169 — a different document with a different rating set.

What voltage is solar PV cable rated for?+

H1Z2Z2-K cable to EN 50618 is rated 1.0/1.0 kV AC and 1.5 kV DC. That 1.5 kV DC rating is what allows it to be used on 1500 V DC string circuits, which is now the standard system voltage for utility-scale PV. Ordinary 0.6/1 kV building cable is not rated for the DC side of a PV array and should not be substituted.

Which cross section should I use for PV string cable?+

Most string circuits use 4 mm² or 6 mm². The current-carrying requirement is usually satisfied well before the voltage-drop requirement, so on long runs the conductor is chosen by voltage drop rather than by ampacity. A common design rule is to keep total DC voltage drop within about 2 percent. Cross sections from 2.5 mm² to 16 mm² cover the usual range from short module jumpers to long home runs.

Why does PV cable use tinned copper instead of bare copper?+

Tinning protects the copper against oxidation and corrosion. PV cable is exposed to moisture, salt and — in agricultural installations — ammonia, and bare copper strands oxidise over time, which raises resistance and makes crimped joints less reliable. EN 50618 assumes a flexible class 5 conductor, so the stranding is also fine enough to survive repeated bending during installation.

Does PV cable need to be UV resistant?+

Yes. On most arrays a large part of the DC cabling is clipped to the mounting structure in direct sunlight for 25 years or more. A cross-linked halogen-free polyolefin insulation and sheath is specified precisely because it resists UV, ozone and weathering; EN 50618 includes an ozone resistance test that ordinary PVC or polyethylene cable would not pass.

What is the difference between EN 50618 and IEC 62930?+

EN 50618 is the European standard for photovoltaic system cables and is the source of the H1Z2Z2-K designation. IEC 62930 is the international counterpart covering the same class of cross-linked, halogen-free PV DC cable. Specifications frequently cite both, and a supplier should state which one the cable is manufactured and tested to.

Can I use standard building cable for the DC side of a PV system?+

No. Standard 0.6/1 kV building cable is not rated for 1.5 kV DC, is not tested for continuous UV exposure, and its insulation is not specified for the temperature and ozone conditions of a rooftop or ground-mount array. The DC side of a PV system is a different electrical environment from an AC installation, which is why it has its own cable standard.

How is PV cable voltage drop calculated?+

Voltage drop is calculated as twice the one-way conductor resistance multiplied by the string current, because the current flows out and back. For a 6 mm² tinned copper conductor the resistance is about 3.39 Ω per kilometre at 20 °C. The practical check is to compare the resulting drop against the design allowance — commonly 2 percent of the string voltage — and increase the cross section if it is exceeded.

Specify PV Cable for Your Project

Tell us the string current, the one-way run length, the system voltage and the standard your project references. We will come back with the cross section that satisfies both the voltage-drop and ampacity checks, together with the cable data you need for the submittal.

What you can receive:

Datasheet with the full EN 50618 construction and ratings
Standard the cable is manufactured and tested to
Recommended cross section for your run and current
Mating connector recommendation for the same cable size
MOQ, lead time and OEM options

Contact the PV cable team

Send us the parameters above and our engineering team will confirm the right cable and the connector that matches it. We normally respond within 24 hours.

Email: info@treasol.com

WhatsApp: +86 186 8861 9157

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