When we talk about long-lived photovoltaic plants, the headlines usually highlight module efficiency, inverter upgrades or bankable offtake contracts. That’s understandable — but it misses a more prosaic truth: many 15-year successes owe their longevity to dozens of tiny, correct decisions made at the connection level. The choices about conductor, insulation, jointing, installation practice and verification multiply over time. One small weakness becomes the failure mode that forces downtime, costly repairs or a full replacement.
This article distils what mature, reliably performing PV plants have in common. These are practical, engineering-first decisions — not marketing claims — that materially change outcomes over a decade and a half.
1. Treat the cable as an engineered asset, not a commodity
Most owners treat cable as “low cost per metre” and focus procurement there. The plants that last 15 years treat cables as critical system assets whose failure modes penetrate the financial model (lost generation, safety incidents, insurance consequences). That mentality flips procurement criteria: you ask how the cable was engineered and validated, not only whether it has a certificate.
Practical shift: Require documentation of manufacturing traceability, retained samples and accelerated ageing evidence as a condition for acceptance.
2. Specify conductor and chemistry to match the environment
Conductor choice matters beyond price. In many long-running plants you’ll find conservative conductor decisions: copper (often tinned) instead of aluminium or CCA in critical runs, particularly where mechanical flexibility, low contact resistance and corrosion resistance matter (e.g., rooftop, agrivoltaic, coastal sites).
Why it matters:
Tinned copper resists corrosion at joints and remains low-resistance over time — reducing hot spots.
Aluminum/CCA can suffer electrochemical issues at terminations and with dissimilar metals.
Decision tip: In high-risk environments (high humidity, salt, irrigation), specify tinned copper conductors for main runs and critical connectors.
3. Design with thermal and electrical margin — not just rated values
A cable’s nameplate rating is useful, but real field conditions are rarely nameplate conditions. Long-lasting plants preserve thermal margin and electrical margin:
Thermal margin: choose insulation and jacket systems that tolerate elevated continuous temperatures and slow heat accumulation (e.g., module backsheet heat, enclosed conduits).
Electrical margin: design conductor size and connection integrity so that transient overcurrents, harmonic content from inverters, and hot-spot aging don’t drive the cable to its limits.
Rule of thumb: Design conductor sizing and derating assumptions to keep continuous operating temperatures well below the insulation’s accelerated aging threshold — that preserves decades of life.
4. Prioritise joint & termination integrity — the true weak link
Field failures are disproportionately concentrated at joints, terminations and interfaces. Even the best cable can be ruined by a poor crimp, incorrect gland, or an under-torqued lug.
What the 15-year plants do differently:
Use trained, certified technicians for terminations.
Apply factory-prefabricated assemblies where possible (factory crimped, pre-sealed connectors).
Require documented torque checks, use calibrated tools, and retain termination photos and QC records.
Hard requirement: Include joint inspection and pull-test records in the as-built package.
5. Make water and moisture management a design requirement
Moisture is a slow killer. Outdoor and agrivoltaic installations expose cables to humidity cycles, irrigation spray, and ponding on floating systems. The best projects anticipate this with materials and specifications:
Use jackets and fillers with proven hydrolytic stability and low water-uptake.
Specify IP-rated connectors for exposed terminations; avoid field-sealed butt joints where water ingress risk is significant.
For floating PV, accept only cables with proven long-term water immersion or submersion ratings.
Engineering note: Don’t rely solely on pass/fail certificate labels — ask for accelerated water-immersion tests and results.
6. Insist on verifiable testing, not just certificates
Certificates matter, but they are the start, not the end. What distinguishes plants that last is an insistence on verifiable, project-specific evidence:
ISO/IEC 17025-grade testing gives confidence that test methods and data are competent and traceable.
Accelerated ageing datasets (UV, thermal, humidity cycling) performed to laboratory protocols provide a practical projection of long-term performance.
Factory production records (online extrusion data, thickness logs, batch material tests) let you correlate later field issues with original production.
Procurement upgrade: Require a test-data submission (sample reports) and the right to witness or commission a third-party sample retest.
7. Build a documented retention & traceability system
If a failure occurs ten years after commissioning, the ability to reconstruct how the failed cable was made is invaluable for root cause and warranty actions. Top plants keep:
Unique identifiers (barcodes/QR) assigned to reels with batch and production data.
Retained sample programme (multi-year) so that any later test can be compared with a matched production sample.
Digital linkage of production data, test reports and site installation records.
Standard practice: 5-year sample retention is minimum; for critical projects, extend to the life of warranty.
8. Enforce conservative installation and post-commissioning practices
Installation choices — bending radii, burial depth, mechanical protection, proper separation from other services — change outcomes more than people expect. After commissioning, include periodic thermographic inspections and targeted PD (partial discharge) checks on high-risk strings.
Operational checklist: Schedule thermography at seasonal extremes (highest ambient & highest irradiance) and after major grid events.
9. Translate technical choices into financial language for the owner
Owners decide on CAPEX vs OPEX. The plants that survive 15+ years quantify the value of connection decisions:
Show the NPV effect of one avoided 48-hour outage.
Compare the lifecycle cost (replacement + lost production) of a low-cost cable vs. a higher-integrity option.
When decisions are reframed as avoided downtime and reduced LCOE, more robust connection specs become obvious.
10. Make a pragmatic checklist owners can use tomorrow
Use this short checklist during bid review and site acceptance:
Does the supplier provide ISO/IEC 17025 test data for project-specific samples?
Are conductors tinned copper where environmental risk exists?
Is there documented online process control for extrusion thickness/temperature/line speed?
Are factory-assembled terminations used for exposed connections?
Is there a retained-sample and batch-traceability system for all reels?
Are post-commissioning thermography and PD scans contractually defined?
Does the spec include water-immersion testing for floating or agrivoltaic deployments?
Conclusion — Connection decisions compound into certainty
A PV plant’s 15-year success is rarely about a single heroic component. It is the product of many modest, deliberate decisions — and nowhere are those decisions more multiply consequential than at the connection level. When a project treats cable as an engineered, data-backed asset; when it insists on verifiable testing (ISO/IEC 17025), durable conductors, thermal and electrical margin, factory-quality terminations, water-resistant systems and traceable production data — the result is predictable: less downtime, fewer replacements, and a clearer path to the promised lifetime economics.
