Utility-scale solar plants live or die by the reliability of their medium-voltage (MV) collector system. Every inverter, recloser, pad-mount transformer, and switchgear line-up depends on miles of 15–35 kV shielded cable, scores of splices, and hundreds of terminations and connectors. When workmanship slips at any one of those interfaces, you don’t just lose a joint—you lose energy production, warranties get strained, and O&M costs balloon.

Below is a practical, standards-anchored guide to why quality MV splicing and terminal connections matter during construction, and how to do them right.

What fails—and why it hurts so much

• Accessories are the weak link. Decades of utility data show that accessories (splices, terminations, connectors) dominate underground cable system failures—one Electric Power Research Institute (EPRI) survey attributes ~55% of failures to accessories.

• Defect mechanisms are invisible—until they aren’t. Improper semi-con cutback, contaminated interfaces, poor stress-control placement, or mismatched connectors can trigger partial discharge (PD), tracking, and thermal runaway after energization.

The core standards you should build to

Think of these as the rulebook for a bankable MV collector system:
• Splices (joints): IEEE 404 establishes electrical ratings and type-test requirements.
• Terminations: IEEE 48 covers test procedures and performance.
• Separable insulated connectors: IEEE 386 defines ratings and interchangeability.
• Mechanical/compression lugs & connectors: ANSI C119.4 sets electrical and mechanical requirements.
• Field testing & acceptance: IEEE 400 family and ANSI/NETA ATS guide testing and acceptance.

Splicing done right: what “good” looks like

1. Use the correct, type-tested kit for the cable.
2. Control the environment—cleanliness and dryness are non-negotiable.
3. Follow precise cutbacks and surface prep per manufacturer guidance.
4. Select the right connector inside the splice—qualified per ANSI C119.4.

Terminations & equipment connections: small torque, big consequences

• Use terminations qualified to IEEE 48 for the environment.
• Specify lugs/connectors to ANSI C119.4 and follow torque values.
• For elbows/junctions, hold to IEEE 386 interchangeability.

Acceptance testing that actually finds the problems

• VLF withstand + diagnostics per IEEE 400 series.
• Use NETA ATS tables & PV sections for documentation.
• Thermography after energization to identify hotspots.

Cost, risk, and bankability

Poor connector selection and workmanship have been an industry-wide theme in PV reliability assessments. While much public reporting focuses on DC module connectors, the lesson is the same on the MV side: compatibility, torque discipline, and environmental sealing materially influence uptime and lifetime costs.

A construction-phase checklist you can enforce

• Standards in the spec: IEEE 404, 48, 386, ANSI C119.4, IEEE 400, NETA ATS.
• Qualified jointers only—manufacturer training/certs required.
• Materials control—no mix-and-match, correct metallurgy.
• Tooling & torque—calibrated tools, documented torque.
• Test & inspect—visual, VLF withstand, PD, IR scan.
• As-built QA package—photos, traceability, torque logs, test reports.

Bottom line

Solar plants are collections of high-value assets connected by MV accessories that must behave like factory-built components. If you build to IEEE 404/48/386, select connectors per ANSI C119.4, and accept to IEEE 400 + NETA ATS, you’ll dramatically reduce early-life failures, protect warranties, and keep generation on line when it matters most.

At Grid Mule Contractors, all of our MV cable splices and terminal connections are performed to the highest quality standards, following the latest IEEE and ANSI/NETA specifications. Every splice and termination is executed by certified technicians and undergoes internal inspections and quality checks to ensure reliability, safety, and long-term performance. By holding ourselves to this standard of excellence, we not only safeguard project investments but also deliver optimal service and system uptime for our clients across the solar industry.

Sources

• NETA-aligned primers on VLF/tan-δ/PD and thermographic inspection practices. TestGuy Electrical Testing NetworkcomAtlantic Testing Services
• IEEE 404—Extruded and Laminated Dielectric Shielded Cable Joints(current edition and history). Intertek InformGlobalSpec Standards
• IEEE 48—Cable Terminations(indoor/outdoor, 2.5–500 kV). TestGuy Electrical Testing Network
• IEEE 386—Separable Insulated Connector Systems(2.5–35 kV). IEEE Standards Association
• ANSI/NETA ATS—Acceptance Testing Specifications; includes PV system sections and MV cable acceptance tables. Netaworld
• IEEE 400 / 400.3—Field testing and PD guidance for shielded MV cables; application notes and primers. Doble Engineering CompanyHigh Voltage Inc
• UFGS 26 05 13—Federal spec example that references IEEE 48/404 and mandates IEEE 400 + NETA ATS. Whole Building Design Guide+1
• ANSI 4—Electrical/mechanical requirements for lugs and connectors (Al-Al, Al-Cu, Cu-Cu). ANSI Webstore
• Manufacturer data showing C119.4-qualified shear-bolt lugs/connectors (3M, TE/Raychem, Prysmian). Distributor Data SolutionsLSI CloudPrysmian Group
• EPRI reliability references highlighting accessory-driven failure prevalence. EPRI Rest Service