Navigating the Testing and Commissioning Process for Solar Projects

Negotiating testing and commissioning requirements during the drafting of an EPC agreement is standard practice in the solar industry. Despite these contractual obligations, confusion often arises between owners and contractors in the middle of construction regarding the importance of certain tests and their timing. Additionally, while testing and commissioning requirements are typically outlined for Mechanical Completion and Substantial Completion milestones, what’s less specified are the tests that should be done before energizing the system. In this article, we aim to bridge the gap between outlined requirements and real-life expectations.

Standard Milestone Requirements

To achieve Mechanical Completion, there are several standard inspections and electrical tests needed for any project type to ensure the system has been built as intended, and most importantly, to be done before initial system energization. These requirements should be outlined explicitly in EPC contracts, but these generally involve:

• Verifying the physical condition, installation, and labeling of major equipment and associated components to ensure conformity with design specifications and standards.
• Electrical testing to verify insulation resistance, grounding system integrity, and continuity.
• Inspecting and testing reclosers and protective relays on-site to ensure functionality and reliability of the protection settings.
• Checking adherence to safety protocols and regulatory standards to mitigate potential hazards and ensure safe operations.

To achieve Substantial Completion, the verification tests and inspections required may vary a bit more depending on project size, project type, and major equipment used, and some of these tests can only be done after the system has been energized. These requirements should also be outlined explicitly in EPC contracts, but these generally involve:

• Performance Testing: Stringent evaluation of PV module performance through tests such as IV curve tracing, thermal imaging, and capacity testing, to ensure optimal efficiency.
• Functional Testing: Validation of monitoring systems, communication interfaces, and protection systems to ensure seamless integration and operation within the system.

What is often unclear is the deliverable that contractors should provide owners after these verifications have been completed, if not covered by a third-party test report. Clear documentation of completed testing is crucial, whether in the form of a checklist, letter, or detailed report. While it may seem like a mere formality, this documentation serves as a tangible record of compliance and aids in project tracking and troubleshooting.

In terms of the EPC contract, updating technical requirements during contract negotiation is important to ensure alignment with project specifics, preventing issues stemming from outdated or non-applicable requirements. All too often contracts get reused for several projects, resulting in a long list of requirements that don’t apply but that a third party or IE will ask for. It’s important to remove non-applicable requirements from the start or understand which requirements will need to be waived for each project.

Pre-Energization Tests

Between Mechanical Completion and Substantial Completion, we have found that the following tests are often unclear but are essential to validate system integrity and readiness for energization.

Transformer Testing:

• Importance: Transformer testing, which includes but is not limited to resistance measurements, insulation resistance test, turns-ratio test, and Dissolved Gas Analysis (DGA), can help in preventing hazardous operating conditions, ensuring the transformer was built to specifications (if custom-made), reducing outages during operation, and guiding maintenance decisions. DGA results in particular provide early detection and diagnosis of faults in oil-immersed transformers, however, are sometimes overlooked due to longer result processing times.
• Protocol: All transformer test results should be received and reviewed before energization for projects of any size. It’s important to note that obtaining a transformer test report incurs additional costs as it requires an expert to conduct the tests, and the DGA results in particular take longer than other transformer testing because an oil sample must be extracted and sent to a laboratory for measurement. For these reasons, it is important to be clear about transformer testing requirements when negotiating contracts and it is important to track during construction to prevent schedule delays.

Cable Testing for AC Low Voltage (LV) and Medium Voltage (MV) Cables:

• Importance: Cable testing is done to assess cable conditions such as aging and defects. This can include insulation resistance testing (also known as Megger testing) for LV cables, and Very Low Frequency (VLF) testing for MV cables. These tests help to prevent potential cable failures, achieve a reliable distribution network, and reduce outages and safety hazards during operation.
• Protocol: For projects of any size, insulation resistance testing on LV cables and VLF testing, HIPOT testing, or other dielectric withstand testing on MV cables must be conducted before initial energization. VLF testing must be done on each MV cable and must be scheduled and done while the circuit is de-energized to properly detect any faults.

Fall of Potential (FOP) Test for Grounding Systems:

• Importance: In addition to other grounding verification tests like performing resistance measurements and point-to-point tests, FOP tests identify inadequate grounding systems before initial operation, help to accurately measure grounding resistance, predict system performance, determine ground potential rise, and ensure safety.
• Protocol: Although this test was typically only done on larger projects with substations, the FOP test is beneficial for any project with primary interconnection. This should be done for projects over 2 MW as it provides critical protection against failures during system startup.

Pre-energization tests play a pivotal role in laying the foundation for reliability, safety, and performance in PV projects, and should be carried out according to their relevant safety standards such as ANSI/NETA-ATS, ICEA, IEC, or IEEE. By identifying potential issues and validating system integrity before energization, stakeholders can minimize downtime, ensure safe operation, and maximize system efficiency from the outset. Prioritizing these essential tests empowers stakeholders to navigate the journey toward energization and operation with confidence, knowing their PV systems are primed for success.

At Camelot Energy Group, we specialize in providing expert guidance and consultancy services throughout the testing and commissioning process for solar projects. Our team of seasoned professionals offers comprehensive support, from contract negotiation to milestone achievement, ensuring clarity, compliance, and success at every stage. Whether it’s through our Technical Advisory or Owner’s Engineering services, we empower stakeholders to navigate the complexities of solar project execution with confidence and ease.

About the Author

Michelle Aguirre is a Project Manager at Camelot Energy Group and manages a variety of technical advisory engagements on C&I and utility scale solar and energy storage projects.