Electrical Control of Photovoltaic Power Plants (PPPs)

Electrical Testing of Photovoltaic Power Plants (PPPs): The Role of the Electrical Testing Laboratory and Compliance with Regulatory Requirements

Photovoltaic power plants (PVPPs) are a key element in the transition to sustainable energy, but their safety, reliability, and efficiency depend on rigorous electrical testing conducted by certified electrical testing laboratories. This article is intended for investors building PV power plants and covers the main aspects of electrical testing, including grounding measurements, lightning protection, and cable insulation resistance, as well as the applicable regulatory documents in Bulgaria.

The Importance of Electrical Monitoring for the FEC

Electrical Control of Photovoltaic Power Plants: What You Need to Know

Electrical inspections at the power plant are intended to ensure the safety of personnel, protect equipment, and ensure compliance with regulatory requirements. They include inspections and measurements of electrical systems before, during, and after the plant is commissioned. These activities are performed by accredited electrical testing laboratories, which issue the reports required for the facility’s legal approval and to obtain permits (e.g., Act 16).

Key Aspects of Electrical Control

1. Testing of the grounding system

• Grounding is a critical safety feature for solar power plants, as it protects against electric shock and equipment damage in the event of a fault. Grounding resistance is measured in accordance with standards such as BDS HD 637 S1 and BDS EN 62305-3. The main requirements include:
• Earth resistance values: For power plants with voltages up to 1000 V, the grounding resistance should generally be less than 4 ohms for protective grounding and less than 10 ohms for lightning protection. For common grounding systems, the resistance should not exceed 1 ohm.

• Measurement Methods: Methods such as the volt-ampere method or the three-pole bridge method are used, with the aid of specialized equipment. The measurements are performed by qualified specialists, taking into account factors such as soil moisture and geological conditions.

• Frequency: Periodic inspections of earthing systems are conducted annually or in accordance with the system design, and additional measurements are performed following repairs.

2. Inspection of the lightning protection system

Power plants are particularly vulnerable to lightning strikes due to their open-air location. Lightning protection is designed and inspected in accordance with BDS EN 62305-3 and Regulation No. 4 of 2011 on lightning protection for buildings, outdoor facilities, and open spaces. The main activities include:

• Measuring the Resistance of Lightning Protection Grounding Electrodes: It must be less than 10 ohms for active lightning protection and less than 20 ohms for conventional lightning protection.
• Visual inspection: The condition of the lightning rods, down conductors, and connections to the grounding electrodes is checked.
• Issuance of reports: Following a successful inspection, a certificate of compliance is issued, which is required to legalize the facility.

3. Measuring the insulation resistance of cables

The insulation resistance of cables is a key parameter for preventing short circuits and equipment damage. Measurements are performed in accordance with BDS 1986:1982 and Regulation No. 3 of 2004 on the installation of electrical systems and power lines. Main requirements:

• Procedure: The measurement is performed using a megohmmeter at the test voltage specified in Table 19 of Regulation No. 3. The minimum insulation resistance depends on the type of cable and the voltage, but is typically over 1 MΩ for low-voltage systems.
• Terms and Conditions: Surge protection devices must be turned off before taking measurements to prevent damage or inaccurate results.
• Frequency: Measurements are taken prior to commissioning and during periodic inspections, typically every 1–3 years, depending on operating conditions.

Regulatory Documents

The electrical control of the FEC is governed by a number of regulations that investors must comply with:

1. Regulation No. 3 of 2004 on the Installation of Electrical Systems and Power Lines – Oversees the design, construction, and testing of electrical systems, including measurements of ground resistance and insulation resistance.
2. Regulation No. 4 of 2011 on Lightning Protection for Buildings, Outdoor Facilities, and Open Spaces – Specifies the requirements for the design and inspection of lightning protection systems.
3. BDS EN 62305-3:2006 – A lightning protection standard requiring an earth resistance of less than 10 ohms for active systems.
4. БДС HD 637 S1 – Provides instructions for measuring ground resistance in electrical networks.
5. BDS 1986:1982 – Establishes the methods for measuring the insulation resistance of cables.
6. Regulation No. 16-116 of 2008 on the Technical Operation of Energy Equipment – Regulates the safe operation of electrical equipment.
7. Regulation No. RD-02-20-1 of 2018 – Sets forth the technical rules for the inspection and acceptance of electrical installation work.

Recommendations for Investors

1. Choosing an electrical laboratory: Hire an accredited laboratory with experience in PV system measurements. Ensure that the staff is qualified and holds the appropriate electrical safety certifications.
2. Scheduling Inspections: Incorporate electrical safety checks into the design, construction, and commissioning phases. Regular inspections are mandatory to ensure safety and efficiency.
3. Documentation: Make sure you receive detailed measurement reports that comply with regulatory requirements. These documents are necessary for certification and insurance purposes.
4. Selecting Equipment: Use certified measuring instruments and lightning protection systems that comply with the relevant standards.
5. Бюджетиране: Budget for the costs of regular inspections and maintenance of grounding and lightning protection systems, as well as for measuring insulation resistance.

Conclusion

Electrical inspections of solar power plants are mandatory to ensure safety, reliability, and compliance with regulatory requirements. Measurements of grounding, lightning protection, and cable insulation resistance are key to preventing accidents and protecting the investment. Investors must work with accredited electrical testing laboratories and comply with regulatory acts such as Ordinance No. 3, Ordinance No. 4, and BDS standards. This will ensure the long-term efficiency and safety of the photovoltaic power plant.