Solar Power World caught up with Andrew Upton, vice president of The Seaward Group, which is a manufacturer of electrical safety testing equipment based in Tampa, Fla. Upton says installers need to test the safety of their solar installations every step of the way to ensure the system complies with national, state and local electrical standards.
SPW: How do you define the success of a solar PV installation?
AU: The success of a PV installation is based upon three key criteria:
- Maximum return on financial investment
- Optimum conversion of solar energy to electricity
- Safe operation throughout the lifetime of the operation.
SPW: Tell our readers how solar installers can ensure they meet those three criteria?
AU: For a solar PV installer to deliver effective solutions, the system must be designed and installed to standards which comply with international, national or state regulation requirements. The only way to do this is to rigorously test and document the results at the initial installation stage, and also on periodic basis, to ensure the system is still working effectively and efficiently
SPW: Can you explain what kind of measurements installers should be taking, what their implications are and how easy it is to take them?
All good PV installers should be carrying out the following tests at the time of installation:
- Ground Continuity – Continuity testing is commonly used to verify grounding and bonding connections in electrical systems. Proper grounding of PV systems reduces the risk of electrical shock to personnel and the effects of lightning and surges on equipment.
- Open Circuit Voltage – These tests simply verify correct installation, and are not intended to verify performance. The PV array should be tested and compared with expectations.
- Short Circuit Current – Short circuit current tests are conducted on PV string source circuits to verify proper readings, and that the circuits are clear from major faults. Similar to the Open Circuit Voltage, these tests are only intended to verify proper system operation, not performance. Measuring of Short circuit current is very difficult without an effective external shorting device.
- Polarity of DC Wiring – As for any DC circuits, the polarity of array wiring and dc equipment is a critical concern for PV Installations. The polarity of every source circuit and the entire PV power source must be verified prior to connecting to any dc utilization equipment, such as inverters, batteries or electrical loads.
- Insulation Resistance (Megger) Test — Insulation resistance tests are used to verify and demonstrate the integrity of electrical wiring systems and equipment, as required by the NEC (110.7). These tests can be used to assess degradation or damage to wiring insulation to locate faults within PV arrays.
The Seaward PV150 Installation tester performs all of the above tests, in a simple manner, without the need for complex shorting devices.
SPW: Who needs to know about the importance of testing?
AU: It’s important to educate installers of the importance of testing to ensure initial system performance, and by effective periodic inspection, an installer will be able to demonstrate the system is performing as expected. If the system is electrically safe, and installed correctly, the system will behave as intended for use, and provide the maximum output possible. This was the purpose of the International Standard IEC62446, which was developed to ensure that PV systems globally were being installed safely, and correctly, to ensure longevity of the systems performance, and thus create a positive vision of Solar PV as a reliable energy alternative.
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