Safety in photovoltaics - MPI-540-PV The very rapid and dynamic development of photovoltaic installations taking place in the world in recent years is impressive. It is largely due to the abandonment of traditional, non-renewable energy sources. Greater social awareness and taking responsibility by the governments of individual countries for the climate around us forces the shift towards green energy. In addition, the technology is constantly evolving, resulting in lower costs. If we add to this the constant increase in energy prices on the market, we will notice that the economic balance is more and more favorable for the photovoltaic sector. This is a key phenomenon in the context of further development of PV systems. Unfortunately, the profitability of investments is often attempted to improve by lowering the quality, and hence - reducing the safety level of the photovoltaic installation itself (and thus increasing the risk of operating and servicing the facility). For this reason, it is very important that the installation meets all safety requirements after assembly, and that its execution complies with applicable regulations. We can only be assured of this by carrying out appropriate tests and acceptance and periodic checks. The legal basis here is primarily the multi-sheet standard EN 62446, defining the method and scope of safety control of photovoltaic installations. Following the guidelines contained therein significantly reduces the risk of electric shock or fire. Measurements allow to determine not only the safety, but also the efficiency of a given installation and its elements.
Fig.1. MPI-540-PV meter with accessories for measuring photovoltaic installations.
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The standard divides the inspection into category 1 and 2 tests and additional tests. However, in order to be able to start the check at all, you must have the appropriate measuring instrument. The rapid development of the renewable energy sector did not go unnoticed by one of the largest Polish producers of high-quality measuring equipment, Sonel S.A. Recently, the company has introduced a new meter to the market, which can be used in the area, where the main goal is to obtain energy from the sun. MPI-540-PV is a multifunction meter of parameters of electrical and photovoltaic installations. The device has been designed to meet the requirements of EN 61557 and EN 61010 standards, to ensure adequate accuracy and safety during work. The meter offers powerful possibilities in the field of electric shock protection tests, power quality analysis, and we will successfully use it for category 1 tests defined by the EN 62446 standard, which includes:
Âť continuity of protective connections,
Âť earth resistance,
Âť insulation resistance on the DC side,
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» open circuit voltage UOC,
» short circuit current ISC,
» operating currents and powers on the DC and AC sides of the inverter,
» efficiency of the inverter.
The standard requires that all tests of the receiving installation on the AC side should be performed before starting category 1 measurements. Their scope is defined by the HD 60364 standard. The MPI-540-PV meter will also prove itself in this field. By measuring the parameters of PV installations, such as short-circuit current Isc or open-circuit voltage Uoc, you can quickly verify the correctness of module connections in the string, their correct polarity and operation. Measurements can be made for the entire chain of panels or for a single module. The manufacturer usually specifies the parameters of individual elements of the PV installation measured in STC (Standard Test Conditions: 25°C, 1000 W/m²). For comparison purposes, the meter can automatically convert the results to STC conditions - the user only needs to enter additional data: irradiance and temperature. In this case, you can save catalog parameters of photovoltaic panels in the module database in the meter. It is also necessary for conversions and for the evaluation of the measurement result.
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Fig.2. The screen of the MPI-540-PV meter showing the measurement of the short-circuit current ISC (left) and the open circuit voltage UOC (right) and their values converted to the STC conditions.
The continuity of protective connections and the grounding resistance on the DC side are measured in the same way as in AC installations. In the case of insulation resistance tests, the difference is that the measurements are carried out under voltage, therefore special care should be taken. The values of operating currents and powers on the DC and AC sides must be checked during the operation of both installations. Based on these measurements, we will verify the efficiency of the inverter and compare it with the efficiency declared by the manufacturer. Thanks to saving the results to the memory of the meter, they can be further used in the test report. For this purpose a dedicated software, Sonel Reports Plus will be useful. MPI-540-PV, apart from a huge number of measuring functions, has a very rich equipment. It includes, among others, accessories dedicated to testing photovoltaic installations: C-PV DC clamp, PVM-1 adapter ensuring safety and protection against electric arc or adapters for MC4 connectors, commonly used in photovoltaics. Together with the whole range of accessories and measuring possibilities, the meter is a valuable tool in the work of a measuring technician. It will be especially appreciated by electro-installers performing acceptance measurements in electrical and photovoltaic installations.
Tomasz Gorzelańczyk SONEL S.A.
Sonel S.A.
www.sonel.com