Rob Barker, Director of Power Quality Expert, assesses the future landscape for solar PV installations and identifies the key characteristics that test equipment must contain to help installers comply with the requirements.
The rapid and dynamic development of photovoltaic installations that has been taking place in the world in recent years is impressive. This is largely due to the departure from traditional, non-renewable energy sources.
Greater social awareness and a desire by government to encourage people and businesses to take responsibility for the climate around us has forced a shift in the energy sector towards green energy. Additionally, we’ve seen the technology constantly evolving, which is resulting in lower costs for consumers to adopt solar PV energy solutions.
This, combined with the constant increase in energy prices, makes an economic shift more favourable for the photovoltaic sector and is a key factor moving customers towards further investment in solar PV systems.
Business should boom
With the push for energy saving increasing it is important to remember that testing the safety of the photovoltaic installation and the servicing of these installations is a growing business.
Because of this, it is vital that the installation complies with all safety requirements after installation and that its operation complies with the applicable regulations. We can only be sure of this by carrying out the appropriate test and inspections and periodic checks.
The requirements for these are described in Section 712 of the 18th Edition Amendment 2 along with the standard EN 62446. The standard also defines the method and scope of safety control of photovoltaic installations.
Measurements allow you to determine not only the safety, but also the efficiency of a photovoltaic installation. The EN 62446 standard divides the tests into category 1 and 2 tests and additional tests.
Meters that meet the requirements
A meter such as the Sonel PVM-1020 allows you to carry out all measurements for the obligatory category 1, which include:
● Measurement of open circuit voltage (for a single panel or a string of PV panels) up to 1000 V DC
● Measurement of short-circuit current (for a single panel or a string of PV panels) up to 20 A DC
● Measurement of the operating current of PV panels with the use of external clamps
● Polarisation test
● Measurement of insulation resistance of PV panels with a test voltage of 250, 500 or 1000 V, simultaneous measurement of two values (plus to earth and minus to earth)
● Measurement of resistance of protective connections and equipotential bonding with ±200 mA current
Additionally, it is possible to perform measurements not included in category 1, which are found in everyday measurement practices. These are:
● RMS voltage of AC network up to 600 V and frequency
● Insulation resistance of AC circuits with the test voltage of 250, 500 or 1000 V
● AC current ● AC/DC power
● Low current resistance with audible and visual signalling
● Diode test with 200 mA current with automatic polarity detection
● Blocking diode test with 1000 V DC voltage
By measuring the parameters of the PV installation, such as the short-circuit current (Isc) or the open-circuit voltage (Uoc), you can quickly verify the correct connections of the modules in the string, their polarity and operation. Measurements can be made for the entire chain of panels or for a single module.
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 always be taken.
The values of operating currents and power 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.
The manufacturer of the inverter will usually specify the parameters of individual elements of the PV system which are measured in STC (Standard Test Conditions: 25°C, 1000 W/m², AM 1,5).
For comparison purposes, solar installation testers like the Sonel PVM-1020 can automatically convert the results to STC conditions. This is done by the use of an irradiance and temperature meter such as the Sonel IRM-1.
Both of these meters cooperate with each other and normally work over long distance through radio link. The automatically transmitted data is then converted to measurement values of short circuit current and open circuit voltage referenced to the standard STC conditions.
Browse the Sonel PVM-1020 product data sheet here
