- Capable of setting within the range of 50Vdc to 2000Vdc (resolution 1V)
- Ability to switch the applied voltage polarity instantly by the switch on the front panel
- The output is floating from the ground potential.
- Capable of measuring the current value between measurement points.
- Information related to PID test
The PID insulation tester (TOS7210S) is designed based on the insulation resistance tester (TOS7200) to carry out the evaluation of the PID (Potential Induced Degradation) effect of the PV module precisely and efficiently. Being equipped with the output ability of 2000V and the ammeter with nA resolution as well as a polarity switching function, the TOS7210S is also applicable not only to the PID evaluation but also the evaluation of the insulators that requires a high sensitivity of measurement. The tester is equipped with the panel memory that is externally accessible and RS232C interface as standard; it can be flexibly compatible with the automated system.
The PID effect is a phenomenon that the amount of power generation by a cell remarkably decreases when high voltage is applied between the solar cell and the frame for long hours. It is supposed that the higher the applied voltage is and/or the higher and more humid the environment is, the further deterioration accelerates. For example, the potential difference in the string becomes extremely higher when the number of sheets that are connected in series increases even if the output voltage of the crystalline silicon solar cell module is just tens of volts. On the other hand, the grounding methods of the PCS (Power Conditioning System) that connects to the system as an AC power supply varies according to the type of PCS. In recent years, the transformerless method, where the input side is in the floating method (the negative polarity is not connected to the ground) is increasing. In this case, a high potential difference occurs between the cell and the ground. Regarding the crystalline silicon solar cell module, it is proved that the cell having a higher negative electric potential than that of the frame (ground) easily causes the PID effect. (See Fig. 1) The PV modules are currently managed with the maximum system of voltage as 600V in Japan and 1000V in Europe. There is a market trend that the maximum voltage of the commercial mega solar system is raised from the perspective of reducing the number of the strings and the total number of the PCS, and improving the efficiency of power generation.
Figure 2 shows the simulation of a crystalline silicon solar cell module being exposed to a high potential difference. It is considered that, in the PID effect of the crystalline silicon solar cell module, the sodium ion in the white tempered plate glass moves to the side of the cell and then causes the deterioration. (The PID ef fec t of the thin f ilm solar cell module is also confirmed, however, the mechanism of the deterioration is different from that of the crystalline silicon solar cell module.) The cause of the PID effect is currently being tested with and researched by various research organizations.
Capable of arbitrary setting of the output voltage
You can set the test voltage that is applied to the DUT within the range of 50 Vdc to 2000 Vdc (resolution 1V). In addition, an insulation resistance test of the electricity/electronic components or the electricity/electronic devices is also possible besides the voltage specified in JIS C 1302:1994. In the range of 50V to 1000V, the output properties are complied to JIS C 1302:1994.
The output is floating from the ground.
The output terminal is floating from the ground electric potential. *1 In
addition, a shield cable is adopted as an output cable. Therefore, it can be measured only an
electric current flowing between test points excluding the one between the DUT and the ground, and
it realizes to conduct the highly-sensitiveand precise evaluation.
*1: Ground voltage of the terminal that polarity is set as an anode (±1000 Vdc) Ground voltage of the terminal that polarity is set as a cathode (+1000 Vdc and -3000 Vdc)
Polarity switching function
You can easily change the output polarity by the switch on the front panel. The PID deterioration is a reversible phenomenon that may recover after the reverse bias voltage is applied. The polarity switching is a convenient function that can avoid a wiring change that connects to the DUT. In addition, switching by the external control through the RS232C interface is also possible.
Analog output terminal
In the resistance display mode, the voltage depending on the measured resistance is logarithmically compressed and output within the range of 0V to 4V. In the current display mode, the current is output in a linear scale depending on the measured current and ranges of measurement (4 ranges). You can analyze the changes or the deterioration status of the DUT by using an external recording device such as the data logger.
Information related to PID test
Reference: National Institute of Advanced Industrial Science and Technology
Test on the PID effect
The experiment to reproduce the PID effect was conducted as the collaborative research theme in “Stage II Consortium of high-reliability PV module development and evaluation” that was established in April 2011 by the Research Center of Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology (hereinafter called “AIST”). Kikusui Electronics Corp. developed TOS7210S as a necessary test equipment contributed for this experiment project.*The contents mentioned above was announced in the 61st academic lecture of Japan Society of Applied Physics on March 19, 2014.
Creation of the single cell module
The 6-inch polycrystalline silicon cell of the test module is laminated, as a unit cell module, with white tempered glass, ethylene vinyl acetate (sealing material), and back sheet.
Materials used for a solar battery module
- Cell substrate: 6-inch polycrystalline silicon cell
- Light-receiving glass: White tempered glass
- Sealing material: Ethylene vinyl acetate (EVA)
- Back sheet: PVF/PET/PVF constituted back sheet
We installed the light receiving surface of the glass covered with an aluminum board in a constant temperature chamber and connected it to the PID insulation tester TOS7210S. We then kept the module temperature at 85°C and applied -1000 Vdc, -1500 Vdc, and -2000 Vdc to each of three pieces of the single cell modules.
Confirmation of the output characteristics by the solar simulator
An output drop can be confirmed with the initial (Pmax/F.F./Isc/Voc) characteristics of the module and the changes with the elapsed time.
Confirmation of the deterioration by EL (electro-luminescence)
The normal par t emits light per fectly, but as the deterioration accelerates, the shaded area increases eventually and ceases to emit light. This method is adopted useful to confirm the PID effect. In addition, it is admitted that the deterioration in the PID effect is reduced with the elapled time by a reversible effect or recovered nearly to the initial state.
Confirm the difference in deterioration by applied voltage
The ratio that the maximum electricity (Pmax) of the module decreases when the applied voltage increases. In addition, as the EL image indicates, the higher the applied voltage becomes, the shaded area in the EL image increases in the same interval.
Recovery examination and the results by applying the reverse voltage
In the PID effect after conducting the reversible effect test, it may be found that the deterioration is reduced or rec over nearly to the initial state in some module by being lef t or t he rever se volt age is being applied. The polarity can be easily changed in TOS7210S with the switch. You are not bothered by the complicated connection to the DUT. The module that the Pmax drops remarkably (less than -99 %), and the recovery is not confirmed even after applying voltage for long hours. On the other hand, the module that the Pmax drops moderately (approximately -53 % to -71 %) recovered almost perfectly in 0.5 to two hours. In addition, it canbe recovered regardless of the applied voltage.
Various evaluation methods
Under the present conditions, any of the evaluation test method or the standard are not established. Each of the research organizations, experiment stations, and module manufacturers in the various countries conducting its own evaluation.
- Water method : Method to apply the water on the module glass surface and apply the voltage
- Chamber method : Method to manage temperature and humidity in the temperature chamber and apply the voltage
- Aluminum method : Method to cover the glass with an aluminum foil or let an aluminum board adhere to the glass surface, and apply the voltage
We continue experiments in each test method to examine each superiority and inferiority, difference by the temperature or humidity for future standardization. The international standard IEC is devising the test method for the PID effect.