Solar power generating systems are using Photovoltaic (PV) technology to absorb sunlight and convert it into electricity that we can use. The array of a photovoltaic power system, or PV system, produces direct current (DC) power which fluctuates with the sunlight’s intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters. Some systems require a battery bank to store the solar electricity for use during night time or cloudy weather, a charge controller to protect the battery bank from overcharge.

We can basically see that solar power generation is a complex system with many electrical parts involved so that we need to measure, monitor, analysis and record the measured data to maintain the system as well as to resolve the problems on a daily basis.

A solar power generation system diagram

Figure 1: A solar power generation system diagram

Electrical testing

Digital multimeters (DMMs) and clamp meters are easy to use with standard voltage and current measurement for maintaining solar power systems.

Hioki DT4254 is dedicated for voltage measurement with high voltage up to DC1700V that is useful for PV system where the DC voltage is normally over 1000VDC.

DT4254 supports up to 1700VDC with Auto DCV polarity check

Figure 2: DT4254 supports up to 1700VDC with Auto DCV polarity check

Identify which string is being affected by the anomaly while continuing to sell power back to the grid.

At the junction box, use a Hioki CM4370 series AC/DC clamp meter to measure the current of each string generating power thatโ€™s being sold back to the grid. The string with the anomaly will have a noticeably lower current. Compare readings for strings in the same junction box and look any discrepancy to identify which string is being affected by the anomaly.

CM4371 for measuring solar power string current

Figure 3: CM4371 for measuring solar power string current

Insulation resistance measurement of solar panels

When measuring the insulation resistance of a solar panel that is generating electricity, remember not to apply the standard method for measuring the circuitโ€™s insulation resistance and bear in mind that the photovoltaic cell voltage affects the test voltage and that there is the risk of damaging other equipment if the array is grounded.

The Hioki IR4053 Insulation Tester can accurately measure insulation resistance without being affected by generating PV.

IR4053 with PV dedicated function for accurate, safe measurements

Figure 4: IR4053 with PV dedicated function for accurate, safe measurements

Measure insolation and temperature wirelessly

Hioki LR8515 mini data logger can be used as a method for wirelessly capturing actinometer and temperature data at the desired timing measurement.

  • Record the output from an actinometer or calibrated sunlight sensor (compact module) and a thermocouple using the Wireless Voltage/Temp Logger LR8515. Use the captured data correcting IV curves and other maintenance and preventive work.
  • Since thereโ€™s no need to connect to an IV curve measuring instrument or other device, bothersome wiring is eliminated.
Using LR8515 for capturing actinometer and temperature data

Figure 5: Using LR8515 for capturing actinometer and temperature data

Manage the voltage of lead-acid storage batteries

The HIOKI LR8400-20 series with 30 channels as standard, expandable to 60 channels can be used to measure the voltage of lead-acid UPS battery cells used for solar power supply for monitoring voltage fluctuations.

LR8400 data logger in an online UPS monitoring system

Figure 6: LR8400 data logger in an online UPS monitoring system

Checking the amount of electricity sold and the power quality of solar power generation systems

The new Hioki PQ3100 Power Quality Analyzer can measure the amount of electricity sold and purchased simultaneously. The data allows you to confirm that the PV system works normally.

The PQ3100 can measure output of the power conditioner and display voltage and frequency changes. Demand and change graphs displayed in colour on the screen of the PQ3100 allow you to check the operation of the PV system on the spot.

Using PQ3100 for energy and power quality measurement

Figure 7: Using PQ3100 for energy and power quality measurement

The PQ3100 is also used to measure all power quality parameters such as voltage/current RMS, voltage dip/swell, interruption, transient overvoltage, inrush current, power, frequency, voltage/current unbalance factor, harmonics simultaneously.

Evaluation of input and output characteristics of power conditioners

The PW6001 Power Analyzer can simultaneously measure and display multiple items including DC/AC voltage/current, voltage ripple factor, power, amount of power energy, power factor, voltage/current distortion factors, frequency, amount of power energy sold and purchased, voltage imbalance rate, and efficiency. It also displays voltage/current waveforms.

One PW6001 can perform completely synchronized measurement of input and output characteristics of power conditioners

Figure 8: One PW6001 can perform completely synchronized measurement of input and output characteristics of power conditioners

Multi-string PV inverter efficiency measurement

PW6001 also can be used to measure the efficiency of multiple strings (arrays) and 50/60Hz output to the grid.

Using PW6001 for multi-string PV inverter efficiency measurement

Figure 9: Using PW6001 for multi-string PV inverter efficiency measurement

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