5. Commissioning
2. Measure the voltage present between the positive and negative wires of each string.
If the open circuit voltage of the string is near the maximum value accepted by the inverter,
verify the string length. Low ambient temperatures cause an increase in the string voltage
causing potential damage to the inverter.
3. Check the polarity of the string. All digital meters have a negative (“-“) indicator that
indicates when a voltage is negative; in this case a string connected in reverse polarity.
WARNING
Input voltages higher than the maximum value accepted by the inverter
(see “Specifications” in Section 9) may damage the inverter.
Although Canadian Solar inverters feature reverse polarity protection,
prolonged connection in reverse polarity may damage these protection
circuits and/or the inverter.
5.4.1.2 Leakage to ground
Measure leakage to ground to check for a DC ground fault.
5. Commissioning
5.4 Preliminary checks
WARNING
High Voltage.
AC and DC measurements should be made only by qualified personnel.
5.4.1 DC configuration
5.4.1.1 VOC and Polarity
To measure the open circuit voltage (VOC) and polarity of the individual strings, perform
the following steps:
5.4.1.1.1 Check string voltage
1. Connect the positive lead of the meter to the positive string cable of the string under test.
Connect the negative lead of the meter to the negative string cable of the string under test.
Verify DC configuration by noting the number of panels in a string and the string voltage.
Measure VOC, and check string polarity. Ensure both are correct and VOC is in specification.
.35.
.34.
5.4.1.2.1 Detection of leakage to ground
Canadian Solar inverters are transformer-less and do not have an array connection to ground.
Any measurement of a fixed voltage between ground and either the positive or negative string
wiring indicates a leakage (ground fault) to ground and must be corrected prior to energizing
the inverter or damage to the inverter may result.
To measure leakage to ground, perform the following steps:
1. Ensure that neither negative nor positive DC conductors are connected to the ground strip.
2. Measure each string positive connection to ground.
3. Measure each string negative connection to ground.
4. Verify the voltage is “floating”, not a consistent voltage to ground. Make sure you notice the
units of the measurement. mV is not the same as V.
Measure VAC and verify voltage is within local grid standards.
1). Measure each phase to ground (L-G).
5.4.2.1 Measure VAC and frequency
2). Measure phases to the other phases in pairs (L-L). PH A to PH B, PH B to PH C and
PH C to PH A.
3). If the meter is equipped, measure the frequency of each phase to ground.
4). Ensure each measurement is within local grid standards and the inverter specifications
as noted in Section 9 “Specifications”.
A phase rotation test is recommended to ensure the phases have been connected in the
appropriate order. Canadian Solar inverters do not require a
specific phase rotation connection.
However, the local utility may require a specific phase rotation or a record of the phase
configuration of the installation.
5.4.2.2 Phase rotation test
Verify AC configuration.
5.4.2 AC configuration
Verify DC connections.
Lightly tug on each DC cable to ensure it is properly connected to the inverter.
5.4.3 DC Connections
Verify AC connections.
1. Lightly tug on each AC cable to ensure it is fully captured in the terminal.
2. Visually check for any stray strands that may not be inserted in the terminal.
3. Check to ensure the terminal screws are the correct torque.
5.4.4 AC Connections
