Grounding And Insulation Resistance Monitoring; Insulation Resistance; Insulation Measurement Unit - ABB PVS980-58 Firmware Manual

Grounding and insulation resistance monitoring

Insulation resistance


According to standard IEC62109-2, the insulation resistance of the PV panel array should
be measured before grid connection. The standard does not state that insulation
resistance shall be measured while the inverter is running. In addition to IEC62109-2
standard, local country grid codes might put forward additional requirements on insulation
measurements. For additional safety, FIMER recommends that insulation resistance is
regularly measured using an earth fault measuring device.

Insulation measurement unit


Insulation resistance measurement is an automatic feature of the inverter. The feature is
preconfigured to prevent the starting of inverter when insulation resistance is low and
notifies the event. Note that low insulation resistance might also be caused by
environmental factors, such as, high humidity.
WARNING!
The devices used to monitor insulation resistance are not personnel safety
devices or fire protection devices against leakage current.
The MIRU unit of the inverter measures the insulation resistance. When insulation
resistance measurement is activated for the first time, wait until a valid measurement
result is received, at least five minutes. If a valid measurement result is not received within
60 minutes, MIRU is determined to be faulty and a warning message is displayed.
The insulation measuring unit can be used to measure any earth fault in the system and
thus prevent any further damages caused by earth faults. Note that obtaining a valid
measurement value can take a long time. For example, measuring a direct zero (earth
fault from the AC side) might take up to five minutes. Measuring a real insulation
impedance value in kilo ohms, can take up to 10 minutes.
Event setting
If a low insulation resistance measurement is configured to trigger a warning or a fault then
it also inhibits grid connection; otherwise it trips the inverter if it is connected to the grid
and generating active power. An automatic recovery can be implemented using the
warning event as a fail action. When insulation resistance increases above the limit
defined in parameter
the inverter connects to grid. If a fault was triggered, it must be reset before grid
connection.
Self-test for grid connection
If grounding is not enabled, the MIRU unit can be configured to run a self-test every day
prior to grid connection. Self-test can be enabled through parameter
test. An input voltage level can be set with parameter
exceeded before the test is run in the morning. The inverter will not connect to the grid
unless the self-test is passed. If the test does not pass the inverter keeps running the self-
test.
210.28 Insulation resistance
limit, the warning event is removed and
210.33 MIRU self-
210.34 Self-test voltage
Program features 45
that must be