Insulation Monitoring Device - SMA SUNNY CENTRAL 500CP XT User Manual

10 Function Description

10.2.3.4 Insulation Monitoring Device

Depending on the order option, an insulation monitoring device can monitor the insulation resistance of the PV power
plant in ungrounded PV arrays.
In the operating state "MPP load operation", the insulation resistance of the entire system, from the PV array to the MV
transformer, will be measured.
If the inverter is in the operating state "Grid monitoring", only the insulation resistance from the PV array to the inverter
will be measured.
Figure 21: Insulation monitoring device
Position
A
A measuring circuit and a relay with a change-over contact are integrated in the insulation monitoring device.
The insulation monitoring device is connected between the PV voltage and the grounding conductor. The contacts of
the relay are routed to the customer terminal plate and can be used by the customer to trip a signal light or siren. The
characteristics of the relay are indicated in the circuit diagram.
If the insulation resistance falls below the warning threshold specified in the parameter RisoCtlWarn, the measuring
circuit closes and the LED ALARM1 on the insulation monitoring device is glowing. The error message 3601‒
Warning insulation failure is generated by the inverter. Simultaneously, the insulation monitoring device activates
the relay with change-over contact. This relay is installed in the inverter.
If the insulation resistance falls below the error threshold (1 kΩ), an insulation error has occurred and the LEDs
ALARM1 and ALARM2 on the insulation monitoring device are glowing. In this case, the operating behavior of the
inverter can be set via parameters as follows:
• If the parameter IsoErrIgn is set to Off, the measuring circuit issues a disturbance when the insulation resistance
falls below the error threshold, the inverter switches off and issues the error message 3501 - Insulation Failure.
The LEDs ALARM1 and ALARM2 are glowing.
• If the parameter IsoErrIgn is set to On, the error message from the measuring circuit is ignored when the
insulation resistance falls below the error threshold. The inverter continues to feed into the grid and generates the
error message 3504 ‒ Insulation failure ignored.
• If the parameter IsoErrIgn is set to Run and the insulation resistance falls below the error threshold, the error
message from the measuring circuit will only be ignored if the inverter is in feed-in operation. In feed-in operation,
the inverter continues to feed into the grid and generates the error message 3504 ‒ Insulation failure ignored.
If the insulation resistance falls below the error threshold in another operating state, the error is not ignored and
the inverter does not switch to feed-in operation. The error message 3501 ‒ Insulation Failure appears on the
touch display. The LEDs ALARM1 and ALARM2 are glowing.
90 SCCPXT-E7-BA-en-58
Designation
Insulation monitoring device
SMA Solar Technology AG
User Manual