SMA Solar Technology AG
3 Product Description
User Manual
SCCP-JP-BA-A4-en-12
25
3.7.3 Insulation Monitoring
3.7.3.1 Insulation Monitoring Device
Depending on the order option, an insulation monitoring device can monitor the insulation resistance of the PV system 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 Sunny Central is in the operating state "Grid monitoring", only the insulation resistance from the PV array to the
Sunny Central will be measured.
Figure 9: Insulation monitoring device in the Sunny Central
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 connection area and can be used 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
RisoCtlWarn
parameter, the measuring
circuit closes and the LED
ALARM1
on the insulation monitoring device lights up. The error message
3601‒ Warning
insulation error
is generated by the inverter. Simultaneously, the insulation monitoring device activates the relay with
changeover contact. This relay is integrated in the Sunny Central.
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 light up. 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 Sunny Central switches off and issues the error message
3501 - Insulation error
.
The LEDs
ALARM1
and
ALARM2
are lit.
• 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 Sunny Central continues to feed into the grid and generates the error
message
3504 ‒ Insulation error 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 Sunny Central continues to feed in and issues the error message
3504 ‒ Insulation error ignored
. If the
insulation resistance falls below the error threshold in another operating state, the error will not be ignored and the
Sunny Central will not go into feed-in operation. The error message
3501 ‒ Insulation error
appears on the touch
display. The LEDs
ALARM1
and
ALARM2
are lit.
