SMA SC 400HE - Manual (Page 22)

3 Product Description SMA Solar Technology AG
22 SC4-63HE-BE-BEN103280 Operating Manual
Overview of the Analog Inputs
3.8 Insulation Monitoring
3.8.1 How Insulation Monitoring Works
Insulation monitoring consists of equipment that ensures plant protection in electrical devices.
There are different types of insulation monitoring:
• In grounded grids
Insulation monitoring is performed via a residual current monitoring device. If an insulation
failure occurs, the residual currents will be detected and interrupted.
• In ungrounded grids
An insulation monitoring device constantly determines the insulation resistance using an active
measurement procedure. If the insulation resistance falls below a certain threshold, an insulation
warning will be displayed on the indicator light and Sunny Central Control. This allows
measures to be taken to prevent errors, for example, personal injury caused by leakage current
or plant failure. If the insulation resistance falls below a limiting value, then the plant can switch
itself off. A parameter can be configured to switch off the unit when an error occurs.
3.8.2 GFDI
Depending on the order, the insulation monitoring in the Sunny Central is carried out via a ground
fault detection interruption, abbreviated GFDI. This process is used to ground one pole of the PV
array.
A high-performance miniature circuit-breaker with adjustable trip current with K characteristics is used
as a GFDI. It is integrated in the inverter and connected between an input busbar and the protective
conductor bar.
Input Description
ExtSolIrr External irradiation sensor
ExtGloIrr Pyranometer (measurement of global solar irradiation)
ExtAlarm External alarm input, e.g., for monitoring the functioning of the
medium-voltage transformer
ExtSolP External target value of active power
ExtSolQ External target value for reactive power
TempExtC External temperature sensor PT 100 (is factory-installed in the
Sunny Central)