MODULAR SUNWAY TG
TE OD
INSTALLATION GUIDE
86/
139
Rev. 03
– 01/06//2018
The Positive Earthed and Negative Earthed options may be integrated with the Earthed Ground Fault
Detection (EGFD) option, enabling detecting first fault to earth conditions in earthed PV fields, also on the
Positive Earthed or Negative Earthed (Blind spot) conductor.
Detecting the first fault to earth of the earthed conductor prevents the double fault condition from occurring,
which is not detected by the earthing fuse.
Figure 56: Fault current loop in case of double fault to earth
The fault loop is shown in the figure above. If the impedance of the short-circuit fault to earth does not cause
the earthing fuse to blow, leakage current occurs in fault 2. That leakage current cannot be detected if the
EGFD option is not fitted, thus causing dangerous situations also leading to fire risks.
8.4.
Soft grounding
DANGER
Earthed-pole systems are NON IT systems.
The Soft Grounding resistor is not a safety device against direct contacts.
Should the Soft Grounding resistor break open, the field may be left floating.
SUNWAY TG TE inverters may be equipped with an optional
Soft Grounding
kit, comprising a resistor and
a series contactor, connected to the negative input pole at the DC side. The kit is meant as a means to
prevent potential induced degradation (PID) on crystalline modules. The degradation is avoided by reducing
the amplitude of the negative voltage between the negative pole of the field and earth. Such voltage, which
is around half of the panels voltage in floating fields, triggers the panel degradation. Reducing it to
significantly lower values scales the degradation down to negligible levels over the entire life of the plant.
All the live parts of the SUNWAY TG TE inverters are floating in relation to the earth potential. By connecting
a floating PV generator to the inverter, the overall low-frequency system upstream from the isolation
transformer is consequently an IT type. On the other hand, connecting the photovoltaic field to earth via a
resistor results in a non-IT system.
