ZIGOR ZGR SOLAR STR 250 Manual De Operación página 74

ZGR SOLAR STR 250
1) The transformer may be a distribution transformer, and it must be designed for the typical cyclical loads of
a PV system (load in the day and no load at night).
2) The transformer may be of the liquid-immersed type or dry type, and shield winding is not necessary.
3) The line-to-line voltage on the LV side of the transformer should endure the output voltage of inverter.
When the transformer is connected to the IT grid, toground withstanding voltage of the LV winding of the
transformer, the AC cables, and the secondary equipment (including the relay protection device, detection
& measuring device, and other related auxiliary devices) should not be lower than 1,100V.
4) The line-to-line voltage on the HV side of transformer should comply with local power grid voltage.
5) A transformer with a tap changer on the HV side is recommended in order to keep consistent with the grid
voltage.
6) At an ambient temperature of 45℃, the transformer can run in 1.1 times of load for long time.
7) Transformer with a short-circuit impedance 6% (permissible tolerance: ±10% ) is recommended.
8) The voltage drop of system cable is no more than 3% .
9) The DC component that the transformer can withstand is 1% of the fundamental current at rated power.
10) For thermal rating, the load curve of the transformer and environment conditions should be taken into
account.
11) The apparent power of the inverter should never exceed the power of the transformer. The maximum AC
current of all inverters connected in parallel must be taken into account. If more than 28 inverters are
connected to the grid, contact ZIGOR.
12) The transformer must be protected against overloading and short circuit.
13) The transformer is an important part of grid-connected PV generation system. The fault tolerance capacity
of the transformer should be taken into account at all times. The fault include: system short circuit,
grounding fault, voltage drop, etc.
14) Take ambient temperature, relative humidity, altitude, air quality, and other environmental conditions into
account when selecting and installing the transformer.
15) When the anti-PID function is enabled, observe the following items:
If the LV side winding is in Y shape, neutral point grounding is prohibited.
o
Surge protective devices (SPD) for the AC combiner box and on the LV side of the transformer are
o
recommended to be connected in the "3+1" manner, as shown in the figure below (Fig. 4-27). The
Min. continuous operating voltages of M1-M4 are 750 Vac.
The LV side winding of the transformer, AC cables, and secondary devices (- including protective
o
relay, detection and measurement instruments, and related auxiliary devices) must withstand the
voltage to ground of at least 906V.
4.4.5.4 Requirements for OT/DT Terminal
The factory default standard SC-75 terminal, if customers need to use OT/DT terminal, they need to purchase
according to the following requirements.

Specification:M12;
Operation manual
Fig. 4-27 LV side winding of the transformer
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