Sungrow MVS6400-LV, MVS8960-LV and 1+X SG6600UD-MV

Short answer

Sungrow offers two types of medium-voltage station for 1,500 V solar plants. The MVS-LV series, such as the MVS6400-LV and MVS8960-LV, has no inverter: it collects the SG350HX string inverters on the low-voltage side and steps them up to medium voltage with an oil-filled transformer and SF6 switchgear, with a 50/51, 50N/51N relay. The 1+X, such as the SG6600UD-MV and SG8800UD-MV, is a modular inverter in a 40-foot container that integrates the inverter modules, the transformer and the medium-voltage output.

What it is and where it is used

Sungrow is the Chinese manufacturer of inverters for solar and storage plants. For utility-scale plants it has two families of medium-voltage station. The first is the MVS-LV series, with models such as the MVS6400-LV and the MVS8960-LV: transformer stations without an inverter (string inverter architecture), designed for the SG350HX string inverters. The second is the 1+X, with models such as the SG6600UD-MV and the SG8800UD-MV: a modular inverter that integrates the conversion, the transformer and the medium-voltage output.

In both, the station sits between the photovoltaic field and the medium-voltage collector network, which ends at the plant step-up substation. The MVS6400-LV datasheet has a version specific to Latin America (LA).

Variants MVS6400-LV, MVS8960-LV and 1+X SG…UD-MV

Model	Application	Main difference
MVS6400-LV	Station for SG350HX / SG350HX-20	6,400 kVA at 40 °C; 0.8 / 10–35 kV; 20-foot container; LA version for Latin America
MVS8960-LV	Station for SG320HX / SG350HX and -20 versions	8,960 kVA; 20–35 kV; ONAN
SG3300UD-MV-20 / SG4400UD-MV-20	1+X with 3 or 4 modules of 1.1 MW	Modular inverter with transformer and MV output
SG6600UD-MV(-20)	1+X with 6 modules of 1.1 MW	6,600 kVA at 45 °C; 10–35 kV; 40-foot container
SG8800UD-MV(-20)	1+X with 8 modules of 1.1 MW	8,800 kVA at 45 °C; 20–35 kV; 40-foot container
SG3125UD-MV-20 / SG6250UD-MV-20 / SG9375UD-MV-20	1+X 2.0	800 kW modules with a split modular design

The MVS-LV family includes other ratings; the exact model and its datasheet are confirmed with the manufacturer.

Main features of the MVS6400-LV

According to the MVS6400-LV datasheet (LA version):

Transformer: PCB-free mineral oil, ONAN, 6,400 kVA at 40 °C and 7,040 kVA at 30 °C, vector group Dy11y11 with two low-voltage windings of 0.8 kV. Medium voltage from 10 to 35 kV, taps of 0 and ±2 × 2.5 %, impedance of 8 % and aluminum windings.
Transformer’s own protections: oil temperature, level and pressure and a Buchholz relay, standard on the step-up transformer.
Medium-voltage switchgear: SF6-insulated, 24 to 40.5 kV and 630 A, with internal arc classification IAC AFL 20 kA 1 s and a 50/51, 50N/51N relay.
Low-voltage panel: two 4,000 A, 800 V ACB main breakers, 260 A disconnect switches and 400 A fuses per input; type I+II surge arresters.
Station service: 15 kVA transformer at 400 V (up to 40 kVA as an option).
Enclosure: 6,058 × 2,896 × 2,438 mm, about 22 t, IP54, operation from −30 °C to 60 °C and 1,000 m as standard.
Declared standards: IEC 60076, IEC 62271-200, IEC 62271-202, IEC 61439-1 and EN 50588-1.

Main features of the 1+X SG6600UD-MV and SG8800UD-MV

According to the SG6600UD-MV and SG8800UD-MV datasheet:

Input: 1,500 V DC, with a DC switch and a fuse per input; 6 or 8 independent MPPT inputs.
Output: 6,600 kVA (SG6600UD-MV) or 8,800 kVA (SG8800UD-MV) at 45 °C, with an ONAN Dy11y11 mineral-oil transformer from 0.63 kV to 10–35 kV or 20–35 kV, and an AC circuit breaker on the medium-voltage output.
Grid functions: active and reactive power control, power ramps, support during voltage dips and overvoltages (L/HVRT) and night-time reactive power as an option.
Enclosure: 40-foot container (12,192 × 2,896 × 2,438 mm), 27.5 t or 31.5 t; inverter IP65 and the rest IP54.
Declared standards: IEC 62109, IEC 61727, IEC 62116, IEC 61683, IEC 62271-202, VDE-AR-N 4110 and 4120, EN 50549-2, among others.

Protection of the transformer switchgear

In the MVS6400-LV, the transformer is protected by the medium-voltage switchgear with a phase and ground overcurrent relay (50/51, 50N/51N), and its own protections (Buchholz, pressure, temperature) are wired to the trip of that switchgear, as is standard for a solar station. In the 1+X, the datasheet declares an AC circuit breaker on the medium-voltage output. In both cases the relay coordinates with the collector network feeder; anti-islanding and the utility’s requirements are resolved at the point of connection.

Communications and integration

MVS6400-LV: RS485, Ethernet and fiber optic as standard.
1+X: RS485 and Ethernet, with LED indicators and a local WebHMI.
Plant monitoring and setpoints reach the inverters through the Sungrow logger or through the power plant controller (PPC) that the design defines.

What is checked at commissioning

In general terms: inspection and grounding of the station. Transformer tests. Verification that the Buchholz, pressure and temperature trip the switchgear. Secondary injection to the 50/51 relay. SF6 pressure and interlocks. Low-voltage panel and auxiliaries. Communications. Energization from the collector network and start-up of the inverters. The guide on commissioning a solar skid details each stage.

According to the manufacturer’s manual

A general summary of the Sungrow manuals we review; it does not replace the manual for your unit:

MVS6400-LV, MVS6840, MVS7040-LV and MVS7320-LV (system manual Ver42, 2024-07, in English). The medium-voltage switchgear consists of one load-break switch panel, one circuit breaker panel and one direct cable panel, with names that change depending on the switchgear manufacturer (§2.6.3, p. 13). To de-energize, the manual’s rule is «low voltage before medium voltage, DC before AC». The inverters are stopped and the output disconnect switches and the ACB of the low-voltage panel, the auxiliaries and the circuit breaker of the V panel are opened. Then its earth switch is closed and, last, the grid-side panel is opened. To energize, «medium voltage before low voltage, AC before DC», with the inverters not started until the end and 24 hours on no load before taking load at commissioning (§6.3 and §6.4, p. 61–63). The manual asks to wait at least 5 minutes after shutdown before servicing the station and 10 minutes before opening its doors (§1.5, §6.4 and §8.1).
1+X for the United States, SG3150UD-MV-US and SG4400UD-MV-US (user manual Ver23, 2025-09, §7.5, p. 79–80, in English). The planned shutdown turns the inverter off from the web interface, sets the DC switch to OFF and opens the output of the combiner boxes and the medium-voltage load-break switch. Then it checks that the breakers of each unit are open. The emergency shutdown opens only the AC breaker and the DC breaker, and the auxiliary supply and the boards stay energized. Minimum wait of 5 minutes.
1+X SG3300UD-MV and SG4400UD-MV for China (system manual SG3300UD_4400UD-MV-SCN-Ver10-202111, §6.3, p. 45 of the PDF; source in Chinese). The shutdown follows a similar order and ends with the transformer load-break switch and the combiner boxes. The manual asks to wait 20 minutes after de-energizing the inverter before servicing it (p. 23 of the PDF). Before working, it asks to confirm the ground cable on the low-voltage panel, the selector on local, the earth switch closed and the load-break switch open (p. 16 of the PDF).

Waiting times differ between manuals of the same brand: take them from the document for the installed model and region.

Frequently asked technical questions

Datasheet by region: Sungrow publishes datasheets by market (EUR, LA, APAC, MEA). For Latin American projects the LA version is the one to use; confirm the 60 Hz frequency and the collector voltage.
Manual: the user manual for each station is on the Sungrow support portal.
1+X or 1+X 2.0: the size of the conversion module changes (1.1 MW or 800 kW) and, with it, the ratings of the container.
Connection requirements: they are set by the local code and the utility’s requirements.

How we help

At Tiza Group we do the testing and commissioning of the medium-voltage stations and of the complete plant: transformer, switchgear and relay, own protections, communications and energization, in Colombia or elsewhere on request. See the scope in testing and commissioning of solar plants. For the coordination of the station relay with the collector network and for engineering, see engineering design and studies. For a quotation, write to us through contact.

References

Sungrow Power Supply, MVS6400-LV datasheet (version 4LA, 2025).
Sungrow Power Supply, MVS8960-LV product page.
Sungrow Power Supply, SG6600UD-MV / SG8800UD-MV datasheet (version 4, 2025) and 1+X modular inverter page.
Sungrow Power Supply, System Manual MV Station MVS6400–LV/MVS6840/MVS7040–LV/MVS7320–LV, MVS6400_6840_7040_7320-LV-SEN-Ver42-202407, in English.
Sungrow Power Supply, SG3150UD-MV-US/SG4400UD-MV-US User Manual, SG3150_4400UD-MV-US-UEN-Ver23-202509, in English.
Sungrow Power Supply, SG3300UD/4400UD-MV 中压并网逆变器系统手册 (system manual of the medium-voltage inverter), SG3300UD_4400UD-MV-SCN-Ver10-202111, in Chinese (info-support.sungrowpower.com).
IEC 62271-202, high-voltage/low-voltage prefabricated substations.
IEC 62271-200, AC metal-enclosed switchgear and controlgear.
IEC 60076, power transformers.

Frequently asked questions

What is the Sungrow MVS6400-LV?

It is Sungrow's turnkey medium-voltage station for 1,500 V SG350HX and SG350HX-20 string inverters. According to its datasheet, it has a 6,400 kVA oil-filled transformer at 40 °C (7,040 kVA at 30 °C), vector group Dy11y11, from 0.8 kV to 10–35 kV, SF6 switchgear of 24 to 40.5 kV and 630 A, and a 50/51, 50N/51N relay in a 20-foot container.

What is the difference between the Sungrow MVS-LV and the 1+X?

The MVS-LV has no inverter inside: it receives, at 800 V, the string inverters installed in the field. The 1+X is a 1,500 V modular inverter that carries inside the 1.1 MW conversion modules (800 kW in the 1+X 2.0), the transformer and the medium-voltage output, in a 40-foot container. The plant architecture changes in each case, not the function of the station.

What protection does the Sungrow MVS6400-LV transformer have?

The datasheet declares oil temperature, level and pressure detection and a Buchholz relay, plus a 50/51 and 50N/51N medium-voltage relay in the switchgear. The low-voltage inputs are protected with a fuse and a disconnect switch. The relay settings and their coordination with the collector network are defined by the protection study.