medium voltage transformer specification - wstech

MV_Transformer_Spec_APS_v010

Medium Voltage Transformer Specification

APS Series – Outdoor Hybrid Inverter

WSTECH is a Wind&Sun Technologies and Siemens Joint Venture.

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Table of Contents

MV_Transformer_Spec_APS_v010 of 17

Table of Contents

1 Specification Medium Voltage Transformer ........................... 5

1.1 Application ...................................................................................................... 5

1.2 Design ............................................................................................................ 5

1.3 Power of LV Windings .................................................................................... 5

1.4 Technical Data ................................................................................................ 6

1.5 Power Derating ............................................................................................. 10

1.6 Mechanical and Electrical Interface .............................................................. 11

2 Usage of other MV Transformer Types ................................ 13

2.1 Vector Groups .............................................................................................. 13

3 Measurements ........................................................................ 14

3.1 Voltage Measurements ................................................................................. 14

3.1.1 Phase to Earth ....................................................................................... 14

3.1.2 Phase to Phase ..................................................................................... 15

4 Revision History ..................................................................... 16

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter List of Figures


List of Figures

Figure 1: Power derating versus ambient temperature ................................................ 10

Figure 2: Relevant mv transformer dimensions part 1 ................................................. 11

Figure 3: Relevant mv transformer dimensions part 2 ................................................. 12

Figure 4: Example of a voltage measurement between phase and earth, measured at the APS ...................................................................................................... 14

Figure 5: Example of a voltage measurement between two phases, measured at the APS ................................................................................................................... 15

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter List of Tables


List of Tables

Table 1: Technical data mv transformer ........................................................................ 6

Table 2: Technical data mv transformer (continued) ..................................................... 7

Table 3: Assignment of rated power and rated low voltage for one LV winding (1000 VDC) ..................................................................................................................... 8

Table 4: Assignment of rated power and rated low voltage for two LV windings (1000 VDC) ..................................................................................................................... 8

Table 5: Assignment of rated power and rated low voltage for two LV windings (1500 VDC) ..................................................................................................................... 9

Table 6: Assignment of rated power and rated low voltage for two LV windings (1500 VDC) (continued) .................................................................................................... 9

Table 7: Assignment of rated power and rated low voltage for two LV windings (1500 VDC) (continued) .................................................................................................... 9

Table 8: Other vector groups and limitations of using.................................................. 13

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Specification Medium Voltage Transformer


1 Specification Medium Voltage Transformer

1.1 Application

This document describes the medium voltage transformer (hereinafter referred to as mv transformer) specification for the APS Outdoor Hybrid Inverter (hereinafter referred to as APS). If the APS is configured as solar inverter or energy storage systems a mv transformer must be used. The mv transformer is the connection between the APS and the medium voltage grid. The mv transformer must be designed for outdoor installation. There is no protection around the mv transformer.

1.2 Design

The LV winding systems are floating (IT system). The DC field can be continuous grounded to earth on the plus or minus side. In consequence, the voltage level of the LV windings can be continuous the rated low voltage above or below ground.

Shielded winding is required between MV and LV windings.

The electrical and mechanical interface of the MV and LV terminals is very important. The corresponding drawings are shown in chapter 1.6.

1.3 Power of LV Windings

The power of the LV windings not always have the same value. During normal operations the loads are almost identical, but under worst case the power can be zero on one system and 100% continuous on the other system.



1.4 Technical Data

Table 1: Technical data mv transformer

ITEM VALUE COMMENTS

1000 VDC 1500 VDC

GENERAL (I)

Transformer type Hermetically sealed

Cooling ONAN (Oil natural, air natural)

Type of oil Mineral oil According to IEC 60296; On request: Esters according to IEC 61099 or IEC 62770

Rated frequency 50 HZ or 60 Hz

Vector group D d0 d0

Max. power unbalance 100%

Short circuit voltage uk 6% If the value of uk deviates, contact WSTECH GmbH. Note: In case of 2 LV windings measured between LV and MV windings.

Short circuit voltage tolerance

-10%...+40% At uk = 6% nominal a range between uk =5.4%...8.4% is allowed

Insulation level MV Up to 24 kV: 24/50/125 kV

Up to 36 kV: 36/70/170 kV

Um/AV/LI

Insulation level LV, between ground and LV windings 3.6/10/- kV Um/AV/LI

Insulation level LV, between LV windings

HIGH VOLTAGE SIDE

Rated voltage 6/10/20/30/33 kV Other voltages possible

Voltage taps -5%, -2.5%, 0%, 2.5%, 5%

Rated power 1 2 Also, at 110% of rated low voltage; Depending on rated low voltage

LOW VOLTAGE SIDE

Rated low voltage 1 2 Specified by customer

Max. THD current (LV Side)

3%

Max. DC-offset current < 0.5%

Max. peak voltage between the LV windings and earth

1500 Vpp 2000 Vpp Continuous at 5 kHz

Max. peak voltage between the LV windings

2250 Vpp 3000 Vpp Continuous at 5 kHz

Max. dV/dt between the LV windings and earth

500 V/µs

1 See Table 3 to Table 4 2 See Table 5 to Table 7



Max. dV/dt between the LV windings

500 V/µs

Table 2: Technical data mv transformer (continued)

ITEM VALUE COMMENTS

1000 VDC 1500 VDC

GENERAL (II) No load losses - According to EU regulation

No. 548/2014

Load losses -

Ambient temperature -20 °C up to +40 °C At rated load, > +40 °C derating according to Figure 1

Typical dimensions (L x W x H)

(2500/1500/2500) In milimeters

Corrosivity category C4-high According to EN ISO 12944

Colour RAL 7035

Sensor of the temperature

1 x PT100 for top oil measurement

Oil level switch



Table 3 and Table 4 show the assignment of rated power and rated low voltage for an DC-link voltage of 1000 VDC.

Table 3: Assignment of rated power and rated low voltage for one LV winding (1000 VDC)

ITEM VALUE

MV SIDE

Rated power (in kVA)

590 1180 650 1000 1300 710 1420 790 1580 820 1640

LV SIDE

1. Winding: Rated low voltage (in V)

3 x 300 3 x 330 3 x 360 3 x 400 3 x 415


- - - - -

Table 4: Assignment of rated power and rated low voltage for two LV windings (1000 VDC)

ITEM VALUE

MV SIDE


1770 2360 1950 2600 2130 2840 2370 3160 2460 3280

LV SIDE


3 x 300 3 x 330 3 x 360 3 x 400 3 x 415


3 x 300 3 x 330 3 x 360 3 x 400 3 x 415



Table 5 to Table 7 show the assignment of rated power and rated low voltage for an DC-link voltage of 1500 VDC.

Table 5: Assignment of rated power and rated low voltage for two LV windings (1500 VDC)

Table 6: Assignment of rated power and rated low voltage for two LV windings (1500 VDC) (continued)

Table 7: Assignment of rated power and rated low voltage for two LV windings (1500 VDC) (continued)

ITEM VALUE

MV SIDE


725 1450 800 1600 870 1740 2175 2900 2400 3200 2610 3480

LV SIDE


3 x 400 3 x 440 3 x 480 3 x 400 3 x 440 3 x 480


- - - 3 x 400 3 x 440 3 x 480

ITEM VALUE

MV SIDE


945 1890 1000 2000 1045 2900 2835 3780 3000 4000 3135 4180

LV SIDE


3 x 520 3 x 550 3 x 575 3 x 520 3 x 550 3 x 575


- - - 3 x 520 3 x 550 3 x 575

ITEM VALUE

MV SIDE


1090 2180 1140 2280 1200 2400 1250 2500 3270 4360 3420 4560 3600 4800 3750 5000

LV SIDE


3 x 600 3 x 630 3 x 660 3 x 690 3 x 600 3 x 630 3 x 660 3 x 690


- - - - 3 x 600 3 x 630 3 x 660 3 x 690



1.5 Power Derating

Figure 1 shows the power derating depending on the ambient temperature.

Figure 1: Power derating versus ambient temperature



1.6 Mechanical and Electrical Interface

Figure 2 and Figure 3 show a typical mechanical design of the mv transformer.

The yellow-marked values in the drawings must be observed for the dimensioning of the mv transformer.

Other mv transformer designs are possible, but they have to be checked and release by WSTECH GmbH.

Figure 2: Relevant mv transformer dimensions part 1



Figure 3: Relevant mv transformer dimensions part 2

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Usage of other MV Transformer Types


2 Usage of other MV Transformer Types

This chapter defines other possible solutions. This is only relevant if there are already existing mv transformers that have to be used.

2.1 Vector Groups

The vector group may vary. Some vector group configurations can lead to functional deviations of the APS.

Table 8: Other vector groups and limitations of using

ITEM VALUE COMMENTS

1000 VDC 1500 VDC

GENERAL

Vector group D d0 d0 Default, preferred version

Y d0 d0 Possible with no limitations

D y11 y11 Only possible in grid feeding operations. Not suitable for island grid operations.

If other configurations are required, please contact our sales department.

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Measurements


3 Measurements

In this chapter several different measurements of the mv transformer usage are shown. These signals are only an example and are not relevant for the specification. They are implemented to provide a deeper understanding of the mv transformer usage with the APS.

3.1 Voltage Measurements

3.1.1 Phase to Earth

Test conditions:

• U = 1350 VDC

• U = 400 VAC (phase to phase)

Figure 4: Example of a voltage measurement between phase and earth, measured at the APS

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Measurements


3.1.2 Phase to Phase

Test conditions:

• U = 1350 VDC

• U = 400 VAC (phase to phase)

Figure 5: Example of a voltage measurement between two phases, measured at the APS

Medium Voltage Transformer Specification APS Series – Outdoor Hybrid Inverter Revision History


4 Revision History

Version 003

• Frist release.

Version 004

• Revise layout all tables;

• Add technical information for 2. Winding.

Version 005

• Add vector group to comments;

• Change “Max. peak voltage between the sec. windings and earth” for 1500 VDC;

• Add comment to item “Short circuit voltage uk”.

Version 006

• Add values and comments for insulation level MV and LV;

• Change “Primary” to “Medium voltage”;

• Change “Secondary” to “Low voltage”.

Version 007

• Add standards and regulations to technical data;

• Delete item “No load temperature”

• Delete “Rated current (LV Side) of tables 3, 4, 5, 6 and 7.

Version 008

• Add chapter “Usage of other MV Transformer Types”;

• Add possible vector groups and define their limitations of using;

• Add chapter “Revision History”.

Version 009

• Add chapter “Measurements”;

• Add voltage measurements of the APS to clarify the usage of the mv transformer.

Version 010

• Add row to table with values for “Short circuit voltage tolerance” in chapter 1.4.

medium voltage transformer specification - wstech

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