NB/T 32004-2018 English PDF (NB/T32004-2018)

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NB/T 32004-2018: Technical specification of PV grid-connected inverter
NB/T 32004-2018
NB
ENERGY INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 29.120.01
K 46
Filing number: 64298-2018
Replacing NB/T 32004-2013
Technical specification of PV grid-connected inverter
ISSUED ON: APRIL 03, 2018
IMPLEMENTED ON: JULY 01, 2018
Issued by: National Energy Administration
Table of Contents
Foreword ... 3 
1 Scope ... 8 
2 Normative references ... 8 
3 Terms and definitions ... 11 
4 Inverter type ... 22 
5 Environmental and use requirements ... 23 
6 Safety requirements ... 24 
7 Basic functional requirements ... 45 
8 Performance requirements ... 45 
9 Protection requirements ... 62 
10 Identification and documentation ... 65 
11 Test method ... 70 
12 Inspection rules ... 115 
Appendix A (Normative) Symbols used on equipment identification ... 119 
Appendix B (Normative) Humidity preconditioning ... 120 
Appendix C (Informative) Measurement of inverter efficiency ... 121 
References ... 128 
Technical specification of PV grid-connected inverter
1 Scope
This standard specifies the product types, technical requirements and test
methods of photovoltaic grid-connected inverters used in photovoltaic (PV)
power generation systems.
This standard applies to photovoltaic grid-connected inverters connected to the
PV source circuit whose voltage does not exceed 1500V DC and whose AC
output voltage does not exceed 1000V. The preparatory photovoltaic inverter
where the integrated step-up transformer is grid-connected to the grid of 35kV
and below voltage level can refer to this standard.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this standard.
GB/T 2423.1-2008 Environmental testing - Part 2: Test methods - Tests A:
Cold
GB/T 2423.2-2008 Environmental testing - Part 2: Test methods - Tests B:
Dry heat
GB/T 2423.3-2016 Environmental testing - Part 2: Testing method - Test Cab:
Damp heat, steady state
GB/T 2423.4-2008 Environmental testing for electric and electronic products
- Part 2: Test method - Test Db: Damp heat, cyclic ( 12h+12h cycle)
GB/T 2423.10-2008 Environmental testing for electric and electronic
products - Part 2: Tests methods - Test Fc: Vibration (sinusoidal)
GB/T 2828.1-2012 Sampling procedures for inspection by attributes - Part 1:
Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot
inspection
GB/T 3805 Extra-low voltage (ELV) - Limit values
GB/T 16842-2016 Protection of persons and equipment by enclosures -
Probe for verification
GB 16895.3 Low-voltage electrical installations - Part 5-54: Selection and
erection of electrical equipment - Earthing arrangements and protective
conductors
GB/T 16895.10-2010 Low-voltage electrical installations - Part 4-44:
Protection for safety - Protection against voltage disturbances and
electromagnetic disturbances
GB 16895.21 Electrical installations of buildings - Part 4-41: Protection for
safety - Protection against electric shock
GB/T 16935.1-2008 Insulation coordination for equipment within low-voltage
systems - Part 1: Principles requirements and tests
GB/T 17626.2 Electromagnetic compatibility (EMC) - Testing and
measurement techniques - Electrostatic discharge immunity test
GB/T 17626.3 Electromagnetic compatibility- Testing and measurement
techniques - Radiated radio-frequency, electromagnetic field immunity test
GB/T 17626.4 Electromagnetic compatibility - testing and measurement
techniques - Electrical fast transient/burst immunity test
GB/T 17626.5 Electromagnetic compatibility - Testing and measurement
techniques - Surge immunity test
GB/T 17626.6 Electromagnetic compatibility - Testing and measurement
techniques - Immunity to conducted disturbances induced by radio-
frequency fields
GB/T 17626.8 Electromagnetic compatibility (EMC) - Part 8: Testing and
measurement techniques - Power frequency magnetic field immunity test
GB/T 17626.11 Electromagnetic compatibility - Testing and measurement
techniques - Voltage dips, short interruptions and voltage variations
immunity tests
GB/T 17626.12 Electromagnetic compatibility - Testing and measurement
techniques - Ring wave immunity test
GB/T 17626.18 Electromagnetic compatibility - Testing and measurement
techniques - Damped oscillatory wave immunity test
GB/T 17626.34 Electromagnetic compatibility - Testing and measurement
techniques - Voltage dips, short interruptions and voltage variations
4 Inverter type
4.1 Classification by the number of output phases on the AC side
According to the number of output phases on the AC side, it can be divided into:
- Single-phase inverter;
- Three-phase inverter.
4.2 Classification by installation environment
According to the installation environment, it can be divided into:
- Indoor Type I (with temperature adjustment device);
- Indoor type II (without temperature adjustment device);
- Outdoor type.
4.3 Classification by electrical isolation
According to the electrical isolation, it can be divided into:
- Isolated type;
- Non-isolated type.
4.4 Classification by access voltage level
According to the access voltage level, it can be divided into:
- A type inverter.
Refers to photovoltaic inverters used in photovoltaic power stations that are
connected to the grid through voltage levels of 35 kV and above, or
connected to the public grid through voltage levels of 10 kV and above;
- Type B inverter.
Refers to photovoltaic inverters used in photovoltaic power generation
systems that are connected to the grid through a voltage level of 380 V and
connected to the user side of the grid through a voltage level of 10 kV and
below, including inverters used in residential environments and directly
connected to residential low-voltage power supply network facilities.
Note: In the electromagnetic compatibility test of the inverter connected to
the grid via an independent power transformer, the type A limit is adopted.
resistance to material aging caused by ultraviolet (UV) radiation; it needs to be
evaluated for resistance to ultraviolet radiation or provide a third-party qualified
test report. After the UV radiation test, the sample shall show no obvious signs
of deterioration, including cracks or breaks. If the degradation of the component
does not affect the protection it provides, the requirements of this clause can
be ignored.
5.8 Pollution degree
In order to facilitate the determination of electrical clearance and creepage
distance, the environmental pollution levels are classified as follows:
1) Pollution level 1: No pollution or only dry non-conductive pollution.
2) Pollution level 2: Generally speaking, only non-conductive pollution occurs,
but temporary conductive pollution caused by condensation must be taken
into consideration.
3) Pollution level 3: Conductive pollution, or dry non-conductive pollution
becomes conductive pollution due to condensation.
4) Pollution level 4: Persistent conductive pollution, such as pollution caused
by conductive dust or rain and snow.
Outdoor type and indoor type II inverters shall meet pollution level 3
environment; indoor type I inverters shall meet pollution level 2 environment.
For special purposes and micro-environment, other pollution levels can be
considered. If the inverter is scheduled to be used in a pollution level 4
environment, measures must be taken to reduce the pollution level of the micro-
environment inside the inverter to levels 1, 2, 3.
6 Safety requirements
6.1 Temperature limit
The temperature of the materials and components used in the equipment must
not exceed the limits specified in Table 1 to Table 3. In general, if the inverter's
related components or their surface temperature does not change more than
1 °C/h, it is considered that the inverter has reached a thermally stable state.
Under full power conditions, the temperature rise test lasts for up to 7 hours
(simulating one day's sun exposure), except that if a longer test can prove that
it will produce greater danger.
1) The voltage of live parts is less than or equal to the specified safe
voltage - It is accessible;
2) The voltage of live parts is greater than the specified safe voltage - It is
not accessible, meanwhile there must be sufficient electrical clearance
between the live parts.
Note: The safety voltage limit is specified in accordance with the requirements
of the standard GB/T 3805.
b) The inverter adopts enclosure or shielding protection; it shall be inspected
according to the method of 11.2.2.1, to prevent the dangerous live parts
from being touched.
6.2.1.2.3 Maintenance personnel contact area
When the enclosure needs to be opened during installation or maintenance,
meanwhile the inverter needs to be energized, protection against contact shall
be provided for live parts with a voltage greater than the specified safe voltage
that may be unintentionally touched during the maintenance process. The
protection requirements shall be inspected according to the method of 11.2.2.1.
6.2.1.3 Insulation protection of live parts
Insulation shall be determined according to the impulse voltage, temporary
overvoltage or working voltage of the inverter; the most severe condition shall
be selected according to the requirements of 6.2.3. Without the use of tools, the
insulation protection shall not be removed.
6.2.2 Requirements for indirect contact protection
6.2.2.1 General requirements
a) In the case where the insulation between the contactable conductor and
the live parts of the inverter fails, in order to prevent contact with the
current that has the risk of electric shock, protection of indirect contact is
required. There are generally 2 ways of indirect contact protection:
Protective class I: Basic insulation and protective grounding;
Protective class II: Double insulation or reinforced insulation.
b) If the indirect contact protection depends on the installation method, the
installation manual shall clearly indicate the relevant hazards and specify
the installation method in detail.
c) Circuits that use insulation for indirect protection shall meet the
requirements of 6.2.3.
external protective grounding conductor shall use a separate connection
method and cannot be used as a mechanical component for other connections.
Short-circuit protection devices such as fuses shall not be installed in the
grounding loop.
The connection of the protective conductor shall be marked with the seventh
symbol in Appendix A; the protective grounding cable shall be in alternative
yellow and green colors.
6.2.2.2.5 Contact current
In order to maintain safety when the protective grounding conductor is damaged
or disconnected, for the inverter connected through the plug, the measured
contact current shall not exceed 3.5mA a.c. or 10mA d.c.; for all other inverters,
if the contact current exceeds 3.5mA a.c. or 10mA d.c., one or more of the
following protective measures shall be adopted and the 15th warning sign of
Appendix A shall be marked:
1) Use a fixed connection and the cross-sectional area of the protective
grounding conductor is at least 10 mm2 (copper) or 16 mm2 (aluminum);
2) Adopt a fixed connection and automatically disconnect the power supply
when the protective grounding conductor is interrupted;
3) Use the industrial connector specified in GB/T 11918.1 for connection;
meanwhile the minimum cross-sectional area of the protective grounding
conductor in the multi-conductor cable is 2.5 mm2.
6.2.3 Insulation coordination
6.2.3.1 Insulation voltage
The impulse withstand voltage and temporary overvoltage are specified in Table
5 according to the circuit system voltage and overvoltage level. The overvoltage
category shall be judged according to the description of clause 443 in GB/T
16895.10-2010.
Under normal circumstances, the overvoltage level of the grid power circuit is
considered to be level III, whilst the overvoltage level of the PV circuit that is
galvanically isolated from the grid power circuit is set to level II; for inverters
that do not have galvanic isolation between the grid power circuit and the PV
circuit, determine the pulse withstand voltage according to the overvoltage level
of the grid power circuit, compare it with the pulse withstand voltage of the PV
circuit, select the larger one as the pulse withstand voltage of the combined
circuit of the PV circuit and the grid power circuit.
For other circuits, make judgement according to the following requirements
of the capacitor after the inverter is powered off. If the discharge time of the
capacitor cannot be accurately calculated, it shall be measured.
6.4 Mechanical protection requirements
6.4.1 General requirements
Operating the inverter under normal use conditions and any fault conditions
shall not cause mechanical hazards. The edges, protrusions, corners, holes,
shields, handles and other parts that can be touched by the operator must be
smooth and free of burrs; meanwhile it shall not cause injury during normal use.
6.4.2 Requirements for moving parts
The moving parts of the inverter (such as the cooling fan, etc.) shall not cause
injury to the operator's body; the dangerous moving parts of the equipment shall
provide adequate protection measures.
During routine maintenance, if the operator is inevitably required to touch
dangerous moving parts due to technical reasons, such as adjusting the moving
parts, the inverter must provide all the following precautions before allowing the
operator to touch:
a) It can be accessed only with the help of tools;
b) The instruction manual shall state that: the operator must be trained to be
allowed to perform dangerous operations;
c) The cover or parts that can be disassembled to reach the d...