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NB/T 32004-2018 English PDF (NBT32004-2018)

NB/T 32004-2018 English PDF (NBT32004-2018)

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NB/T 32004-2018: Technical specification of PV grid-connected inverter

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.
NB/T 32004-2018
NB
ENERGY INDUSTRY STANDARD OF
THE PEOPLE 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 dangerous part must have warning signs, to prevent accidental contact by untrained
operators;
d) There is no automatic reset thermal circuit breaker, overcurrent protection device or automatic timing start device, etc.
For inverters that have not taken the above precautions, the test finger shall not touch the dangerous moving parts from any direction with insignificant force. For the hole to prevent the test finger from entering, it is necessary to further use a straight test finger without joints and apply a 30N force to test. If such a test finger can enter the hole, a new test finger shall be used for the test; if necessary, the test finger shall be pushed into the hole with a force of 30N. 6.4.3 Stability
If the inverter is not fixed to the building component, it must have physical stability during normal use. After the operator opens the door or drawer of the inverter, the inverter itself needs to be able to maintain stability. If not, the than the conductor cross-section as specified in the temperature rise test of 11.2.1. The conductors that can be used for the terminal shall be of the same type (hard wire or flexible wire, single-core wire or multi-strand wire). 6.4.6.3 Design of terminal blocks
The terminal shall be designed so that it can clamp the wire between the metal surfaces with sufficient contact pressure without damaging the wire. The design or configuration of the wiring terminal shall ensure that the wire does not slip off when the screw or nut holding the wire is tightened.
Terminals shall be equipped with appropriate accessories for fixing the wires (such as nuts and washers).
The terminal shall be fixed so that the accessories holding the wire are tightened or loosened,
- The terminal itself will not loosen;
- The internal wiring does not bear stress;
- The clearance and creepage distance will not be reduced to less than the specified values in 6.2.3.3 and 6.2.3.4.
6.5 Fire hazard protection
6.5.1 General requirements
Inside the inverter and outside the inverter, use appropriate materials and components and use the appropriate structures, in order to reduce the risk of ignition and flame spread.
- Method 1: Select and use components, wiring and materials that can
reduce the risk of ignition and the possibility of flame spread; use a fireproof enclosure if necessary.
Note: For inverters with a large number of components, method 1 is
recommended.
- Method 2: All simulation tests will not cause components to ignite, or bring the temperature to the ignition point, or cause other signs of fire hazard. Therefore, this type of inverter or part of the inverter does not require a fireproof enclosure.
Note: For inverters with a relatively small number of components, method 2 is recommended.
6.5.2 Flammability requirements of materials
b) For non-isolated inverters or inverters that are isolated but their leakage current does not meet the requirements, faults shall be indicated and their access to the grid shall be restricted.
At this time, it is allowed to continue to monitor the insulation resistance of the square array; when the insulation resistance meets the above
requirements, it is allowed to stop the alarm and also allow to connect to the grid.
6.7.1.2 Inverters requiring functional grounding
If an inverter with an integrated resistor is needed to realize the functional grounding of the photovoltaic array, the inverter shall meet the requirements of a) and c), or b) and c) of this clause.
a) Including the preset resistance for functional grounding, the total
grounding resistance shall not be less than R=Umaxpv/30mA. The expected insulation resistance value can be calculated based on the insulation
resistance of 40M?? per square meter of the square array when the area
of the connected photovoltaic array is known. It can also be calculated based on the rated power of the inverter and the efficiency of the worst photovoltaic array to which the inverter can be connected.
b) If the resistance is less than that specified in a), then the inverter shall be able to provide a method to monitor the current through the resistor and any parallel network line (such as the test line) during operation. If the response time of the sudden current exceeds the limit in Table 14, the
resistor shall be disconnected or use other methods to limit current. If it is a non-isolated inverter, or an inverter that is isolated but cannot meet the minimum leakage current requirements, it must be disconnected from the
grid.
c) Before normal operation, the inverter must be able to test the grounding resistance.
6.7.2 Testing of array residual current
6.7.2.1 General requirements
a) Ungrounded photovoltaic arrays working above the safe voltage level may cause electric shock hazards. The inverter is not isolated, or although it has isolation measures but cannot guarantee that the contact current is within a reasonable range, if the user touches the live part of the array and the ground at the same time, the connection between the grid and the
ground (such as the grounded neutral line) will provide a loop for the
contact current, thereby creating a risk of electric shock. This hazard can be eliminated by the protection method described in 6.7.2.4, or the contact measured continuous maximum input current or power shall not exceed 110% of the nominal maximum input va...

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