Safety Precautions for Solar Photovoltaic Power Plants

According to statistics, cable damage ranks first in the loss of system power generation. Cables and fire protection for large power stations are very important. For example, the total output current of a sub-array in a 2.5MW system is more than 3000 A, and it is recommended to use flame-retardant copper core cables.

Cables should be checked every six months during the operation of the power station. This can ensure good continuity and safety. In winter, the outdoor temperature is low, reaching tens of degrees below zero in some areas. Although the cable may be insulated during laying, repeated temperature fluctuations may cause damage to the outer layer of the cable. If found, it should be replaced in time.

4mm² or 6mm² PV dedicated cable for DC side. The 4mm² specification is more widely used and fully meets the input requirements of component current. However, judging from many actual cases, it is more common for the DC terminal to be burned. Generally, it is mainly caused by not tightening the pressure line during installation. If the DC side terminal is found to be damaged during daily inspection, it should be replaced with a terminal of the same specification and model in time. And be sure to press the metal core of the terminal tightly, and the pressing length should be ≥ 40mm. And pay attention to the positive and negative polarity when connecting.

That’s right, after wires, damage to wire connectors ranks second in loss of system power generation.

The root cause of connector failure: under the condition of flow, the increase of resistance leads to an increase of temperature rise and exceeds the temperature range that the plastic shell and metal parts can withstand. In addition to the product quality itself, improper installation is one of the main factors that cause the increase in resistance.

The stripping length is 6~7.5mm, and the number of copper wires cut during stripping shall not exceed 5. It is recommended to use professional wire strippers to ensure the quality of the stripped wires.

Tool Recommendation:

PV-AZM wire stripper: Suitable for conductors with cross-sectional area of 1.5mm2, 2.5mm2, 4mm2, 6mm2, and 10mm2, with insert (marked with cross-sectional area), equipped with length locator.

Open the well and hold down the clips to place the metal core in the appropriate section area. With the opening facing up, press until the opening touches the crimp die. Then insert the stripped end of the cable until the insulation of the cable touches the crimp core, and finally crimp completely.

Qualified crimping should have no broken wires, missing wires and burrs in appearance, and the left and right should be well-proportioned, and the front and rear positions of the copper wires should be correct. Taking the 4mm2 cable as an example, it is aimed at the open crimping end of the metal pin on the market. The IEC 60352-2 standard requires a pull-off force of at least 310N and a crimping resistance of less than 135μΩ.

Insert the cable end into the insulation and you will hear a “click” when it is in place. Gently pull back to make sure the connection is secure, then use a wrench to tighten. Finally, plug the positive and negative connectors together. Hearing the sound of “ding” means that the mating is in place.

Although photovoltaic connectors account for a low proportion of the cost of photovoltaic power plants, the key components still need to be given sufficient attention. Reliable photovoltaic connectors and correct installation methods are one of the conditions to ensure the normal and stable operation of photovoltaic power plants. The stable operation of the photovoltaic power station can guarantee the power generation of the power station and ensure the continuous income of investors.

The grounding of the various components of the photovoltaic system is also an important step. Improper grounding will cause errors due to low insulation resistance of the equipment to the ground or excessive leakage current, which will affect the power generation. It may even endanger personal safety.

一. Photovoltaic Module Grounding

1. The Frame of The Component is Grounded

Many people think that the components and brackets are metal bodies, and they are in direct contact with each other. As long as the grounding treatment of the bracket is done, there is no need to make components. In fact, the aluminum frame of the module and the galvanized bracket or the aluminum alloy bracket have been plated, which cannot meet the grounding requirements. And there is an aging problem with components. There may be problems with excessive leakage current or low insulation resistance to ground. If the frame is not grounded, after a few years, the inverter is likely to report a corresponding fault and the system cannot generate power normally.

Component-to-Component Connections

Connection Between Components And Bracket

2. The Component Bracket is Grounded

The lightning protection grounding resistance of photovoltaic modules should be less than 10Ω. The grounding resistance of the inverter and distribution box should be less than 4Ω. For those that do not meet the grounding resistance requirements, usually add a resistance reducing agent or choose a place with a low soil rate to bury.

二. Inverter Side Grounding

1. Work Grounding

Generally, the working ground (PE terminal) is connected to the PE row in the distribution box, and then grounded through the distribution box.

2. Protective Grounding

There is a grounding hole on the right side of the inverter body for repeated grounding. takeyi protects the safety of inverters and operators.