Electric power industry

Moist air can cause various hazards to facilities such as power distribution rooms and substations:

1. Decline in insulation performance of electrical equipment

Principle: Moist air contains more water vapor. When this water vapor adheres to the surface of the insulation materials of electrical equipment, the insulation resistance of the insulation materials will decrease. Insulation resistance is an important indicator for measuring insulation performance. Its decline means that the insulation material's ability to resist current weakens. For example, for commonly used solid insulation materials (such as epoxy resin, etc.), in a normal dry environment, its insulation resistance may be as high as hundreds of millions of ohms, but in a humid environment, it may drop to tens of millions of ohms or even lower.

Hazard: This can cause leakage in the equipment. Minor leakage can cause the equipment's shell to have a certain static electricity, posing a threat to the safety of operators; severe leakage may cause short-circuit faults, causing the current to increase instantaneously. When the current is too large, excessive heat will be generated, which can then damage the electrical components of the equipment. For example, the windings of the transformer may be burned due to the heat generated by the short-circuit current, causing power outages and affecting the reliability of power supply.

2. Corrosion of metal components

Principle: The moisture in moist air combines with oxygen to form a thin layer of electrolyte solution on the metal surface, creating an electrochemical corrosion environment. For metal equipment in distribution rooms and substations (such as the metal shells of switch cabinets, the metal connection parts of busbars, etc.), taking iron as an example, iron atoms will lose electrons in this electrolyte solution and turn into ferrous ions to enter the solution. Oxygen gains electrons on the metal surface and reacts with water to generate hydroxide ions. Ferrous ions and hydroxide ions further react to form ferrous hydroxide, which is then oxidized to ferric hydroxide, and finally forms rust.

Hazard: After metal components are corroded, their mechanical strength will decline. For example, if the connection part of the busbar is corroded, the firmness of the connection will deteriorate, resulting in an increase in contact resistance. According to Joule's law (Q = I²Rt, where Q is heat, I is current, R is resistance, and t is time), more heat will be generated when current passes through, resulting in local overheating. Local overheating not only accelerates the further corrosion of metals but may also cause serious accidents such as fires. Moreover, severely corroded metal components may break, affecting the normal structure and function of the equipment.

3. Damage to electronic components

Principle: Many electronic components (such as integrated circuits, capacitors, etc.) have strict requirements for the humidity of the working environment. Moist air may cause electronic components to get damp. For example, for capacitors, after getting damp, the performance of their internal dielectric materials may change, resulting in a change in capacitance value. At the same time, moisture may form conductive channels between the pins of electronic components, causing short circuits.

Hazard: Damage to electronic components can lead to failures in the control and monitoring systems of the equipment. For example, in the automated control system of a substation, if some control chips are damaged, equipment such as circuit breakers may not be controlled properly, resulting in the loss of monitoring and regulating capabilities of the power system. This may cause the power grid to fail to cut off faulty lines in time when faults occur, expanding the fault range and even causing the paralysis of the entire substation or distribution room.

Mold growth

Principle: The humid environment provides favorable conditions for the growth of mold. In distribution rooms and substations, some surfaces of equipment (such as the inner walls of distribution cabinets, cable trays, etc.) may breed mold due to suitable humidity.

Hazard: During mold growth, some acidic substances may be secreted, which can corrode the shells of equipment and internal circuits. Moreover, if the mycelium of mold grows inside the electrical equipment, it may cause electrical short circuits. In addition, the growth of a large amount of mold will also affect the heat dissipation performance of the equipment, because the mycelium and mold spots will cover heat dissipation components such as heat sinks, reducing the heat dissipation efficiency and increasing the internal temperature of the equipment, thereby affecting the normal operation and service life of the equipment.