Poor insulation of the water-resistant cabinet – how to solve it.
Thread Content
In 10kV systems, high-voltage water resistance cabinets have an unreasonable design; after the motor starts, the water resistance device cannot be disconnected from the system, resulting in it remaining under voltage for an extended period. The following problem has arisen: when the outer surface of the box is inspected using a high-voltage detector, many points trigger alarms, and discharge occurs to adjacent metal objects (with a gap of 1–2 millimeters). First, some information is provided for everyone to analyze: The equipment has been in use for 8 years – is it possible that the materials have aged and the insulation quality has declined? Does the continuous operation (for water replenishment) on the surface of the enclosure cause dielectrics to form creepage paths on the material surface? The high-voltage voltage tester indicates that the object is charged, but it can be touched; is it induced electricity? The metal structure of the cabinet and its channel steel base are painted; the cabinet may have poor grounding, and the air inside is humid (due to continuous rainy weather recently).
“After the motor starts, the water resistor cannot be disconnected from the system and remains powered on for an extended period. ” This is the main reason for the problem; the issue of separating the system should be easy to resolve. This not only wastes electricity and reduces the motor’s output power, but it also tends to shorten the lifespan of the water resistance cabinet. Regarding the issue of surface charging, call the manufacturer to ask; it’s likely time to replace it
What the original poster means is: from the moment of startup until it’s complete, do the plates of the water resistance cabinet not get short-circuited, and remain connected to the water resistance element throughout?
The water resistance cabinet is not located at the motor’s star point; rather, it is situated between the starting cabinet and the motor, with a short-circuit cabinet connected in parallel across both ends of the water resistance cabinet. Since no isolating switch was designed, after the short-circuit cabinet is closed, the water resistance cabinet cannot be disconnected from the 10kV system and remains energized.