The 10KV high-voltage power grid adopts a three-phase three-wire neutral point ungrounded system operation mode.

Most user transformers use the neutral point direct grounding system operation mode of Yyn0 junction mode for power supply, which can realize three-phase four-wire or five-wire power supply, such as TN-S system. The primary and secondary side coils of an ordinary transformer are placed concentrically on a core column, with a low-voltage winding inside and a high-voltage winding outside. ( The primary and secondary side coils of the transformer of the electric welding machine are mounted on two iron core columns respectively). When the transformer is running with load, when the secondary side current increases, the transformer must maintain the main magnetic flux in the core unchanged, and the primary side current must also increase accordingly to achieve the balanced secondary side current.

Secondary active function of transformer = rated capacity of transformer (KVA) X0.8 (power factor of transformer) = KW

High-pressure end

Example: 100KVAX0.8=80KW. Generally, transformers have no-load voltage regulation and need to be powered off: constant division I, II, III three gears +5%, 0%, -5% L3 L2 L1 N (one time is 10.5KV, 10KV, 0.95KV) and the second time is 380V, 400V, 420V). When exiting), it is generally placed in II gear.

1. Transformer primary current = S/(1.732*10)' secondary current = S/(1.732*0.4).

2. Transformer primary fuse selection = 1.5~2 times the primary rated current of the transformer (transformer above 100KVA).

3. Transformer secondary switch selection = transformer secondary rated current.

4. In addition to installing gas relays and protection lines for transformers of 800KVA and above, the system circuit should also be equipped with appropriate overcurrent and quick-break protection, fixed value setting and regular verification.

Rated capacity: Transformer under rated operating conditions, guaranteed value of transformer output capacity. That is: S=1.73 XULILX10-3 (KkVA) where: UL transformer low voltage side line voltage (V):

Transformer low voltage siding current (A); grounding of power transformer

1. The shell of the transformer should be reliably grounded, the working neutral line and the neutral point grounding line should be laid separately, and the working neutral line cannot be buried underground.

2. The neutral point grounding circuit of the transformer should be made into detachable connecting bolts near the transformer.

3. The grounding of a transformer equipped with a valve arrester should meet the requirements of trinity, that is, the neutral point of the transformer, the transformer shell, and the arrester

The grounding shall be connected at one common ground.

4. The grounding resistance should be ≤4 ohms.

The safe distance of 1-10kV high-voltage lines is 6 meters; the safe distance of 154-220kV high-voltage lines is 10 meters; the safe distance of 35-110kV high-voltage lines is 8 meters; the safe distance of 350-500kV high-voltage lines is 15 meters.