Basic Knowledge of High Voltage Power Distribution

A switching station is literally understood as an electrical place containing only pure switching equipment. It only acts as a shunt for electric energy and does not change the voltage level of the incoming and outgoing lines. It is a power distribution device equipped with power distribution incoming and outgoing lines to redistribute power. If necessary, a distribution transformer can be attached.

A power distribution room is simply a room that distributes electrical energy. It plays the role of protecting, measuring and distributing electric energy.

What are the differences and connections between switching stations and distribution rooms?

1. Switching station: It is a fully metal-sealed switch cabinet combination with a voltage level below 10KV that can operate outdoors;

2. Power distribution room: The voltage level is below 35KV, and switches, transformers, capacitors and related protection and measurement devices are installed inside. 10KV power distribution room switch cabinet and its functions:

Function: The power supply system is used to step down the high voltage through the transformer to the voltage level required by the user and is equipped with an indoor comprehensive system that integrates protection, metering and distribution.

Composition: incoming cabinet, metering cabinet, PT cabinet, outlet cabinet, contact cabinet, isolation cabinet.

Incoming line cabinet: It is a switch cabinet that introduces power from the outside. Generally, 10KV power is introduced from the power supply network. The 10KV power supply sends power to the 10KV busbar through the switch cabinet. This switch cabinet is the incoming line cabinet.

Composition: vacuum circuit breaker, isolating switch, three sets of three-coil current transformers, lightning arrester, live display, voltage transformer, wires and other components.

The main function is to distribute electricity. The incoming cabinet is generally equipped with a vacuum circuit breaker for breaking. The vacuum circuit breaker has protection functions such as short circuit and overcurrent prevention. It is also equipped with an isolation switch for maintenance and protection of maintenance personnel. In addition, it is used for maintenance. The line cabinet is also equipped with current and voltage transformers as well as measuring current and voltage values. Therefore, the incoming cabinet has protection, measurement, monitoring, etc. to achieve more comprehensive functions.

Relevant protective equipment of the incoming cabinet: Protection of the power incoming end:

1. Prepare an automatic switching device, that is, a backup power automatic switching device.

2. Lightning protection device.

3. Overvoltage and undervoltage protection.

4. Inrush protection: When the circuit breaker is closed with load, the main line generates an inrush current that is much larger than the operating current of the circuit breaker, causing the switch to fail to reliably close with load. The inrush protection device prevents false tripping caused by inrush current at the moment of closing and ensures that the short circuiter trips reliably with load.

5. Quick-break protection, over-current protection.

6. Zero sequence protection, grounding protection.

7. Reclosing device.

8. Low cycle protection (low frequency load shedding protection).

Outlet cabinet: It is a switch cabinet that distributes electric energy from the busbar and sends the next-level switch to the power transformer. This switch cabinet is one of the 10KV outlet cabinets.

Composition: three sets of three-coil current transformers, isolation switch, circuit breaker, knife switch, and live display device.

Function: The main function is to distribute electric energy, distribute the main power to each branch circuit switch, and connect and disconnect the branch power supply to the overcurrent and overload protection box of each branch.

Metering cabinet

Main components: current transformer, fuse, voltage transformer for VV wiring, and live display.

Function: It is a kind of electric energy metering device. It adopts the method of high power meter to measure the electricity consumption and reflect the electricity consumption of the load through current transformer, voltage transformer, electric energy meter and other measuring devices. For measuring devices installed at the user's premises, the user is responsible for keeping the seal intact and the device itself from being damaged or lost.

PT cabinet

Main components: voltage transformer, isolation knife, fuse, arrester. effect:

1. Voltage measurement, providing the voltage circuit of the measuring meter;

2. Can provide operating power supply for the operation box;

3. Installation of overvoltage protectors for each bus section;

4. The need for relay protection, such as busbar insulation, overvoltage, undervoltage, and automatic switching conditions.

Wiring method: Vv wiring, Y, yn wiring, YN, yn wiring.

Contact cabinet: Also called busbar segmentation cabinet, it is a device used to connect two sections of busbars. Busbar contact cabinets are often used in single busbar segmentation and double busbar systems to meet the user's requirements for selecting different operating modes or to ensure failure Cases with selective load resection.

Composition: isolation switch, circuit breaker, current transformer, live display device.

Generally, it functions as a contact bus. When two power supplies send power at the same time, the contact is disconnected from the middle (two different power supplies usually cannot be overlapped). When one of the power supplies is outage or outage due to an accident, the contact bus is disconnected.

The contact cabinet is automatically connected to ensure the user's power consumption. When the power is restored at the end of the original power outage, the contact cabinet is automatically disconnected and is in the original standby state.

Isolation cabinet

The isolation cabinet consists of: isolation switch, grounding switch, lightning arrester charged display device.

Function: It is used to isolate the busbars at both ends or to isolate powered equipment and power supply equipment. It can provide a visible endpoint for operators to facilitate inspection and maintenance operations.

The function of each component:

Circuit breaker: When a short circuit or overcurrent fault occurs in the circuit, it can quickly cut off the power supply to prevent the fault from expanding. It can also be used as a general switch to realize the distribution and control of electric energy and adopts electric operation.

Fuse: When the current abnormally rises to a certain height and at a certain time, it will fuse itself and cut off the current, thereby protecting the safe operation of the circuit.

Isolating switch: used to isolate the power supply and disconnect high-voltage maintenance equipment from live equipment. It has a clearly visible disconnect point; the isolating switch cooperates with the circuit breaker to perform switching operations according to the needs of the system operation mode to change the system. Run the wiring method.

Voltage transformer, current transformer: convert high voltage or high current into standard low voltage (100V) or standard small current (5A or 1A, both refer to rated value) in order to realize measuring instruments, protection equipment and automatic control Standardization and miniaturization of equipment. At the same time, transformers can also be used to isolate high-voltage systems to ensure the safety of life and equipment.

Lightning arrester: Through the action of parallel discharge gaps or nonlinear resistors, the amplitude of the intruding flow wave is clipped, and the overvoltage value of the protected equipment is reduced.

HZ-6300C Transformer Capacity Testing