Electrical system of blast furnace divides into High-voltage (HV) and Low-Voltage (LV) power supply and distribution,electrical transmission and control, process detection and control, basic automation.
The high-voltage power distribution of blast furnace is generally 10kV, and the total power supply of upper level is generally 110kV, 35kV or 10kV, and the power distribution system adopts radial system. High-voltage power distribution facilities in the blast furnace area mainly include raw fuel supply, blast furnace body, slag treatment, main circulating pumping station, ventilation and dust removal, air compressed station, gas residual pressure power generation device (TRT) power generation and distribution system and cable bridges required for high-voltage power supply and distribution.
Blast furnace area generally set up a number of 10kV switching station, respectively, located in the load center of each main equipment, typical blast furnace system engineering switching station mainly has the main circulating pumping station, raw materials complex, the main control building switching station and so on. The main wiring of 10kV system of each station generally adopts single busbar segmentation mode, metal armored withdrawable middle-mounted high-voltage switchgear, and microcomputer backstage monitoring system. It realizes the measurement, monitoring, alarm and printing functions of all 10kV switchgears in the switching station.
TRT is generally grid-connected to the system at the 10kV busbar of the 10kV distribution room of the 110kV or 35kV main step-down substation, and the grid-connection point is located at the generator side of the TRT.
High-voltage power supply and distribution cables are generally laid in underground corridors or buried underground.
The low-voltage power supply and distribution is generally AC380V, AC220V, DC24V, which is designed according to the Class I load, two-way power supply and a substation with a built-in transformer.
Low-voltage distribution according to the process equipment location, general layout, system composition and load center and other factors to consider, a typical blast furnace project is generally set up power substations for the blast furnace body, slag treatment, iron field, (are set up in the main control building), above trough,under trough, coal injection, soft / clean circulating water treatment, gas dedusting. Generally, the substation adopts 2 sets of maintenance-free fully sealed low-loss transformers for power supply
The electrical transmission adopts full AC transmission and uses the MCC system. Generally motors<110kW (depending on the situation of individual enterprises) adopt full voltage direct starting mode, motors≥110kW usinghigh-quality soft starting device starting.
According to the power supply situation and enterprise requirements, considering uninterruptible power supply UPS or emergency power supply EPS as a power failure emergency measures. EPS is used to supply power for some plants which is prone to major equipment accidents and human safety after a power failure, such as water-cooled system of the bell-less furnace top, probe scale, dry oil lubrication, cold air bleeder valve and hydraulic valve of the hot air furnace, and so on,
Low-voltage power distribution system set up the following protection measures:
- Short-circuit protection, using circuit breakers with instantaneous overcurrent disconnectors to protect the lines and equipment;
- Overload protection, using circuit breakers with long-delay overcurrent strippers and thermal relays to protect lines and equipment that are likely to be overloaded, respectively;
- Grounding protection, using the transformer neutral point direct grounding system, the metal shells of all energized equipment are connected to the PE wire of the system.
