1. What is electrical primary and Secondary distribution system?
Reflected in the difference between electrical primary equipment and secondary equipment:
Primary equipment refers to high-voltage electrical equipment used directly in the production process of producing, transmitting, and distributing electrical energy.
It includes generators, transformers, circuit breakers, disconnectors, automatic switches, contactors, knife switches, bus bars, transmission lines, power cables, reactors, motors, etc.
Electrical equipment that is connected to each other by primary equipment to form power generation, transmission, distribution, or other production processes is called primary equipment.
Secondary equipment refers to the low-voltage electrical equipment needed to monitor, control, regulate, protect, and provide operating conditions or production command signals for operation and maintenance personnel. Such as fuses, control switches, relays, control cables, etc.
The secondary equipment is connected to each other to form the electrical equipment that monitors, controls, regulates and protects the primary equipment.
2. the classification of electrical
Electric primary equipment can be divided into six categories according to its role in production:
(1) Equipment for producing and converting electrical energy. For example, generators convert mechanical energy into electrical energy, motors convert electrical energy into mechanical energy, and transformers increase or decrease the voltage to meet the needs of transmission and distribution.
(2) Switching appliances that turn on or off the circuit. Such as circuit breakers, disconnectors, fuses, contactors, etc. They are used to close or open circuits when the power system is in a normal or accidental state.
(3) Electrical appliances that limit fault current and protect against overvoltage. Such as reactors that limit short-circuit current and surge arresters that protect against overvoltage.
(4) Grounding device. It is a metal conductor buried in the ground that directly contacts the ground and a metal wire connected to electrical equipment. Whether it is the working ground of the neutral point of the power system or the protective ground that protects personal safety, it is connected to the grounding device buried in the ground.
(5) Current-carrying conductor. Such as bare conductors, cables, etc. Connect the relevant electrical equipment according to the design requirements.
(6) Conversion equipment between primary and secondary of AC electrical. Such as voltage and current transformers, through which the voltage and current on the primary side are converted to the secondary system.
3. Small classification of electrical secondary circuits
1) Control (operation) loop: It is composed of the transmission mechanism and the execution (or operation) mechanism of the control switch and the control object (such as circuit breaker and isolation switch). Its role is to “close” and “divide” the primary equipment.
2) Regulating circuit: refers to regulating automatic device. For example, the device for on-load voltage regulation of the main transformer by the VQC system, the excitation adjustment device of the generator. It is composed of measuring mechanism, transmission mechanism, regulator and actuator.
Its function is to adjust the working state of the primary equipment online in real time according to the changes of the primary equipment operating parameters to meet the operational requirements.
3) Relay protection and automatic device circuit: it is composed of measurement circuit, comparison part, logic part and execution part.
Its function is to automatically issue a trip command to selectively remove the fault according to the operation status of the primary equipment and the system, and issue a corresponding signal. When the fault or abnormal disappears, quickly put in the relevant circuit breaker ( Reclosure and automatic backup power supply device) to restore the normal operation of the system. (Note: The above mainly refers to the protection and automatic devices composed of conventional electromagnetic relays, etc.)
4) Measuring circuit: It is composed of various measuring instruments and related circuits.
Its role is to indicate or record the operating parameters of the primary equipment and system, so that the operating personnel can master the operating conditions of the primary system, and it is also the main basis for analyzing power quality, calculating economic indicators, understanding the system power flow and the operating conditions of the main equipment. (Note: Integrated automation has made the boundary between the loop and the tertiary loop more and more blurred)
5) Signal loop: composed of signal sending mechanism and signal relay.
Its role is to reflect the working state of the primary and secondary equipment.
6) Operating power supply system: It consists of power supply equipment and power supply network. It often includes DC power supply system and AC power supply system.
Its main function is to provide working power and operating power for control, protection, signal and other equipment, for power equipment such as cooling, water and coal formation of the main transformer, and to ensure that all equipment in power plants and substations work normally.