The construction of distribution automation in smart grids is accelerating, starting with the transformation of a large number of online switchgear. Early switchgear designs were primarily manual. The main task of equipment upgrades is to add drive motors to the operating mechanisms, upgrading from manual operation using levers to electric push-button operation. Switchgear is classified according to different uses and installation locations into circuit breaker cabinets, recloser cabinets, incoming line cabinets, outgoing line cabinets, and load switchgear. Some have isolating knife operating mechanisms, some only have ground wire disconnect switches, and some rely on fuse cylinder protection.
I. Classification and Control Mechanism of Electric Operating Mechanisms
The operating mechanisms of switchgear are classified into four types.
1. Circuit Breaker Mechanism
This type is modular and can be combined into an expandable switchgear. The original design uses overcurrent trip units, with standard rated currents of 630A and 1250A. Contact opening and closing are achieved by releasing the power of a mechanical energy storage device. The main working principle is based on torsion spring linkage energy storage, using the stored energy as power to realize the circuit breaker's opening and closing operations. There are three types of opening operations: opening electromagnet, overcurrent trip electromagnet, and manual button operation.
2. Circuit Breaker/Recloser Mechanism
The recloser consists of an arc-extinguishing chamber, an operating mechanism, and a control system. After initial energy storage, the recloser can perform two operations: breaking and closing. The driving force for the contacts can be either a permanent magnet or a spring. Instantaneous breaking and reclosing are achieved through an electronic control system.
The function of the recloser is to work in conjunction with other high-voltage electrical appliances. Through its ability to break the circuit, sequence the reclosing operation, reset and lockout, and identify the location of the fault, it minimizes the power outage area. In contrast, a circuit breaker only breaks short-circuit faults, resulting in a larger power outage area. The recloser has its own control equipment; its detection, control, and operation are self-contained, enabling automatic and rapid closing to restore power supply to the line under system intervention.
3. Load Switch with Grounding Knife Structure
Electric and manual operation are on the same drive shaft. Manual operation is initiated by inserting the manual lever into the operating hole and engaging the transfer clutch. The opening and closing torque is accurate and greater than 80 Nm.
4. Fuse Structure
Fuses are the simplest protective electrical devices, inexpensive, and suitable for areas with low electrical loads. They allow the load current to pass within specified standards. In the event of overload or short-circuit current in electrical equipment, the fuse quickly and automatically disconnects the power supply line. Common types include drop-out fuses for outdoor overhead lines and embedded fuses in indoor switchgear.
II. Control Mechanism of Electric Operating Mechanism
After the circuit breaker's energy storage is complete, an anti-pumping control circuit is also set up. The control circuit should be able to reflect the circuit breaker's position status and the integrity of the trip and close circuits in a timely manner. To ensure that every step of the circuit breaker's operation is safe and reliable, multiple interlocking measures are also installed in the control circuit. When conditions are not met, the operation of the circuit breaker is prohibited. When the circuit breaker's operating system malfunctions, the trip and close circuits are interlocked. When the hydraulic/pneumatic operating mechanism pressure is too high or too low, the spring of the spring operating mechanism is not energized, or the SF6 pressure of the SF6 circuit breaker is low, these will cause the normally closed contacts connected in series in the trip and close circuits to open, preventing the circuit breaker from tripping or closing.
III. New Multifunctional Electric Operating Controller
1. The controller is the core unit of the intelligent ring main unit. It is a master control device that controls the starting, speed regulation, braking, and reversing of the motor by changing the wiring of the main circuit or control circuit and changing the direction of current in the circuit according to a predetermined sequence.
2. Main Functions and Roles of the Electric Operating Mechanism Controller
(1) The controller needs to receive and recognize commands from higher authorities: The control center's program can send various commands to the controller, and the equipment controller should be able to receive and recognize these commands. The controller continuously sends electronic queries to various sensors of the equipment and replies with execution results to higher authorities.
(2) The controller is the control component, while peripheral equipment is the execution component relative to the controller. One connection between the control component and the execution component is through control lines.
(3) The control component sends various control commands to the execution component through control lines. Another connection between the control component and the execution component is feedback information. The execution component reflects the operating status to the control component through feedback lines, so that the control component can issue new action commands based on the status of the execution component; this is also called "status testing".
(4) Controllers are categorized into unidirectional and bidirectional controllers based on the function of each drive motor.
(5)The controller also needs to be equipped with constant current control technology for the motor: ensuring consistent matching between the motor's starting torque and dynamic operating current, improving the balance of the motor's starting torque, and providing safety protection for the motor and the overall equipment in the event of increased torque due to mechanical gear failure. Therefore, the controller must have suitable selection of current control elements, be applicable to any type of motor, and have a sufficiently safe control effect, eliminating the need for matching and improving the universal adaptability of the electric vehicle controller. This eliminates the need for on-site equipment matching between the electric vehicle motor and the controller, facilitating installation and use.
(6) The controller automatically detects the status of related interfaces, such as external switch signals. In the event of a fault, the electric operating mechanism implements protection, fully ensuring the safety of the equipment. The controller's protection status automatically recovers after the fault is cleared.
(7) The controller should have integrated automatic/manual operation functions, allowing for flexible configuration according to different usage environments. The automatic transfer switch controller is an intelligent dual-function switching system. The controller's electrical interlocking, combined with mechanical interlocking, ensures automatic adjustment of controller parameters.
(8) Control Functions
Load Switch Opening/Closing: Upon receiving an opening/closing command, the switch begins outputting a current not exceeding 24V 10A to the motor, driving the motor in both forward and reverse directions.
Circuit Breaker Tripping/Closing: The circuit breaker releases energy in its energy storage structure to drive the mechanism to open/close.
Mechanism Auxiliary Contacts Interlock with Grounding Position; Interlock with Cable Box Door; Interlock with Air Pressure Detection Device:
Operation of any circuit with the interlocked contact grounding prevents closing/opening and tripping.
3. The control circuit of a circuit breaker is the most basic secondary circuit.
Distribution network safety controller products integrate high efficiency, reliability, safety, flexibility, and compactness, and can adapt to various harsh environments. The compact and modular design can meet the needs of future switchgear upgrades, renovations, and capacity expansions. The product's unique electronic and mechanical interlocking design, along with its torque-driven constant current protection system, ensures operator safety and can promptly handle mechanical transmission faults in the electric operating mechanism.
Contact Us
Shaanxi Huadian's independently developed integrated circuit breaker spring energy storage mechanism, disconnector electric mechanism, and grounding switch mechanism are perfectly compatible with mainstream domestic and international switchgear models. A professional technical team provides selection guidance and drawing coordination. For inquiries, please contact us：pannie@hdswitchgear.com.
