This article will systematically explain how to scientifically and effectively select automatic circuit reclosers within the voltage range of 11KV to 33KV.
How to choose a suitable automatic circuit reclosing device? Factors to consider include technical parameters, functional requirements, proper installation methods and environmental adaptability, manufacturer selection, price, and supply chain factors.
The key parameters for selecting automatic reclosing are as follows:
System Voltage Matching: The rated voltage (UR) of the automatic reclosing device must be equal to or higher than the system’s highest operating voltage.
Note: For systems with rated voltages of 11kV, 27kV, and 33kV, automatic reclosing devices with rated voltages of 12kV, 15kV, and 36kV should be selected respectively. For example, a 33kV system should use equipment with a rated voltage of 36kV or 38kV.
Insulation Class: The power frequency withstand voltage and lightning impulse withstand voltage must comply with local power grid standards and be compatible with the insulation class of other relevant equipment on the line to ensure safety under overvoltage conditions.
Rated current: This refers to the current required for long-term normal operation of the automatic reclosing system. Selection should be based on the maximum load current of the line (and consider potential future current increases). Common specifications include 400A, 630A, 800A, and 1250A.
The key indicators for evaluating the fault handling capability of an automatic reclosing system are the rated short-circuit breaking current and closing current. The maximum expected short-circuit current (symmetrical RMS value) at the installation point must be determined through system short-circuit current calculations.
The rated short-circuit breaking capacity of the selected ACR must be greater than this value, with a certain margin (typically 10-20%).
For 11kV-33kV distribution networks, the breaking capacity is typically between 12.5kA and 25kA; automatic reclosing manufacturers advise that higher breaking capacities may be required for critical lines or lines near power sources. The current (peak) capacity must be able to withstand the impact of short-circuit current.
The core of modern intelligent automatic circuit reclosing lies in its integrated protection relay (controller).
Protection Curves: The controller should provide flexible and adjustable overcurrent protection curves (such as definite-time and inverse-time curves), as well as instantaneous overcurrent protection and ground fault protection (sensitive directional ground fault protection is crucial for improving safety).
Reclosing Program: This must be programmable, including the number of reclosing attempts (typically 1-4), the delay for each reclosing attempt, and the fast/slow sequence.
Communication and Automation: Support for standard communication protocols is fundamental to achieving distribution automation (DA) and feeder automation. Automatic circuit reclosing can improve operational and maintenance efficiency by providing remote monitoring, data logging, and fault waveform recording capabilities.
Power Supply: The power supply method for the automatic circuit reclosing controller needs to be considered. Common options include: built-in battery (charged by solar panels), external PT (voltage transformer) power supply, or a combination of both.
Installation Methods:
Pole Mounting: Pole mounting is characterized by its compact structure, directly installed on utility poles, suitable for overhead lines in rural and suburban areas. This is the most common installation method.
Ground Mounting: Commonly used at substation outgoing lines or urban ring network units, providing more controllable environmental conditions.
Arc Extinguishing Media:
Vacuum Extinguishing: The current mainstream technology. It is characterized by being environmentally friendly, having a long service life, low maintenance costs, and being suitable for frequent operation.
SF6 Gas Extinguishing: It has excellent insulation and arc extinguishing performance, but produces greenhouse gases, which may limit its future application.
Oil Immersion Extinguishing: A traditional technology, rarely used in new projects nowadays.
Environmental Conditions: Clearly define the climatic conditions of the installation site, such as altitude (affecting insulation performance), ambient temperature range, humidity, pollution levels, wind speed, etc., to ensure that the ACR protection rating (IP code) and weathering rating (IK code) meet the requirements.
Manufacturer Selection, Pricing, and Supply Chain
Evaluating Manufacturers: Choose manufacturers with a good reputation in the industry, mature technology, and rich experience. Consider their R&D capabilities, product line completeness (can they provide a full range of products from 11KV to 33KV), localization support (technology, spare parts), and past project performance.
We recommend GOTO Electrical, which has 11 years of development experience, a 1500-square-meter factory, and is equipped with finished product testing equipment, material testing equipment, and relevant certifications.
Price Factors: The price of automatic reclosing devices is affected by voltage level, current and breaking capacity, complexity of protection functions, arc extinguishing technology, and brand. Don’t just focus on the lowest price; conduct a holistic evaluation. Evaluation points include total life cycle cost (TCO), initial purchase cost, installation cost, operation and maintenance cost, and outage loss cost. If the goal is to significantly reduce economic losses caused by power outages, choose reliable equipment with a higher initial investment.
Customs Codes and Import: Imported equipment must clearly indicate its customs commodity code (Customs Code). The specific code needs to be determined based on the specific description of the equipment, which is closely related to tariffs and customs clearance procedures.
How to balance advanced features with cost control when selecting an ACR?
The selection should be made within the overall framework of the distribution automation plan, taking into account future system expansion and interconnection needs, and choosing a platform with a certain degree of functional scalability to avoid future duplicate investments.
Different Application Scenarios of 11KV, 27KV, and 33KV Automatic Circuit Reclosers
11KV Automatic Circuit Recloser: Responsible for supplying power to residential areas, commercial areas, and small and medium-sized factories.
33KV Automatic Circuit Recloser: Commonly used for: High-capacity power supply trunk lines in urban core areas; direct incoming lines to large industrial parks; grid connection points for medium-sized distributed power sources such as wind farms and photovoltaic power stations; and as backbone lines for long-distance power supply in rural or remote areas to reduce voltage loss.
27KV Automatic Circuit Recloser: Primarily found in countries adopting American standards (such as the United States, Canada, and some Latin American and Middle Eastern countries). Its application scenarios are similar to the role of 33KV in the IEC system, used for feeders with heavier loads and longer distances, or as the main incoming line for industrial users.
Design and Cost of 11KV, 27KV, and 33KV Automatic Circuit Reclosers
11KV automatic circuit reclosers have mature design capabilities, a complete industry chain, relatively low cost, and the widest selection.
27KV automatic circuit reclosers require stringent insulation requirements, demanding high standards for the arc-extinguishing chamber and insulation materials, and are typically the most expensive.
33KV automatic circuit recloser, due to their higher voltage, have higher breaking capacity and insulation requirements than 11KV ACRs. Their cost falls between that of 11KV and 27KV ACRs, but is still higher than that of 11KV equipment of the same standard.
Automatic circuit reclosers, as the nerve endings and execution units of smart distribution networks, are crucial for enhancing the resilience of 11KV to 33KV distribution networks and achieving efficient operation and maintenance.
To avoid economic losses and time costs caused by prolonged power outages, please contact our team of automatic circuit recloser experts immediately for a customized automatic circuit reclosing solution.
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