What are Reclosers and How Do They Work?
Reclosers are specialized circuit breakers designed for overhead distribution lines that automatically interrupt fault currents and then reclose to restore service after a predetermined time delay. Unlike standard circuit breakers that remain open after operation, reclosers can execute multiple open-close sequences, allowing temporary faults (which represent 80-90% of distribution line faults) to clear without requiring manual intervention or prolonged outages.
Reclosers work by detecting fault currents on distribution lines and opening their contacts to interrupt the circuit. After a programmed time delay (typically a few seconds), the recloser automatically recloses its contacts to restore power. If the fault was temporary (e.g., a tree branch momentarily touching the line), normal service resumes. If the fault persists, the recloser opens again and repeats the sequence according to its programmed reclose operations (typically 1-4 attempts). After exhausting the programmed reclose attempts, the recloser locks open, requiring manual reset, indicating a permanent fault requiring repair.
Key components of reclosers include:
- Interrupter: Vacuum bottles or SF6 gas chambers that physically break the circuit
- Operating Mechanism: Spring, hydraulic, or magnetic actuator that opens and closes contacts
- Control Unit: Microprocessor-based system that manages protection and reclosing operations
- Current Sensors: Detect fault currents and normal load conditions
- Voltage Sensors: In some models, provide voltage measurement for advanced functionality
- Bushings: Connect the recloser to overhead line conductors
- Tank/Housing: Contains the interrupters and may be filled with insulating medium
- Communication Interface: For remote monitoring and control
Uses and Applications
Reclosers serve important functions in electrical distribution systems:
Utility Distribution Networks
- Overhead distribution feeder protection
- Sectionalizing long distribution lines
- Lateral line protection
- Protection coordination with downstream fuses
- Automatic service restoration after temporary faults
- Remote-controlled points for distribution automation
Rural and Extended Networks
- Protection for long rural distribution lines
- Sectionalizing in areas with limited access
- Reducing outage areas in extended networks
- Minimizing crew dispatch for temporary faults
- Improving reliability metrics in challenging service territories
Special Applications
- Distributed generation interconnection protection
- Loop scheme automation
- Self-healing grid implementations
- Smart grid applications with advanced communication
- Voltage regulation integration
- Areas with high lightning exposure
Important Considerations Before Buying Used Reclosers
Usage and Maintenance History
The operational history significantly impacts reliability and remaining service life:
- Verify total number of operations (particularly fault interruptions)
- Check maintenance records and service history
- Confirm interrupter contact condition
- For hydraulic reclosers, verify hydraulic fluid condition and checks
- For electronic controls, verify firmware version and update history
- Check for evidence of overheating or mechanical wear
- Verify bushing condition and insulation integrity
- For oil-filled units, check oil quality and dielectric strength tests
- For vacuum units, verify vacuum integrity tests
Specifications and Compatibility
Ensure the recloser meets your system requirements:
- Voltage rating must match your system (typically 15kV, 27kV, 38kV)
- Current rating appropriate for the load and fault levels
- Interrupting capacity sufficient for available fault current
- BIL (Basic Impulse Level) rating suitable for your location
- Control voltage compatibility with your power source
- Single-phase vs. three-phase configuration as needed
- Control interface compatibility with your SCADA or automation system
- Physical mounting compatibility with existing structures
- Environmental rating appropriate for installation location
Purpose and Application
Select equipment appropriate for your specific needs:
- Standalone vs. integrated voltage sensing capability
- Required protection functions (overcurrent, directional, etc.)
- Coordination requirements with upstream and downstream devices
- Communication protocol needs (DNP3, IEC 61850, etc.)
- Environmental conditions (pollution, lightning exposure, ice loading)
- Control power source availability (battery backup requirements)
- Local vs. remote control requirements
- Future grid automation compatibility
How Much Should I Budget for Reclosers?
Pricing varies based on voltage class, features, and condition:
New Reclosers
- Single-phase hydraulic reclosers: $5,000-$12,000
- Three-phase hydraulic reclosers: $12,000-$25,000
- Single-phase electronic/vacuum reclosers: $8,000-$15,000
- Three-phase electronic/vacuum reclosers: $18,000-$40,000
- Advanced three-phase reclosers with controls: $30,000-$60,000
- Smart reclosers with advanced communication: $40,000-$80,000
- Control cabinets and accessories: $5,000-$20,000
- Installation costs: $10,000-$25,000
Used/Reconditioned Reclosers
- Typically 35-65% of new pricing depending on age and condition
- Factory reconditioned with warranty: 50-75% of new pricing
- Field reconditioned: 40-60% of new pricing
- As-is condition: 25-45% of new pricing
- Testing and certification costs: $1,000-$5,000
- Control upgrades (if needed): $5,000-$15,000
- Transportation costs: $500-$2,000
Cost Factors to Consider
- Age: Newer units typically command higher prices
- Operation Count: Lower operation counts increase value
- Manufacturer: Premium brands maintain higher resale value
- Technology: Electronic/vacuum types generally more valuable than hydraulic
- Control Features: Advanced protection and communication increase value
- Documentation: Complete manuals and test reports add value
- Accessories: Mounting hardware, bypass switches, wildlife protection
- Compatibility: Ability to integrate with modern control systems
When purchasing used reclosers, thorough testing is essential to ensure reliable operation. Critical tests include contact resistance, insulation resistance, timing tests, and control functionality. For hydraulic reclosers, operating mechanism condition is particularly important, while for vacuum types, the integrity of the vacuum interrupters is critical. Factory reconditioned units with warranty coverage often provide the best balance of cost savings and reliability. Modern microprocessor-controlled reclosers may offer significant advantages over older electromechanical or hydraulic units, including better protection capabilities, remote operation, and data collection. Consider the availability of spare parts and service support, especially for older models, when making purchasing decisions.