Multi-Stage Protection Approach
Effective telecommunications protection requires a coordinated multi-stage approach:
Primary Protection (Coordinated Devices)
Primary protection devices must handle the majority of surge energy, typically gas discharge tubes positioned at the building entrance or main grounding panel:
- 3-pole GDT: B72200S0101 for 100V sparkover applications
- Energy coordination with downstream devices
- Connected to main grounding system
- Minimum response time for lightning protection
For 5G base stations with higher component density, use lower sparkover voltage devices such as B72200S075K (75V breakdown) to provide earlier protection onset while coordinating with secondary devices.
Secondary Protection (Fine Protection)
Secondary protection provides voltage clamping for transients that pass through primary protection:
- Varistors: B72220S075K10 (75V, 10kA rated) for secondary clamping
- Proper voltage coordination to prevent premature firing
- Placed near sensitive equipment
- Low clamping voltage to protect downstream components
Tertiary Protection (Component Level)
For ultra-sensitive circuits, implement tertiary protection close to critical components:
- TBU devices for data line protection
- Low-capacitance TVS diodes for high-frequency signals
- Close coupling to protected circuitry
- Minimal lead inductance for fast response
Protection Coordination Principles
Proper coordination prevents damage to upstream devices from downstream failures and ensures sequential operation:
Voltage Coordination
The voltage protection level (VPL) of downstream devices must be lower than the withstand voltage of protected equipment but higher than the follow current limiting voltage of upstream devices. Typically maintain at least a 50% margin between the upper limit of the upstream device and the lower limit of the downstream device.
Energy Coordination
Primary devices must handle the majority of energy without degradation affecting their performance. The let-through energy from primary devices must be within the ratings of secondary devices. Consider the cumulative effects of multiple surge events on component degradation.
Grounding and Bonding Considerations
Effective protection depends on proper grounding and equipotential bonding:
- Separate grounds for lightning protection and equipment grounding
- Low-impedance grounding paths
- Proper grounding electrode system
- Grounding conductor sizing for fault currents
- Equipotential bonding between systems
For coaxial feed line applications, proper grounding of the outer conductor at multiple points helps divert lightning energy to ground before it enters the equipment.
Installation Best Practices
Installation details significantly affect protection effectiveness:
- Short, direct connections to minimize inductance
- Proper conductor sizes to handle fault currents
- Appropriate spacing between primary and secondary devices
- Labeling and documentation for maintenance
- Regular inspection schedules for outdoor installations
For rooftop installations, consider the separation between structures and equipment, and implement appropriate lightning protection zone (LPZ) concepts using the EPCOS protection devices.
