CITEL Surge
Protection
Electrical Installations
Photovoltaic
Telecom
Data
Radiocommunication
AC Surge Protection Overview
Overview of Transient Overvoltages
The users of electronic equipment, telephone and data-processing systems must face the problem of
keeping this equipment in operation in spite of the transient overvoltages induces by lightning. There are
several reasons for this fact:
- The high level of integration of electronic components makes the equipment more vulnerable,
- Interruption of service is unacceptable
- Data transmission networks cover large areas and are exposed to more disturbances.
Transient overvoltages have three main causes:
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Lightning
Industrial and switching surges
Electrostatic Discharge (ESD)
Lightning
Lightning, investigated since Benjamin Franklin’s first research in 1749, has paradoxically become a
growing threat to our highly electronic society.
Lightning formation
A lightning flash is generated between two zones of opposite charge, typically between two storm clouds
or between one cloud and the ground.
The flash may travel several miles, advancing toward the ground in successive leaps: the leader creates a highly ionized channel. When it reaches the ground, the real flash or return stroke takes place. A
current in the tens of thousands of Amperes will then travel from ground to cloud or vice versa via the
ionized channel.
Direct Lightning
At the moment of discharge there is an impulse current flow that ranges from 1,000 to 200,000 Amperes
peak, with a rise time of about a few microseconds. This direct effect is a small factor in damage to
electric and electronic systems, because it is highly localized.
The best protection is still the classic lightning rod or Lightning Protection System (LPS), designed to
capture the discharge current and conduct it to a particular point.
Indirect effects
There are three types of indirect lightning effects:
Impact on overhead line
Such lines are very exposed and may be struck
directly by lightning, which will first partially or
completely destroy the cables, and then cause
high surge voltages that travel naturally along the
conductors to line-connected equipment. The extent
of the damage depends on the distance between the
strike and the equipment.
Rise in ground potential
The flow of lightning in the ground causes earth
potential increases that vary according to the current
intensity and the local earth impedance. In an
installation that may be connected to several grounds
(e.g. link between buildings), a strike will cause a very
large potential difference and equipment connected
to the affected networks will be destroyed or severely
disrupted.
Electromagnetic radiation
The flash may be regarded as an antenna
several miles high carrying an impulse current of
several tenths of kilo-amperes, radiating intense
electromagnetic fields (several kV/m at more than
1km). These fields induce strong voltages and
currents in lines near or on equipment. The values
depend on the distance from the flash and the
properties of the link.
Industrial Surges
An industrial surge covers a phonemena caused by switching electrical power sources on or off.
Industrial surges are caused by:
• Starting motors or transformers
• Neon and sodium light starters
• Switching power networks
• Switch “bounce” in an inductive circuit
• Operation of fuses and circuit breakers
• Falling power lines
• Poor or intermittent contacts
These phenomena generate transients of several kV with rise times of the order of the microsecond, disturbing
equipment in networks to which the source of disturbance is connected.
Electrostatic Overvoltages
Electrically, a human being has a capacitance ranging from 100 to 300 picofarads, and can pick up a charge
of as much as 15kV by walking on carpet, then touch some conducting object and be discharged in a few
microseconds, with a current of about ten Amperes. All integrated circuits (CMOS, etc.) are quite vulnerable to
this kind of disturbance, which is generally eliminated by shielding and grounding.
Effects of Overvoltages
Overvoltages have many types of effects on electronic equipment in order of decreasing importance:
Destruction
• Voltage breakdown of semiconductor junctions
• Destruction of bonding of components
• Destruction of tracks of PCBs or contacts
• Destruction of triacs/thyristors by dV/dt.
Interference with operations:
• Random operation of latches, thyristors, and triacs
• Erasure of memory
• Program errors or crashes
• Data and transmission errors
Premature ageing:
Components exposed to overvoltages have a shorter
life.
Surge Protection Devices
The Surge Protection Device (SPD) is a recognized
and effective solution to solve the overvoltage
problem. For greatest effect, however, it must be
chosen according to the risk of the application and
installed in accordance with the rules of the art.
Coaxial Surge Protection Overview
Protection for Radio Communication Equipment
Radio communication equipment deployed in fixed, nomadic or mobile applications is especially
vulnerable to lightning strikes because of their application in exposed areas. The most common disruption
to service continuity result from transient surges originating from direct lightning strikes to the antenna
pole, surrounding ground system or induced onto connections between these two areas.
Radio equipment utilized in CDMA, GSM/UMTS, WiMAX or TETRA base stations, must consider this risk
in order to insure uninterrupted service. CITEL offers three specific surge protection technologies for Radio
Frequency (RF) communication lines that are individually suited for the different operational requirements
of each system.
RF Surge Protection Technology
Gas Tube DC Pass Protection
P8AX series
Gas Discharge Tube (GDT) DC Pass Protection is the only surge protection component usable on very
high frequency transmission (up to 6 GHz) due to its very low capacitance. In a GDT based coaxial surge
protector, the GDT is connected in parallel between the central conductor and the external shield. The
device operates when its sparkover voltage is reached, during an overvoltage condition and the line is
briefly shorted (arc voltage) and diverted away from sensitive equipment. The sparkover voltage depends
on the rise front of the overvoltage. The higher the dV/dt of the overvoltage, the higher the sparkover
voltage of the surge protector. When the overvoltage disappears, the gas discharge tube returns to its
normal passive, highly insulated state and is ready to operate again.
The GDT is held in a specially designed holder that maximizes conduction during large surge events and
still very easily removed if maintenance is required due to an end of life scenario. The P8AX Series can be
used on coaxial lines running DC voltages up to -/+ 48V DC.
Hybrid Protection
DC Pass - CXF60 series
DC Blocked - CNP-DCB series
Hybrid DC Pass Protection is an association of filtering components and a heavy duty gas discharge tube
(GDT). This design provides an excellent low residual let through voltage for low frequency disturbances
due to electrical transients and still provides a high surge discharge current capability.
Quarter Wave DC Blocked Protection
PRC series
Quarter Wave DC Blocked Protection is an active band pass filter. It has no active components. Rather
the body and corresponding stub are tuned to one quarter of the desired wave length. This allows only a
specific frequency band to pass through the unit. Since lightning operates only on a very small spectrum,
from a few hundred kHz to a few MHz, it and all other frequency’s are short-circuited to ground. The PRC
technology can be selected for a very narrow band or wide band depending on the application. The only
limitation for surge current is the associated connector type. Typically, a 7/16 Din connector can handle
100kA 8/20us while an N-type connector can handle up to 50kA 8/20us.
Selecting a Coaxial Surge Protector
The information required to properly select a surge protector for your application is the following:
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Frequency Range
Line Voltage
Connector Type
Gender Type
Mounting
Technology
INSTALLATION
The proper installation of a coaxial surge protector is largely dependent on its connection to a low impedance
grounding system. The following rules must be strictly observed:
• Equipotential Grounding System: All the bonding conductors of the installation must be interconnected to
each other and connected back to the grounding system.
• Low Impedance Connection: The coaxial surge protector needs to have a low resistance connection to the
Ground System.
• Location of Protection: The protectors should be placed at the entrance of installation to limit the
penetration of lightning current inside the facility in addition to direct placement in front of the sensitive
equipment.
Mounting options include:
1) Feed through Mounting by Bulkhead or Mounting Bracket: This is the direct mounting of the surge
protector onto the ground frame or ground plate at the installations service entrance.
• Provides perfect connection to the grounding system
• Located at optimal point where surge currents enter at the entrance of the installation
• Good mechanical withstand capability
2) Ground Screw: Connection to the grounding system is directly by wire via ground screw on the chassis
and then to grounding system (4 mm² minimum).
MAINTENANCE
CITEL coaxial line surge protectors require no maintenance or replacement under normal conditions. They
are designed to withstand repeated, heavy duty surge currents without damage.
Nevertheless, it is prudent to plan for the worst case scenario and, for this reason; CITEL has designed for
the replacement of protection components where practical. The P8AX Series incorporates an easy to use
GDT holder that allows for the protective component to be replaced without the need for special tools or
knowledge. The failure mode for a coaxial surge protector is either fail short to ground or fail open.
The status of your coaxial surge protector can be tested with CITEL’s model T1000KE. This unit is designed
to test for the DC sparkover voltage of the GDT. The T1000KE is a compact, single push button unit with a
digital display. The voltage range of the tester is 0 to 999 volts.
Data Line Overview
Introduction
Telecommunication and data transmission devices (PBX, modems, data terminals, sensors, etc...) are
increasingly more vulnerable to lightning induced voltage surges. They have become more sensitive, complex and have an increased vulnerabiity to induced surges due to their possible connection across several
different networks. These devices are critical to a companies communications and information processing. As such, it is prudent to insure them against these potentially costly and disruptive events. A data line
surge protector installed in-line, directly in front of a sensitive piece of equipment will increase their useful
life and maintain the continuity of the flow of your information.
Technology of Surge Protectors
All Citel telephone and data line surge protectors are based on a reliable multistage hybrid circuit that combines heavy duty Gas Discharge Tubes (GDTs) and fast responding Silicon Avalanche Diodes (SADs). This
type of circuit provides,
• 5kA Nominal Discharge Current (15 times without distruction per IEC 61643)
• Less than 1 nanosecond response times
• Fail-safe disconnection system
• Low capacitance design minimizes signal loss
Parameters for Selecting A Surge Protector
To select the correct surge protector for your installation, keep the following in mind :
• Nominal and Maximum Line Voltages
• Maximum Line Current
• Number of Lines
• Data Transmission Speed
• Type of Connector (Screw Terminal, RJ, ATT110, QC66)
• Mounting (Din Rail, Surface Mount)
Installation
To be effective, the surge protector must be installed in accordance with the following principles.
• The ground point of the surge protectro and of the protected equipment must be bonded.
• The protection is installed at the service entrance of the installation to divert impulse current as soon as
possible.
• The surge protector must be installed in close proximity, less than 90 feet or 30 meters) to protected
equipment. If this rule cannot be followed, secondary surge protectors must be installed near to the equipment.
• The grounding conductor (between the earth output of the protector and the installation bonding circuit)
must be as short as possible (less than 1.5 feet or 0.50 meters) and have a cross sectional area of at least
2.5 mm squared.
• The earth resistance must adhere to the local electrical code. No special earthing is necessary.
• Protected and unprotected cables must be kept well apart to limit coupling.
Special Conditions : Lightning Protection Systems
If the structure to be protected is equipped with a LPS (Lightning Protection System), the surge protectors
for telecom or data lines that are installed at the buildings service entrance need to be tested to a direct
lightning impulse 10/350us wave form with a minimum surge current of 2.5kA (D1 category test IEC-6164321).
DC Power Surge Protection Overview
Background and Protection Considerations
Utility-Interactive or Grid-Tie Solar Photovoltaic (PV) Systems are very demanding and cost intensive projects. They often require the Solar PV System to be operational for several decades before it can yield the
desired return on investment.
Many manufacturers will guarantee a system life of greater than 20 years while the inverter is generally
guaranteed for only 5-10 years. All costs and return on investments are calculated based on these time periods. However, many PV systems are not reaching maturity due to the exposed nature of these applications
and its interconnection back to the AC utility grid. The solar PV arrays, with its metallic frame and mounted
in the open or on roof tops, act as a very good lightning rod. For this reason, it is prudent to invest in surge
protection to eliminate these potential threats and thus maximize the systems life expectancy. The cost for a
comprehensive surge protection system is less than 1% of the total system expenditure.
To analyze the full threat level of the installation, we must make a risk assessment.
Operational Downtime Risk – Areas with severe lightning and unstable utility power are more vulnerable.
Power Interconnection Risk – The greater the surface area of the solar PV array, the more exposure to
direct and/or induced lightning surges.
Application Surface Area Risk – The AC utility grid is a likely source of switching transients and/or induced lightning surges.
Geographic Risk – Consequences of system downtime are not only limited to equipment replacement.
Additional losses can result from lost orders, idle workers, overtime, customer/management dissatisfaction,
expedited freight charges and expedited shipping costs.
Recommend Practices
1) Earthing System
Surge Protectors shunt transients to the earth grounding system. A low impedance ground path, at the
same potential, is critical for the surge protectors to function properly. All power systems, communication
lines, grounded and ungrounded metallic objects need to be equipotentially bonded for the protection
scheme to work efficiently.
2) Underground Connection from External PV Array to Electrical Control Equipment
If possible, the connection between the external Solar PV Array and the internal power control equipment
should be underground or electrically shielded to limit the risk of direct lightning strikes and/or coupling.
3) Coordinated Protection Scheme
All available power and communication networks should be addressed with surge protection to eliminate PV
system vulnerabilities. This would include the primary AC utility power supply, Inverter AC output, Inverter
DC input, PV string combiner and other related data/signal lines such as RS-485, 4-20mA current loop, PT100, RTD, and telephone modems.