mobile | classic
Dataweek Electronics & Communications Technology Magazine

Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


Gas-filled surge arresters and varistors protect basestations
25 October 2000, Circuit & System Protection

Mobile telephone systems have become one of the most important ‘vital nerves’ of our society. One of the most self-evident expectations which users place on the network operators is that they can make use of this service at all times with no interruptions. The network operators must consequently ensure that their installations have a high operational reliability. Rugged gas-filled surge arresters and varistors from Epcos make an effective contribution to protecting these systems from external influences such as thunderstorms and noise voltages caused by switching processes.

Only a dense network of basestations of differing output powers allows the continually increasing requirements of network coverage to be fulfilled. The user's expectations of this technology can be summed up in a simple formula: "Interference-free mobile communications services must be available at all times". Various communications services have been set up to do this job: they include not only conventional telephones but also systems for transmitting high data rates - today up to about 2 Mb - as well as terminals for Internet access.

A seamless service provision

The seamless provision of mobile telephony to major urban centers as well as extensive rural areas requires a network of mobile telephone basestations of varying density. These range from micro basestations of small output (2 to 8 W) via microcellular networks - designed to provide services to utilities such as office buildings, subway stations, tunnels, shopping centres, hotel foyers and exhibition halls - up to powerful units (eg 50 W) for macro radio cells with a broad regional coverage. These can reach ranges of up to about 30 km.

Basestations are vulnerable

The basestations are frequently set up at exposed locations in order to ensure maximum regional coverage. This often results in a considerable hazard potential. As a rule, the basestations to be protected have three interfaces to the outside: the power supply, the connection to the operator's fixed network and the antenna's input/output for the radio link to the mobile telephone. Thus interference caused by thunderstorms can destroy the basestation along all three of these paths: via the inductive coupling of partial lightning currents into the power supply system, by coupling of impermissibly high voltages into the signal lines to the fixed network or of lightning energy into the antenna.

Although the proximity of power lines (such as overhead transmission lines) and communications lines should in principle be avoided, this is not always possible in practice. Thus a short circuit on a power line can lead to considerable induction currents or overvoltages on the feed lines to the basestation. In the worst case, even a direct contact between power and communications lines is conceivable. Unless the basestation is sufficiently protected, its operation will inevitably be interrupted.

Arresters and varistors provide reliable protection

Epcos offers an extensive range of proven and attractively priced protective components in the form of gas-filled surge arresters. Thanks to their exceptionally high current-handling capacity, these arresters are particularly well suited to provide protection against the dangerous effects of atmospheric discharges (thunderstorms). They represent an ideal first-stage protection element fitted directly in the access network of the basestation. Gas-filled surge arresters offer optimum protection as they limit the overvoltage resulting from these disturbances at the inputs of the basestation quickly and reliably. They reduce the voltage to noncritical values and reliably conduct the dangerous excess currents away to ground.

A gas-filled overvoltage arrester can be described in a simplified way as a symmetrical low-capacitance switch that is set during manufacture to a specific switching voltage known as the sparkover voltage. In addition, gas-filled surge arresters have the added benefit of not affecting the circuits to be protected in the basestation equipment, because they assume a high resistance of several gigaohms during undisturbed operation. Their low capacitance, typically 1 pF, proves to be very helpful for the layout of the protective circuit at the RF input and outputs of the radio antenna and the fixed-network link via PCM systems (see Figure 1).

Figure 1. Base station with overvoltage protection circuits at the inputs and outputs. Top left: Surge arrester in the antenna input. Bottom left: Protection circuits in the power supply system with varistors and surge arresters. Right: Protection circuit for the fixed network with symmetrical surge arresters. The most common types of surge arresters are shown for each respective application
Figure 1. Base station with overvoltage protection circuits at the inputs and outputs. Top left: Surge arrester in the antenna input. Bottom left: Protection circuits in the power supply system with varistors and surge arresters. Right: Protection circuit for the fixed network with symmetrical surge arresters. The most common types of surge arresters are shown for each respective application

The antenna-side protection circuit is, as a rule, integrated in the RF part of the receiver. On the transmit side, use is often made of filters. Depending on their layout, they may offer sufficient protection even without the need for surge arresters. A common solution is to secure the input of the fixed-network connection by a separate lightning-protection module onto which the surge arresters are mounted. The spatial separation of the lightning protection module from the actual input circuit is important in order to intercept the currents expected from the interference sources as closely as possible after the input and thus to avoid carry-overs into the system.

In order to protect the power supply, terminated and ready-to-install overvoltage protection devices with surge arresters have become widely used. The circuitry requirements depend on the power of the basestation and the network structure. The examples in Figure 1 (below left) are typical configurations, showing the layout of the surge arresters and varistors in installation packages.

Additional protection is available from a temperature-controlled isolation key not shown here. The current status can be displayed through an optical detection system or a remote signal in case the varistors become thermally overloaded.

Application know-how

When used in power networks, surge arresters are always connected together with varistors in a series circuit. The varistor limits the current through the surge arrestor which could otherwise assume impermissibly high values because of the negative current/voltage characteristic of the arrester. These two overvoltage protection components from Epcos thus complement each other ideally in practice.

Supplied By: Electrocomp
Tel: +27 11 458 9000
Fax: +27 11 458 9034/5
  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • Coaxial RF surge protectors
    23 October 2019, RF Design, Circuit & System Protection
    Pasternack has launched a new series of coaxial surge protectors designed to protect valuable communications equipment from power surges and indirect lightning strikes. Pasternack’s new surge protectors ...
  • Waterproof Micro USB connector
    23 October 2019, Electrocomp, Interconnection
    As part of a new product line from GCT, the aquanex waterproof range brings together high-performance USB connectors with IP67 rated sealing. The first connector launched from the aquanex range, the USB3500, ...
  • Evaluation kit for environmental sensors
    23 October 2019, Electrocomp, Design Automation
    Sensirion’s SEK-Environmental Sensing evaluation kit allows engineers to evaluate sensors and develop innovative sensor applications quickly and easily. The kit combines plug-and-play hardware with easy-to-use ...
  • Miniature resettable thermal cutoff devices
    23 October 2019, Electrocomp, Circuit & System Protection
    A new addition from Bourns is the Model CB series of miniature resettable thermal cutoff (TCO) devices. These are the smallest TCO devices Bourns has produced and represent the company’s next generation ...
  • Surge arrestor for satellite antenna systems
    23 October 2019, Conical Technologies, Circuit & System Protection
    Nextek announced the release of its new lightning surge arrestor for use with satellite antenna systems. The new PTC-C030 was designed with two F-type connectors for easy connection to V-SAT or DSTV satellite ...
  • New EPCOS power line chokes
    23 October 2019, Electrocomp, Passive Components
    TDK has extended its range of EPCOS power line chokes to include six new types. The new components are available in three different core shapes with different rated currents and inductance values, delivering ...
  • Steering diode TVS array
    23 October 2019, Altron Arrow, Circuit & System Protection
    ProTek Devices has introduced a new steering diode transient voltage suppressor (TVS) array for circuit protection across popular consumer electronic display interfaces. The new PUSB403 device is ideal ...
  • EMI compliance testing vs. pre-compliance testing
    25 September 2019, Concilium Technologies, Circuit & System Protection
    Electromagnetic interference (EMI) is caused by unintentional emissions from electronic equipment. Compared to natural sources of EMI, such as lightning and solar storms, engineers are more concerned ...
  • Die-cast enclosures in extended lengths
    25 September 2019, Electrocomp, Enclosures, Racks, Cabinets & Panel Products
    The 1590 die-cast enclosures family from Hammond Manufacturing consists of 41 different sizes in the standard rectangular and Stomp Box, painted variants. Stomp boxes, colour coded to provide quick ...
  • Conductive rubber gaskets
    25 September 2019, Conical Technologies, Circuit & System Protection
    A range of conductive O-profile silicone rubber gaskets is available from Holland Shielding Systems, developed for high-performance shielding up to 18 GHz and used where environmental and EMI screening ...
  • High-temperature TVS MLVs
    25 September 2019, Future Electronics, Circuit & System Protection
    The new TransGuard VT Series multilayer varistors (MLV) made by AVX are rated for transient voltage suppression (TVS) applications operating at very high temperatures. They provide reliable, bidirectional ...
  • Test unit controls access to ESD protected areas
    25 September 2019, Altico Static Control Solutions, Circuit & System Protection
    In the electronics manufacturing industry, an electrostatic discharge (ESD) can cause irreparable damage to electronic components. This micro-lightning bolt can burn holes through insulating layers and ...

Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Terms & conditions of use, including privacy policy
PAIA Manual


    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.