16-01-2013, 03:52 PM
Lightning Surge Protectors for Electronic Equipment - M RESTER Series
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Understanding the Problem
Electric charges generated in a thunderstorm discharge
to the ground with a current of approximately
20kA to 150kA.
Lightning induced surges occur in a
cable as a result of rapid and violent
changes in the magnetic field intensity
generated around the cable.
The surge propagates in the cable, and instantaneously
applies high energy to the electronics equipment
connected to both ends of the cable.
Interline breakdowns occur when electronic components
are directly hit and destroyed by lightning surges
generated between two cable conductors connected
to the equipment.
In discharge breakdowns, a lightning surge creates
a very high potential difference between two conductors
and ground.
As a result, a discharge occurs between some parts
of the circuit and areas electrically grounded, such as
the metal housing. Electronic components are damaged
by some of the discharge current that flows
through the circuit.
The effects of induced surges on connected equipment
are more severe when the connecting cable is longer;
the induced current is higher; or the equipment is located
closer to the site of the lightning strike.
DC or pulse signal lines
Absorb lightning surges transmitted in 4-20 mADC
and pulse signal wiring to ensure the line potential
will remain at a low voltage.
Receiving instruments from thermocouples
Absorb lightning surges entering the temperature
transmitter or a controller through the thermocouple
and/or thermocouple transmitter wire.
RTD and RTD wire receiving instruments
Protect RTD transmitters from damage caused by
surges on the RTD wiring.
Potentiometer and receiving instruments
Protect potentiometer transmitters from lightning
surges that enter the wiring between the
potentiometer and the transmitter in applications
such as water level sensors and valve position
indicators.
Pulse generating or receiving devices
Protect frequency generating devices such as
flowmeters and frequency transmitters from lightning
surges that enter the wiring between these
instruments.
ON-OFF signal lines – eight channel capacity
Protect semiconductor switches used for ON-OFF
outputs from the computer or PLC from lightning
surges entering through the wiring.
Large instrumentation panels,
computer systems or telemetering systems
Designed to protect large instrumentation panels,
computer systems and telemetering systems in
central control rooms or operations centers. Incorporates
air-core reactors, large-capacity discharge
elements and electromagnetic contactors. Thermal
fuse, in parallel with the discharge elements, opens
the operating circuit for the electromagnetic contactor,
offering fail-safe protection in severe lightning
strikes.