SIEMENS
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Siemens KT 10.1 · 2016
15
Technical information and configuration
Possible mains disturbances and causes
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Overview
The quality of the mains voltage has become a decisive factor in
the functioning, reliability, maintenance costs and service life of
highly sensitive electronic installations and devices (computers,
industrial controls, instrumentation, etc.).
Mains disturbances cause system failures and affect the func-
tion of plants as well as electronic loads. They can also result in
total failure of the installation or equipment.
The most frequent types of disturbance are:
•
Long-term overvoltages
•
Long-term undervoltages
•
Interference pulses and transients
•
Voltage dips and surges
•
Electrical noise
•
Momentary network failure
•
Long-term network failure
Mains disturbances can be caused by a number of things, e.g.:
•
Switching operations in the supply system
•
Long cable paths in the supply system
•
Environmental influences such as thunderstorms
•
Mains overloads
Typical causes of mains disturbances generated in-house are:
•
Thyristor-controlled drives
•
Elevators, air-conditioning, photocopiers
•
Motors, reactive-power compensation systems
•
Electrical welding, large machines
•
Switching of lighting equipment
Disturbances in mains voltages can occur individually or in com-
bination. Possible reasons for these disturbances, their effects
and countermeasures can include:
System disturbances
Percentage of total
disturbance
Result
Measure
Overvoltage
The supply voltage is exceeded by more than
+6% for a prolonged period (acc. to IEC 60038)
Approx. 15% - 20%
Can result in overheating and even
thermal destruction of individual
components. Causes total failure.
SITOP power supplies with their
wide operating voltage range offer
sufficient protection against minor
network overvoltages outside the
permissible tolerance
Line undervoltage
The supply voltage is undershot by more
than –10% for a prolonged period
(acc. to DIN IEC 60038)
Approx. 20% - 30%
Can result in undefined operating
states of loads. Causes data errors.
Use of a SITOP DC-UPS
(uninterruptible DC power supply)
see Section 11
Interference pulses
Energy-rich pulses (e.g. 700 V/1 ms) and
energy-poor transients (e.g. 2500 V/20 μs) result
from switching operations in the supply system
Approx. 30% - 35%
Can result in undefined operating
states of the loads and can lead to the
destruction of components.
Use of surge protectors, see
Catalog LV 10.1 2013, Section 6
Voltage dips and surges
The voltage level changes suddenly and in an
uncontrolled manner, e.g. due to changes in
loading and long cable routes
Approx. 15% - 30%
Can result in undefined operating
states and destruction of components.
Cause data errors.
Thanks to their internal buffer time,
SITOP power supplies offer suffi-
cient protection against short
power failures
Electrical noise
A mix of frequencies superimposed on the mains
due to bad grounding and/or strong HF emitters
such as radio transmitters or thunderstorms
Approx. 20% - 35%
Can result in undefined operating
states of loads. Causes data errors.
Due to internal switching measures,
SITOP power supplies offer suffi-
cient immunity to electromagnetic
interference
Voltage interruption
Short-term interruption of the supply voltage
(up to approx. 100 ms) due to short-circuiting
in neighboring supply systems or starting of
large electrical machines.
Approx. 8% - 10%
Can result in undefined operating
states of loads, especially those with
insufficient mains buffering. Causes
data errors.
Use of a SITOP buffer module
(in connection with SITOP smart
or SITOP modular)
see Section 10
Voltage interruption
Long interruption of the supply voltage
(longer than approx. 100 ms)
Approx. 2% - 5%
Can result in undefined operating
states of loads, especially those with
insufficient mains buffering. Causes
data errors.
Use of a SITOP DC-UPS
(uninterruptible DC power supply)
see Section 11
© Siemens AG 2016