3WL air circuit breakers
3.3 Metering functions
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
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Harmonics can be generated by the following:
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Domestic electronics, lighting and computers
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Single-phase power supply units
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Uninterruptible power supplies via inverters
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Saturated iron cores with inductances (transformers and reactors)
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Converters
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Rectifiers and inverters (especially in the case of speed-controlled asynchronous
machines)
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Induction and arc furnaces, welding equipment
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Spark erosion machines
The harmonic currents thus caused instigate voltage drops at the system reactances. These
result in significant overvoltages or power surges if there is a resonance condition due to
additional series resonant circuits or anti-resonant circuits.
Harmonic currents can cause the following problems in plants:
Overload of the neutral conductor
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Overheating of transformers and reactors
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Overheating of cables and switching elements
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Overloading of compensation capacitors
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Voltage distortions
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Overheating and power-up difficulties for rotating-field motors
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Zero point faults
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Signal corruption on bus lines
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Interference with electronic components
Costs arise as a result of the following:
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Insufficient system quality increases the risk of failure of plant sections and can result in
production standstills.
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If the provided power is exceeded, energy costs increase
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Faults in the open-loop and closed-loop control systems result in production faults and
failures
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Occurrence of luminance changes, flickering, lighting failure
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Defective compensation systems and thus plant standstill
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Spurious tripping of protection equipment can result in standstill of plant sections
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Overload of the transformer and the cable result in increased fire hazard
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Reduction in the service life of electronic components
