Siemens SENTRON VL Series System Manual page 45

Harmonics can be generated by the following:
● Domestic electronics, lighting and computers
● Single-phase power supply units
● Uninterruptible power supplies via inverters
● Saturated iron cores with inductances (transformers and reactors)
● Converters
● Rectifiers and inverters (especially in the case of speed-controlled asynchronous
machines)
● Induction and arc furnaces, welding equipment
● 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
● Overheating of transformers and reactors
● Overheating of cables and switching elements
● Overloading of compensation capacitors
● Voltage distortions
● Overheating and power-up difficulties for rotating-field motors
● Zero point faults
● Signal corruption on bus lines
● Interference with electronic components
Costs arise as a result of the following:
● Insufficient system quality increases the risk of failure of plant sections and can result in
production standstills.
● If the provided power is exceeded, energy costs increase
● Faults in the open-loop and closed-loop control systems result in production faults and
failures
● Occurrence of luminance changes, flickering, lighting failure
● Defective compensation systems and thus plant standstill
● Spurious tripping of protection equipment can result in standstill of plant sections
● Overload of the transformer and the cable result in increased fire hazard
● Reduction in the service life of electronic components
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
3WL air circuit breakers
3.3 Metering functions
45