How Power Circuit Breaker Closing
Operation Works?
Circuit breakers are designed to
perform the closing and reclosing operations as per standard
requirements. When operated to close on long lines,
extra-high-voltage circuit breakers require special measures to keep
switching overvoltages within specified limits.
Such measures may be single or multiple
step closing resistors, synchronously closing at the moment of
voltage zero, or polarity-controlled-closing, which means closing
during the period of equal polarity at the line and source side of
the breaker. When operated to close on capacitor banks special
measures may be taken to limit transient currents and voltages.
Such measures may be closing resistors;
controlled closing at the moment of voltage zero for grounded wye
capacitor banks; or controlled closing on ungrounded wye capacitor
banks where the first phase is closed at the moment of voltage zero
and the other two phases are closed at a point where the voltage
difference between the two phases is zero.
When operated to close on power
transformers or shunt reactors special measures may be taken to limit
inrush transient currents and transient voltages. Such measures may
be single or multiple step closing resistors, or controlled closing
at the moment of voltage peak.
The magnitude of overvoltages on
energizing and reenergizing is influenced by the nature and variables
of the power system. Parameters of supply side and line must be taken
into account in order to compute the overvoltages or to determine
them using transient network analyzers or transient analysis
software, such as electromagnetic transients programs (EMTP), power
systems computer aided designs (PSCAD), or alternative transient
program. (ATP).
For a summary of the magnitude of
overvoltages occurring when energizing high-voltage lines, based on
numerous studies and measurements in high-voltage networks, see Table
10-9. Surge arresters may also be used to limit switching
overvoltages.
Overvoltages Occurring When Energizing
High-Voltage Lines
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