Pressure:
Gas pressures can be expressed in several units, such as MPa, bar, P.s.i etc.
1 MPa = 106 Pa = 10 bar = 145 P.s.i
Rated Filling Pressure:
The rated filling pressure is given at the reference temperature of +20 °C and may be expressed in relative or absolute terms.
The rated filling pressure is the pressure to which the circuit breaker is filled before being put into service. (0.70 MPa = 7 bar )
Alarm Pressure:
The alarm pressure is given at the reference temperature of +20 °C and may be expressed in relative or absolute terms.
The alarm pressure is the pressure at which a monitoring (alarm) signal indicates that replenishment is necessary for a relatively short time. (0.64, 0.62 MPa = 6.4, 6.2 bar)
Minimum pressure:
(Lockout, interlocking or blocking pressure) The minimum pressure is given at the reference temperature of +20 °C and may be expressed in relative or absolute terms.
The minimum pressure is the pressure at which the circuit breaker becomes interlocked for further operation and when replenishment is necessary. (0.60 MPa = 6 bar)
All type tests, except mechanical endurance test, are performed at this pressure.
All type tests, except mechanical endurance test, are performed at this pressure.
Maximum pressure:
The maximum pressure is given at the reference temperature of +20 °C and may be expressed in relative or absolute terms.
The maximum pressure is the pressure at which the circuit breaker is carrying its normal current at maximum ambient temperature. (0.80 MPa = 8 bar)
Grading capacitors:
Grading capacitors are sometimes used on circuit breakers of multi-break design (two or more identical making/breaking units connected in series) to obtain a uniform distribution of the voltage stresses across the open gaps.
The grading capacitor is connected in parallel with each and every making/breaking unit and has a standard value of 1600 pF/capacitor.
The total capacitance across one open pole is calculated as follows:
Ctot = Cgr/n
Where:
Cgr = is the capacitance of each grading capacitor.
n = is the number of making/breaking units connected in series
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