Switchgear & circuit breakers 3

The rating of a c.b.:
In general, the rating of a circuit breaker is the limit of the range of operating characteristics under well defined conditions, this can include, where applicable: rated maximum voltage, rated voltage range factor K, rated frequency, rated continuous current, rated dielectric strength (dry and wet, where applicable, low frequency withstand voltage, dry impulse withstand voltage, dry chopped wave impulse withstand voltage & dry/wet switching impulse withstand voltage, rated standard duty cycle, rated interrupting time, rated permissible tripping delay, rated re-closing time, rated SCC, rated transient recovery voltage, load current switching vs. life of device, rated capacitance current switching, rated line closing switching surge factor, rated out of phase switching current, rated shunt reactor current switching, rated excitation current switching, rated control voltage, rated fluid operating pressure (if hydraulic/pneumatic control). The rated maximum voltage for the different breaker voltage classes in KV: 4.76, 8.25, 15, 25.8, 38 with rated continuous current at 60HZ in A rms: from 600 to 3000 with rated SCC (at rated maximum KV) in KA rms (nominal voltage): 9.1-30 (4.16KV), 35(7.2KV), 19.3-38(13.8KV), 25(24.6KV), 20(34.5KV). The rated insulation levels, which withstand low frequency and impulse in KV rms and crest, respectively, are: 19 & 60, 26 & 75, 36 & 95 and 70 & 150. The K factor can vary from 1 to 2. The short time ratings (3 seconds) in KA rms are: 44, 25, 37.5 and 31.5.

To download/read more, click here.

Switchgear & circuit breakers 2

Vibration, kinetics, kinematics:
Vibration is an oscillating motion, periodic/transient in nature. Study of vibration rely on dynamics (the field in mechanics that deals with bodies in motion and the forces causing such motions).
Kinetics is the study relating between the motion of the bodies and the forces acting upon them.
Kinematics is the study of the geometry of motion, without reference to force or mass. Kinematics is primarily concerned with displacement, velocity, acceleration and time. 

To download/read more,  click here.

Switchgear & circuit breakers 1

The different types of switchgear assemblies, their sub-classification & the standards governing switchgear assemblies & circuit breakers:
The different types for switchgear assemblies are: indoor and outdoor. The sub-classification for the indoor is: standard, sprinkler proof, arc proof, dust proof, seismic proof, metal-clad construction vs. metal enclosed, enclosure with or without a drip hood; for the outdoor is: walk in, walk in with working area, walk-in double row, non-walk in with or without working area, enclosure for cable/bus entry or transformer throat, enclosure with thermal insulation/isle heaters and finally indoor cubicle design installed in an outdoor house.
The standards that govern circuit breakers/switchgear design testing and application are: ANSI C37 series including .09 "Test procedure for A.C. high voltage circuit breakers rated on a symmetrical current basis", .04 "Rating structure for A.C. high voltage circuit breakers rated on a symmetrical current basis", .06 "Preferred ratings and related required capabilities for A.C. high voltage circuit breakers rated on a symmetrical current basis", .20 "Switchgear assemblies", IEC 56 "High voltage A.C. circuit breakers", IEC 60 series "High voltage test techniques", IEC 694 "Common clauses for high voltage switchgear and controlgear", C22.2#31" switchgear assemblies" and CAN3-C13 "Instrument transformers.

The main parts of a low voltage (l.v.) switchgear:
The main elements for l.v. switchgear assemblies with moulded case or power (air magnetic) circuit breakers (draw-out or fixed) complete with or without integral overcurrent protection device (thermal- magnetic, solid state or microprocessor based) with or without zone interlocking provision are the cradle for drawout version only, fixed potential and control power transformers, current transformers, interframe and back barriers, main bus bars, run backs, bus risers, cable lugs (compression or mechanical), protective fuses for breaker control circuits, instrument compartments, breaker accessories, breaker lifting devices (integral with gear), fused or unfused interrupter switches, protective/monitoring/ auxiliary relays, metering devices (ammeters, voltmeters,

To download/read more, click here.