RRB JE CBT 2 Electrical case studies
RRB JE CBT 2 Electrical · Put your knowledge to work in context.
RRB JE CBT 2 Electrical is the second-stage computer-based test used by the Railway Recruitment Board in India to shortlist candidates for Junior Engineer posts in the electrical discipline. It is aimed at diploma and degree holders in electrical engineering who have already cleared CBT 1, and it is a screening gate rather than a licence: qualifying puts you into document verification and the final merit list for Indian Railways posts. The RRB JE CBT 2 Electrical case studies are 5 cases and about 4,516 words.
1Bay 4 sub-main: undersized cable or a hidden series resistance?
During a night shift at a coaching depot, the 230 V single-phase sub-main feeding pit lighting and socket outlets in Bay 4 dims visibly whenever a 2 kW portable heater is switched on. The sub-main is 40 m of 4 mm2 copper twin-and-earth drawn in conduit from the depot main board; take copper resistivity as 0.0172 ohm·mm2/m.
839 words, about 4 min2Fan bank failed, top oil rising, and 35 ppm of acetylene
A 1000 kVA, 11 kV/433 V, Dyn11 oil-immersed distribution transformer serves a traction maintenance depot. The nameplate states ONAN 700 kVA, ONAF 1000 kVA, guaranteed top-oil temperature rise 45 K at rated load, oil-temperature alarm at 90 °C and trip at 105 °C.
913 words, about 5 min3Both relays trip: grading two IDMT overcurrent relays on an 11 kV feeder
A 33/11 kV substation feeds a depot distribution board through 11 kV feeder F1. Two overcurrent relays use the standard inverse curve t = 0.14 × TM / ((I/Is)^0.02 − 1).
925 words, about 5 min4The energy meter reads exactly one third of the logged consumption
A workshop is billed on a 415 V, three-phase, four-wire static energy meter connected through three 400/5 A current transformers; the voltage circuits are connected directly, with no PTs. Over a 30-day billing period the meter dial advanced by 480 units.
862 words, about 4 min545 kW pump drive tripping at 40 Hz after an impeller change
A 45 kW, 415 V, four-pole IE3 motor drives a cooling-water pump through a voltage-source PWM drive rated 90 A at 40 °C ambient. The motor nameplate full-load current is 82 A.
977 words, about 5 min