Haryana BSEH Senior Secondary NSQF Power common mistakes
Haryana BSEH Senior Secondary NSQF Power · Understand the traps and how to avoid them.
When asked to identify whether a supply is AC or DC from its stated frequency and waveform description, candidates label a 50 Hz sinusoidal supply as DC or describe it as 'unidirectional', confusing frequency with current direction.
Trainees memorise 'AC changes direction, DC does not' as a slogan but never link it to the numeric frequency value, so a figure like 50 Hz is treated as a separate fact rather than proof of alternating polarity. ITI-level teaching often shows AC and DC side by side without forcing the frequency-to-direction link.
What to do instead
Adopt a one-line decision rule and apply it to every such question: any non-zero frequency in Hz means the polarity reverses every half cycle, so it is AC; 0 Hz means steady polarity, so it is DC. Practise by classifying ten given supplies (50 Hz, 60 Hz, 0 Hz battery, pulsed DC) and writing the reason in one sentence each.
Candidates rank energy sources by installed capacity when the question asks about the share of electricity generated, or vice versa, and give a single national figure without noting that Haryana's own mix is dominated by thermal generation.
Capacity (MW) and generation (MU/kWh) are both quoted in news reports and are easy to conflate. Candidates also generalise from national renewable targets to the state, ignoring that Haryana's generation is largely coal-based with growing solar and biomass.
What to do instead
Keep two separate columns in revision notes, one for installed capacity and one for actual generation, and always state the unit. For state-level questions, memorise the qualitative picture (coal-dominant, rising solar, some biomass and small hydro) rather than a single precise percentage, and state the basis of any figure you quote.
In questions on thermal power plant flow, candidates place the economiser, superheater and air preheater in the wrong order, or say the economiser heats incoming air.
The names are learned as a list without the water/steam/air path attached, so 'economiser' is guessed to be about air because it sounds like an air-side device. Diagrams in notebooks are copied without tracing which fluid enters and leaves each component.
What to do instead
Draw the path once from memory: boiler feed pump, economiser (flue gas heats water), drum, superheater (flue gas heats steam), turbine, condenser, feed pump; air preheater sits on the air side using flue gas before the chimney. Then answer by tracing the fluid named in the question, not by recalling the list order.
Candidates describe a step-up transformer as 'increasing power' or state that transmission at high voltage reduces power losses because 'voltage kills current' without tying it to I squared R.
The transformer equation is memorised as V ratio equals turns ratio, but the conservation of power and the loss formula are treated as unrelated topics. The phrase 'high voltage reduces loss' is learned as a slogan with no mechanism behind it.
What to do instead
Write the chain every time: transformer keeps power constant, so raising voltage lowers current by the same ratio; line loss equals I squared R, so lower current means much lower loss. Practise three numeric examples where voltage is doubled and the loss falls to one quarter, and state that the transformer itself does not create power.
When asked why transmission uses three-phase three-wire while distribution uses three-phase four-wire, candidates answer 'for safety' or 'because domestic loads are single phase' without mentioning the neutral return and unbalanced load.
The four-wire arrangement is seen in every LT line but the reason for the neutral is never connected to unbalanced single-phase loads and the resulting neutral current. Candidates also mix up the star and delta connections.
What to do instead
Learn the pairing: star connection gives a neutral point, which is why distribution can supply mixed single-phase loads and carry the out-of-balance current; delta has no neutral and suits balanced transmission. Answer with the words 'unbalanced load' and 'neutral return' explicitly, and sketch both connections with the neutral marked.
Candidates confuse a transformer's rated kVA with its kW output, or claim a transformer can be loaded to its kVA rating at any power factor without affecting the useful power delivered.
Rating is quoted in kVA because it is limited by heating, not by real power, but this reason is rarely taught. Candidates plug kVA into power calculations as if it were kW and ignore power factor entirely.
What to do instead
Fix the relation kW equals kVA times power factor and explain the rating basis in one line: kVA limits current and heating, so the same transformer delivers less kW at low power factor. Work two examples at 0.8 and 0.95 power factor to see the kW change while kVA stays fixed.
On protection questions, candidates select a fuse rating or MCB rating by matching it to the load current exactly, or state that an earth wire and a neutral wire serve the same purpose.
The distinction between overload protection, short-circuit protection and earth leakage protection is blurred, and the earth wire is seen only as 'the green one' without its role in providing a low-resistance fault path that operates the protective device.
What to do instead
Learn the three duties separately: fuse and MCB protect against overload and short circuit; ELCB or RCCB detects earth leakage current; the earth wire provides the fault path so that protective device trips. For rating questions, state that the device rating must exceed normal load current but sit below the cable's safe current, and never treat neutral and earth as interchangeable.
Candidates compute energy savings as a percentage of the wrong base, for example dividing the saving by the new consumption instead of the original, or report savings in kW when the question asks for kWh.
Energy audit questions mix power (instantaneous) and energy (over time), and the base of a percentage is not identified before dividing. Trainees often stop at the arithmetic without checking units against the question wording.
What to do instead
Before calculating, write the base explicitly: percentage saving equals saving divided by original consumption, multiplied by 100. Convert every load to kWh by multiplying kW by hours of use, and finish each answer by naming the unit and checking it matches what was asked. Do five mixed kW/kWh drills.
In entrepreneurship questions, candidates describe a business plan as only a source of finance request, omitting market, cost, break-even and risk sections, or calculate break-even without separating fixed and variable costs.
Business plans are studied as a document to submit to a bank rather than as a working tool. Fixed and variable costs are defined in theory but not applied, so rent and salaries get mixed into per-unit cost.
What to do instead
Memorise a plan skeleton: product or service, customers and market, operations, cost structure, pricing, break-even, risk and finance needed. For break-even, sort costs first, then use fixed cost divided by contribution per unit (price minus variable cost). Practise with a small electrical-service workshop example.
Candidates answer workplace-scenario questions about reporting a hazard or a near miss by choosing the option that resolves the issue quietly themselves, rather than following the reporting chain and recording it.
Scenarios are read as technical puzzles, so the candidate picks the fastest practical fix. The employability domain rewards procedure, documentation and escalation, which feel slower and are therefore skipped.
What to do instead
For any scenario, apply a fixed order: make safe, isolate or warn, report to the supervisor, record it. Choose the option that includes reporting and documentation even when a self-fix looks quicker, and practise by rewriting three near-miss scenarios into the make-safe, report, record format.