Maharashtra SSC Power Consumer Energy Meter Pre-Voc/NSQF flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's law

For a resistive circuit, voltage equals current multiplied by resistance (V = I × R). Power equals voltage times current, or current squared times resistance.

One kWh unit

One kilowatt-hour equals 3.6 million joules and is the unit shown on a consumer bill. A 1000 W load running one hour consumes exactly one unit.

Power factor

Ratio of real power in kW to apparent power in kVA, equal to cosine of the phase angle. Low power factor raises current for the same kW and increases losses.

Meter constant

Number of disc revolutions per kWh on an induction meter, or pulses per kWh on an electronic meter. Energy equals pulses counted divided by the constant.

Accuracy class

Maximum permissible percentage error of a meter under reference conditions. Class 1.0 allows plus or minus one percent; class 0.5 is twice as tight.

Creep test

Test with rated voltage applied and zero current. The disc must make less than one revolution, and an electronic meter must emit no energy pulse.

Starting current

Lowest current at which the meter begins to rotate continuously. Induction meters must start at 0.5 percent of basic current at unity power factor.

Induction energy meter

Electromechanical meter with voltage and current electromagnets driving an aluminium disc. A permanent magnet brakes the disc so speed is proportional to power.

Static energy meter

Electronic meter with no moving parts. Voltage and current signals are multiplied by a metering chip and integrated into kWh registers stored in memory.

Prepaid meter

Meter that supplies energy only while purchased credit remains. A built-in relay disconnects the load at zero balance and reconnects after recharge.

Smart meter

Electronic meter with two-way communication, remote reading, time-of-day registers, and tamper event logging. It supports remote connect and disconnect commands.

Braking magnet

Permanent magnet in an induction meter that produces braking torque proportional to disc speed. Moving it radially changes the full-load error adjustment.

Shading coil

Copper ring on part of a voltage magnet pole that shifts flux phase. It creates the torque angle needed for correct registration at unity power factor.

Light-load compensation

Small adjustable copper loop or vane near the voltage magnet that adds slight driving torque to overcome bearing and register friction at very low currents.

Meter terminal block

Insulated block carrying incoming and outgoing phase and neutral conductors. Screws are tightened to the maker's torque to prevent heating and contact resistance.

Meter mounting height

Meters are fixed vertically on a rigid dry surface roughly 1.5 to 1.8 metres above floor level, so the display and terminal cover are accessible.

CT secondary open circuit

Opening a current transformer secondary while primary current flows produces dangerous high voltage. Short the secondary at the test block before removing the meter.

CT burden

Total volt-ampere load on a current transformer secondary, including meter and leads. Exceeding rated burden causes ratio and phase errors in metering.

Multiplying factor

CT ratio multiplied by PT ratio. Primary energy equals the meter reading difference multiplied by this factor, used for all transformer-operated metering.

Pointer dial reading

Read pointer dials from the lowest-value dial upward. When a pointer lies between two numbers, record the lower number, then apply the multiplying factor.

Maximum demand register

Records the highest average kVA or kW over the demand interval, usually thirty minutes, during the billing cycle. It is reset after each billing.

Percentage error formula

Error equals meter energy minus standard energy, divided by standard energy, multiplied by one hundred. Positive means fast, negative means slow.

Disc revolution timing

Time for N revolutions equals N times 3600, divided by meter constant in rev/kWh times applied kW. Compare measured time with this calculated value.

Calibration traceability

Reference standards used for meter testing must have valid calibration certificates linked to a national laboratory, so measured errors are legally defensible.

Hot terminal symptom

Discoloured or warm terminal block indicates loose screw or overload. Isolate supply, clean or replace the block, and retighten to specified torque.

Jewel bearing wear

Worn disc bearings cause slow registration or rubbing. Replacing the bearing restores accuracy, and the meter must be recalibrated afterwards.

Meter not registering

With load on, check supply at meter terminals, meter fuse, voltage coil or input, and loose connections. A failed voltage circuit gives zero registration.

Wrong CT ratio setting

If the ratio programmed in the meter differs from the installed CT, all readings scale wrongly. Verify the setting against the CT nameplate.

Two-part tariff

Consumer charge made of a fixed or demand charge based on connected load or contract demand, plus an energy charge per kWh actually consumed.

Slab tariff

Per-unit rate increases in consumption bands. Each band's rate applies only to units falling in that band, not to the whole consumption.

Prove dead

After isolation, test the conductors with a proven voltage tester before touching them. Treat every conductor as live until this test confirms otherwise.

Clamp meter use

Measures current by clamping around one conductor without breaking the circuit. Clamping around both phase and neutral cancels the field and reads near zero.