Question { Bhel, 68087 }

What is the max demand on your transformer and your company?

Answer

Maximum Demand (kVA) is your peak demand of electricity from the grid. ... Your energy distribution company charges you for the maximum demand, so it costs you money. Maximum demand (MD) is the peak level of electricity demand recorded by TNB meter during a 30-minute interval in a month. The amount charged to a user is based on the recorded MD in kilowatt (kW) multiplied by the respective MD rate.

Company MD is sanctioned MD which you have to maintain to avoid penalty from Electricity Board

Question { L&T, 52948 }

How do you connect the capacitors on polyphase circuits?

Answer

A delta-connected bank of capacitors is usually applied to voltage classes of 2400 volts or less. In a three-phase system, to supply the same reactive power, the star connection requires a capacitor with a capacitance three times higher than the delta connected capacitor.

Capacitors shall be connected near to the load.Some times Capacitor Banks are connected with the Motor Control Center (MCC) or Power Control Center (PCC) for improving the P F of the system. The voltage rating shall be 10% higher than the system voltage.

Question { ACC, 122715 }

why the generating voltage in India is 11kV or why is it be
transmitted as multiples of 11

Answer

See all, It is cheaper to generate at a relative lower voltage and then step it up for transmission. Hence, most power generating plants are designed to operate at 11KV. Also generating voltages are designed in multiples of 1.11 or less considering the 10% or less voltage drop in the transmission lines & distribution lines.In olden days when the electricity becomes popular, the people had a misconception that in the transmission line there would be a voltage loss of around 10%.

Question { 132008 }

What is the meaning of Dyn11 of Transformer.

Answer

Dyn11 transformer means

Transformer has a delta connected primary winding (D) a star connected secondary (y) with the star point brought out (n) and a phase shift of 30 deg leading (11). ... The 11 indicates the LV winding leads the HV by 30 degrees.

Question { 23338 }

what is the use of Antipumping in HT breakers.

Answer

The function of Anti Pumping relay is to cut off the supply to CB closing coil in case of TNC switch spring failure and prevent CB hunting effect i.e. continuous closing, opening operation.

Question { Nalco, 11180 }

Does increase or decrease of reactive load affects the
Voltage.

Answer

Yes it will drop down vtg
increase in var can increase vtg

Question { HSL, 22669 }

What is PF? Formula for calculating PF in HT side?

Answer

It is ratio of True Real Power to Apparent power.
Cos phi = KW/KVA = R/Z = True Real Active Power / Apparent power

KW = sq root of 3 x V x i x Cos Phi

hence cos phi = KW / ( sq root of 3 x V x I)

Question { 14826 }

What is the difference between INVERTER and UPS?

Answer

In UPS after Mains failure power supply remains the same uninterrupted continuous without disturbance to the load.... While in inverter switching from Mains to the batteries will have momentary disturbance in power supply interruption will be observed

Question { 6285 }

is there or does RCCB work for single phase connection?

Answer

Yes, it works on Single phase.

Question { Emerson, 19701 }

what is the use of capacitor in online ups?

Answer

Not All UPSs Must Have Input Harmonic Filter Capacitors
Though almost all UPS systems use capacitors in their output, one UPS topology demonstrates that reliance on capacitors in the input is not required. Delta Conversion UPS configurations are now gaining wide acceptance as a means to assure maximum compatibility and stability of engine generators without adding large input capacitor-based harmonic filters.

Instead, this design applies two bidirectional power converters so that the primary delta converter acts like an active harmonic filter, maintaining less than 5% THD current distortion from no load to full load, without the use of capacitor-based filters. The UPS maintains power factor at an ideal unity PF, never falling leading or causing voltage problems on the generator.

The double conversion UPS consists of a one-direction rectifier/battery charger driving a one-direction inverter that powers the critical load.

The two converters of the Delta Conversion UPS are bidirectional, enabling the UPS to aid in the engine-generator's stability. These two converters are controlled so that, as a load, the delta conversion is a constant unity power factor load of a sine wave form from no load to full load And, the Delta Conversion UPS achieves this ideal unity power factor and low input harmonic distortion without the need of a large input capacitor bank.

Both capacitors I/p and o/p - AC AND DC Capacitor in UPS ARE USED FOR VTG FILTRATION OR SMOOTH OUTPUT POWER

Question { Emerson, 19701 }

what is the use of capacitor in online ups?

Answer

UPS systems also contain large banks of both DC electrolytic and AC polymeric film capacitors that degrade with time. The function of capacitors within the UPS is to filter out electrical fluctuations and provide clean power to the equipment being protected called “Supply Voltage Filtering” They are not static electrical components that operate in a circuit. Their design life is a mathematical function of manufacturers’ rated voltage, the voltage actually applied, the current running through them, ambient temperature, and thermal resistance. For all practical purposes, estimating service life would be based on manufacturers’ rated voltage combined with the device’s operating temperature.

Commonly at 7 year's service life span capacitor expires.

Question { 21685 }

What are protection of transformer on HT side & on LT side?

Answer

HT
Overvtg/undervtg, Earth fault,Surge protection, differential protection

LT
Undervtg, REF protection,Buccholz relay, sudden pressure relay, Overcurrent protection.

Question { Bhel, 2518 }

how work a harmonics filter(L-C combition).

Answer

Passive Flitering-

An LC circuit, tuned to each harmonic order to be filtered, is installed in parallel with the non-linear load. This bypass circuit absorbs the harmonics, thus avoiding their flow in the distribution network.

Generally speaking, the passive filter(LC series ckt in parallel with Non linear load ) is tuned to a harmonic order close to the order to be eliminated. Several parallel-connected branches of Passive filters can be used if a significant reduction in the distortion of a number of harmonic orders is required. It offers both power-factor correction and high current-filtering capacity .Passive filters also reduce the harmonic voltages in installations where the supply voltage is disturbed. If the level of reactive power supplied is high, it is advised to turn off the passive filter at times when the percent load is low.

AHC Active harmonics filter-
AHC comprising power electronics and can be installed in series or parallel with the non-linear load, compensate the harmonic current or voltage drawn by the load. A parallel-connected active harmonic conditioner (AHC) compensating the harmonic current (Iharm = -Iactiv) by injecting Iactiv in opposite phase.
The AHC injects in opposite phase active current the harmonics drawn by the non-linear load, such that the line current Is remains sinusoidal.

Hybrid Filtering (Combined Active & Passive Filter)
Passive and active filters are combined in a single system to constitute a hybrid filter. This new filtering solution offers the advantages of both types of filters and covers a wide range of power and performance levels.

Question { 6233 }

why control circuit voltage always chooses to be 110v and
220v? and in where it is 110v and 220v? and in where it AC
and DC?

Answer

Agreed with above answer additional missing information is control circuit vtg is DC fed from battery bank provided in the substation

Question { MSEB, 84889 }

What is full form of G.O.D in 11kv distribution?

Answer

It's Gang Operated Device, It is a most commonly used switch in small to medium substations, Pole mounted Substations is a gang-operated, air-break disconnect switch.

The “Gang” refers to the three phases being electrically or mechanically tied together so that the 3 phases open at the same time. The “Air Break” refers to a visible break in the air that allows crews to see that the switch is truly open.