Distribution

Electric Power Distribution

  • Final Stage in the delivery of electric power

  • Carries Electricity from transmission system to individual consumer

Distribution System

  • All facilities and equipment connecting a transmission system to consumer’s equipment

  • Distribute electrical energy

  • Sequential flow of procedures, system, and activities which are designed and linked to facilitate and monitor the movement of goods and services from the source to the consumer

Measured in the Distribution System during Normal Conditions

  • Quality of voltage

  • frequency

  • resulting current

Primary Metering

  • direct to primary voltage

Primary Nominal Voltage

  • 13.2kV 13.8kV 24.5kV 69kV 115 kV

Secondary Nominal Voltage

230V 400V 460 V

Power Quality

  • knowing the characteristics of the distribution utility, its capabilities, and limitations

Voltage THD - Voltage Total Harmonic Distortion

Voltage Unbalance

  • Ave - low value / ave x 100

Voltage Mismatch

  • di tugma ang supply sa equipment

Tap Setting

  • increase by 2.5%

  • up to 5 tap only

LINE TO NEUTRAL - PHASE VOLTAGE

NEUTRAL - PASSAGEWAY

GROUND - RETURN TO EARTH

TRIPLEX ALL ALUMINUM CONDUCTOR 3/O

Effect of Utility Variations on Equipment Ratings

  • Must operate satisfactorily within the -10% to +10% voltage variation

Primary Voltages

  • large consumers are fed directly from distribution voltages

  • utility customers are connected to a transformer that reduces the distribution voltage to the low voltage "utilization voltage", "supply voltage" or "mains voltage" used by lighting and interior wiring systems.

Transformer

  • Passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits.

  • Primary winding of a transformer is connected to the input voltage supply and converts or transforms the electrical power into a magnetic field.

  • Electrical device that uses electromagnetic induction to pass an alternating current (AC) signal from one electric circuit to another, often changing (or "transforming") the voltage and electric current.

    PARTS
NAMEPLATE

SYMBOLS USED IN TRANSFORMER VOLTAGE RATINGS

Dash (-)

  • separate the voltage rating or ratings of separate windings.

  • 34500 Grd. Y / 19920 V – 240 / 120 V

Slant or Slash (/)

  • separate voltage to be applied or to be obtained from the same winding.

  • 13200 GRDY / 7620 V – 120 / 240 V

Cross (X)

  • separate voltages which can be obtained by reconnecting the coils of a winding in series or multiple combinations.

  • 34500 Grd. Y / 19920 V – 240 / 120 V X 139 / 277 V

PRIMARY VOLTAGE RATING COMMONLY USE

34500Grd. Y / 19920

  • Single-bushing DTs for line-to-ground connections on effectively grounded systems with line-to-line voltages of 34.5kV.

3600 / 6240Y

  • Two-bushing DTs for line-to-ground connection on system with line-to-line voltages of 6.24kV.

2400 / 4160Y

  • Two-bushing DTs for line-to-ground connection on system with line-to-line voltages of 4.16kV.

4800 / 8300Y

  • Two-bushing DTs for line-to-ground connection on system with line-to-line voltages of 8.3kV or for line-to-line connection on system with line-to-line voltage of 4.8kV.

13200

  • for line-to-line connection on system of 13.2kV line-to-line.

13200Grd.Y / 7620

  • Single-bushing DTs for line-to-ground connection on effectively grounded systems with line-to-line voltages of 13.2kV.

7620 / 13200Y

  • Two-bushing DTs for line-to-ground connection on system with line-to-line voltages of 13.2kV

DT NUMBER CODING SYSTEM OF MERALCO

DIFFERENCE BETWEEN 120/240- & 240/120-VOLTRATINGS

120/240

  • 2 Section secondary winding which can be connected in parallel for output voltage 120V, in series for output voltage 240V, or in series for 3-wire service for 120/240V output voltage.

  • 120V (2) = 240V

240/120

  • Mid-tapped secondary suitable for 2-wire service at voltage 240V, or for 3-wire service. Cannot be connected for 2-wire service at voltage 120V.

  • 240V/2 = 120V

Secondary Voltage

  • provided by distribution transformers that are connected to the primary system, which are usually associated with utilization voltages.

Electrical Load

  • consumes electric power such as appliances

  • converts electricity into other energy such as heat, light, motion etc.

Nature of Load

  • Resistive load

    • Obstruct the flow of electricity

    • consist of a coil and winding made up of copper or aluminum

    • produces magnetic field

    • Include any type of heating element

  • Inductive load

    • stores energy in the form of a magnetic field

    • current lags behind the supply voltage

    • lagging power factor

    • provide power to electric motor

  • Capacitive load

    • stores electrical energy in the form of an electrostatic charge

    • current leads behind the supply voltage

    • leading power factor

Power System Load

  • Domestic load

    • household appliances

    • usually single phase ac loads

    • operated by single phase ac supply

    • either lagging or unity factor

    • Resistive or inductive loads

  • Commercial load

    • business like office

  • Industrial load

    • small to large factories and manufacturing

    • induction motors

    • composite loads

  • Agriculture load

    • use in agriculture works

    • motor

Electrical Power Plant

  • Power Station

  • Generate Electricity

DT NAMEPLATEExternal Tap Changers

Operation

1. De-energize the DT

2. Loosen lock screw

3. Rotate switch to desired position

4. Tighten lock screw

5. Energize the DT

Internal Tap ChangerSchematic InnerSchematic Outer

Additive

  • 200kVA or smaller

  • 8.66 kV below

Subtractive

  • does not meet the criteria