Electrical Circuits: Definitions and Components

• Electric circuits involve the interconnection of electrical components.
• Charge, denoted as q(t), is a fundamental quantity in electrical circuits.

Electrical Units and Definitions

• Current (i(t)) is the rate of charge flow, measured in Amperes (A): i = dq/dt.
• Voltage (v(t)) represents the rate of work done per unit charge, measured in Volts (V).
• Power (p(t)) is the rate at which work is done, measured in Watts (W).
• Energy is the capacity to do work, measured in Joules (J); 1 Wh = 3,600 J.
• Conductance (G) is the reciprocal of resistance (R), measured in Mhos or Siemens (S): G = 1/R.
• Power can be calculated using: P = vi = i²R = v²/R watts.

Circuit Components and Laws

• Circuit elements are the basic building blocks of a circuit.
• Active elements can generate energy (e.g., batteries, generators).
• Passive elements absorb energy (e.g., resistors, capacitors, inductors).
• Independent sources supply voltage or current regardless of other elements.
• Dependent sources rely on other elements to supply voltage or current.
• Ohm's Law: v = iR (relates voltage, current, and resistance in a resistor).
• Kirchhoff's Laws relate currents and voltages in an electrical network:
  • Kirchhoff's Current Law (KCL)
  • Kirchhoff's Voltage Law (KVL)

Basic Circuit Concepts: Nodes, Branches and Loops

• Branch: Represents a single element (i.e. voltage, resistor & etc)
• Node: The Meeting point between two or more branches.
• Loop: Any closed path in a circuit

Electrical Supplies and Safety

• Supply materials, consumables, and utilities are designed for general use.
• Convenience outlet: A device providing a convenient source of electrical energy for appliances.
• Male plug: Inserted into an outlet to conduct electricity.
• Lamp holder: Holds and protects incandescent or fluorescent lamps.
• Switch: Connects or disconnects electric current flow.
• Fuse: A circuit protection device that blows and cuts current when overloaded.
• Circuit breaker: Automatically cuts current during circuit trouble.
• Utility box: Encloses outlets and switches.
• Junction box: Connects or joins wires.

Wires and Cables

• Flat cord: Used for temporary wiring and extensions.
• Electrical wire/conductor: Material for electrical conduction.
• Stranded wire: Multiple strands joined.
• Solid wire: Single strand.
• Cables are larger than wires and contain two or more insulated wires in a jacket.

Electrical Conduits/Pipes

• Electrical conduits/pipes are materials used to protect and insulate wires.
• Rigid Non-metallic conduit (PVC) and Metallic conduit
• Flexible Non-metallic conduit or corrugated plastic conduit (CPC)
• Electrical tape protects and covers live wires.
• Rigid Steel Conduit - heavy-duty pipe has threaded ends
• Electrical Metallic Tubing (EMT) - relatively easy to bend, cut, and form. known as thin wall conduit
• Nonmetallic Conduits or PVC Conduits - circular in shape and generally corrugated, used in underground installations
• Galvanized Rigid Conduits (GRC) - coated with zinc for increasing resistance to corrosion and abrasion
• Intermediate Metal Conduits (IMC) - circular raceways that are rigid and have thinner walls as compared to rigid metal conduits
• Flexible Metallic Conduit - used to hold electrical wires and similar cabling
• Condulets - fitting resembling a pipe or box with a removable cover for access to electric conduits

Fastening devices

• Clamps: Used to hold and anchor electrical conduits to their proper position.
• Connectors: Join electrical circuits as an interface.
• Fasteners: Secure conduits to walls etc.

PEC (Philippine Electrical Code)

• PEC consists of rules for safe electricity use.
• PEC1: For electrical installation inside buildings.
• PEC2: For electrical installation outside buildings.
• Mandatory rules use "SHALL."
• Advisory rules use "SHOULD."

Objectives and Safe Use of Electricity

• Safe use of electricity aims to establish standards for various electrical applications.
• Adequacy ensures safety, but not necessarily efficiency or future expansion.

Wire and Cable Classifications

• Wires: Conductors 3.26mm or No.8AWG and smaller, typically copper or aluminum.
• Cables: Larger than wires, with two or more insulated wires wrapped in a jacket.
• Stranded Wires: A group of wires twisted to form a metallic string
• Solid Wires: Consists only of single conductor

Types of Conductors

• Copper or aluminum conductors: 1.60mm-500mm2 Stranded and Solid which may be used for overhead transmission lines and for ground wires.
• Thermoplastic Wires (Type TW): Copper 1.60mm- 500mm2 Solid and Stranded are flame retardant, moisture and oil resistant and used for building wiring in dry and wet locations & Heat
• Heat, Moisture Resistant and Flame Retardant Cable (Type THW) has usually seven strands of conductors in a cable used for building wiring in dry or wet locations
• Thermoplastic-Covered Fixture Wire (Type TF) 0.60mm-0.30mm2 Solid and Stranded may be solid or stranded used for wiring lighting fixtures and as terminal wires.
• Non-Metallic Sheathed Cable (Type NM) is 1.60mm-2.60mm Solid has 2 or 3 conductors inside the cable used for exposed or concealed installation in buildings
• Copper or Aluminum PE Insulated Wire has 2.60mm-1,000MCM which is weather resistant wire is used for line wire and primary distribution.
• Flat Cord (Type SPT) 1.02mm-1.60mm Stranded which has two sets of stranded conductors separated by insulators and is usually used for portable electrical equipment and for extension wiring of a single bulb.
• Air Conditioning Unit Safety Cord (Type SPT) is 1.60mm-2.00mm which consists of two conductors and a ground used for wiring air conditioning unit
• Underground Feeder and Branch Circuit Cable (Type UF) has 1.60mm-11.68mm which a jacketed cable and used for wiring installation direct burial
• Thermo Plastic Portable Cords (Types SJT & ST) Type SJT 1.02mm-2.05mm Type ST 1.02mm-4.11mm consists of 2 to 4 stranded conductors used for wiring construction of portable motors and appliances
• Intercome cable has 0.65mmis a shielded or unshielded cable has 3 conductors to 100 pairs, used for wiring interior communications, system and sound distribution jacketed
• Telephone Cable (Type CCP) is 0.40mm-0.91mm and is installed aerial and duct type for telephone wiring with color coded conductor insulators.
• Submersible Pump Cable is 1.60mm-11.68mm which is a thermoplastic insulated cable used for wiring submersible pumps of deep well water systems.
• Hypertemp 2000 Wire (Magnet Wire) is 0.078mm-4.11mm and is used for winding motors, oil filled transformers, high speed winding, and wet winding operations.
• Service Drop Cable is 4.11 mm - 11.68 mm, aluminum conductor with neutral messenger used for a service drop cable
• Armored Cable (Type ACT), (BX) is 1.60mm-6.54mm & has 2 or 3 conductors used for wiring installation in buildings
• Welding Cable is 1.29mm-11.68mm, flexible portable cable used for wiring cable of electric arc welding.
• Control Cable 1.60mm-2.05mm is a PVC insulated and jacketed multi-conductor control cable used for wiring installation of machinery controls.
• Power Cable is 3.36 mm - 1,000 MCM, used for underground, aerial, duct and direct burial wiring from 6,000 volts to 35 kilovolts.
• Temperature Wire (Type HI)is 1.02mm-3.26mm & is commonly used for wiring automobile engines and appliances with high temperature, and for switch board wiring.
• Royal Cord is 1. 65mm-5.19mm has 2 to 4 conductors, stranded and used for portable cords in electrical equipment.
• Telephone Cable (Type ADT) 0.65mm, consists of 6 pairs through 909 pairs used for aerial and duct installation.
• Appliance Or Electric Heater Cable is O. 65mm-2.05mm is used for wiring cord of heating equipment in dry locations.
• Asbestos Covered Nickel Cord (Rockbestos)is 0.25mm-1.60mm and is used for wiring electric ranges, water heater, stoves and hairdryers where both heat and moisture resistance is desirable.
• Automotive Wire 1.02mm-6.54mm is used for wiring spark plug and battery cable of automobile, trucks, and other vehicles.
• Auto Cable PVC and Braided is used for wiring automobile light and for hook- up wires.
• Service Entrance Cable (Type SE) consists of two or more insulated conductors with one or more bare conductors for grounding.
• Self-Supporting Aerial Telephone Cable is used for aerial telephone wiring with color code insulation of conductors.
• Machine Tool Wireis used for wiring machine tools, appliances and control circuits.
• Coaxial Cableis used for radio frequency antenna installation and radar receiver installation.
• Direct Burial Telephone Cable is used for wiring installation of telephone lines conductors have different colors on insulations.
• Durex Wire is used for building wiring especially for interior wiring.
• Steel Tape Armored Cable With Ground Wires is used for general wiring installation including underground.
• Duralene (Type WP) is polyethylene insulated line wire used for wiring installation of residential buildings.
• Switchboard Semi- Rigid Plastic Insulation is a stranded cable for wiring switch boards inside power plant.
• All Plastic Parallel Cordis used for wiring pendant or portable equipment or device.
• Nonmetallic Sheathed Cable (Type NMC) is a multi- conductor cable used for interior wiring in dry and wet location

Governing bodies of PEC

• The use of PEC is mandated BY R.A 7920 (formely R.A 184) als known as the new electrical engineering law.
  • P.D 1096- national building code
  • P.D 1185 - fire code of the philippines
  • Structural code R.A 7920 - for registration of electrical engineers and electricians.
• Government authorities who implement PEC:
  1. Office of the building official
  2. Office of the city electrician (city electrical supervising engineer).
  3. Office of the municipal electrician ( municipal electrical supervising engineer)
  4. Regional office of the dole.

Scope of PEC (Philippine Electrical Code)

1. Public and private buidlings
2. Electrical generating plants
3. Temporary and permanent substation
4. Industrial plants
5. Transformer stations
6. Railway switchyards
7. Yards carnival parking etc
8. Water craft
9. Dockyards
10. Airfields
11. Quarries and mines
12. Mobile homes, travles trailers and recreational vehicles
13. Offshore facilities
14. other premises which requires electrical installation except to those which are done in:
    • Aircraft
    • Motor vehicles
    • Railway rolling stocks

Requirements for Permits and Inspections

• A permit is required before electrical installation.
• An inspection is also required after the installation.
• Certificate to final electrical inspection (CFEI) issued by the authority.
• A permit is not required for;
  • The installation of electrical portable equipment rated not more than 1,200 va
  • Reconnection of disconnected service due to non-payment of electric bill or change of occupants for a period of one year.
• Requirements for Electrical Permit a) An application form (DPWH form No. 77-001-E) signed by a duly registered Professional Electrical Engineer.

Plans requirement

• The application shall include additionally, the name and signature and seal of the electrical practitioner who will take charge of the installations as well as the signature of the owner or his authorized representative.
• Five sets of plans and specifications bearing the signature and seal of the responsible Professional Electrical Engineer shall be submitted together with the application

Electrical Circuits in Buildings

• Buildings should be supplied by only one service, with exceptions.
• EXCEPTIONS
  1. For fire pump separate service is required.
  2. For emergency electrical system where a separate service is required.
  3. Multiple-Occupancy building
  4. Capacity Requirements
  5. Building of Large Area (10,000 m2 or more Total Area ).
  6. For different voltage characteristics

Service Wires

• OVERHEAD SERVICE: Drop conductor has adequate mechanical strength.
• The conductors shall not be smaller than 8 mm2 copper, 14 mm2 aluminum or copper-clad aluminum

Clearance Requirements

CLEARANCES a) Above Roofs. Conductors shall have a vertical clearance of not less than 2,500 mm from the roof surface.

• Vertical Clearance from Ground
  • 3,100 mm at the electric service entrance to buildings, or at the drip loop of the building electric entrance, or above areas or sidewalks
  • 3,700 mm - for those areas listed in the 4,600 mm classification when the voltage is limited to 600 volts to ground.
  • 4,600 mm - over residential property and driveways, and those commercial areas not subject to truck traffic.
  • 5,500 mm - over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land transversed by vehicles such as cultivated, grazing, forest, and orchard.

Underground Service

• UNDERGROUND SERVICE: LATERAL CONDUCTOR connects street main to building wall.
• Insulated service-lateral conductor shall withstand atmospheric exposure.
• The conductors shall not be smaller than 5.5 mm 2copper or 8.0 mm2 aluminum or copper-clad aluminum.

Enclosures

• Where two to six service disconnecting means in separate enclosures supply separate loads from one service drop or lateral, one set of service entrance conductors shall be permitted to supply each or several such service equipment enclosures.
• EXCEEPTIONS For installations to supply only limited loads of a single branch circuit such as small polyphase power, controlled water heaters and the like, they shall not be smaller than 3.5 mm2 copper or 5.0 mm2aluminum or copper- clad aluminum.

Service Entrance

• The service is defined as the portion of the supply which extends from the street main duct or transformer to the service switch or switchboard of the building supply.
• TYPES: 1. Overhead Service Entrance The most common type of service entrance employed by the power companies supplying electricity which is either a 2, 3 or 4-wire connection. 2. The Underground Service Entrance The underground service entrance consists extending of a raceway conduit from the building to the property line where it is tapped to the main.
• EXCEPTIONS: 1. Buildings with more than one occupancy. 2. Where two to six service disconnecting means in a separate enclosures are grouped at one location and supply separate loads from one service drop or lateral.
• INSTALLATION OF SERVICE CONDUCTORS: Service entrance conductors shall be installed in accordance with the applicable requirements

Service Entrance Protection

• PROTECTION: Service entrance conductors subjected to physical protected in any of the following ways or methods:
  1. By RMC
  2. By IMC
  3. By RNMC suitable for the location
  4. By EMT
  5. Type MC cable or other approved means
• The damage shall be SERVICE EQUIPMENT: DISCONNECTING MEANS GENERAL: The service disconnecting means shall be provided to disconnect all conductors in a building or other structures from the service-entrance conductor
  • NUMBER OF DISCONNECTING MEANS: The service disconnecting means for each set or each subset of service entrance conductor shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, or in a switchboard.
  • LOCATION: The service disconnecting means shall be installed either inside or outside the building or other structure at a readily accessible location nearest the point of entrance of the service
  • ENTRANCE CONDUCTOR RATING: The service disconnecting means shall have a rating of not less than the load to be carried. In no case shall the rating be lower than specified through:
  1. One circuit installation The service disconnecting means shall have a rating of not less than 15 amperes.
  2. Two circuit installation - The service disconnecting means shall have a rating of not less than 30 amperes.
  3. One family dwelling The service disconnecting means shall have a rating of: 60 A
  4. Others For all other installations, the service disconnecting means shall have a rating of not less than 40 amperes. NOTES: The service disconnecting means shall simultaneously disconnect all ungrounded conductors and shall be capable of being closed on a fault equal to or greater than the maximum available short-circuit current.

Feeders:

• Essential considerations being adapted or followed. 1.On large installation, one feeder is provided for each floor.

2. In small installations, one or two feeders is satisfactory.
3. Feeder for motor must be separate and independent from the light circuits.
4. Feeders requiring more than 50 mm diameter conduit should not be used.
5. Feeders should be subdivided if there are several bends or offsets because a 50 mm conduit is the largest that could be economically used.
6. Feeders radiating from the distributing panel should be provided each with a properly rated switch and circuit breaker.
7. Good practice dictates that feeders and main shall be installed inside a conduit pipe as it carries high voltage that should be well protected.

• REQUIRED PARTS OF A STANDARD ELECTRICAL PLAN

General Notes:

A. GENERAL NOTES / SPECIFICATION Specification written on electrical plan should indicate :

1. That the design is done in accordance with the P.E.C. and all electrical works shall comply with the provisions of all authorities having jurisdiction on the use of electrical power.
2. The nature of the service including voltage, phase and frequency .
3. The type of approved wiring to used in installing service entrance, feeders, sub-feeders, branch circuit conductors, remote control system, fire protection, signal and communication system.
4. All other aspects and details that the designer and the owner would want to be done in the actual construction of the project. - EXAMPLE:
5. Works here under shall comply with the latest edition of the P.E.C, the national building & Meralco. code, municipal or city ordinances, office of the municipal or city electrician,
6. Type of services shall be 230 volts, 1 phase, 2 wire system, 60 hertz and there shall be only one service drop to the building.
7. Method of wiring shall be EMT both exposed and embedded work with proper fitting and supports.
8. All materials and equipment shall be new and approved type for both location and purpose intended.
9. All lighting and convenience outlet circuit homeruns shall be wired with no less than 2 sq. mm and 3.5 sq. mm respectively, unless otherwise indicated on the plan.

Symbols and Locations

• B. LEGEND AND SYMBOLS The legend or symbols shall show symbols or configurations and figures of devices and equipment used. LOCATION PLAN Location or site plan with proposed structures and owner's land drawn to appropriate metric scale shall show:
• Bordering areas showing public or well known streets.
  • Location of service drop, service equipment and nearest pole of the utility company furnishing electrical energy.
  • Clearance of the path or run of service drops and service structure wires to adjacent existing or proposed structures.
• Lighting and power panel board shall be circuit breaker type surface or flushed mounted or as indicated on the plan; door shall be provided with locked and milled key, a line circuit directory card and holder shall be provided in innerface or door. Whenever required and necessary, full boxes and junction boxes of proper sizes shall be installed at convenient and inconspicuous locations although. such boxes are not shown on the plans nor mentioned in the specification

Electricity and EMF

• Electricity- is energy transported by the motion of electrons, due to Faraday Effect. Basic Concepts: Voltage - V - Potential to Move Charge (volts); Current - I-Charge Movement (amperes or amps); Resistance - R-V = IxR (R in =ohms); PowerPIxV = I2xR (watts electric current means the flow of electrons from one end of a conductor to another end. Its symbol is 'I'. And its unit is ampere.
• Current (I) = Q/t = Ampere Ampere : When charge of 1 coulomb passes through a point in 1 seconds, it is said that a current of 1 Ampere is flowing. Ampere =Coulomb/Second
• Potential Difference: Defined as Work/energy Required to be done to move unit charge from one point to another in the circuit is called voltage or potential difference
• Voltage or Potential Difference= W/Q =
• Work/Charge Conductors: Material which allow the current to flow easily through them are called Conductors and Insulator: Material which greatly oppose the current flow i.e. do not allow the current to pass through it are called Insulators.
• Resistance: Resistance is the opposition that a substance offers to the flow of electric current It is represented by the uppercase letter R. Resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (1)

Resistance Units

■Specific resistance : Defined as the electrical resistance offered by unit length and unit cross section of a material when a known voltage is applied at its ends. Mathematically P = RA/l, where P is specific resistance. ■Conductance: is inverse to the Resistance, and defined as Ratio of Current to voltage and is denoted as G unit is mho,siemens Conductor: allows the flow of an electrical current in one or more directions. Semiconductors:crystalline or amorphous solids with distinct electrical characteristics. Insulator: Material whose internal electric charges do not flow freely, and therefore make it nearly impossible to conduct an electric current.

• Alternating Current :AC, magnitude and direction both changes with time, Direct Current In DC, the direction and magnitude of current remains constant.

Domestic Electricity

• Domesticelectric Supply is supplied to houses in two different phases of 240 - 420 V
• Single phase supply consists of two wires Live wire (red) and Neutral Wire (black)
• Three phase supply consists of 4 wires three live wires and one neutral wire.
• Fuseis a thin piece of wire with low melting point connected at its end in a fuse plug with the function of fuse wireis to protect the electrical appliances from heavy current.

Fuse Types

• Rewirable Fuses : Most commonly used in domestic wiring and small scale usage. Consists of porcelain base which holds the wires being cheaper and normally in circuits 15 A fuse is used.
• Cartridge Fuses: Fuse with a completely closed container and there are contacts on either side.

Circuit Breakers

• Miniature Circuit Breaker: MCBis a device that is used to break the circuit at the time of excess of current and protects the device from the appliances from the damage.
• ELCB:Earth Leakage Circuit Breaker: a device is which breaks the circuit when there is leakage of the current in the system.
• RCCB: Residual Current Circuit Breaker, a circuit breaker that breaks the circuit when there is imbalance of current between the live and the neutral wire this imbalance can be due to the current leakage.

Earthing

• Earthing is used to protect us from an electrical shock. By providing a path for a fault current to flow to earth and to protect the building machinery and appliances from short circuit.

Earthing Types

• Conventional Earthing: system , calls for digging of a large pit into which a GI pipe or a copper plate is positioned in the middle layers of charcoal and salt with requires maintenance and pouring of water at regular interval.
• Wire Earthing: usually adopted in the rocky terrain. using a copper wire.
• Rod Earthing: a G.I. rod buried to a depth of 200 to 300 to this rod the earthing wire is clamped.
• Pipe Earthing: pipe of 38mm diameter and 2m long is used as an earth electrode and the pipe covered by charcoal.
• Plate Earthing Used to set plate by 0.3mmx 0.3mm covered to dirt.

Ceiling Accessories

• Ceiling Roses are either the Two-Plate Ceiling Rose or the Three-Plate Ceiling Rose
• Adapter is used to power supply to small Instruments and made of backalite material. Connector generally use to connect relay and timers; with tube light and fans. Distribution board is used to connected to two circuits or more
• Socket Outlets consists socket base with two or three terminals which is used to gain power from socket outlet with Two pin plugs consists of Brass pins one is phase and other is Neutral or Three pin plugs and Three pin plugs. Used to connect celling,mounting blocks

Wall switches

• Main switch: to control electrical system, type Double pole Iron clad Switch or Triple pole Iron clad switch
• Wiring types based on insulation
• Tough rubber sheathed wire or Cab Tyre Sheathed(T.R.S)
  • Poly Vinyl Chloride wire (P.V.C.)
  • Lead Covered Wire
  • weather proof wires
  • Flexible wire
  • MICC wire (Mineral Insulated Copper Covered Wire)

Other types of Wires

• T.R.S. (Tough Rubber Sheathed) wires: Consist of the ordinary rubber coated conductors with an additional sheath of tough rubber used in house wiring & industrial wiring and available in 250/440V only
  • Weatherproof wire has cotton breeding with water proof. But it is flammable so no in use now. LC wire: Lead pipe on rubber insulation & its coating on conductor and its coating on conductor.
  • It is called mineral insulated copper covered wire,where copper conductor coated is with magnesium oxide.

Pvc wires:

Advantages as follows:

• High dielectric strength
• High tensile strength
• More defense against moisture
• High life Flexible wires: Composed with thin conductor where flexibility of wire is more important and insulated to household purposes.

Wiring Systems and Advantages

• Cleat wiring : wherecost is the main criteria
• Easy installation.
  • Materials can be retrieved for reuse.
  • Flexibility provided for inspection, modifications and expansion. relatively economical.

Cleat Wiring:Disadvantages

• Apperance is not good.
• Open system of wiring requiring regular cleaning.
• Higher risk of mechanical injury.

Battern Wiring

• Wires sheathed in tough rubber are used which are quite flexible. and gives a good appearance if properly erected.

Battern Wiring

Advantages Easy Installation,Durable, lower Risk of Short Cicut and Cheaper than Casing and Capacity,Gives and good Apperance if Properly Erected

Battern Wiring: Disadvantages

Risk of Mechanical injury and Skilled workers are required

Metal sheated

Advantages: easy interllation, highly durable Dissadvantages: expensive, Requires Skiled labour and very Expensive

Casing and Caping

Cheap but gives good Isalation, easy to fix

Conduit wiring

Cable run through pvc pipes and protection against meshanical injury

• No risk of Fire and protection against Mechanical
• Earthing and continuty assured
• shock Proof and aesthetic in apparence Disadvantage: Complicated to Elect

Affecting The Choice Of Wiring

• Affect Factors System: Affecting The Choice, Wiring wiring system for a depending factors:
• Durbility,Safety,Apperance,Cost,Durability,mMechanical Safety ,Maintenance Cost ,Mechanical safety,Accessibility 4