Electrical Systems and Materials PDF

ELECTRICAL SYSTEMS AND MATERIALS I. Service and Utilization THE FIRST STEP IN DEVELOPING AN understanding of building electrical systems is to examine the means by which electric service is brought into a facility. I. ELECTRIC SERVICE - Electric service is the delivery of electrica...

ELECTRICAL SYSTEMS AND MATERIALS I. Service and Utilization THE FIRST STEP IN DEVELOPING AN understanding of building electrical systems is to examine the means by which electric service is brought into a facility. I. ELECTRIC SERVICE - Electric service is the delivery of electrical power from a utility company to a building or facility. - It's the process of bringing electricity from the power grid to your location, enabling you to use appliances, lights, and other electrical equipment. The importance of Electric Service - Electric service is the foundation of any building’s electrical system. - Understanding the process of bringing electricity into a facility is crucial for safety, efficiency, and compliance. TYPES OF SERVICE CONNECTIONS 1. Overhead - Wires running from pole to the building, typically suspended above ground on utility. 2. Underground - Wires buried underground to the building, running from the utility company’s underground infrastructure to the building. 3. Lateral- the wires run horizontally from a utility line to the bui FEATURES LOCATION APPEARANCE COMMON USE Service Drop Overhead Visible wires Residential areas Service Lateral Underground Hidden underground Commercial/ industrial/ areas where overhead lines  are impractical CODES AND STANDARDS: 1. National Electrical Code © National Fire Protection Association; in particular, Section 230. Article 230: provides the installation requirements for service conductors and service equipment. 2. National Electrical Safety Code, published by (IEEE) This code is recognized by the American National Standards Institute (ANSI). It deals with clearances for overhead lines, grounding methods, underground construction, and related matters. 3. Utility Standards Each electric utility company has its own standards and requirements for service connection. UTILITY RESPONSIBILITY - Public utilities are required to provide service up to your property SERVICE TAP - The point where the service connection is made to the utility lines. SERVICE TAP LOCATION - The connection point is typically at or beyond your property line, agreed upon by both you and the utility. USER’S RESPONSIBILITY - Electrical works on your property is usually your expense AESTHETICS - Utilities are increasingly focused on “beautification” programs to improve the appearance of their equipment. FACTORS INFLUENCING SERVICE TYPE Length of the service run Type of terrain Customer participation in the cost of service installation Service voltage Size and nature of the electric load Importance of appearance  Local practices and ordinances Maintenance and service reliability Weather conditions Type of interbuilding distribution, if applicable II. Overhead Service Advantages & Considerations FEATURE DESCRIPTION Cost Lower installation cost compared to underground lines. Distance & voltage Often preferred for long distances and high voltages (above 5000V) due to cost-effectiveness. Terrain & Load More economical in rocky terrain or when heavy electrical loads are involved. Maintenance & Repairs Easier to maintain and repair, with faults readily identified. Reliability Can be susceptible to weather-related outages, especially in severe conditions. Weather Resistance Less resistant to severe weather conditions (snow, wind, ice) compared to underground lines. Redundancy Reliability can be improved by taking service from two separate overhead lines. Cable Type Various types available, including bare, weatherproof, and preassembled aerial cable, each suited for different voltage levels and applications. III. Underground Service Advantages, Disadvantages, and considerations Pros: FEATURE DESCRIPTION Aesthetic Eliminates visual clutter of overhead wires, improving the look of the area. Reliability Less susceptible to weather-related outages caused by wind, ice, of falling trees. Longevity Protected from the elements, leading to a longer lifespan. Cons: FEATURE DESCRIPTION Cost Significantly more expensive to install that overhead lines. Maintenance & Repairs Direct-buried cables are harder to repair, as tey can’t be easily pulled out, leading to longer restoration times. Considerations: FEATURE DESCRIPTION Cost Premium The additional cost of raceway installation, including any required handholes. Repair service The cost and availability of repair services for customer-owned underground laterals. Outage history The history of outages for direct-buried installations in the area by the same installer. Outage impact The impact of an outage in terms of time delays, inconvenience, and potential costs for businesses. IV. Underground Wiring UNDERGROUND WIRING - The methods available for underground wiring are: Direct burial - Low cost and easy installation, but challenging to repair. Installation in Type I, concrete-encased duct - High strength and permanence, but the most expensive option.  Installation in Type II, direct burial duct - Moderate cost with less strength, suitable for undisturbed earth or light paving. NONMETALLIC DUCT (CONDUIT) - intended for underground electrical use. - most frequently used without concrete encasement for low-voltage and signal wiring and with encasement for high-voltage wiring. - Advantages over steel conduit include lower cost and corrosion resistance. - available in two wall thicknesses. NEMA (National Electrical Manufacturers Association) Type I - Thinner wall, requires at least 2 inches of concrete encasement. NEMA (National Electrical Manufacturers Association) Type II - Heavy wall for direct burial without concrete encasement. Duct Installation: When runs exceed several hundred feet, a pulling handhole or manhole is needed.  Handholes: Suitable for low-voltage cables and small runs. Manholes: Designed for high-voltage cables and larger duct banks. - Precast handholes and manholes: Available in standard sizes and typically cheaper than field-formed units. Cable Requirements: Underground wiring requires specially manufactured and approved cables. Type SE (service entrance) cable: Basic service entrance cable with moisture- and flame-resistant covering. SE type U or USE cable: SE cable with moisture proofing for underground use. Type UF (underground feeder) cable:. Underground cable for other than service runs. To distribute power from an existing building to outdoor lighting fixtures, pumps, outbuildings and other outdoor equipment. V. Service Equipment Transformers: a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits.  interposed between the high-voltage incoming utility lines and the secondary service conductors. essential when the building's utilization voltage differs from the service voltage supplied by the utility. Location ○ Pole-mounted - mounted on high electrical-grade poles for power distribution or pad-mounted - a ground-mounted electric power distribution transformer in a locked steel cabinet mounted on a concrete pad. Outside of the building. ○ Installed in a room or vault inside the building LAGAY PICTURE HEHEHE VI. Service Equipment Arrangements and Metering Metering: - Measures the amount of electrical energy consumption.  - must be installed before the building’s service entrance switch. It can be done at the utility or facility voltage, and either at the service point or inside the building. Accessibility for utility personnel is crucial. Remote Meter Reading: Many facilities now utilize remote meter reading, but meters must still be available for inspection by the utility. High-Voltage vs. Low-Voltage Service: High-Voltage Service: The owner provides transformers and related equipment beyond the service connection, usually resulting in lower billing rates. Low-Voltage Service: The utility supplies all necessary equipment, leading to higher billing rates to cover costs associated with transformers. Single Meter: For single-occupant buildings or those with included electric energy in rent, only one meter is needed, which can be integrated into the main switchboard or mounted independently. Master Metering vs. Submetering: Master Meter: the meter that measures the utility usage of an entire building. Federal regulations prohibit master metering in new constructions to prevent energy waste. Submeter: built out past the master meter, and it measures a certain area of the building that the master meter measures. Submetering is beneficial for conservation and monitoring energy usage. Contract Drawings: Low-voltage underground service details should show separate mounting for the service switch and meters. VII. Service Switches ELECTRICAL SERVICE SWITCHES Disconnect all the wiring in the building from the electrical power supply.  Prevents electrical hazards during emergencies (e.g., fires). Readily accessible near service conductors' entry point. If not feasible, service conductors may be run in concrete encasement under a building—and are considered “outside the building” up to the point at which they emerge from the floor in the building 1 to 6 properly rated switches. Also, frequently assembled into a switchboard. Components: - Switches - Circuit Breakers - Fuses From book from google VIII. Switches TRADITIONAL ELECTRICAL SWITCHES - Used to control the flow of electricity in a circuit by physically connecting or disconnecting two electrical conductors. - Mechanical switches close and open an electric circuit Close circuit - physically moving two conductors into contact with each other. Open circuit - physically separating two conductors. - The motive force can be supplied by hand, an electrical coil, a spring, or a motor - Solid-state switches perform the same electrical switching function but by a completely different process, without moving parts and have a longer operational lifetime. (that will be discussed by other group) COMMON TYPES OF SWITCHES 1. Single-pole single-throw switch. - one output and one input - on-off switching - Basic function: Controls a single circuit from one location. - Example: A simple light switch in your home. 2. Two-pole single-throw switch. - Basic function: Controls two separate circuits from one location. When the switch is in the "on" position, it connects both circuits. When it's in the "off" position, it disconnects both circuits. - Example: Used in electrical panels to control two different branches of a circuit. 3. Three-pole and solid-neutral (3P and SN) switch. - Basic function: Connects or disconnects three circuits independently, with a shared neutral. A 3P and SN switch is like a three-way switch that controls three separate circuits instead of just one. - Example: Commonly used in motor control applications. 4. Single-pole double-throw switch (also called, in small sizes, a 3-way switch). - Basic function: Controls a single circuit from two locations. It has three terminals: one common terminal and two traveler terminals. - Example: Used to control a light from both ends of a hallway.  5. Single-pole double-throw switch with center “off” position (in control work called hand-off automatic switch). - similar to a regular 3-way switch, but it has an additional center position that acts as an "off" position. This center position disconnects the circuit completely, providing a manual override for automatic control systems. - Basic function: Controls a single circuit from two locations, with a neutral "off" position. - Example: Used in control systems to provide a "manual-automatic" switch. - This switch allows you to manually turn a circuit off, even if it's normally controlled automatically. 6. Use of two single-pole, double-throw (3-way) switches for switching a lighting circuit from two locations - Two 3-way switches that can provide more flexibility in lightning control from two locations. - Operation: Flipping either switch will change the path of electricity, allowing the light to be turned on or off from either location. LOVELY IGDI POON SA OPEN CONTACT HANGGANG BABA NAKAKARIBONG SA LIBRO Open contact: This represents a pair of electrical terminals that are not connected. When a switch or relay is in this position, the circuit is open and no current can flow. Closed contact: This represents a pair of electrical terminals that are connected. When a switch or relay is in this position, the circuit is closed and current can flow. Latching contact: This is a special type of contact that maintains its position even after the activating force is removed. It can be either open or closed, and its position is determined by the previous state. Position 1: This represents the initial state of the latching contact. It can be either open or closed. Position 2: This represents the alternative state of the latching contact. It is the opposite of Position 1.  Operating coil: This is an electromagnetic coil that is used to activate the switch or relay. When a current flows through the coil, it creates a magnetic field that causes the switch or relay to move and change the position of the contacts. Control Equipment Enclosures NEMA Designation: Type Description Application 1 General-purpose Dry, indoor use 2 Dripproof Indoor, subject to dripping 3 Dust-tight, rain-tight, and Indoor/outdoor, where subject sleet-resistant to windblown dust and water 3R Rainproof and sleet-resistant Outdoor, subject to falling rain, snow, and sleet 3S Dust-tight, rain-tight, and Outdoor, subject to sleet-proof windblown water, dust, and sleet; most severe exterior duty 4 Watertight and dust-tight Indoor/outdoor, subject to water from all directions; not sleetproof 4X Watertight, dust-tight, Same as type 4 with added corrosion-resistant corrosion protection 7-9 Hazardous Differing in application by class and group of hazardous use; see NEC 12 Industrial use, dust-tight, and Indoor only, general use,  drip-tight industrial and other “dirty” environments An ELECTRICAL SWITCH is characterized by several ratings and specifications, including current and voltage ratings, duty type, poles and throws, fusibility, and enclosure type. Current Rating: the amount of current that the switch can carry continuously and interrupt safely. Switches intended for motor control are rated in horsepower (kW Voltage Rating: Specifies the voltage class (e.g., 250 V, 600 V, 5 kV) of the switch. General-Duty vs. Heavy-Duty: General-duty switches are for occasional use in lighting and power circuits, while heavy-duty (HD) switches are designed for frequent operation and high fault currents. Poles and Throws: Switches can have multiple poles (1-5) and throws, with "P" denoting poles (e.g., 3P for three poles). A single-throw switch is the default unless specified otherwise. Solid Neutral Switches: Most switches maintain an unbroken neutral connection, referred to as a solid neutral (SN) switch, following NEC guidelines. Fusibility: Switches can be fusible (with fuses) or nonfusible (without fuses). Enclosures: All switches are housed in enclosures, standardized by NEMA for various applications. Example: A switch describes:HD, 3P & SN, 200A/150AF, 600 V, in NEMA 12 enclosure.might be described as “heavy-duty, 3 poles, solid neutral, 200A with 150A fuses, rated for 600V, in NEMA 12 enclosure,” summarizing its key attributes.