SPM Pendawaian Domestik flashcards
SPM Pendawaian Domestik · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's law
- Current through a conductor is directly proportional to voltage and inversely proportional to resistance, expressed as V = I x R for DC and resistive AC circuits.
- Electrical power formula
- Power in watts equals voltage multiplied by current; for resistive loads also I squared times R or V squared divided by R.
- Series circuit rules
- The same current flows through every component, voltages add, and total resistance is the sum of individual resistances.
- Parallel circuit rules
- Voltage is the same across every branch, branch currents add, and total resistance is found from the reciprocal sum of branch resistances.
- Voltage drop formula
- For a single-phase circuit, Vd = (2 x rho x L x I) / A, with the factor two accounting for the outgoing and return conductors.
- Power factor
- Ratio of true power in watts to apparent power in volt-amperes; equals cosine of the phase angle between voltage and current.
- RCD trip time limits
- A 30 mA RCD should trip within 300 ms at rated residual current and within 40 ms at five times rated current when used for supplementary protection.
- TN-C-S earthing system
- Supply neutral and protective earth are combined in the distributor's network and separated at the installation origin into neutral and protective conductors.
- TT earthing system
- The installation has its own earth electrode independent of the supply earth, so earth fault protection normally relies on an RCD.
- Main protective bonding
- Connection of extraneous-conductive-parts such as water and gas pipes to the main earthing terminal to equalise potential and limit touch voltage.
- Discrimination
- Coordination of protective devices so the device nearest a fault operates first, preventing unnecessary loss of supply to healthy circuits.
- Breaking capacity
- Maximum prospective short-circuit current a protective device can safely interrupt without damage; must exceed the fault level at its point of installation.
- Loop-in lighting method
- Each luminaire is fed from a ceiling rose carrying permanent live, neutral, earth and switched live, with the switch drop connected at the rose.
- Two-way switching
- Two two-way switches connected by strapper conductors allow one lamp to be controlled from either of two positions.
- Diversity in maximum demand
- Assumption that not all connected load operates simultaneously; used to size the supply and consumer unit protective devices realistically.
- Ring final circuit
- A socket circuit where the cable forms a closed loop from the protective device, allowing smaller conductors and reducing voltage drop.
- Fused connection unit
- An accessory containing a fuse that supplies a fixed appliance or a spur, limiting the current the downstream cable must carry.
- Insulation resistance test
- Dead test at 500 V DC between live conductors and earth, with loads disconnected; acceptable result is at least 1 megohm.
- Earth fault loop impedance
- Total impedance of the earth fault path from the origin through the protective conductor and back to the supply; determines disconnection time.
- Prospective short-circuit current
- Maximum current that would flow at a point in the installation if a zero-impedance fault occurred there; used to verify breaking capacity.
- Polarity test
- Confirms line conductors connect to switch and to the centre pin of lamp holders, and that sockets have line, neutral and earth in correct positions.
- Ring circuit continuity test
- End-to-end resistance readings of line, neutral and earth are compared with cross-connected socket readings to confirm the ring is complete.
- Electricity Regulations 1994
- Malaysian regulations made under the Electricity Supply Act 1990 covering installation requirements, competent persons, inspection and testing.
- MS IEC 60364
- Malaysian standard for low-voltage electrical installations, covering design, protection, earthing, selection of equipment and verification.
- Conductor colour code
- Line is brown, neutral is blue, and protective earth is green-yellow; green-yellow must never be used for any other purpose.
- Suruhanjaya Tenaga role
- The Energy Commission regulates the electricity supply industry in Malaysia, issues competency certificates and enforces installation safety requirements.
- Schematic diagram
- Drawing showing electrical connections between components using standard symbols, independent of their physical position in the installation.
- Wiring diagram
- Drawing showing physical routing and terminal connections of conductors, including colour coding, used for installation and fault finding.
- Schedule of test results
- Document recording circuit details, protective device ratings, insulation resistance, loop impedance, short-circuit current, RCD times and polarity.
- Circuit chart
- Notice fixed at the consumer unit listing each protective device, its rating and the circuit it protects, updated whenever circuits change.
- Lockout-tagout
- Isolation procedure where every energy source is locked and tagged, then the circuit is proved dead before work begins.
- Hierarchy of control
- Order of risk reduction: eliminate the hazard, substitute, apply engineering controls, then administrative controls, with PPE as the last resort.
- Cable derating factors
- Correction factors for ambient temperature, grouping, thermal insulation and installation method applied to tabulated current-carrying capacity.