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electrical glossary
Welcome to an A-to-Z Electrical Glossary for test, measure, and electrical terms. This comprehensive guide is tailored for professionals requiring precision and clarity in electrical testing, measurement, and equipment hire. Whether you're looking to brush up on industry terminology or improve your understanding of key concepts, this resource is here to assist.
A
Active Power
Also known as real Power, active Power is the energy consumed by electrical equipment to perform actual work, such as powering lights or operating machinery. Measured in watts (W), it’s what drives the practical functionality of devices, unlike reactive Power, which doesn’t directly contribute to useful tasks.
Alternating Current (AC)
Alternating current is a type of electric current that periodically changes direction and varies in magnitude in a sinusoidal pattern. This is the form of electricity commonly used in homes and businesses, providing the energy required to Power everyday appliances.
The Aluminium Association (AA)
This refers to “All Aluminium,” specifically in the context of All Aluminium Conductors. These conductors are essential in various applications due to their lightweight properties and excellent conductivity.
Ampere (A)
The ampere, often shortened to “amp,” is the standard unit for measuring electric current in the International System of Units (SI). One ampere represents the flow of electric charge produced by a potential difference of one volt across a resistance of one ohm. Simply put, it’s a way to measure how much electricity is moving through a conductor.
Apparent Power (Volt-Amps)
Apparent Power is the combination of voltage and current in an AC circuit, expressed as volt-amps. However, it’s important to note that apparent Power doesn’t represent the true Power of the circuit, as it doesn’t account for the power factor involved.
B
Balanced Load
A balanced load in a three-phase system ensures that the electrical load is equally distributed across all three phases. This even distribution, with equal impedance and power consumption in each phase, results in equal current magnitudes and a precise 120-degree phase difference between phases. In such a system, the neutral wire remains inactive, carrying no current.
Bandwidth
Bandwidth refers to the range of frequencies within a given band, often used for transmitting electrical signals. It indicates a cable’s or device’s capacity to handle data or electrical flow, making it a key factor in determining efficiency and performance.
Bias Current
Bias current is the current used as a reference quantity in a biased relay. It plays a critical role in adjusting the relay’s sensitivity to actuation.
Biased Relay
A biased relay is designed with modified characteristics, achieved by introducing a biasing quantity that usually opposes the actuating force. This ensures that the relay operates only under specific and controlled conditions.
Breaker Tester
A Breaker Tester is an essential device designed to evaluate the performance and functionality of circuit breakers. It tests their ability to interrupt currents under specific conditions, ensuring reliable and safe operation in electrical systems.
Breakdown Voltage
Breakdown voltage is the maximum voltage a material, such as a dielectric, can withstand before breaking down. Beyond this point, the material allows current to pass, highlighting the importance of selecting materials with appropriate voltage tolerances.
Booster Transformer
A booster transformer is a specialised electrical transformer engineered to increase voltage levels. It is commonly used in applications requiring temporary or localised voltage boosts.
Bushing (on transformers)
A transformer bushing enables an electrical conductor to safely pass through a conducting barrier. It provides insulation and mechanical support, ensuring safe and reliable electrical connections in high-voltage systems.
C
Calibration
The process of fine-tuning a device to ensure its output remains within a specified range while accurately aligning with the input values. Proper calibration ensures reliability and precision in device performance.
Capacitance
The capacity of a system to store an electric charge, measured in farads (F). Capacitance is a key characteristic of capacitors, which play a vital role in circuits by smoothing voltage supply or storing energy for later use.
Centre Tap
A midpoint connection along the winding of an inductor, transformer, or the element of a resistor or potentiometer. Centre taps are crucial for specific circuit configurations, enabling balanced voltage outputs.
Circuit
A pathway that allows electric charge to flow. Circuits are foundational to modern electrical systems, enabling the movement of electricity to power devices and systems efficiently.
Circuit Breaker
A resettable safety device designed to protect electrical circuits. Circuit breakers interrupt current flow when faults, such as overloads or short circuits, are detected, ensuring the safety of people and equipment.
Conductor
A material that allows electrical current to pass through it easily, such as metals. Conductors are fundamental to the design of electrical and electronic systems, supporting efficient current flow.
Creepage Distance
The shortest distance between two conductive parts is measured along the surface of the insulating material that separates them. Creepage distance is a critical design factor in insulators, influencing their performance and safety.
Current
The rate at which electric charge flows past a point in a circuit. Current is often described as the “flow” of electrons and is a core concept in electrical engineering.
D
Decibel (dB)
A unit for measuring the intensity of an electric signal or sound. It expresses ratios on a logarithmic scale — for instance, a voltage ratio of 1 to 10 equals -20dB, while 10 to 1 equals 20dB. For power ratios, a 10 to 1 ratio corresponds to 10dB, as Power is proportional to the square of voltage. Understanding dB measurements is essential for managing signal performance and sound levels.
dBm
This unit measures power levels in decibels relative to one milliwatt. The greater the dBm value, the higher the Power a device transmits or receives, making it a key factor in assessing device efficiency and output.
Direct Current (DC)
An electrical current that flows consistently in a single direction, unlike alternating current (AC), which reverses direction periodically. DC is widely used in everyday devices like batteries and other low-voltage applications due to its steady flow.
DC Voltage (Direct Current)
Electrical current flowing in one constant direction at a consistent rate. It’s the standard type of current for specific applications where steady voltage is critical.
Dielectric Material
A type of material that acts as an insulator because it poorly conducts electricity. It’s specially used to inhibit electrical flow and create reliable insulation systems.
Dielectric Polarisation
When an electric field is applied to a dielectric material, the internal charges shift, forming dipoles within the material. This shift results from the separation of positive and negative charges and is an important phenomenon in understanding material behaviour under electrical stress.
Dielectric Strength
This measures the maximum electric field a material can handle without its insulating properties breaking down. It’s a vital parameter for designing safe and effective insulation in electrical systems.
Dielectric Withstand
The capacity of an insulating material or system to endure specific overvoltages for a predetermined duration (typically one minute unless stated otherwise) without experiencing electrical flashovers or puncture. It ensures long-term reliability in electrical insulation.
E
Earth Testing
The process of measuring earth resistance is critical for maintaining electrical safety. This ensures the proper operation of grounding systems to protect people and equipment from electrical shocks, providing peace of mind in every application.
Earthing Transformer
A three-phase transformer is specifically designed to provide a neutral point in a power system for grounding purposes. These devices play a vital role in maintaining system stability and safety.
Effectively Grounded
This refers to intentionally connecting conductors or electrical equipment to the earth using low-impedance connections. These connections are crucial for safely conducting fault currents and ensuring a reliable electrical system.
Electrical Hazard
An electrical hazard represents any dangerous condition where contact or equipment failure could result in electric shock, arc flash burns, thermal burns, or explosive blasts. Mitigating these risks is essential for creating a safe environment.
Electrical Load
Electrical load refers to the total Power demanded by devices, measured in watts (W). Depending on the type of system, loads can be resistive, inductive, or capacitive, and understanding these demands helps optimise performance.
Electrical Relay
An electrical relay is a device engineered to trigger sudden, predetermined changes in electrical circuits when specific conditions are detected in the controlling circuit. This ensures precise and reliable system operations.
End-of-Discharge Voltage
This is the voltage of a battery measured at the end of its discharge cycle, right before the discharge concludes. Monitoring this ensures better performance and longevity of battery systems.
F
Farad (F)
The unit of measurement for capacitance. One farad represents the ability to store one coulomb of charge with a potential difference of one volt. It’s a key measure that highlights the storage capacity of electrical components.
Fault Current
The electrical current that flows due to a short-circuit condition. Identifying and managing fault current is critical for maintaining the safety and stability of electrical systems.
Feeder
A three-phase distribution line circuit that serves as a primary source for additional three-phase and single-phase circuits. Feeders are essential components in distributing Power efficiently across networks.
Float Charge
A charging method that uses a continuous, long-term, constant voltage to keep a battery or cell fully charged. This approach balances self-discharge and ensures the battery is always ready for use.
Flooded Cell
A type of cell design that includes an excess of electrolyte, allowing for efficient battery operation and maintenance. Flooded cells are known for their durability and reliability in various applications.
Frequency
The number of cycles per second in an alternating current (AC), measured in hertz (Hz). Residential systems commonly operate at either 50 Hz or 60 Hz, depending on the regional standard. Understanding frequency is crucial for ensuring compatibility with electrical systems.
Fuse
A safety device designed to protect equipment by interrupting the current flow when over-current conditions occur. Installed in the conductive path, fuses have a specific melting point tailored to the load current, preventing equipment damage reliably.
G
General Purpose Outlet (GPO)
Commonly found in homes and businesses, a General Purpose Outlet (GPO) is your standard power outlet, designed to provide electricity for everyday devices and equipment, ensuring convenience and reliability.
Ground
“Ground” refers to the electrical connection made directly to the earth. It’s a fundamental safety measure that reduces risks by providing a path for stray electrical currents to dissipate safely.
Ground Fault
An unintentional connection between an electrical circuit and the earth, a ground fault, can lead to significant risks such as electric shocks and damage to electrical systems. Staying alert to these issues helps maintain safety and system efficiency.
H
Henry (H)
The unit of inductance, Henry (H), describes how effectively a circuit can generate voltage when the current changes. For example, 1 Henry produces one volt when the current varies at a rate of 1 Ampere per second.
High Voltage
High voltage represents a considerable electrical potential, which can be dangerous if mishandled. Proper precautions must be taken to avoid injuries or equipment damage in high-voltage environments.
High Voltage Tester
This essential device ensures the safe operation of electrical systems by verifying the insulation strength and performance of equipment under high voltage. It’s a vital tool for assessing system reliability.
Hookstick
A hookstick is a long, insulated tool—commonly made of fibreglass—that allows operators to safely interact with energised overhead conductors and control electrical equipment from a safe distance.
HVAC (Heating, Ventilation, and Air Conditioning)
HVAC systems are critical for maintaining comfortable and controlled indoor environments by managing air quality, temperature, and humidity with efficiency and precision.
Hz (Hertz)
Hertz is the unit of frequency, measuring cycles per second. For instance, a 50 Hz frequency means the current alternates direction 50 times every second, a standard figure in many electricity systems.
I
Impedance
The opposition to the flow of alternating current (AC) within a circuit is measured in ohms (Ω). Unlike simple resistance, impedance also takes into account reactance, which occurs due to the presence of capacitors or inductors.
Insulation Tester
A reliable tool designed to evaluate the integrity and resistance of electrical insulation in wires and equipment, helping to ensure safety and efficiency in your systems.
Insulation
1) A material that does not conduct electricity, used to isolate conducting materials within a circuit.
2) The protective, non-conductive layer used in the production of insulated cables enhances safety and performance.
Incident Energy
The total energy that impacts a surface at a specific distance from its source during an electrical arc event. This is typically measured in calories per square centimetre (cal/cm²).
Induced Voltage
A voltage is generated in a circuit due to the influence of a nearby electric field, keeping your systems powered without a direct connection.
Induced Current
Current that flows through a conductor as a result of a neighbouring electromagnetic field, providing efficient energy transfer in specific applications.
J
Joule (J)
The standard unit of energy in the International System of Units (SI). A joule represents the work done when one ampere flows through a resistance of one ohm for one second.
K
Kilovolt-Ampere (kVA)
A measure of apparent Power in an electrical system that combines active and reactive Power. It’s a key unit for determining the right size of transformers and generators to meet your needs.
Kilowatt-Hour (kWh)
This standard unit of energy consumption reflects using 1 kilowatt of Power for 1 hour. It’s how electricity usage is typically measured and tracked.
kVAR
kVAR measures the additional reactive current flow when voltage and current are not perfectly synchronised or “in phase.” This is crucial for understanding the efficiency of your system.
kW
Actual Power, expressed in kilowatts (kW), represents the real energy being used in your electrical system.
L
L
A symbol representing inductance (L) – Measured in “Henry,” this indicates the ability of a circuit to store energy in a magnetic field.
Lag
This occurs when the current is delayed relative to the voltage in an AC circuit, a common scenario with inductive loads.
Lateral Circuit
This refers to a tap-off line designed to take the primary distribution from the main power line to a nearby load centre, ensuring power delivers where it’s needed most.
LDC
A Line Drop Compensator is used to maintain consistent voltage levels, ensuring reliable power delivery to your load.
Lead
This is the opposite of lag—the current precedes the voltage in an AC circuit, typical with capacitive loads.
LED
A Light Emitting Diode is an energy-efficient and long-lasting source of illumination widely used in various applications.
Limit Switch
A protective device used to open or close electrical circuits when specific operational limits, such as temperature or pressure, are reached to ensure safety and reliability.
Line Hose
A rubber dielectric cover for conductors, used to electrically insulate workers from energised conductors. These are commonly made by W.H. Salisbury & Company.
Load
The total electrical power required by connected equipment.
The combined impedance of all items within the output circuit.
Load Factor
A measure of electrical usage efficiency, this ratio compares the average electrical load over a period of time to the maximum possible load.
Loop Impedance
A critical parameter to ensure an electrical circuit can safely carry fault currents without excessive voltage drops.
Lumen
The standard measurement for light output, lumens, indicates the energy or brightness produced by a light source. A lamp’s light output, for example, is measured in lumens.
LV
Low Voltage (LV) describes electrical systems designed for smaller power needs, contributing to safe and efficient energy use.
M
Main Protection
The primary defence mechanism is designed to activate during a fault within a designated zone, ensuring safety and reliable system operation.
Megohmmeter
This essential device measures the insulation resistance of conductors or equipment, applying DC voltage to ensure reliability and safety in electrical systems.
Micro-Ohmmeter
A highly accurate tool for measuring extremely low resistance values, often in the milliohm (mΩ) range. It plays a crucial role in testing cables and electrical contacts to guarantee optimal performance.
Multimeter
A versatile instrument created to measure electric current, voltage, and resistance across a variety of ranges, making it a must-have for diagnosing electrical issues.
MVA
Apparent Power expressed in Million Volt-Amps, a key measurement for understanding and evaluating electrical power systems.
N
Neutral
The wire in a circuit that facilitates current return from devices or appliances is integral to maintaining an effective and safe electrical system.
Neutral Conductor
The conductor is responsible for returning current to its source in an electrical circuit, completing the flow path and maintaining balance.
Nominal Voltage
The typical operational voltage level for an electrical system, such as 230V in many residential circuits, provides a standard benchmark for design and safety.
Normal Mode Rejection Ratio (NMRR)
Indicates how well a device can reject common-mode signals, ensuring equipment accuracy and reliability in measurements.
Notching Relay
A precision relay that responds after a predetermined number of applied impulses, catering to specific electrical system requirements.
O
Ohm (Ω)
The standard unit for electrical resistance represents the opposition encountered by current flow in a conductor.
Ohm’s Law
A foundational rule in electricity, detailing the relationship between current (I), voltage (V), and resistance (R): I = V/R. This principle is crucial for designing and troubleshooting electrical circuits.
Oil Breakers
An older type of high-voltage circuit breaker that uses mineral oil as both an insulator and an interrupting medium. Once widespread for voltages from 35 kV up to 345 kV, they are now largely obsolete in modern systems.
OPGW (Optical Ground Wire)
A ground wire that integrates optical fibres, enabling safe grounding while also serving as a communication link in modern power systems.
Outage
The downtime of a power system component, resulting from external factors such as weather or accidental events, has durations ranging from seconds to hours.
Overcharge (Battery)
Occurs when current continues to flow into a fully charged cell, leading to the breakdown of water in the electrolyte into hydrogen and oxygen gas—a process best avoided to preserve battery health.
Overshoot Time
The time difference between a relay’s operation at a specified input value and the maximum allowable duration before its response ceases is critical for precise system performance.
P
Peak to Peak
Refers to the amplitude of an AC waveform measured from its highest positive peak to its lowest negative peak.
PF (Power Factor)
Another way to denote the power factor is a key measure for efficiency in electrical systems.
Phase Angle
The angular displacement between current and voltage waveforms, measured in degrees or radians. It helps in understanding the relationship between these two key electrical quantities.
Phase Rotation
The sequence of rotation in a poly-phase system is typically stated as “1-2-3” in counterclockwise rotation. U.S. utilities often use “A-B-C” to define respective phase names, while in Europe, “R-S-T” is used. Some variations might include “A-C-B” or “C-B-A,” depending on the system.
Polarity
1) A term that denotes the voltage relationship to a reference potential, usually indicated as positive (+).
2) For transformers, it indicates the direction of current flow through the high-voltage terminals in relation to the low-voltage terminals.
Portable Appliance Testing (PAT)
This is routine testing performed on portable electrical devices to ensure their safety for ongoing use. It’s a crucial practice in industrial and commercial environments to maintain safety and compliance.
Power Factor
The ratio of active Power to apparent Power in an AC system. A higher power factor means that electrical energy is being used more efficiently, which is beneficial for reducing energy waste and operational costs.
Q
Quality Factor
A measure of an electrical device’s efficiency, showing how well it stores energy compared to the energy it loses. Higher quality factors indicate better performance.
Quick Break
A safety feature in circuit breakers that ensures rapid interruption of electrical current during faults, greatly enhancing operational safety.
R
Range
Defines the nominal operating limits of a device, specified from the lowest calibration point to the highest.
Real Power
The average value of the instantaneous product of volts and amps over a fixed cycle in an AC circuit. It represents the actual Power consumed by a system.
Reference Conditions
The prescribed conditions of use for a transducer are established to ensure consistent performance testing and accurate comparison of measurement results.
Reference Range
A defined range of values of an influencing quantity within which a transducer continues to meet specific performance standards.
Reference Value
This is a single, specified value of an influencing quantity where the transducer complies with required intrinsic error standards.
how much energy is dissipated as heat within a conductor or device.
Relay
An electrically operated switch used for control and automation within circuits. Relays enable low-power signals to control much larger currents, making them valuable in various applications.
Residual Current
The algebraic sum of all the line currents in a multi-phase system. Residual current helps identify imbalances, which could pose safety risks.
Resistance
The opposition to the flow of electrical current in a circuit, measured in ohms (Ω). Resistance determines
S
Secondary Injection Testing
A modern approach to testing protection relays by injecting simulated electrical signals instead of using high currents or voltages. This method ensures both safety and efficiency, making relay verification more straightforward and reliable.
Short Circuit
- An unintended connection that occurs when an ungrounded conductor contacts another conductor or grounded object, often leading to excessive current flow.
- A low-impedance connection, whether accidental or intentional, between two points of differing electrical potentials.
Sinusoid/Sine Curve
A fundamental concept in electronics, representing periodic oscillations of constant amplitude, as described by a sine function.
Split Phase
Common in residential and light commercial applications (up to approximately 100 kVA), this 3-wire single-phase electric distribution system is widely used in North America. It is the AC equivalent of the former Edison direct current distribution system.
Static Relay
An advanced relay design that utilises electronic, magnetic, optical, or similar components to generate a response, eliminating mechanical motion. However, this excludes relays based on digital technology.
Step-Down Transformer
A vital device that reduces voltage from higher levels to lower levels, enabling safe and efficient power transmission for domestic and commercial use.
T
Tan Delta
Also referred to as the loss angle or dissipation factor, Tan Delta measures energy loss in insulating materials, ensuring quality and reliability in electrical systems.
Thermal Imaging Camera
A state-of-the-art tool that detects and displays heat signatures, playing a key role in electrical inspections by identifying overheating components efficiently.
THD
Total Harmonic Distortion (%THD) quantifies the proportion of harmonic frequency currents or voltages in relation to the fundamental frequency, expressed as a percentage. It’s a critical measure for assessing power quality.
Transformer
A crucial component in power systems, transformers transfer energy between circuits through electromagnetic induction, effectively modifying voltage levels as needed.
Transformer Insulation
Specialised materials are designed to electrically insulate transformer windings operating at different voltage levels. These materials also prevent contact between energised components and the transformer’s metal tank, ensuring safe operation, particularly in large transformers used for power applications.
True RMS
True Root-Mean-Square (RMS) provides accurate measurements of effective alternating current and voltage values, regardless of waveform distortions. While many clamp meters measure average values calibrated for RMS, only True RMS devices provide precise results when the input waveforms differ from a sine wave.
U
Unbalanced Loads
Occurs when the phases in a three-phase electrical system are loaded unevenly, potentially causing inefficiencies or damage.
Underground Cable Fault Locator
An advanced tool used to precisely locate faults in underground cables by pinpointing breaks or short circuits.
Unit Protection
A targeted protection system designed to respond exclusively to abnormal conditions within a specific, clearly defined zone of the power system.
Unrestricted Protection
A versatile protection system without a strictly defined zone of operation, achieving selectivity through time grading.
Utility-Grade Equipment
Reliable, high-performance electrical equipment designed to meet the rigorous standards and challenges of utility-scale energy operations.
V
VA
- Represents electrical capacity or load, measured in Volts * Amps.
- Indicates the output capacity of a transformer at rated voltage and frequency, accounting for heat rise limits.
VAR (Volt Ampère Reactive)
A measure of reactive Power in an AC circuit, helping to indicate the energy stored and returned by inductive or capacitive components.
Volt (V)
The standard unit of electric potential represents the driving force behind the movement of electric charge in a circuit.
Voltage Drop
The loss of electrical potential along a circuit due to resistance and impedance in wires and connections.
W
Watt (W)
The fundamental unit of Power, measuring how quickly energy is transferred. One watt equals one joule per second.
Wavelength
The physical distance of one complete cycle in an alternating signal is inversely related to its frequency.
Wire Lubricant
A specially formulated compound that reduces friction, making it easier to pull cables into ducts or conduits.
X
X
Reactance, measured in Ohms, represents the opposition to changes in current in an AC circuit.
X-Rated Capacitor
Special capacitors designed to suppress surge voltages are often used in electronic equipment to ensure safe operation.
XHHW-2
A durable building wire with cross-linked polyethylene insulation, suitable for residential, commercial, and industrial electrical applications.
Y
Yield Voltage
The critical voltage level at which a material or component begins to break down or deform under electric stress.
Z
Z (Impedance)
The total opposition to the flow of alternating current, comprising both resistance and reactance, is expressed in Ohms.
Zener Diode
A specialised diode designed to allow reverse current flow at a specified breakdown voltage, commonly used for maintaining voltage stability in circuits.
Zero Crossing
The moment when a sinusoidal waveform transitions through the zero-reference level is crucial in many electronic control applications.
Zero Sequence Current
A portion of the fault current that flows evenly in all three phases of a grounded power system during faults is often used for fault analysis.
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