Electrical & Power Systems Glossary
Transformers, breakers, VFDs, motors, switchgear, protective relays, and power quality. 233 terms in this topic - each defined in plain English on its own page.
Everything in a plant runs on power, and a surprising share of automation work is electrical: motor control and VFDs, protective relaying and switchgear, power quality, grounding, and the panel hardware that houses it all. These definitions cover that electrical layer, from utility-scale concepts (synchrophasors, load shedding) down to DIN-rail components and site power budgets for remote installations.
233 Terms
What Is a 12-Pulse Rectifier Drive?
How phase-shifting transformers feed 12 or 18 pulse rectifiers to cancel dominant harmonics at the source.
Read → GlossaryWhat Is a 250-Ohm Sense Resistor?
The precision resistor that converts a 4-20 mA loop to 1-5 V and gives HART the loop resistance it needs.
Read → GlossaryWhat Is a Ground Loop on a 4-20 mA Signal and How Does It Corrupt a Reading?
How two grounds at different potentials inject stray current into a current loop, why an isolator fixes it, and how it differs from an open loop.
Read → GlossaryWhat is Across-the-Line (Full-Voltage) Starting?
The simplest starting method: full line voltage hits the motor instantly through a contactor, drawing full inrush.
Read → GlossaryWhat Is an Active Front End (Regenerative VFD)?
The IGBT rectifier stage that returns braking energy to the grid and draws near-sinusoidal, low-harmonic current.
Read → GlossaryWhat Is an Amine Contactor?
The absorber tower where lean amine chemically strips H2S and CO2 from sour gas counter-currently to make sweet gas.
Read → GlossaryWhat Is an Antenna Surge Arrestor?
The in-line coax device that shunts lightning surges to ground before they reach the radio.
Read → GlossaryHow Does Automatic Power Factor Correction Capacitor Step Control Work?
How an APFC controller senses reactive demand and switches capacitor steps to a target PF, with C/k, deadband, and detuning.
Read → GlossaryArc Flash
The explosive release of energy from an electrical arc - incident energy, the arc-flash boundary and the NFPA 70E PPE it demands.
Read → GlossaryWhat Is Arc Flash Incident Energy?
How incident energy in cal/cm2 is calculated per IEEE 1584 and how it sets the arc-flash boundary and PPE.
Read → GlossaryArc-Flash Study
The IEEE 1584 analysis that sets incident energy, boundaries and PPE labels per equipment.
Read → GlossaryWhat is a solar array oversizing factor?
The multiplier that lets an array recover the bank after cloudy weather, and why meeting load differs from restoring autonomy.
Read → GlossaryAutomatic Transfer Switch
The switch that moves a load from utility to generator on power loss and back - open vs closed transition and its unmanned-site role.
Read → GlossaryHow do you size a battery bank for a remote RTU?
Convert daily load and days of autonomy into amp-hours, then derate for depth of discharge and cold to installed Ah.
Read → GlossaryBattery Storage Site Monitoring
The BMS, power conversion, thermal, and fire-safety layers a grid BESS watches, and how they combine.
Read → GlossaryWhat is battery sulfation in a solar SCADA power system?
Chronic undercharge hardens sulfate on lead-acid plates, cutting capacity and showing as early voltage sag.
Read → GlossaryWhat is battery thermal runaway?
The self-sustaining exothermic cell failure that can cascade through a BESS module, and how it is detected.
Read → GlossaryBESS BMS Monitoring Points
The cell, module, and derived signals a battery management system reports and why divergence matters most.
Read → GlossaryBESS State-of-Health Monitoring
How state of health tracks battery capacity fade and drives augmentation, distinct from state of charge.
Read → GlossaryBESS Thermal and Fire Monitoring
The thermal, off-gas, and suppression signals that keep a battery site safe and give early warning.
Read → GlossaryWhat Is a Black Start?
Restarting a power system from a total blackout with no external supply - black-start sources and the sequenced rebuild.
Read → GlossaryWhat is a blocking diode in a solar array?
The series diode that stops nighttime battery discharge through the panel, how MPPT controllers replace it, and its voltage-drop cost.
Read → GlossaryWhat Is Bonding and Grounding for Loading?
Connecting a truck to the rack and earth to dissipate static, verified as a load permissive in rack SCADA.
Read → GlossaryBootlace Ferrule (Wire-End Ferrule)
A crimped metal sleeve that consolidates stranded wire strands for a reliable terminal-block connection.
Read → GlossaryWhat Is a VFD Braking Resistor and Brake Chopper?
The IGBT chopper and resistor that dump regen energy as heat across the DC bus, and how the resistor is sized by duty.
Read → GlossaryWhat Is a Breaker Failure Relay (50BF)?
50BF backup protection that trips adjacent breakers when a breaker fails to clear a fault.
Read → GlossaryWhat is a broken rotor bar signature?
Sidebands around line frequency in a motor's current spectrum, spaced at twice slip, that reveal a broken rotor bar.
Read → GlossaryBuild an arc-flash program
The full sequence from data collection and study through labeling, PPE, training, and revalidation that makes a program work.
Read → GlossaryBusbar
The rigid copper or aluminum conductor that distributes power to many circuits in switchgear and MCCs - ratings and bus configurations.
Read → GlossaryHow does busbar differential protection work?
Summing all feeder currents at a node with high- and low-impedance schemes and check zones.
Read → GlossaryCable Ferrule
The printed sleeve that shows a wire number, tying each conductor to the loop diagram and cable schedule.
Read → GlossaryCable Tray
The open support system that routes power and instrument cables across a facility, with segregation and fill limits.
Read → GlossaryWhat is capacity factor for a solar or wind plant?
Actual energy over full-nameplate energy, why it reflects resource and curtailment, not equipment health.
Read → GlossaryHow do you check battery specific gravity?
Sample every cell, correct for temperature, and read the pattern: all low means undercharge, one low means a bad cell.
Read → GlossaryCHP Engine Monitoring Points
The combustion, per-cylinder, mechanical, and electrical signals that keep a CHP gas engine reliable.
Read → GlossaryWhat Is a Circuit Breaker?
The resettable protective switch (MCB, MCCB, air, vacuum) with trip curves and interrupting ratings for power distribution.
Read → GlossaryWhat Is Common-Mode Rejection Ratio (CMRR)?
The spec measuring how well a differential input rejects common-mode voltage, in dB, and how to read it on a datasheet.
Read → GlossaryWhat Is a String Combiner Box?
The enclosure that gathers many PV strings onto one DC feeder with per-string fuses and monitoring.
Read → GlossaryHow do you commission a soft-starter ramp for a pump?
Set initial torque so the shaft turns immediately, tune ramp time and current limit to the load, and enable the soft stop that prevents check-valve slam.
Read → GlossaryHow do you commission battery temperature compensation?
Mount the sensor on the battery case, enter the datasheet coefficient, and prove charge voltage tracks temperature.
Read → GlossaryWhat Is the Difference Between Common-Mode and Normal-Mode Noise?
The two noise types on analog wiring, how each couples in, and why isolation kills one while twisting handles the other.
Read → GlossaryConduit or cable tray for a wiring method?
A selection guide comparing mechanical protection, cable capacity, future changes, and cost for conduit versus cable tray.
Read → GlossaryWhat Is Conformal Coating on I/O Modules and When Do You Need It?
How coating seals a PCB against humidity, salt, and corrosive gases, the ISA-71.04 classes, and when to spec it.
Read → GlossaryWhat Is a Contactor?
The electromagnetic power switch that starts and stops motors, how it works, and how it differs from a relay.
Read → GlossaryWhat Is an Impressed Current CP Rectifier?
The DC power unit that drives protective current into a pipeline through an anode groundbed.
Read → GlossaryWhat Is Motor Current Signature Analysis (MCSA)?
An online diagnostic that FFTs stator current to find broken rotor bars, eccentricity, and bearing faults from sidebands.
Read → GlossaryWhat Is a Current Transformer (CT)?
The instrument transformer that steps current down for meters and relays, with CT ratio, burden, and the open-secondary hazard.
Read → GlossaryWhat Is a Current-Limiting Fuse?
A fuse that clears a fault in under a half-cycle to cut peak let-through current and arc-flash energy.
Read → GlossaryHow do you size DC cable for voltage drop at a solar site?
Choosing conductor gauge so cable resistance does not waste the charge a remote array produces, using percent-drop targets.
Read → GlossaryWhat Is VFD DC Injection Braking?
A stopping method that applies DC to the stator for a stationary braking field, no resistor, for firm stops or light holds.
Read → GlossaryHow do you verify power supply load sharing?
Measure each supply's output current, match setpoints per the manual, and prove failover by removing input power one side at a time.
Read → GlossaryWhat is a deep-cycle battery versus a starting battery?
Why solar sites need thick-plate deep-cycle chemistry, what happens with a starting battery, and how to tell them apart on the datasheet.
Read → GlossaryWhat is a demand meter?
A meter that captures the maximum average power over a defined interval, setting a large share of an industrial bill.
Read → GlossaryHow do you diagnose a ground loop in panel analog signals?
Correlate the error with running equipment, hunt the second earth reference, confirm with current checks, and break the loop without touching safety grounds.
Read → GlossaryHow do you diagnose a pump tripping on motor overload?
Compare running amps to the nameplate and relay setting first, then check for runout, a heavier fluid, or a mechanical bind, sorted by likelihood.
Read → GlossaryDifferential Relay (87)
How device 87 compares in-and-out current to trip instantly on internal zone faults.
Read → GlossaryWhat Is a DIN Rail?
The 35 mm snap-on rail that mounts terminal blocks and components inside a control panel, and why it is the wiring backbone.
Read → GlossaryDIN-rail or panel-mount components?
A selection guide comparing serviceability, density, vibration resistance, and heat for DIN-rail versus panel-mount mounting.
Read → GlossaryHow does directional earth fault (67N) protection work?
How residual current plus a zero-sequence reference decides fault direction on ring and parallel feeders.
Read → GlossaryWhat Is Displacement vs True Power Factor?
Why a drive can show good displacement power factor yet be penalized once harmonic distortion lowers true power factor.
Read → GlossaryDNP3 CROB Control Output
The control relay output block and its trip, close, pulse, and latch codes.
Read → GlossaryWhat is dV/dt and Reflected Wave on VFD Cables?
Fast IGBT edges plus long motor leads double the voltage at the motor terminals, destroying winding insulation.
Read → GlossaryWhat is Dynamic Braking on a VFD?
A VFD stops a high-inertia load by dumping regenerated energy into a brake resistor to prevent DC-bus overvoltage.
Read → GlossaryWhat is battery equalization charging?
A periodic controlled overcharge that remixes electrolyte and rebalances flooded cells, and why it must be off for sealed and lithium.
Read → GlossaryWhat Is an ESP Motor?
The oil-filled downhole induction motor that drives an ESP - horsepower stacking, winding temperature, and current telemetry.
Read → GlossaryWhat Is an ESP Motor Current Signature?
How the amp chart's shape reveals pumped-off, gas, sand, and scale, and drives ESP alarms and trips.
Read → GlossaryWhat is ESP motor temperature monitoring?
Tracking downhole motor winding and oil temperature to catch overheating from low flow or gas and protect ESP run life.
Read → GlossaryESP Switchboard
The surface panel that powers and protects a downhole ESP with underload/overload trips.
Read → GlossaryHow do you find a ground fault on floating 24 VDC?
Read both rails to ground, spot the pinned pole, and pull branch fuses one at a time until the bus floats again.
Read → GlossaryWhat is Motor Full-Load Amps (FLA)?
The nameplate rated running current every overload setting, cable size, and high-current alarm is referenced to.
Read → GlossaryHow do you check fuse and breaker coordination?
Build the protection ladder, overlay time-current curves pair by pair, and scrutinize the high-fault region where selectivity fails.
Read → GlossaryFuses or breakers for control-panel protection?
A selection guide comparing interrupting rating, current limitation, resettability, and coordination - and when a panel should use both.
Read → GlossaryFusible disconnect or breaker disconnect?
A selection guide comparing service disconnects on interrupting rating, current limitation, resettability, and cost - with lockout common to both.
Read → GlossaryWhat Is a Gel Breaker?
The chemical that degrades frac gel after placement so proppant packs and fluid flow back cleanly.
Read → GlossaryWhat is generator auto-start on low battery?
The battery state-of-charge logic that fires a backup genset on a hybrid solar site, with hysteresis and run-hour minimization.
Read → GlossaryGenerator Paralleling
Synchronizing multiple generators onto one bus for capacity and redundancy - the four sync conditions and how load is shared.
Read → GlossaryWhat Is Glycol Carryover in a TEG Contactor?
Lean TEG entrained out the top of the contactor into sales gas - a cost and a downstream contamination problem.
Read → GlossaryWhat Is a Glycol Contactor Tower?
The absorber tower in a TEG unit where wet gas meets lean glycol counter-currently across trays or packing to dry the gas.
Read → GlossaryHow do you ground and surge-protect a radio mast?
Bond the mast and antenna to earth, fit a coax arrestor at entry, and route every ground to one single-point bar, with power protected too.
Read → GlossaryWhat Is a Ground Fault?
An unintended current path to earth, how it differs from a phase-to-phase short, and how it is detected early.
Read → GlossaryWhat Is a Ground Loop in Instrumentation?
How two grounds at different potentials drive stray current through a signal path, corrupting analog readings.
Read → GlossaryGrounded or ungrounded control transformer secondary?
A selection guide comparing first-fault behavior, safety, and troubleshooting for grounded versus ungrounded control circuits.
Read → GlossaryWhat Is Grounding (Earthing)?
Safety ground, system ground, and signal reference explained, plus bonding, ground loops, and why it is critical in oil and gas.
Read → GlossaryWhat Is Instrument Grounding?
Single-point signal grounding, clean vs safety earth, and shield grounding - keeping measurements quiet.
Read → GlossaryWhat Is Insulation Resistance Testing?
Applying DC with a megohmmeter to trend winding insulation health using PI, DAR, and the one-megohm rule.
Read → GlossaryWhat Is an Interposing Relay?
The control relay that isolates and amplifies a PLC output so it can switch real field loads safely.
Read → GlossaryHow do you interpret VFD DC-bus voltage readings?
The bus should sit near 1.35 times line voltage: low means sags or a weak source, high during decel means regeneration, and ripple means phase loss or tired capacitors.
Read → GlossaryIS Signal Isolator
The galvanic DIN-rail barrier that energy-limits hazardous-area loops and separates field from control, versus a Zener barrier.
Read → GlossaryWhat Is Inverter Clipping?
The flat-topped midday plateau when an oversized DC array is capped at the inverter's AC rating.
Read → GlossaryHow do you insulation-resistance test a motor circuit?
Isolate and verify dead, disconnect the drive, test winding-to-ground at the IEEE 43 voltage, read the one-minute value, and split cable from winding faults.
Read → GlossaryWhat is a Line Reactor vs Load Reactor?
The impedance choke on a drive's input tames harmonics; on the output it protects the motor and cable.
Read → GlossaryHow does line current differential (87L) protection work?
How relays at both line ends exchange current phasors over fiber and compare them.
Read → GlossaryWhat Is Line Drop Compensation on a Voltage Regulator?
How a regulator uses modeled R and X to estimate and control the far-end load-center voltage, plus setting pitfalls.
Read → GlossaryWhat is electric line heater load shedding on solar power?
Cutting or duty-limiting a resistive heater as battery or generator capacity drops to protect off-grid autonomy.
Read → GlossaryLinear or switch-mode DC power supply?
A selection guide comparing efficiency, heat, output noise, and size for linear versus switch-mode supplies feeding a control-panel rail.
Read → GlossaryWhat Is Load Shedding?
The prioritized dropping of non-essential loads that keeps a power system from cascading into a total blackout.
Read → GlossaryHow do you load-test a battery bank?
Full rested charge, known steady load, per-unit voltage logging, and a hard stop at the datasheet end voltage.
Read → GlossaryWhat is Locked Rotor Current (LRA)?
The several-times-rated current a motor draws at zero speed; NEMA code letters classify it and it sizes protection.
Read → GlossaryWhat Is a Loop Power Supply?
The 24 VDC source that energizes 2-wire 4-20 mA loops, and how to size its voltage budget.
Read → GlossaryHow Do You Size a Loop Power Supply?
Add the voltage budget from compliance and drops, total the current budget for shared supplies, then add margin.
Read → GlossaryHow do you check 4-20 mA loop voltage headroom?
Sum every series drop at maximum loop current, then measure the transmitter's terminal voltage in fixed-output mode and compare to datasheet minimum.
Read → GlossaryWhat is a low-voltage disconnect (LVD)?
The last-line switch that opens the load before a battery is over-discharged, with disconnect and reconnect hysteresis.
Read → GlossaryWhat is a low-voltage disconnect recovery threshold?
The reconnect setpoint and hysteresis band that decide whether an RTU recovers cleanly at dawn or chatters or strands itself all day.
Read → GlossaryWhat is the difference between a maintained and a momentary contact?
Momentary springs back and needs hold logic; maintained stays put. Mis-reading one causes drop-out.
Read → GlossaryWhat is a met mast (meteorological tower)?
The reference tower of anemometers and vanes that measures the true wind for resource and power tests.
Read → GlossaryWhat is commutation in a servo motor?
Energizing a brushless motor's phases in sync with rotor position for smooth torque via Halls or encoder FOC.
Read → GlossaryWhat Is a Motor Control Center (MCC)?
The central assembly that houses starters and protection for a facility's electric motors, and how it connects to SCADA.
Read → GlossaryWhat is Motor Inrush Current?
The transient surge at energization causes voltage dip and nuisance trips and drives generator and transformer sizing.
Read → GlossaryWhat Is Motor Insulation Class?
How classes A, B, F, and H set a winding's maximum temperature and how ambient plus rise determines insulation life.
Read → GlossaryMotor Overload
Sustained overcurrent that overheats a motor - how overload relays sense and time the trip, trip class, and overload vs short-circuit protection.
Read → GlossaryMotor Protection Relay
The multifunction relay guarding motors against overload, stall, unbalance and ground fault.
Read → GlossaryHow do you verify a motor protection relay setting?
Match the full-load current, service factor, and trip class to the nameplate so protection is neither loose nor nuisance-tripping.
Read → GlossaryWhat Is Motor Service Factor?
The nameplate multiplier like 1.15 that sets continuous overload margin, its cost in insulation life, and overload settings.
Read → GlossaryWhat Is a Motor Starter?
Contactor plus overload relay - how motors start and stay protected, and starter vs soft starter vs VFD.
Read → GlossaryVFD vs soft starter vs across-the-line: which starting method?
A three-way selection guide: when to use a VFD, a soft starter, or a direct across-the-line start, with the pitfalls that reverse the obvious pick.
Read → GlossaryWhat Is Maximum Power Point Tracking?
How a solar inverter hunts the knee of the I-V curve to extract peak DC power as conditions change.
Read → GlossaryWhat Is a Mud Motor (PDM)?
The downhole motor that spins the bit from mud flow, steers with a bent housing, and shows stalls in standpipe pressure.
Read → GlossaryNEC Article 500
The Class, Division, and Group scheme for hazardous electrical locations and how it drives equipment and wiring choices.
Read → GlossaryNEC division vs zone classification
Compare the Article 500 division scheme against the Article 505 zone scheme, how they map, and which to standardize on.
Read → GlossaryNEMA or IEC motor starters: which to specify?
A selection guide comparing sizing philosophy, utilization categories, panel space, and serviceability between NEMA and IEC starters.
Read → GlossaryWhat is a network conduit under IEC 62443?
The controlled communication pathway between zones, the security controls that sit on it, and how to document its flows.
Read → GlossaryNeutral Grounding Resistor
How an NGR limits ground-fault current to cut arc-flash energy and enable run-through.
Read → GlossaryNFPA 70E program elements
The written program, risk assessment, hierarchy of controls, work permit, training, labeling, and audits that make up NFPA 70E.
Read → GlossaryHow Does On-Load Tap Changer (OLTC) Voltage Control Work?
How an AVC relay holds busbar voltage in a deadband using target, bandwidth, time delay, and SCADA supervision.
Read → GlossaryOvercurrent Relay (50/51)
Instantaneous and inverse-time overcurrent protection: pickup, time-dial and curves.
Read → GlossaryWhat is an Overload Relay Trip Class?
The class number sets how long an overload tolerates locked-rotor current, matched to the motor's acceleration time.
Read → GlossaryHow do you verify panel bonding and shields?
Measure continuity from every metal part to the ground bar, then audit each shield for one deliberate landing.
Read → GlossaryHow do you test a panel UPS transfer?
Confirm the real UPS loads, pull input power on purpose, hold a meaningful battery run, and verify alarms and recharge.
Read → GlossaryWhat Is a Panelboard?
The low-voltage distribution panel with main and branch breakers on a bus that feeds lighting, instruments, and small loads.
Read → GlossaryWhat Is a Power Distribution Unit?
The rack or floor device that distributes, meters, and remotely switches power to control-room and server equipment.
Read → GlossaryWhat Is Resonant Earthing (Petersen Coil) and Sensitive Earth Fault Protection?
How a Petersen coil tunes the neutral so earth arcs self-extinguish, and how wattmetric SEF finds the faulted feeder.
Read → GlossaryWhat is the Peukert effect in a deep-cycle battery?
Why usable amp-hours shrink as you discharge faster, what the Peukert exponent means, and why C20 versus C100 breaks autonomy math.
Read → GlossaryWhat Is a PF Correction Capacitor Bank?
How fixed and switched kVAR banks supply reactive power locally to dodge utility penalties, plus resonance cautions.
Read → GlossaryWhat Is Point-on-Wave Controlled Switching of Capacitor Banks?
How synchronous closing to the voltage zero crossing kills capacitor inrush, versus pre-insertion resistors.
Read → GlossaryWhat Is a Potential Transformer (VT)?
The instrument transformer that steps voltage down for meters and relays, distinct from a power transformer and a CT.
Read → GlossaryHow do you build a power budget worksheet for a remote site?
Tally every load by current draw and duty cycle into a daily watt-hour figure that sizes your array and battery.
Read → GlossaryPower Factor
The ratio of useful (kW) to total (kVA) power - why a lagging power factor costs money and how capacitor banks correct it.
Read → GlossaryHow Does Redundant Power Supply Load Sharing and Diode ORing Work?
Why paralleled supplies need an ORing module, how diode/MOSFET isolation works, and N+1 sizing with fail alarms.
Read → GlossaryWhat Is Power System Harmonics?
The waveform distortion from VFDs and nonlinear loads, measured as THD, that overheats equipment and trips breakers.
Read → GlossaryPremium-efficiency or standard motor?
A selection guide comparing run hours, energy cost, and payback that decide which motor efficiency class a load justifies.
Read → GlossaryWhat is a quadrilateral characteristic on a distance relay?
A four-sided trip zone that catches high-resistance ground faults a mho circle misses.
Read → GlossaryWye-delta, autotransformer, or soft start?
A selection guide comparing three reduced-voltage starting methods on torque, inrush, transition risk, and complexity.
Read → GlossaryWhat Is a Redundant Power Supply in a SCADA Cabinet?
Dual PSUs through a diode-OR module, dual DC buses and AC feeds, and how it pairs with a UPS.
Read → GlossaryWhat is a Regenerative Drive?
An active front end returns braking energy to the grid instead of burning it in a resistor, and cuts harmonics.
Read → GlossaryWhat Is a Relay?
The coil-and-contact switch behind industrial control logic, NO vs NC contacts, and how relay states reach SCADA.
Read → GlossaryWhat Is Protective Relay Coordination?
How breakers and relays are graded with time-current curves so the device nearest a fault trips first.
Read → GlossaryWhat Is the Difference Between Relay, Transistor, and Triac Digital Outputs?
How the three output switching technologies differ in AC/DC, speed, contact life, and inrush - and which to spec.
Read → GlossaryWhich battery chemistry for a remote SCADA site?
A selection guide comparing flooded, AGM, gel, and LiFePO4 on temperature, cycle life, maintenance, and cost for off-grid sites.
Read → GlossaryWhat is restricted earth fault (REF) protection?
How a neutral CT versus phase-CT residual catches winding-to-earth faults near the star point.
Read → GlossaryWhat Is a Reverse Power Relay (32)?
The ANSI device 32 relay that detects a motoring generator after prime-mover failure and trips it.
Read → GlossaryHow Do You Size a Solar Power Budget for an RTU?
The load-versus-generation math that matches RTU and radio draw to panel wattage and site sun-hours.
Read → GlossaryHow do you calculate backup power runtime?
Usable amp-hours divided by average load, corrected for the Peukert effect, and predicted live by a SCADA host.
Read → GlossaryWhat Is a Safety Relay?
The force-guided relay that builds hardwired safety interlocks and trip circuits without a programmable logic solver.
Read → GlossaryWhat Is Sensorless Vector Control on a VFD?
The VFD mode that estimates rotor flux from a motor model to give near-full torque at low speed without an encoder.
Read → GlossaryWhat is the difference between series and parallel battery wiring?
Series stacks voltage, parallel stacks amp-hours, and the resulting bus voltage cascades into controller and cable sizing.
Read → GlossaryHow do you set a motor overload relay from nameplate FLA?
Read the right FLA column, set the dial on the manufacturer's basis, pick trip Class 10, 20, or 30 to match the start, and verify with a clamp meter.
Read → GlossaryWhat is a setpoint ramp generator?
How a ramp moves a control target gradually at a set rate to protect equipment and cut overshoot.
Read → GlossaryShould a cable shield be grounded at one end or both?
One-end grounding avoids ground-loop noise on analog loops; both-ends grounding improves high-frequency immunity.
Read → GlossaryShort-Circuit Study
Calculating available fault current to verify breaker AIC and equipment withstand ratings.
Read → GlossaryWhat Is a Signal Isolator?
The module that breaks ground loops on a 4-20 mA signal with galvanic isolation - and when you need one.
Read → GlossaryWhat Is a Single-Line Diagram?
The simplified schematic of a facility's sources, transformers, buses, breakers, and protection.
Read → GlossarySingle-phase or three-phase power for a site?
A selection guide comparing motor capability, delivery efficiency, load balance, and availability for single-phase versus three-phase supply.
Read → GlossaryWhat Is Single-Phasing?
How losing one of three supply phases overheats a running motor fast, and how phase-loss relays prevent burnout.
Read → GlossaryWhat Is a VFD Skip Frequency?
A configured speed band the drive refuses to dwell at, dodging mechanical resonance and the vibration it causes.
Read → GlossarySoft Starter
Solid-state reduced-voltage starting that limits motor inrush and mechanical shock - and how it differs from a DOL starter and a VFD.
Read → GlossaryHow to size a solar battery bank for a remote RTU?
Stack daily amp-hours, days of autonomy, depth-of-discharge limit, and cold derate to get the bank size.
Read → GlossarySolar Farm Monitoring Points
The weather, DC, inverter, and grid layers a utility solar plant watches, and how they form performance ratio.
Read → GlossarySolar Inverter Monitoring Points
The AC, DC, thermal, and event signals a PV inverter exposes and how SunSpec Modbus carries them.
Read → GlossaryWhat is a solar methanol injection pump?
A DC solar-driven metering pump that injects methanol for hydrate control with no vented gas, replacing pneumatic pumps.
Read → GlossaryHow do you derate a solar panel for an RTU?
Knock nameplate PV watts down via temperature, soiling, wiring, tilt, and worst-month sun to real delivered energy.
Read → GlossaryWhat is solar panel string shading loss?
Series wiring lets one shadow throttle a whole string; bypass diodes and siting limit the disproportionate loss.
Read → GlossaryWhat is the right solar panel tilt angle for winter sizing?
Why a steep winter tilt near latitude plus fifteen degrees suits year-round loads, and how tilt sheds snow and shapes worst-month sizing.
Read → GlossaryWhat is the right solar panel tilt angle for winter charging?
Tilt steeper than summer-optimal to catch the low winter sun and shed snow; size to worst-month insolation.
Read → GlossarySolar Performance-Ratio Monitoring
How performance ratio normalizes for weather so real solar losses stand out, and how to read a decline.
Read → GlossaryWhy does a solar site brown out overnight?
Four causes in order: lost battery capacity, load growth, short daytime harvest, and voltage-drop illusions.
Read → GlossarySolar String and Combiner Monitoring
How per-string DC current comparison localizes shading, soiling, blown fuses, and module faults.
Read → GlossarySolid-state relay or contactor to switch a load?
A selection guide comparing switching frequency, heat, inrush, isolation, and failure mode for SSRs versus electromechanical contactors.
Read → GlossaryWhat Is a Standby Generator?
The engine-driven backup power source that keeps critical loads alive through outages - ratings, sequencing, and remote monitoring.
Read → GlossaryWhat is a pump station standby generator and transfer run strategy?
How a lift station rides through an outage on generator power, often on one pump, and how SCADA adapts control.
Read → GlossaryWhat is state of charge for a battery bank?
The battery fuel gauge, how controllers estimate it from resting voltage and coulomb counting, and why voltage lies under load.
Read → GlossaryWhat Is a String Inverter?
The inverter that converts a string of solar panels' DC to AC and isolates faults per string.
Read → GlossaryWhat is a Motor Surge Comparison Test?
Fast high-voltage pulses into each phase whose ringing waveforms are compared to find turn-to-turn insulation weakness.
Read → GlossaryWhat Is Surge Protection?
How surge protective devices divert lightning and switching transients to ground, and why remote SCADA field gear depends on it.
Read → GlossaryWhat is a surge protection device (SPD) for instrumentation?
A multi-stage device using a gas discharge tube and a fast clamp to divert transients off signal wiring.
Read → GlossarySurge protection or isolation for an instrument loop?
A selection guide clarifying which device defends against transients, which breaks ground loops, and why a hostile loop needs both.
Read → GlossaryWhat Is a Surge Suppressor?
The sacrificial device that clamps lightning and switching transients on instrument signal and power lines.
Read → GlossarySwitchgear
Breakers, buses and protective relays that switch, protect and isolate electrical circuits - and how LV and MV switchgear differ.
Read → GlossaryWhat Is a Sync-Check Relay (25)?
The ANSI device 25 relay that permits a paralleling breaker to close only when two sources match.
Read → GlossaryHow much fuel does a thermoelectric generator use?
Estimating a TEG's continuous gas burn per watt at low efficiency and weighing its lifetime cost against solar.
Read → GlossaryWhat Is a Terminal Block?
The modular clamp that joins field and panel wiring, its main types, and why it is the backbone of a serviceable panel.
Read → GlossaryHow do you test a UPS transfer?
Plan a controlled outage, open the upstream feed, hold on battery, and verify transfer, alarms, and recharge.
Read → GlossaryWhat Is Total Harmonic Distortion?
How THD and TDD quantify harmonics and how IEEE 519 sets enforceable limits at the point of common coupling.
Read → GlossaryWhat is a thermoelectric generator (TEG)?
A gas-fired solid-state DC power source with no moving parts for remote RTUs and cathodic protection, and where it beats solar.
Read → GlossaryWhat Is a Three-Phase Separator?
The vessel that splits well fluid into gas, oil, and water - interface control, the weir, and dual liquid dumps - explained.
Read → GlossaryTime-delay or fast-acting fuse?
A selection guide comparing how inrush tolerance, motor starting, and semiconductor protection decide which fuse curve a branch needs.
Read → GlossaryWhat Is a Transfer Switch?
The device that moves a load between utility and generator - manual, open, closed, or bypass-isolation transition.
Read → GlossaryTransformer
Static device that steps AC voltage up or down by mutual induction and turns ratio - the link between transmission and usable plant power.
Read → GlossaryWhat is harmonic restraint in transformer differential protection?
How second- and fifth-harmonic content stop 87T tripping on inrush and overexcitation.
Read → GlossaryWhat is transmitter terminal surge protection?
Built-in or add-on protection that shunts lightning and switching surges to earth at the terminal block before they reach the electronics.
Read → GlossaryHow do you wire a transmitter terminal block?
Land loop power on the polarity terminals, read output at the test terminal, bond the ground screw, and torque to spec.
Read → GlossaryWhat Is an Undervoltage Relay (27)?
The ANSI device 27 relay that trips or blocks loads on a voltage sag and coordinates restart.
Read → GlossaryUPS
Battery backup that rides through outages with no interruption and conditions power - and how online, line-interactive and standby types differ.
Read → GlossaryWhat Is UPS Battery Monitoring?
Per-cell voltage, impedance, and temperature monitoring that catches a weak UPS battery before it kills runtime.
Read → GlossaryHow do you run a UPS runtime test?
Define the pass line, discharge with the real load, stop at a planned margin, and trend the measured runtime.
Read → GlossaryHow do you verify a generator auto-start on utility loss?
Walk the documented ATS sequence, remove utility by the approved method, time every stage, confirm retransfer and cooldown, and log what telemetry saw.
Read → GlossaryHow do you verify LVD operation?
Map what the LVD really controls, ramp voltage down slowly, and confirm disconnect, reconnect, and alarm order.
Read → GlossaryHow do you verify three-phase balance at a VFD?
Measure all three phase pairs with a true-RMS meter, compute unbalance from the average, and localize the cause upstream or at the drive.
Read → GlossaryWhat Is a VFD?
Variable frequency drives - AC motor speed control for pumps and ESPs - explained, plus VFD vs soft starter.
Read → GlossaryHow do you set VFD accel and decel times?
Match each ramp to the load's inertia, lengthen accel to stop overcurrent and decel to stop overvoltage, then verify.
Read → GlossaryHow do you size a VFD braking resistor?
Peak braking power and the drive threshold set the resistance; the average braking duty sets the continuous wattage rating.
Read → GlossaryVFD bypass or a redundant drive?
A selection guide comparing a bypass contactor against a redundant spare drive on what each preserves, cost, and complexity.
Read → GlossaryHow do you check VFD cable length for reflected wave?
Compare the measured run against the drive's stated limit, weigh carrier frequency and motor insulation, and filter if over.
Read → GlossaryWhat is VFD Carrier Frequency?
The PWM switching frequency knob that trades quieter motors for more switching heat and forces drive derating.
Read → GlossaryHow do you derate a VFD?
Reduce usable current for carrier frequency, ambient temperature, and altitude from the maker's tables, then confirm it covers the load.
Read → GlossaryWhat Is a VFD Flying Start?
How a drive detects a still-spinning motor's speed before applying power, avoiding a damaging out-of-phase restart.
Read → GlossaryHow do you set up flying start on a VFD?
Enable speed search so the drive finds a spinning load's speed and direction, then verify a smooth catch without a jolt.
Read → GlossaryHow do you set VFD min and max frequency?
Base the minimum on cooling and process, the maximum on the load and supply, then verify the drive clamps both.
Read → GlossaryWhy does my VFD trip on ground fault at start?
Separate a real insulation fault from a capacitive nuisance trip, then test the motor and cable to ground in order.
Read → GlossaryLine reactor or output filter for a VFD?
A selection guide mapping line reactors, load reactors, dV/dt filters, and sine-wave filters to the input- or output-side problem each one solves.
Read → GlossaryWhy won't my VFD motor reach full speed?
Check the frequency limit and reference first, then current and torque foldback, then a mechanical overload or weak supply.
Read → GlossaryHow do you enter motor nameplate data into a VFD?
Transcribe voltage, FLA, base frequency, and rated speed for the actual connection so the drive models the motor before autotune.
Read → GlossaryWhich VFD output filter for a long cable?
Match a load reactor, dv/dt filter, or sine-wave filter to the run length, motor rating, and carrier frequency.
Read → GlossaryWhy does my VFD trip on overcurrent at start?
Work the likely causes in order: accel too short, too much boost, a stalled load, then a shorted or grounded output.
Read → GlossaryWhy does my VFD trip on overtemperature?
Check the drive's cooling fan and airflow, the ambient and enclosure heat, the carrier frequency, and the load in order.
Read → GlossaryTwo-wire or three-wire VFD start control?
Two-wire restarts on power return; three-wire stays stopped until someone presses start. Match the scheme to the machine and verify.
Read → GlossaryWhy does my VFD trip on undervoltage?
Measure the supply and phases first, check input connections, then suspect a failing DC bus capacitor or rectifier.
Read → GlossaryWhat Is VFD Volts-per-Hertz (V/f) Control?
The scalar drive mode that holds voltage-to-frequency constant to keep motor flux and torque steady across speeds.
Read → GlossaryWhat Is a Vortex Breaker?
The cross-plate over a vessel liquid outlet that stops a draining vortex from pulling gas into the liquid line.
Read → GlossaryWhat Is VT Fuse Failure Supervision (VTFF)?
How a lost voltage signal can false-trip distance and directional relays, and how VTFF detects and blocks it.
Read → GlossaryWhat Is Wetting Voltage on a Dry Contact Digital Input?
Why a dry-contact input needs a small wetting current to stay reliable, and how it causes intermittent reads.
Read → GlossaryWhat is Motor Winding Resistance Testing?
Milliohm-level DC resistance across each phase to find loose connections, broken strands, and turn-to-turn shorts.
Read → GlossaryWhat is worst-month design in solar sizing?
Sizing a remote solar system against its least-sunny month via the load-to-insolation ratio, so it survives winter.
Read → GlossaryWhat is Wye-Delta (Star-Delta) Motor Starting?
Reconfiguring a six-lead motor from wye to delta cuts starting inrush; open vs closed transition explained.
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