6a Glossary of Terms.pdf

Glossary of Terms

Glossary of Terms Page 1

1/C: A circuit comprised of three separate or individual cables, one for each phase. There are discrete cables for each phase A, B, and C. Each cable contains one conductor.

3/C: Three separate conductors all encased in the same overall outer jacket. Interstitial ground wire(s) may or not be part of the cables construction.

ANSI: American National Standards Institute.

Base case: The basic design of a power system’s one-line.

Branch (NEC): The circuit following the final overcurrent device protecting.

Branch (software): The elements of an electrical circuit that are terminated by two or more buses.

Examples include transformers, feeders, and series reactors.

Bus: A connection point, bus bar, or node in which branches (software) terminate and rated voltage is specified.

CAD: Computer Aided Drafting.

Circuit Breaker: is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

Close and latch: The maximum asymmetrical current capacity of a switch or a medium or high voltage circuit breaker to close and latch instantly thereafter for normal frequency making current.

Derating: The reduction in equipment’s rated capacity caused by increased internal losses due to external factors or ambient conditions or both. Conductors and transformers may also be derated due to losses caused by harmonic voltages and currents.

Device function: A relay function specifically intended to operate upon selective system conditions or parameters. An example is a ground relay that is insensitive to phase overcurrent conditions.

Duty: The maximum rated short circuit current for with a device or equipment is rated to operate per manufacturer specifications.

ECF: Eddy Current Factor.

Eff (motor): A motor’s efficiency.

EPR: Ethylene propylene rubber.

EPR-133%: Ethylene propylene rubber with 133% insulation.

EPR-NJ: Non-jacketed ethylene propylene rubber.

EPRS: Shielded Ethylene propylene rubber.

EPRS:-133%: Shielded Ethylene propylene rubber with 133% insulation.

Essential Electrical System: A system comprised of alternate sources of power and all connected distribution systems and ancillary equipment, designed to ensure continuity of electrical power to designated areas and functions of a health care facility during disruption of normal power sources, and also to minimize disruption within the internal wiring system.

Glossary of Terms Page 2

Fault: An abnormal condition typically characterized by having high magnitude short circuit currents.

Feeder breaker: A breaker or fused switch typically associated with switchgear serving downsteam equipment or loads.

FLA: Full load amps. Nominal operating current for equipment at full capacity.

Frame: Low voltage circuit breaker are manufactured in standard sizes designated in frame size measured in amps.

Frequency scan: A plot showing a system’s response to a range of frequencies. This plot may also show impedance as a function of the frequency.

Fully Rated: Overcurrent Protective Devices (OCDP) are evaluated individually to ensure that the interrupting (AIC) rating of the OCDP meets the short circuit rating at the equipment where the OCDP are installed.

Fused switch: A sectionalizing switched for switching loads and having an integral fuse providing circuit overcurrent protection.

I THD: Total harmonic distortion in current.

IAA (cables): Interlocked Armor Aluminum.

IAS (cables): Interlocked Armor Steel.

ICCB: Insulated Case Circuit Breaker.

IEEE: Institute of Electrical and Electronic Engineers, Inc.

Interrupting cycle: Medium voltage breakers require multiple cycles to interrupt a circuit. The is designated as interrupting cycle. Common manufacturer medium voltage breakers are rated 3, 5, and 8 cycles to clear a fault.

IRSS: The root sum of squares of harmonics in current.

K-factor (breakers): The ratio of a breaker’s maximum rated operating voltage to its lowest limit operating range for which asymmetrical and symmetrical interrupting capabilities vary inversely proportional to the operating voltage.

K-factor (transformers): A transformer rating system used to classify the harmonic carrying capability of a transformer. Reference ANSI Standard C57.110.

LTC (transformer): Load tap changer

LVPCB: Low voltage power circuit breaker.

MCC: Motor control center. Typically modular constructed enclosures specifically design to house motor starters, feeder breakers and other load serving devices.

MCCB: Molded case circuit breaker.

Momentary current rating: The total rms current that a switch is rated to carry for one cycle including any dc component.

Momentary: The current during the first half cycle is the momentary fault current.

Glossary of Terms Page 3

NACD ratio: No ac decrement ratio.

Non Solid State Trip: A trip unit that is usually made of solely mechanical components. Instantaneous trip devices are typically magnetic solenoids and time delay function achieved by bimetallic elements.

One-line: An electrical system diagram represented as a single line diagram where a single line is used to symbolize the three phases.

PCC: Point of common coupling.

Percent Impedance (Transformer): The industrial standard for rating a transformer on its nameplate.

PF: Power factor.

PILC: Paper insulated lead sheath.

PILC-133%: Paper insulated lead sheath with 133% insulation.

Rating plug: A component of a field modifiable circuit breaker. The rating plug in conjunction with the breakers sensing unit establish a breakers maximum Long Time Trip amps.

PVC: Polyvinyl chloride.

R0: Sequence reactance is zero.

R1: Sequence reactance is positive.

Reference kV: The voltage used on time current plot as a reference for plotting system currents which maybe at another voltage. Transformer voltage transformation ratios are applied for this conversion.

Remote bus: A power source (including the utility) that is considered far enough away from a fault not to have its contribution influenced over time..

R-EXP: The exponent of a harmonic numbed for resistance factor.

RH: Rubber insulated/heat resistant, NEC rated at 75 degrees.

RHH: Heat resistant rubber.

RHW: Moisture and heat resistant rubber.

RPM: Revolutions per minute.

SCADA: Supervisory Control And Data Acquisition.

Scenario: A variation of the one-line from the base case or an alternative system configuration.

Sensor: Measures low voltage circuit breaker amp flow and translates measurement into a signal (voltage or current) suitable for relaying trip unit.

Series Rate: Downstream Overcurrent Protective Device (OCPD) have a lower interrupting rating but the combination of the upstream device has an interrupting rating at least equal to the available fault current, thus assisting the downstream device.

Short circuit: An abnormal condition in an electrical circuit where a normally insulated and separated

Glossary of Terms Page 4 conductors have come in contact creating a low impedance path resulting in excessively high current.

Selective Coordination: Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings or settings.

SST: Solid state trip.

Swing source: In mathematical system analysis the swing source makes up the difference to balance the system the system equations. For an electrical system model the swing source is typically a fixed voltage and can deliver or absorb infinite real or imaginary power. In the real world the utility represents a swing source.

Symmetrical amps/asymmetrical amps: Asymmetrical amps are the current that has both a dc and ac component. Symmetrical amps only have a purely ac component.

Symmetrical components: 3 phase elements that are expressed in terms of positive, negative, and zero sequence components. These are mathematical transforms of the phase quantities.

Tap: A tap is commonly the time-overcurrent pickup of a relay. Tap could also pertain to the tap settings in a transformer used to set voltage ratio. Tap could also refer to the tap setting in a current sensor used to scale down the current.

TCC: Time-current curve.

THHN: Heat resistant thermoplastic

THW: Moisture and heat resistant thermoplastic.

THWN: Moisture and heat resistant thermoplastic.

Tie-breaker: A circuit breaker or switch connecting two buses together.

Time dial: Used with conventional electro-mechanical relays as the delay setting for time-overcurrent trip functions.

Total/Symmetrical basis(rating): The ANSI standard used to rate protective devices. Used for equipment that is rated in both symmetrical and asymmetrical amps.

Violation: Any short circuit or power flow value that falls outside of a range that is specified or rated.

VTHD: Total harmonic distortion in voltage. VTHD is calculated as the root sum of squares of the harmonics excluding the fundamental.

X/R ratio: The ratio of rated frequency reactance an effective resistance used for short circuit calculations.

X’dv: Transient reactance based on equipment’s MVA base.

X”dv: Subtransient reactance based on equipment’s MVA base.

X0: Zero sequence inductive reactance.

X1: Positive sequence inductive reactance.

Xc: Positive capacitive reactance.

Glossary of Terms Page 5

Xc0: Zero capacitive reactance.

XXHW: Moisture and heat resistant crosslinked synthetic polymer.

XLPE: Crosslinked polyethylene.

XLPE-133%: Crosslinked polyethylene with 133% insulation.

XLPE-NJ: Non-jacketeed crosslinked polyethylene.

XLPE-NJ-133%: Non-jacketeed crosslinked polyethylene with 133% insulation.

XLPES: Shielded crosslinked polyethylene with 133% insulation.

Xlr: The locked rotor impedance of an induction machine.