Notation

Capital English Letters

A

component availability (Chapter 11)

A

levelized annual cost, $ (Chapter 7)

A

weighted average Btu/kWh net generation (Chapter 2)

A, B, C

phase designation

A, B, C, D

general line (circuit) constants (Chapter 5)

AFDR

feeder availability (Chapter 11)

Ai

availability of component i (Chapter 11)

An

area served by one of n substation feeders, mi2

ASD

service-drop conductor size, cmil (Chapter 6)

ASL

secondary-line conductor size, cmil (Chapter 6)

Asys

system availability (Chapter 11)

AEC

annual equivalent of energy cost, $

AEICc

annual equivalent of total installed capacitor bank cost, $ (Chapter 8)

AIC

annual equivalent of feeder investment cost, $

B

average fuel cost, $/MBtu (Chapter 2)

BEC

original (base) annual kWh energy consumption

BVR

bus voltage regulator

BW

bandwidth of voltage-regulating relay

C

capacitance, F

C

common winding (Chapter 3)

CF

installed feeder cost, $/kVA (Chapter 8)

CG

generation system cost, $/kVA

CS

distribution substation cost, $/kVA

CT

transmission system cost, $/kVA

CT

transmission cost, $/kVA (Equation 8.26)

CT

total reactive compensation (= cn) (Equation 8.85)

CR

corrective ratio (Chapter 9)

CTP

primary-side rating of current transformer (Chapter 9)

CTR

current transformer ratio

D

distance or separation, ft

D

load density, kVA/mi2

D

ratio of kWh losses to net system input (Chapter 2)

Dg

coincident maximum group demand, W

Di

demand of load i, W

DFi

demand factor of load group i

DTA(ij, k)

downtime array coefficients (Chapter 11)

E

source emf; voltage

Ei

event that component i operates successfully (Chapter 11)

EC

energy cost, $/kWh

ECoff

incremental cost of off-peak electric energy, $/kWh

ECon

incremental cost of on-peak electric energy, $/kWh (Chapter 6)

ECL1

eddy-current loss at rated fundamental current

E(T)

expected time during which a component will survive

F

fault point

F’LD

reactive load factor (= Q/S)

Fc

coincident factor

FD

diversity factor

FLD

load factor

FLL

load-location factor (Chapter 7)

FLS

loss factor

FLSA

loss-allowance factor (Chapter 7)

FPR

peak-responsibility factor

FR

reserve factor

Fu

utilization factor

FCAF

fuel cost adjustment factor, $/kWh

FDR

feeder (Chapter 11)

F(t)

unreliability function (Chapter 11)

H

transformer higher-voltage-side winding

HFI

current harmonic factor

HFV

voltage harmonic factor

I

failed zone-branch array coefficient (Chapter 11)

I

rms phasor current, A

I

current matrix

IAB

current in higher-voltage-side winding between phases A and B, A

Iab

current in lower-voltage-side winding between phases a and b, A

Ia,3ϕ

current in phase a due to single-phase load, A

IB

base current, A

IC

current in common winding (Chapter 3)

Ic

core-loss component of excitation current (Chapter 3)

Ie

excitation current (Chapter 3)

Iexc

per unit excitation current (Chapter 6)

If,a, If,b If,c

fault currents in phases a, b, and c

If,3ϕ

three-phase fault current, A

If,3ϕ

three-phase fault current referred to subtransmission voltage, A (Chapter 10)

(IF,3ϕ)max

maximum three-phase fault current, A (Chapter 10)

IF, HV

fault current in transformer high-voltage side, A

If,L–G

line-to-ground fault current, A

If, LV

fault current in transformer low-voltage side, A

If,L–L

line-to-line fault current, A

Iϕ1

current due to single-phase load, A

Ih

harmonic current

IL

line current; load current, A

Im

magnetizing current component of excitation current (Chapter 3)

Im

current in feeder main at substation, A

IN

current in primary neutral, A

In

current in secondary neutral, A

Iop

operating current, A

IP, pu

no-load primary current at substation transformer, pu

Ira

rated current, A

IS

current in series winding (Chapter 3)

ICc

installed cost of capacitor bank, $/kvar (Chapter 8)

ICcap

total installed cost of shunt capacitors, $

ICF

installed feeder cost, $ (Chapter 7)

ICPH

annual installed cost of pole and its hardware, $ (Chapter 6)

ICSD

annual installed cost of service drop, $ (Chapter 6)

ICSL

annual installed cost of secondary line, $ (Chapter 6)

ICsys

average investment cost of power system upstream, $/kVA

ICT

annual installed cost of distribution transformer, $

K

percent voltage drop per kilovolt-ampere-mile

K~

per unit voltage drop per 10,000 A · ft

K  ^

constant (Equation 5.63)

Kh

watt-hour meter constant (Chapter 2)

KR

conversion factor for resistance (Chapter 7)

Kr

number of watt-hour meter disk revolutions (Chapter 2)

KX

conversion factor for reactance (Chapter 7)

K1

a constant to convert energy-loss savings to dollars, $/kWh (Equation 8.87)

K2

a constant to convert power-loss savings to dollars, $/kWh (Equation 8.87)

K3

a constant to convert total fixed capacitor size to dollars, $/kWh (Equation 8.95)

Lsc

system inductance, H (Equation 8.108)

LCDH

losses in capacitors due to harmonics

LD

load diversity, W

LD

load (Chapters 2 and 5)

LDC

line-drop compensator

LS

loss

LTC

load tap changer

LV

low voltage

MTTR

mean time to repair (r¯) (Chapter 11)

MTBF

mean time between failures (T¯) (Chapter 11)

MTTF

mean time to failure (m¯) (Chapter 11)

N

expected duration of normal weather (Chapter 11)

N

neutral primary terminal

0

row vector of zeros (Chapter 11)

OCexc

annual operating cost of transformer excitation current, $ (Chapter 6)

OCSD, Cu

annual operating cost of service-drop cable due to copper losses, $ (Chapter 6)

OCSL, Cu

annual operating cost of secondary line due to copper losses, $ (Chapter 6)

OCT, Cu

annual operating cost of transformer due to copper losses, $ (Chapter 6)

OCT, Fe

annual operating cost of transformer due to core losses, $

P

average power, W

P

transition (or stochastic) matrix (Chapter 11)

P’LS

power loss after capacitor bank addition, W (Equation 8.46)

Pav

average power, W

PLS, av

average power loss, W

Pi

peak load i, W

PLD

average power of load, W

PLS

average power loss, W

PLS, i

peak loss at peak load i, W

PLS, max

maximum power loss, W

PLS,1ϕ

single-phase power loss, W (Chapter 7)

PLS,3ϕ

three-phase power loss, W (Chapter 7)

Pn

load at year n, W (Chapter 2)

P0

initial load, W

Pr

receiving-end average power, VA

PT, Cu

transformer copper loss, W (Chapter 6)

PT, Fe

transformer core loss, W (Chapter 6)

PSL, Cu

power loss of secondary line due to copper losses, W

PF

power factor

PTR

potential transformer ratio

PTN

turns ratio of potential transformer (Chapter 9)

Q

average reactive power, var

Qc

reactive power due to corrective capacitors, var (Chapter 8)

Qc,3ϕ

three-phase reactive power due to corrective capacitors, var (Equation 8.30)

Qi

unreliability of component i (Chapter 11)

Qr

receiving-end average reactive power, VA

Qsys

system unreliability (Chapter 11)

R

resistance, Ω

Reff

effective resistance, Ω (Chapter 9)

RL

resistance of load impedance, Ω

Rset

R dial setting of line-drop compensator (Chapter 9)

Rsys

system reliability (Chapter 11)

RIA(ij, k)

recognition and isolation array coefficients (Chapter 11)

RP

regulating point

S

apparent power, VA

S¯

= P + jQ, complex apparent power, VA

S

expected duration of adverse weather (Chapter 11)

S

series winding (Chapter 3)

SB

base apparent power, VA

Ssc

short-circuit apparent power, VA

Sckt

circuit capacity, VA (Chapter 9)

SG

generation capacity, VA (Chapter 8)

SL

load apparent power, VA

SLi

apparent power of load i, VA

S

apparent power rating of an open-delta bank

Slump

apparent power of lumped load, VA

SL,3ϕ

three-phase apparent power of load, VA (Chapter 8)

Sm

total kVA load served by one feeder main

Sn

kVA load served by one of n substation feeders

SPK

feeder apparent power at peak load, VA

Sreg

regulator capacity, VA (Chapter 9)

SS

substation capacity, VA (Equation 8.27)

ST

transformer apparent power, VA

ST

transmission capacity, VA (Equation 8.24)

ST, ab

apparent power rating of single-phase transformer connected between phases a and b, VA

STi

apparent power rating of transformer i, VA

ST,3ϕ

three-phase transformer apparent power, VA

S1ϕ

single-phase VA rating

S3ϕ

three-phase VA rating

SΔ–Δ

apparent power rating of a delta-delta bank

SD

service drop (Chapter 6)

SW

switchable capacitors (Chapter 8)

T

a random variable representing failure time (Chapter 11)

T

time

T

transformer

TAn

total area served by all n feeders, mi2

TAC

total annual cost, $

TAELcu

total annual energy loss due to copper losses, W

TCDi

total connected group demand i, W

TD

time delay

TECL

total eddy-current loss (Chapter 8)

TSn

total kVA load served by a substation with n feeders

U

component unavailability (Chapter 11)

UFDR

feeder unavailability (Chapter 11)

UG

underground

URD

underground residential distribution

V

volt, unit symbol abbreviation for voltage

V

voltage matrix

Vab, pu

voltage between phases a and b, pu

VB,ϕ

single-phase base voltage, V

VB,3ϕ

three-phase base voltage, V

VC

voltage across common winding (Chapter 3)

VH

higher-voltage-side voltage, V (Chapter 3)

Vh

rms voltage of hth harmonic

VL-L

line-to-line distribution voltage, V (Chapter 10)

VL-L

line-to-line voltage, V

VL-N

line-to-neutral voltage, V

Yl, pu

per unit voltage at feeder end (Chapter 9)

VP

primary distribution voltage, V (Chapter 9)

VP, max

maximum primary distribution voltage, V

Vr

receiving-end voltage

Vreg

output voltage of regulator, V

VRP

voltage at regulating point, V

VS

voltage across series winding (Chapter 3)

VS

sending-end voltage

VST

subtransmission voltage, V (Chapter 9)

VST, L–L

line-to-line subtransmission voltage, V (Chapter 10)

VX

lower-voltage-side voltage, V (Chapter 3)

VD

voltage drop, V

VDpu

per unit voltage drop

VDpu,1ϕ

single-phase voltage drop, pu

VDpu,3ϕ

three-phase voltage drop, pu

VDSD

voltage drop in service-drop cable, V

VDSL

voltage drop in secondary line, V

VDT

voltage drop in transformer, V

% VDab

percent voltage drop between a and b

% VDm

percent voltage drop in feeder main

VDIP

voltage dip, V

VDIPSD

voltage dip in service-drop cable, V

VDIPSL

voltage dip in secondary line, V

VDIPT

voltage dip in transformer, V

VRl, pu

per unit voltage rise at distance 1 (Chapter 9)

VRpu

per unit voltage regulation

% VR

percent voltage regulation

% VR

percent voltage rise (Chapter 8)

% VRNSW

percent voltage rise due to nonswitchable capacitors (Chapter 8)

% VRSW

percent voltage rise due to switchable capacitors (Chapter 8)

VRR

voltage-regulating relay

VRRpu

per unit setting of voltage-regulating relay

W

wire (in transformer connections) (Chapter 3)

X

reactance, Ω; transformer lower-voltage-side winding

Xc

capacitive reactance

XL

reactance of load impedance, Ω

Xsc

system reactance, Ω (Equation 8.107)

Xset

X dial setting of line-drop compensator (Chapter 9)

X(tn)

sequence of discrete-valued random variables (Chapter 11)

Y

admittance, Ω; wye connection

Y

admittance matrix

Z

impedance, Ω

Z

secondary-winding impedance, Ω (Equation 10.71)

Z

impedance matrix

Zeq

equivalent (total) impedance to fault, Ω (Chapter 10)

Zf

fault impedance, Ω

ZG

impedance to ground, Ω

ZG, ckt

impedance to ground of circuit, Ω

ZLD

load impedance, Ω

ZM

impedance of secondary main, Ω

ZT

transformer impedance, Ω

ZT

equivalent impedance of distribution transformer, Ω

ZT, pu

per unit transformer impedance

ZΔ

equivalent delta impedance, Ω (Equation 10.54)

Z0

zero-sequence impedance, Ω

Z0, ckt

zero-sequence impedance of circuit, Ω

Z1

positive-sequence impedance, Ω

Z1, ckt

positive-sequence impedance of circuit, Ω

Z1, SL

positive-sequence impedance of secondary line, Ω (Chapter 10)

Z1, ST

positive-sequence impedance of subtransmission line, Ω

Z1, sys

positive-sequence impedance of system, Ω

Z1, T

positive-sequence impedance of transformer, Ω

Z2

negative-sequence impedance, Ω

Lowercase English Letters

a, b, c

phase designation

c

capacitor compensation ratio (Chapter 8)

ci

contribution factor of load i

dn

mutual geometric mean distance of phase and neutral wires, ft

dp

mutual geometric mean distance between phase wires, ft

f¯

mean failure frequency (Chapter 11)

fP

parallel resonant frequency, Hz

f1

fundamental frequency, Hz

fsys

average failure frequency of a system (Chapter 11)

f(t)

probability density function

h

harmonic order

h(t)

hazard rate (Chapter 11)

i

investment fixed charge rate (Chapter 6)

ic

annual fixed charge rate for capacitors

iF

annual fixed rate for feeder

iG

annual fixed charge rate for generation system

is

annual fixed charge rate for distribution substation

iT

annual fixed charge rate for transmission system

k

constant used in computing loss factor (Chapter 2)

l

inductance per unit length; leakage inductance

l

feeder length, mi

ln

linear dimension of primary-feeder service area, mi

mi

observed time to failure for cycle i (Chapter 11)

m¯s

mean time to failure of series system (Chapter 11)

n

total number of cycles (Chapter 11)

n

transfer ratio (inverse of turns ratio) (Chapter 10)

n

= n1/n2, turns ratio; neutral secondary terminal; number of feeders emanating from a substation

n1

number of turns in primary winding

n2

number of turns in secondary winding

P(n)

vector of state probabilities at time tn (Chapter 11)

pij

transition probabilities (Chapter 11)

pij

probability of proper operation of isolating equipment in zone branch ij (Chapter 11)

q

probability of component failure (Chapter 11)

qij

probability of failure of isolating equipment in zone branch ij (Chapter 11) receiving end

r

radius; internal (source) resistance; resistance per unit length

ra

resistance of phase wires, Ω/ 1000 ft

re

earth resistance, Ω/ 1000 ft

req

transformer equivalent resistance, Ω

ri

observed time to repair for cycle i (Chapter 11)

rl

lateral resistance per unit length

rm

resistance of feeder main, Ω/ mi

r¯s

mean time to repair of series system (Chapter 11)

s

sending end; effective feeder (main) length, mi (Chapter 4)

s

series system (Chapter 11)

t

time

x

line reactance per unit length; internal (source) reactance

xa

self-inductive reactance of a phase conductor, Ω/ mi

xap

reactance of phase wire with 1 ft spacing, Ω/ 1000 ft

xan

reactance of neutral wire with 1 ft spacing, Ω/ 1000 ft

xd

inductive reactance spacing factor, Ω /mi

xdn

mutual reactance between phase and neutral wires, Ω/ 1000 ft

xdp

mutual reactance of phase wires, Ω/ 1000 ft

xe

earth reactance, Ω/ 1000 ft

xeq

transformer equivalent reactance, Ω

xi, opt

optimum location of capacitor bank i in per unit length

xL

inductive line reactance (Chapters 5 and 8)

x1

lateral reactance per unit length

xm

reactance of feeder main, Ω/ mi

xRP

regulating point distance from substation, mi (Chapter 9)

xT

transformer reactance, % Ω (Chapter 8)

Z

impedance per unit length

Zl

lateral impedance per unit length

zm

impedance of feeder main, Ω/ mi

Z0, a

zero-sequence self-impedance of phase circuit, Ω/ 1000 ft

Z0, ag

zero-sequence mutual impedance between phase and ground wires, Ω/ 1000 ft

Z0, g

zero-sequence self-impedance of ground wire, Ω/ 1000 ft

Capital Greek Letters

Δ

delta connection; determinant

Δ

difference; increment; savings; benefits

ΔACE

annual conserved energy, Wh (Chapter 8)

ΔBEC

additional energy consumption increase

ΔEL

energy-loss reduction

ΔPLS

additional decrease in power loss, W (Chapter 8)

ΔPLS, opt

optimum loss reduction, W (Chapter 8)

ΔQc

required additional capacitor size, var (Chapter 8)

ΔSF

released feeder capacity, VA (Chapter 8)

ΔSG

released generation capacity, VA (Chapter 8)

ΔSS

released substation capacity, VA (Equation 8.29)

ΔST

released transmission capacity, VA (Equation 8.24)

ΔSsys

released system capacity, W (Chapter 8)

Δ$ACE

annual benefits due to conserved energy, $ (Chapter 8)

Δ$F

annual benefits due to released feeder capacity, $ (Equation 8.36)

Δ$G

annual benefits due to released generation capacity, $ (Chapter 8)

Δ$S

annual benefits due to released substation capacity, $ (Equation 8.29)

Δ$T

annual benefits due to released transmission capacity, $ (Equation 8.26)

Δ

transition rate matrix (Chapter 11)

Π

unconditional steady-state probability matrix (Chapter 11)

Σ

total savings due to capacitor installation, $ (Equation 8.86)

Lowercase Greek Letters

α

a constant [=(1 + λ + λ2)]−1 (Chapter 11) 6

δ

power angle

θ

power-factor angle

θmax

power-factor angle at maximum voltage drop

λ

ratio of reactive current at line end to reactive current at line beginning

λ

failure rate (Chapter 11)

λ¯

complex flux linkages, (Wb · T)/m

λCT

annual fault rate of cable terminations (Chapter 11)

λFDR

annual feeder fault rate (Chapter 11)

λij

total failure rate of zone branch ij (Chapter 11)

λijB

breaker failure rate in zone i branch j (Chapter 11)

λijM

zone branch ij failure rate due to preventive maintenance (Chapter 11)

λijW

zone branch ij failure rate due to adverse weather (Chapter 11)

λOH

annual fault rate of overhead feeder section (Chapter 11)

λs

failure rate of supply (substation) (Chapter 11)

λUG

annual fault rate of underground feeder section (Chapter 11)

μ

mean repair rate (Chapter 11)

μij

zone branch ij repair rate (Chapter 11)

μsijc

reclosing rate of reclosing equipment in zone branch ij (Chapter 11)

μsijo

isolation rate of isolating equipment in zone branch ij (Chapter 11)

ϕ

= tan−1(X/R), impedance angle

ϕ

magnetic flux; phase angle

ω

radian frequency

Subscripts

A

phase a

a

phase a

B

phase b

b

phase b

B

base quantity

C

phase C; common winding (Chapter 3)

c

phase c

c

capacity; capacitive; coincident (Chapter 3)

cap

shunt capacitor

ckt

circuit

CT

cable termination (Chapter 11)

Cu

copper

eff

effective

eq

equivalent circuit quantity

exc

excitation

D

diversity

F

feeder; fault point; referring to fault

f

referring to fault

FDR

feeder

Fe

iron

H

high-voltage side (HV)

L

inductive (reactance); load (Chapter 3)

L

line; load

l

lateral; inductive (reactance); length

LD

load

L-G

line-to-ground

L-L

line-to-line

LL

load location (Chapter 7)

L-N

line-to-neutral

LS

loss (Chapters 2 and 5)

LSA

loss allowance

M

secondary main

m

feeder main

max

maximum

min

minimum

N

turns ratio

N

primary neutral

n

number of feeders emanating from a substation

n

neutral

NSW

nonswitchable (fixed) capacitors (Chapter 9)

off

off-peak

OH

overhead (Chapter 11)

op

operating

opt

optimum

on

on-peak

primary

PK

peak

PR

peak responsibility (Chapter 7)

pu

per unit

r

receiving end

ra

rated

reg

regulator

S

substation; series winding (Chapter 3)

s

sending end

sc

short circuit

SD

service drop

set

dial setting (line-drop compensator)

SL

secondary line (Chapter 6)

ST

subtransmission

SW

switchable (capacitors)

sys

power system

T

transformer

Ti

transformer i

X

low-voltage side (LV)

Y

wye connection

1ϕ, 3ϕ

single-phase, three-phase

0, 1, 2

zero-, positive-, negative-sequence quantity

Δ

delta connection

open-delta connection

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