Multistation Control, Telemetering, and Communication on Single-Frequency Carrier

VV. A. D E R R T . C . W R E N J . V . Κ R E S S E R M E M B E R A I E E M E M B E R A I E E

PO W E R - L I N E ca r r i e r a n d associa ted e q u i p m e n t w e r e

r e c e n t l y p l a c e d in service by the S ie r ra Pacific P o w e r

C o m p a n y for the cen t ra l i zed con t ro l of p a r t of the system.

I n p l a n n i n g this cen t r a l i zed con t ro l system, cons ide ra t ion

w a s g iven to the use of t e l ephone- l ine wires , power - l ine

ca r r i e r , a n d m i c r o w a v e r a d i o to p r o v i d e the necessary

i n t e r c o n n e c t i n g c h a n n e l s . E c o n o m i c cons ide ra t ions led to

t h e select ion of power - l i ne ca r r ie r .

T h i s first use of power - l ine ca r r i e r e q u i p m e n t o n t he

S i e r r a Pacific P o w e r C o m p a n y system exemplif ies t he

efficient use of ca r r i e r e q u i p -

m e n t b y c o m b i n i n g m u l t i -

s t a t ion superv i sory con t ro l ,

select ive t e l eme te r i ng , a n d

c o m m u n i c a t i o n on a s ingle-

f r equency c h a n n e l . A m u l t i -

s t a t ion superv i sory con t ro l

sys tem is o n e in w h i c h m o r e

t h a n o n e s ta t ion is o p e r a t e d

f rom a c o m m o n set of e q u i p -

m e n t a t t he con t ro l l i ng s ta t ion . T h e sys tem to be d e -

sc r ibed r equ i r e s n o a u d i o - t o n e m o d u l a t i n g e q u i p m e n t since

on ly a single s igna l - rece iv ing re l ay is r e q u i r e d a t the con-

t ro l l ing loca t ion a n d a t e a c h con t ro l l ed loca t ion .

P O W E R S Y S T E M

FI G U R E 1 is a p a r t i a l s ingle-l ine d i a g r a m of t he S ie r ra

Pacific P o w e r C o m p a n y system showing the s ta t ions in-

volved in this c en t r a l i z ed con t ro l ins ta l la t ion . T h e a p -

p r o x i m a t e d i rec t - l ine a n d t ransmiss ion- l ine d i s tances be -

t w e e n t h e s ta t ions a r e also s h o w n in F i g u r e 1.

E q u i p m e n t is n o w in service w h i c h p rov ides for the r e -

m o t e o p e r a t i o n of t he F a r a d H y d r o S t a t i on , t he V e r d i

H y d r o S t a t i on , a n d the V i r g i n i a C i ty S u b s t a t i o n . T h e

e q u i p m e n t r ecen t ly ins ta l led p rov ides for t he con t ro l of

these t h r e e s ta t ions f rom t h e W a s h o e H y d r o S t a t i on . All

sys tem d i s p a t c h i n g is d o n e f rom the W a s h o e H y d r o S ta t ion .

T h i s r e m o t e - c o n t r o l sys tem will be e x t e n d e d to i nc lude

a n o t h e r s ta t ion in t he n e a r fu ture .

T h e F a r a d H y d r o S t a t i o n h a s t w o 1,750-kva gene ra to r s

p r o v i d i n g a n o r m a l o u t p u t of 2 ,900 k w a n d 2,100 reac t ive

ki lovolt a m p e r e s . T h e V e r d i H y d r o S t a t i o n has one 3,000-

kva g e n e r a t o r p r o v i d i n g a n o r m a l o u t p u t of 2,300 kw a n d

1,200 r eac t i ve ki lovol t a m p e r e s . T h e o u t p u t of the F a r a d

P l a n t is d e t e r m i n e d by the forebay level a t F a r a d . T h e

o u t p u t of t h e V e r d i P l a n t is d e t e r m i n e d by the r iver level.

B o t h p l a n t s c a r r y base load w h i c h m u s t be ad jus ted per i -

od ica l ly to confo rm to the w a t e r level. T h e w a t e r level

a t b o t h s ta t ions is d e t e r m i n e d by the flow of w a t e r in

t h e T r u c k e e R i v e r . T h e reac t ive k i l ovo l t - ampe re o u t p u t

of the p l an t s is d e t e r m i n e d from the system vol tage con-

d i t ions .

I n F igu re 2 the ca r r ie r , supervisory con t ro l , t e l eme te r ing ,

a n d c o m m u n i c a t i o n c o m p o n e n t s w h i c h h a v e been a p p l i e d

a t t he W a s h o e , F a r a d , a n d V e r d i H y d r o S ta t ions a n d the

V i rg in i a Ci ty Subs t a t i on a re shown in block d i a g r a m form.

P O W E R - L I N E C A R R I E R E Q U I P M E N T

"C 1 X A C T L Y d u p l i c a t e s t a n d a r d ca r r i e r assemblies a re in-

stal led a t e a c h of the four locat ions shown in F igu re 2.

T h e s e s t a n d a r d assemblies

a r e exac t ly t he s a m e as those

w h i c h a r e a p p l i e d for ca r -

r ier r e l a y i n g of t he d i s t ance -

m e a s u r i n g t y p e . 1 ' 2 T h e as-

semblies a r e also the d u p l i c a t e

of those used for p h a s e - c o m -

pa r i son r e l ay ing excep t for the

omiss ion of a con t ro l u n i t

w h i c h is r e q u i r e d for p h a s e -

c o m p a r i s o n r e l a y i n g . 3 All of t he ca r r i e r e q u i p m e n t is

o p e r a t e d from 125-volt s ta t ion ba t t e r i e s .

T h e ca r r i e r e q u i p m e n t a t e a c h loca t ion is m o u n t e d on a

s t a n d a r d re lay r a c k in a n i n d o o r - t y p e cab ine t . T h e as-

sembly consists of i nd iv idua l t r a n s m i t t e r , receiver , a n d

m o d u l a t o r pane l s a n d a t es t -mete r un i t .

T h e t r a n s m i t t e r p a n e l consists of a Colp i t t s osci l lator

(one t u b e ) a n d a 6 - tube push -pu l l amplif ier . T h e a m p l i -

fied ca r r i e r - f r equency o u t p u t is fed in to a n i ron-cored

r ad io - f r equency t r ans fo rmer whose s e c o n d a r y couples the

ca r r i e r to t he l ine t h r o u g h the l ine t u n i n g un i t a n d c o u p l i n g

capac i t o r . T h e t r a n s m i t t e r h a s a f requency r a n g e of 50

to 150 kc a n d a f requency s tabi l i ty of one-ha l f pe r cen t .

T h e t r a n s m i t t e r ha s a n o m i n a l p o w e r o u t p u t of t en wa t t s .

T h e rece iver p a n e l consists of a n a r r o w - b a n d s a t u r a t e d

rece iver a n d a b r o a d - b a n d receiver . T h e n a r r o w - b a n d

receiver is used for all u n m o d u l a t e d ca r r i e r signals such as

superv isory con t ro l a n d t e l eme te r ing impulses . T h e

b r o a d - b a n d rece iver is su i tab le for the h i g h - q u a l i t y r ecep -

t ion of speech . T h e f requency r a n g e of b o t h receivers is

50 to 150 kc . O n this ins ta l la t ion b o t h receivers a r e t u n e d

to t he s a m e f requency . T h e n a r r o w - b a n d rece iver will

o p e r a t e t h r o u g h a n a t t e n u a t i o n of 30 decibels w h e n used

w i t h a 10-wat t t r a n s m i t t e r . T h e b r o a d - b a n d rece iver will

Essentially full text of paper 50-175, "Multistat ion Supervisory Control, Telemetering, and Communication on Single-Frequency Carrier Channel , " recommended by the AIEE Committees on Carrier Current and Substations and approved by the AIEE Technical Program Committee for presentation at the AIEE Summer and Pacific General Meeting, Pasadena, Calif., J u n e 12-16, 1950. Scheduled for publication in AIEE Transactions, volume 69, 1950.

W. A. Derr is with the Westinghouse Electric Corporation, Pittsburgh, Pa. ; T. C Wren is with the Sierra Pacific Power Company, Reno, Nev. ; and J. V. Kresser is with the Westinghouse Electric Corporation, San Francisco, Calif.

A centra l i zed control s y s t e m ut i l i z ing p o w e r -

l ine carrier w a s r e c e n t l y ins ta l l ed b y t h e Sierra

Pacific P o w e r C o m p a n y . T h i s s i n g l e - f r e q u e n c y

mul t i s ta t ion s y s t e m is u s e d for s u p e r v i s o r y

control , as w e l l as se l ec t ive t e l e m e t e r i n g a n d

c o m m u n i c a t i o n .

862 Derr, Wren, Kresser—Multistation Control, Telemetering, and Communication E L E C T R I C A L E N G I N E E R I N G

o p e r a t e t h r o u g h a n a t t e n u a t i o n of 50 dec ibe ls w h e n used

w i t h a 10 -wa t t t r a n s m i t t e r .

T h e m o d u l a t o r p a n e l has re lays , v o l t a g e - d r o p p i n g resis-

tors , a n d a t e l e p h o n e h a n d s e t j a c k - m o u n t e d on it. I t is

des igned for use w i t h a push- to - t a lk t e l e p h o n e h a n d s e t .

T h e v o l t a g e - d r o p p i n g resistors furnish p r o p e r m i c r o p h o n e

c u r r e n t a n d o p e r a t i n g vol tages for t he relays. T h e re lays

a n d c o n t a c t s a r e w i r e d so t h a t t he ca r r i e r t r a n s m i t t e r c a n be

keyed w h e n t he t e l e p h o n e push - to - t a lk key is o p e r a t e d .

T h e t e s t -me te r u n i t is a p o r t a b l e assembly of i n s t r u m e n t s

for r o u t i n e c i rcui t tes t ing. I t c a n be m o u n t e d in the ca r r i e r

cab ine t . All of the ca r r i e r pane l s h a v e test j a cks in the

m a i n c i rcui ts to p r o v i d e for the m e a s u r e m e n t of c u r r e n t s

a n d vol tages w i t h the tes t -mete r un i t .

T h e power - l ine ca r r i e r e q u i p m e n t o p e r a t e s f rom phase to

g r o u n d . As s h o w n in F i g u r e 2, t he ca r r i e r t r a n s m i t t e r

a n d rece iver a t W a s h o e a r e c o u p l e d to the 60-kv lines to

F a r a d as well as to t he t w o 60-kv lines to V i rg in i a Ci ty .

S ingle- f requency ca r r i e r l ine t r a p s a r e insta l led in e a c h of

these lines so t h a t a n essential ly fixed i m p e d a n c e is p r e -

sented to all ca r r i e r s ignals regard less of swi tch ing o p e r a -

t ions a t W a s h o e . T h i s is the on ly loca t ion a t w h i c h ca r r i e r

l ine t r aps a re used. T h e ca r r i e r e q u i p m e n t is c o u p l e d to

b o t h 60-kv lines b e t w e e n W a s h o e a n d V i r g i n i a C i ty to

o b t a i n a d d i t i o n a l re l iabi l i ty .

S ince no a t t e n u a t i o n d a t a were ava i l ab le a n d since t he re

is no o the r ca r r i e r on the system, it was a rb i t r a r i ly dec ided

to t ry o p e r a t i o n a t a f requency of 100 kc. A satisfactory

s ignal was o b t a i n e d a t all locat ions , a n d the system is still

o p e r a t i n g a t this f requency .

T h e r e was no p r o b l e m involved in t u n i n g the para l le l

c i rcui ts a t W a s h o e . T h e 4-line tune r s a re e a c h c o n n e c t e d

to the ca r r i e r e q u i p m e n t by a s epa ra t e coaxia l cab le .

E a c h of the lines was t u n e d i n d e p e n d e n t l y of the o thers ,

a n d it was found t h a t the division of the rad io - f requency

c u r r e n t was fairly even . N o difficulty is a n t i c i p a t e d w h e n

a n o t h e r line ou t of W a s h o e is a d d e d to this ca r r i e r system

for the con t ro l of a four th s ta t ion .

A satisfactory s ignal is o b t a i n e d a t V i rg in i a Ci ty wi th

e i ther of the two 60-kv lines ou t of service.

S U P E R V I S O R Y C O N T R O L E Q U I P M E N T

' I ' H E SUPERVISORY con t ro l e q u i p m e n t a p p l i e d is of the

direct -se lect ion a l l - re lay coded - impu l se t y p e . 4 T h i s

V E R D I HYDRO STATION WASHOE HYDRO STATION

I 3 0 0 0 60 /2 .3KV X I KVA V J_

το RENO F i g u r e 1. Partial s ing le - l ine d iagram

HYDRO STATION s h o w i n g part of the system i n v o l v e d in

carrier instal lat ion

VIRGINIA CITY - LOCAL

ι το T R U C K E E SUBSTATION

[6 ] Ε*]

O C T O B E R 1950 Derr, Wren, Kresser—Multistation Control, Telemetering, and Communication 863

6 0 KV. LINE , TOVEROÎ

60KVLINE . TO FARAB

^Ch^- CARRIER - ^ C ^ " CARRIER

çrry- TRAPS ^ j-rtj - COUPLING CAPACITORS—

H—LINE-COUPLING TUNERS-*-

\ T W 0 60KV. f LINES TO

-^VIRGINIA CITY

CARRIER CARRIER TRANSMITTER RECEIVER

Figure 2 . Block d iagram

s h o w i n g carrier, supervisory

control, t e l emeter ing , a n d

communicat ion c o m p o n e n t s

(left) W a s h o e , ( lower left)

Farad a n d V e r d i , ( lower

r ight ) Virg in ia City

SUPERVISORY CONTROL SELECTION AND CONTROL

KEYS

SUPERVISORY

CONTROL RELAYS

SUPERVISORY CONTROL

INDICATING LAMPS

6. T e l e m e t e r i n g of fore-

b a y w a t e r level.

7. Superv is ion of a l a r m s

for w h i c h g e n e r a t o r shu ts d o w n .

8. Supervis ion of a l a r m s

w h i c h d o no t shu t d o w n gen-

e ra to r .

9. T e l e p h o n e r i ng ing .

TELEMETERING RECEIVERS

TELEPHONE CALLJANSWER

TELEPHONE TRANSMITTER

TELEPHONE RECEIVER

EQUIPMENT AT WASHOE HYORO STATION

60KV LINE TO

WASHOE 1 . ^COUPL ING •^CAPACITOR

TWO 60KV LINES TO WASHOE

^ LINE-COUPLING TUNERS

1

CARRIER TRANSMITTER

CARRIER RECEIVER

-COUPLING CAPACITORS

-LINE-COUPLING TUNERS

INTERPOSING RELAYS

FOR BREAKER CONTROL.ETC.

SUPERVISORY

CONTROL RELAYS

TELEMETERING TRANSMITTERS

Ϊ

CARRIER CARRIER TRANSMITTER RECEIVER

L I SWITCH CONTACTS FOR ALL DEVICES INTERPOSING

RELAYS FOR 8REAKER CONTROL.ETC

C D — O k /

TELEPHONE TRANSMITTER

SUPERVISORY

CONTROL RELAYS

1

AUXILIARY SWITCH CONTACTS FOR ALL DEVICES

SUPERVISED

TELEPHONE RECEIVER

-Cf> TELEPHONE TRANSMITTER

TELEPHONE RECEIVER

EQUIPMENT AT FARAO AND VEROI HYORO STATIONS EQUIPMENT AT VIRGINIA CITY

t y p e of system e m p l o y s a series of impulses t r a n s m i t t e d a t

t h e r a t e of a p p r o x i m a t e l y 15 p e r s econd for al l se lect ion a n d

c o n t r o l codes . C h e c k o r ver if icat ion codes a r e used to

insure p r o p e r select ions. T h i s t ype of sys tem r equ i r e s only

a single s igna l - rece iv ing e l e m e n t a t e a c h s t a t ion . O n l y

such a s ingle-signal sys tem c a n be used for t h e con t ro l of

several s ta t ions o n a s ingle- f requency ca r r i e r c h a n n e l .

T h e superv isory e scu tcheons a r e a r r a n g e d in a m i m i c

bus a r r a n g e m e n t a t t he W a s h o e H y d r o S t a t i o n to dep ic t

the essentials of t h e p o w e r sys tem. A n i n d i v i d u a l es-

c u t c h e o n is p r o v i d e d for t he con t ro l a n d superv is ion of e a c h

c i rcu i t b r e a k e r , for e a c h selective t e l eme te red ind ica t ion ,

a n d so for th.

T h e superv isory con t ro l p rov ides for the con t ro l a n d

superv i s ion of t h e c i rcu i t b r eake r s a t V i r g i n i a Ci ty S u b -

s t a t ion a n d for all of t he essent ia l funct ions a t t he F a r a d

a n d V e r d i H y d r o S ta t ions . T h e superv isory con t ro l also

p rov ides a selective t e l e p h o n e - r i n g i n g funct ion to e a c h of

the con t ro l l ed s ta t ions . Fo l lowing is a c o m p l e t e list of the

funct ions p r o v i d e d a t t he V e r d i H y d r o S ta t ion . E a c h such

c o m p l e t e func t ion is usual ly referred to as a po in t of the

superv isory con t ro l .

1. S t a r t - s t op con t ro l of g e n e r a t o r w i th supervis ion of

m a s t e r re lay .

2. C o n t r o l of g e n e r a t o r field rheos t a t w i t h t e l eme t e r i n g

of r eac t ive k i lovo l t - ampere o u t p u t .

3 . C o n t r o l of g e n e r a t o r - g o v e r n o r synch ron i z ing m o t o r

w i t h t e l e m e t e r i n g of g e n e r a t o r k i lowa t t o u t p u t .

4. C o n t r o l a n d supervis ion of 60-kv c i rcui t b r e a k e r .

5. C o n t r o l a n d supervis ion of g e n e r a t o r c i rcui t

b r e a k e r .

T E L E M E T E R I N G E Q U I P M E N T

Τ M P U L S E - T Y P E te lemeter i ng

e q u i p m e n t is used for t he

selective t e lemete red ind ica -

tions previously l i s t ed . 5 , 6 R a t e

of impulse t e l eme te r ing e q u i p -

m e n t is used for t he i n d i c a -

tions of k i lowat t s a n d r eac t ive

k i lvo l t -amperes . T h e r a t e of

impu l s ing is b e t w e e n 80 a n d

220 pe r m i n u t e . T h e left-

h a n d r e a d i n g o n the rece iver

is o b t a i n e d w i t h a r a t e of 80

impulses p e r m i n u t e , a n d the

r i g h t - h a n d or full-scale r e a d i n g

is o b t a i n e d w i t h a r a t e of 220

impulses p e r m i n u t e .

Since the r e a d i n g s a r e se-

lective, a single t r a n s m i t t e r is

used a t the F a r a d a n d V e r d i

H y d r o S ta t ions for t e l eme te r ing k i lowat ts a n d reac t ive k i lo-

vol t a m p e r e s . T h e supervisory con t ro l e q u i p m e n t c o n -

nec ts t he t r a n s m i t t e r to the p r o p e r po t en t i a l a n d c u r r e n t -

t r ans fo rmer c i rcui ts . A r e a c t i v e - c o m p o n e n t c o m p e n s a t o r

is a u t o m a t i c a l l y c o n n e c t e d in the p o t en t i a l c i rcui ts to the

t r a n s m i t t e r b y t he superv isory con t ro l e q u i p m e n t for t e lem-

e t e r i ng reac t ive ki lovolt a m p e r e s .

A t the W a s h o e H y d r o S ta t ion , a single receiver is p r o -

v ided for all k i lowat t ind ica t ions , a n d a single receiver is

p r o v i d e d for all r eac t ive k i lovo l t - ampere ind ica t ions .

D u r a t i o n of impu l se - type t e l eme te r ing e q u i p m e n t is

used for t he selective ind ica t ions of w a t e r level. T h e

t r ansmi t t e r s a r e of t he p re s su re -bu lb t y p e . W i t h this

system, t he r e a d i n g o b t a i n e d is based o n the l eng th of

impu l se t r a n s m i t t e d d u r i n g e a c h 5-second cycle.

A U T O M A T I C S W I T C H I N G E Q U I P M E N T

Τ Ν P R O V I D I N G for t he r e m o t e o p e r a t i o n of t h e F a r a d a n d

V e r d i H y d r o S ta t ions it w a s necessary to a d d ce r t a in

a u t o m a t i c - s w i t c h i n g a n d p ro tec t ive e q u i p m e n t a t e a c h of

these s t a t i ons . 7 T h e m e t h o d of o p e r a t i o n p r o v i d e d for the

t w o s ta t ions is s o m e w h a t different .

A t the F a r a d H y d r o S ta t ion , a n a u t o m a t i c e lec t ron ic

synchron ize r , a speed m a t c h e r , a n d a vo l t age -ba l ance re lay

a r e p r o v i d e d . U p o n rece ip t of a s t a r t ing s ignal f rom the

supervisory con t ro l e q u i p m e n t , all of these devices a re

a u t o m a t i c a l l y c o n n e c t e d to t he g e n e r a t o r to b e s t a r t ed .

T h u s the speed a n d vo l tage of t he g e n e r a t o r a r e a u t o -

ma t i ca l ly m a d e to m a t c h the system f requency a n d vo l t age .

T h e a u t o m a t i c synchron ize r causes t he g e n e r a t o r c i rcui t

b r e a k e r to close w h e n the i n s t a n t a n e o u s f requency differ-

864 Derr, Wren, Kresser—Multistation Control, Telemetering, and Communication E L E C T R I C A L E N G I N E E R I N G

once a n d the p h a s e - a n g l e difference a re satisfactory for

p r o p e r synchron iz ing .

T h e con t ro l of t he V e r d i H y d r o S t a t i on is based on all

s y n c h r o n i z i n g b e i n g d o n e on the c i rcui t b r e a k e r at the

W a s h o e e n d of the l ine. The re fo re , no a u t o m a t i c syn-

c h r o n i z i n g or s p e e d - m a t c h i n g e q u i p m e n t is used a t the

V e r d i H y d r o S ta t ion . T h e o p e r a t o r a t t he W a s h o e H y d r o

S t a t i o n is ab l e to s tar t the g e n e r a t o r a t t he V e r d i H y d r o

S t a t i on a n d to con t ro l ind iv idua l ly the g e n e r a t o r a n d l ine

c i rcu i t b r eake r . T h e o p e r a t o r c a n also con t ro l the speed

a n d vo l tage of t he g e n e r a t o r a t the V e r d i H y d r o S ta t ion to

be ab le to effect m a n u a l synch ron i z ing of the c i rcu i t b r e a k e r

a t the W a s h o e H y d r o S t a t i on .

After t h e g e n e r a t o r s a t t he F a r a d a n d V e r d i H y d r o Sta-

t ions a r e c o n n e c t e d to the system, t h e o p e r a t o r at W a s h o e

can con t ro l t he k i lowat t a n d reac t ive k i lovo l t - ampere ou t -

pu t of t he m a c h i n e s .

O P E R A T I O N O F R E M O T E - C O N T R O L S Y S T E M

H P H E SUPERVISORY con t ro l system a p p l i e d in this cen-

t ra l ized con t ro l ins ta l la t ion c a n p rov ide for a n u l t i m a t e

of 1 0 0 funct ions o r po in t s . T w o series of impulses , bo th of

wh ich a r e a u t o m a t i c a l l y checked , a r e r e q u i r e d for the

selection of e a c h ind iv idua l po in t . T h e first series of im-

pulses selects a g r o u p of ten po in ts , a n d the second series of

impulses selects t he i nd iv idua l po in t in t he g r o u p of ten

poin ts . T h e necessary n u m b e r of g r o u p s to p rov ide for the

desired n u m b e r of funct ions is assigned to a p a r t i c u l a r

s ta t ion .

T h e two series of impulses r e q u i r e d for t he selection of a n

ind iv idua l p o i n t a r e des igna ted as g r o u p - a n d point -se lec-

tion codes . T h e c o r r e s p o n d i n g check or ver if icat ion codes

a r e de s igna t ed as g r o u p - a n d p o i n t - c h e c k codes . I n this

ins ta l la t ion , t he m i n i m u m n u m b e r of impulses for a n y g r o u p

select ion code is seven. T h i s e l imina t e s t he possibil i ty of

a n y a c t u a l g r o u p selection resu l t ing f rom r a n d o m in ter -

ference w h i c h cou ld o p e r a t e a ca r r i e r - rece iver re lay .

T h e c o r r e s p o n d i n g g r o u p - c h e c k codes a r e in all cases six

impulses less t h a n the g roup-se lec t ion codes . T h e po in t -

selection a n d po in t - check codes a r e t h e s a m e a n d m a y h a v e

from o n e to t en impulses . S ince t he impulses a r e t r ans -

mi t t ed a t t he r a t e of a p p r o x i m a t e l y 1 5 pe r second, t he

longest select ion t ime for a n y p o i n t of the u l t i m a t e system

is less t h a n four seconds .

T h e group-se lec t ion codes now in use a re as follows:

V e r d i 7 a n d 8 impulses

F a r a d 9 a n d 1 0 impulses

V i rg in i a Ci ty 1 1 a n d 1 2 impulses

If a select ion key is o p e r a t e d at W a s h o e , the g r o u p - a n d

poin t -se lec t ion codes o r ig ina te at W a s h o e a n d the g r o u p -

a n d po in t - check codes o r ig ina te a t the s ta t ion selected.

In t he case of a n a u t o m a t i c o p e r a t i o n r e p o r t i n g f rom o n e of

the r e m o t e l y con t ro l led s ta t ions , the g r o u p - a n d poin t -

select ion codes o r ig ina te a t the r e m o t e s ta t ion a n d the g r o u p -

a n d po in t - check codes o r ig ina te a t W a s h o e .

Fo r con t ro l funct ions a n d for the supervis ion of devices

s imi la r series of impulses a r e used. T h e n u m b e r of such

impu l ses is t h e s a m e for all po in ts since on ly o n e p o i n t c an be

selected a t a t i m e .

Since the ca r r i e r t r ansmi t t e r s a n d receivers a r e t u n e d to

the s a m e f requency a t all locat ions , key ing a t r a n s m i t t e r a t

one or m o r e loca t ions results in o p e r a t i o n of the single

ca r r ie r - rece iver re lay a t every s ta t ion . T h i s pa r ty - l ine

a r r a n g e m e n t m a k e s it possible for the supervisory con t ro l

to select a p a r t i c u l a r s ta t ion a n d s imul taneous ly to lock out

all o t h e r s ta t ions . T h e group-se lec t ion code is recognized

as a lockout code by all s ta t ions excep t the one b e i n g se-

lec ted. T h e s e s ta t ions r e m a i n locked ou t unt i l a reset im-

pulse is t r a n s m i t t e d from W a s h o e a t the end of a c o m p l e t e

funct ion. T h e reset impulse is a p p r o x i m a t e l y one- four th

second long . R e c e i p t of a ca r r i e r impulse of this l eng th or

longer a t a n y s ta t ion releases a po in t w h i c h m a y h a v e been

selected a t t h a t s ta t ion or unlocks t h a t s ta t ion if it h a d been

Table I. Superv i sory Control I m p u l s i n g for Typ ica l Opera t ions

Washoe (Controlling

Station)

Verdi (Controlled

Station)

Farad (Controlled

Station)

Virginia City (Controlled

Station)

A. Closing of Circuit Breaker at Virginia City from Washoe

Group Selection Code

(\\ Impulses)

Group Check

Point Selection Code

;'3 Impulses)

Point Checked

Close Control Code O g.

Croup Selected

Group Check Code

(5 Impulses)

Point Selected

Point Check Code

(3 Impulses)

Circuit Breakci Closes

Close Supervision C o d e

(5 Impulse^

{5 Impulses)

Lamp Indication Changed

Reset Impulse

System Restored to Normal At-Rest Condition

Reporting of Automatic Circuit-Breaker Trip from Farad to Washoe

Group Selection Code

Group Selected

Group Check Code

(3 Impulses)

Point Selected

Point Check Code

(1 Impulse)

Lamp Indication Changed

Reset Impulse

Locks Out (9 Impulses)

Group Checked

Point Selection Code

5 «

Ο α

(1 Impulse)

Point Checked

Tr ip Supervision Code

(3 Impulses)

Kvslein Res tored to N o r m a l A t - R e s t C o n d i t i o n

O C T O B E R 1 9 5 0 Derr, Wren, Kresser—Multistation Control, Telemetering, and Communication 8 6 5

locked ou t by select ion a t a n o t h e r s ta t ion . A reset impul se

res tores t h e en t i r e superv isory con t ro l sys tem to its n o r m a l

a t - res t c o n d i t i o n so t h a t it is r e a d y for a n o t h e r select ion.

T a b l e IA i nd ica tes t h e i m p u l s i n g w h i c h resul ts if t h e

c i rcu i t b r e a k e r a t V i r g i n i a Ci ty Subs t a t i on , w h i c h is

ass igned a g roup-se lec t ion code of 1 1 impulses a n d a po in t -

select ion code of t h r e e impulses , is selected a n d closed.

T a b l e IB i nd ica tes t he i m p u l s i n g for t he a u t o m a t i c t r i p p i n g

of a c i rcu i t b r e a k e r a t F a r a d H y d r o S t a t i o n w h i c h is ass igned

a g roup-se lec t ion code of n i n e impulses a n d a poin t -se lec t ion

code of o n e impu l se .

As i n d i c a t e d in b l o c k - d i a g r a m form in F i g u r e 2, t h e

superv i sory con t ro l re lays a t e a c h s ta t ion a r e in te rposed

b e t w e e n t he ca r r i e r e q u i p m e n t a n d all of t he services p r o -

v i d e d . T h i s m a k e s it possible to give preference to t h e

i m p o r t a n t superv i sory c o n t r o l funct ions r a t h e r t h a n to t he

t e l e m e t e r i n g o r c o m m u n i c a t i o n services.

S E L E C T I V E T E L E M E T E R I N G

/^Λ P E R A T i O N of a po in t - se lec t ion key for a n y of the selective

t e l e m e t e r e d ind ica t ions resul ts in t he a u t o m a t i c

t r ansmiss ion of group-se lec t ion , g roup -check , point -se lec-

t ion , a n d p o i n t - c h e c k codes of impulses as desc r ibed for t he

select ion of a c i r cu i t -b r eake r con t ro l po in t . H o w e v e r , a t

t h e conc lus ion of t he po in t - check code , t he p r o p e r t e lem-

e t e r i n g t r a n s m i t t e r ha s its key ing c o n t a c t c o n n e c t e d to t he

ca r r i e r t r a n s m i t t e r , a n d the p r o p e r t e l eme te r i n g receiver

is c o n n e c t e d to receive t he ca r r i e r impulses . T h u s , a n

ind i ca t i on is o b t a i n e d as soon as t he po in t is selected.

T h e c i rcui ts a r e a r r a n g e d so t h a t t he t e l eme t e r i n g im-

pulses, w h i c h a r e long w i t h respec t to t he l eng th of the

superv isory con t ro l impulses , d o n o t cause t he p o i n t to be

re leased e i the r a t t h e W a s h o e con t ro l l ing s ta t ion or a t the

con t ro l l ed s ta t ion selected. H o w e v e r , t he t e l eme t e r i n g

impulses d o reset t he o t h e r con t ro l l ed s ta t ions w h i c h w e r e

locked o u t w h e n the group-se lec t ion code was t r a n s m i t t e d .

T h e t e l e m e t e r e d i nd i ca t i on m a y be m a i n t a i n e d as long as

des i red . O p e r a t i o n of t he reset key resul ts in the super -

v isory-cont ro l reset impu l se b e i n g t r a n s m i t t e d a t the ter-

m i n a t i o n of a t e l e m e t e r i n g impulse w h i c h m a y h a v e b e e n in

progress a t t he t i m e . O p e r a t i o n of t he car r ie r - rece iver

re lay a t the s ta t ion selected w i t h o u t t he t e l eme te r i n g t r ans -

m i t t e r c o n t a c t b e i n g closed resul ts in the selected po in t be ing

re leased a n d the en t i r e system res to red to n o r m a l .

I n t he case of po in t s in w h i c h a con t ro l funct ion is c o m -

b ined w i t h t he selective t e l eme te r ing , t he con t ro l impulses

f rom the W a s h o e H y d r o S t a t i o n a r e t r a n s m i t t e d d u r i n g the

off pe r iod of the t e l e m e t e r i n g impulses . T h e con t ro l is of

the i n c r e m e n t t ype w i t h t he con t ro l c i rcui ts a t t he con-

t rol led s ta t ion b e i n g ene rg ized for a defini te pe r iod of t ime

for e a c h o p e r a t i o n of a con t ro l key a t the W a s h o e H y d r o

s ta t ion . A n a r r a n g e m e n t is p r o v i d e d so t h a t t he con t ro l

i n c r e m e n t for e a c h of t he devices con t ro l l ed is ind iv idua l ly

v a r i a b l e . I t is possible for the o p e r a t o r a t t he W a s h o e

H y d r o S t a t i o n to o b t a i n a c c u r a t e l y t he des i red k i lowat t a n d

reac t ive k i l ovo l t - ampe re o u t p u t of t he gene ra to r s since a

t e l e m e t e r e d i nd i ca t i on is o b t a i n e d whi le the con t ro l l ing

is b e i n g d o n e .

S ince t he c o n t i n u o u s t ransmiss ion of ca r r i e r from a n y

s ta t ion w i t h such a s ingle-f requency ca r r i e r system w o u l d

m a k e the en t i re system inopera t ive , a t i m i n g c i rcui t is

p r o v i d e d to d i sconnec t a u t o m a t i c a l l y a t e l eme te r i ng t r a n s -

m i t t e r w h i c h keys the ca r r i e r t r a n s m i t t e r con t inuous ly d u e

to a fai lure in t he t e l eme te r ing t r a n s m i t t e r or loss of a-c

p o w e r o n the t r ansmi t t e r .

C O M M U N I C A T I O N

1 I ' H E SUPERVISORY con t ro l p rov ides for selective r i ng ing

from the W a s h o e H y d r o S ta t ion to a n y of the t h r e e

s ta t ions con t ro l led . I t also p rov ides for a n y of the con-

trol led s ta t ions ca l l ing the o p e r a t o r a t the W a s h o e H y d r o

S ta t ion . T h e t e l ephone r i ng ing is accompl i shed by po in t s

of the supervisory con t ro l .

A t e l ephone deskset a n d a t e l ephone call a n d answer b o x

is loca ted in the W a s h o e H y d r o S ta t ion . T h e call a n d

answer box has a t e l ephone key a n d l a m p for e a c h of t h e

con t ro l l ed s ta t ions . T o in i t ia te a t e l ephone call f rom

W a s h o e , it is on ly necessary to o p e r a t e the t e l ephone cal l

key for the des i red s ta t ion a n d to lift the t e l e p h o n e h a n d s e t

f rom the c r ad l e . T h i s results in the a u t o m a t i c t ransmiss ion

of the p r o p e r g r o u p - a n d point -se lec t ion codes from W a s h o e

a n d the c o r r e s p o n d i n g check codes from the s ta t ion b e i n g

cal led. W h e n the po in t - check code is rece ived a t W a s h o e ,

a con t ro l code is a u t o m a t i c a l l y t r a n s m i t t e d to r i ng t he

t e l ephone bell a t the s ta t ion b e i n g cal led . W h e n the call

is a n s w e r e d by the r e m o v a l of the t e l ephone h a n d s e t f rom

the c r ad l e a t t he cal led s ta t ion , a supervis ion code is t r ans -

m i t t e d w h i c h is followed b y a reset impulse from W a s h o e

to res tore the en t i r e supervisory con t ro l system to the n o r m a l

a t - res t cond i t ion . W h e n the supervisory con t ro l e q u i p m e n t

resets, c i rcui ts a r e c o m p l e t e d from the t e l ephone to the

car r i e r e q u i p m e n t a t W a s h o e as well as a t the s ta t ion ca l led .

T h i s es tabl ishes c o m m u n i c a t i o n of the push- to - t a lk type

b e t w e e n W a s h o e a n d the s ta t ion cal led. O p e r a t i n g t he

push- to - ta lk key on e i the r t e l e p h o n e h a n d s e t keys the ca r r i e r

t r a n s m i t t e r a t t h a t loca t ion a n d the t e l ephone t r a n s m i t t e r

c a n t h e n m o d u l a t e the car r ie r . T h i s is the same type of

c o m m u n i c a t i o n w h i c h is p r o v i d e d on the usua l single-

f requency ca r r i e r -p ro tec t ive r e l ay ing ins ta l la t ion .

Ca l l ing the o p e r a t o r a t W a s h o e from o n e of the con t ro l l ed

s ta t ions is accompl i shed in a s imilar m a n n e r . I t is on ly

necessary to r e m o v e t he t e l ephone h a n d s e t from the c rad le

a t t he cont ro l led s ta t ion to in i t ia te a call to W a s h o e .

T h e t e l ephone a t the con t ro l l ed s ta t ions is m o u n t e d on a

supervisory con t ro l p a n e l . W h e n the supervis ion code is

rece ived a t W a s h o e , the t e l e p h o n e bell is s o u n d e d a n d the

call l a m p ind i ca t i ng w h i c h s ta t ion is ca l l ing is l ighted . T o

answer the call , t he o p e r a t o r r emoves the t e l ephone h a n d s e t

from the c r a d l e a n d ope ra t e s the t e l ephone call key for the

s ta t ion m a k i n g the call . T h e supervisory con t ro l system

t h e n a u t o m a t i c a l l y resets a n d conversa t ion c a n s tar t .

W i t h this c o m m u n i c a t i o n system it is possible for the

o p e r a t o r a t W a s h o e to per form the necessary r i ng ing

funct ions to es tabl ish c o m m u n i c a t i o n be tween two or m o r e

of t he r emote ly cont ro l led s ta t ions .

After c o m m u n i c a t i o n is es tabl i shed, t he supervisory con-

trol system is locked o u t whi le a t e l ephone push- to - t a lk

key is o p e r a t e d a t a n y of the s ta t ions . H o w e v e r , t h e super -

visory system takes con t ro l a t t he first i n s t an t t h a t n o tele-

p h o n e push- to - t a lk key is o p e r a t e d . T h u s , if a c i rcui t

8 6 6 Derr, Wren, Kresser—Multistation Control, Telemetering, and Communication E L E C T R I C A L E N G I N E E R I N G

breake r is t r i p p e d by a p ro tec t ive re lay o p e r a t i o n a t a n y

s ta t ion , it will r e p o r t its n e w posi t ion to W a s h o e in the usua l

m a n n e r a t the first pause in t he conve r sa t ion . T h e first

superv isory con t ro l impu l se d i sconnec t s the t e l ephone from

the ca r r i e r e q u i p m e n t a t e a c h s ta t ion a n d p r even t s t he

s t a r t i ng of ca r r i e r by a t e l e p h o n e push - to - t a lk key un t i l t he

en t i r e superv isory con t ro l func t ion is c o m p l e t e d . T h e

conver sa t ion c a n be i m m e d i a t e l y r e s u m e d after the several

seconds r e q u i r e d to c o m p l e t e supervisory con t ro l funct ion .

T h e ci rcui ts for key ing the ca r r i e r t r an smi t t e r s w i t h the

t e l e p h o n e push- to - t a lk keys a r e a r r a n g e d so t h a t it is on ly

possible to t r a n s m i t a n impulse long e n o u g h to cons t i tu te a

reset impu l se for the supervisory con t ro l regard less of h o w

shor t a pe r iod of t ime the push- to - t a lk key is o p e r a t e d .

T h i s m a k e s it impossible to s tep the supervisory con t ro l f rom

its n o r m a l a t - res t cond i t ion .

C O N C L U S I O N

Γ I ' H E R E a r e m a n y ins ta l la t ions of power - l ine ca r r i e r for

supervisory con t ro l , t e l emete r ing , a n d c o m m u n i c a t i o n

services. I n mos t of these ins ta l la t ions a s e p a r a t e c h a n n e l is

used for e a c h one of these services. I n qu i t e a n u m b e r of

cases ca r r i e r r e l ay ing has b e e n c o m b i n e d w i t h a n y of

these th ree services on a single 2 - t e rmina l c h a n n e l . 8 T h e r e

a re also ins ta l la t ions of supervisory con t ro l c o m b i n e d w i t h

t e l eme te r ing , a n d of supervisory con t ro l c o m b i n e d w i t h

c o m m u n i c a t i o n on a 2 - t e rmina l c h a n n e l . H o w e v e r , the

ins ta l la t ion descr ibed was the first in w h i c h a single-fre-

q u e n c y c h a n n e l was used for mul t i s t a t ion supervisory con-

trol , t e l emete r ing , a n d c o m m u n i c a t i o n . T h i s p rov ides t h e

mos t e c o n o m i c a l possible a r r a n g e m e n t since a m i n i m u m of

ca r r i e r e q u i p m e n t is r e q u i r e d .

T h e fact t h a t on ly a single ca r r i e r f requency is r e q u i r e d for

this en t i r e system is n o t p a r t i c u l a r l y i m p o r t a n t in this in-

s tance , since n o o t h e r ca r r i e r is in use on the S ie r ra Pacific

P o w e r C o m p a n y system. H o w e v e r , this is a n ex t r eme ly

i m p o r t a n t cons ide ra t ion in m a n y sections of the c o u n t r y

w h e r e it is b e c o m i n g increas ingly difficult to choose n e w fre-

quenc ie s d u e to t he l a rge n u m b e r of c h a n n e l s a l r e a d y in use .

T h e c a r r i e r - o p e r a t e d r e m o t e - c o n t r o l ins ta l la t ion d e -

scribed has simplified system d i s p a t c h i n g a n d i m p r o v e d

system o p e r a t i o n .

R E F E R E N C E S 1. A New High-Speed Distance-Type Carrier-Pilot Relay System, E. L. Harder, B. E. Lenehan, S. L. Goldsborough. Electrical Engineering (AIEE Transactions), volume 57, January 1938, pages 5-10.

2. The Application of Power-Line Carrier, R. C. Cheek. Power Plant Engineering (Chicago, 111.), November 1945.

3. A New Carrier Relaying System, T. R. Hal man, S. L. Goldsborough, H. W. Lensner, A. F. Drompp. Electrical Engineering (AIEE Transactions), volume 63, August 1944, pages 568-72.

4. By a Flick of the Finger, W. A. Derr. Westinghouse Engineer (Pittsburgh, Pa.) , November 1945.

5. Telemetering Circuits—Metallic and Carrier, M. A. Bostwick. AIEE Transac~ tions, volume 67, part I I , 1948, pages 1081-8.

6. Telemetering (book), P. A. Borden, G. M. Thynell . Reinhold Publishing Com-pany, New York, Ν. Y. 1948. Chapter 7.

7. Automatic Control of Hydroelectric Generating Stations, M.J . Brown, W. A. Derr. AIEE Transactions, volume 66, 1947, pages 343-55.

8. A Versatile Power-Line-Carrier System, H. W. Lensner, J. B. Singel. Electrical Engineering (AIEE Transactions), volume 63, 1944, March section, pages 129-33.

Handling Power System Problems on an A-C Network Calculator

P. O . B O B Ο M E M B E R A I E E

US E of t h e a-c ca l cu -

l a t i n g b o a r d h a s b e -

c o m e s t a n d a r d p r a c t i c e

a m o n g p o w e r c o m p a n i e s in

t h e U n i t e d S ta tes . I t is used

for t h e solu t ion of o p e r a t i n g

p r o b l e m s , p l a n n i n g n e w a d -

d i t ions to systems, a n d for

s t u d y i n g p r o p o s e d i n t e r con -

nec t ions . I t is b e c o m i n g a m a j o r tool in t h e d e v e l o p m e n t

of sys tem loss f o r m u l a s , 1 a n d n o d o u b t will see m u c h serv-

ice in p r o b l e m s of e c o n o m i c p l a n t l o a d i n g . 2

P o w e r sys tem g r o w t h h a s b e e n r a p i d since t h e w a r .

T h e c o m p l e x i t y of c a l c u l a t i n g b o a r d n e t w o r k s h a s inc reased

p r o p o r t i o n a t e l y . Because of this fact, c o u p l e d w i t h t h e

Essentially full text of a conference paper presented at the AIEE Winter General Meeting, New York, Ν. Y., January 30-February 3, 1950. P. O. Bobo is with the Westinghouse Electric Corporation, East Pittsburgh, Pa.

Calcu la t ing b o a r d n e t w o r k s h a v e b e c o m e m o r e

a n d m o r e c o m p l i c a t e d as p o w e r s y s t e m s h a v e

g r o w n a n d e x p a n d e d . A s a g r e a t e r n u m b e r

of a n d m o r e c o m p l e x p r o b l e m s h a v e b e e n

s u b m i t t e d for so lu t ion , n e w t e c h n i q u e s h a v e

b e e n e m p l o y e d a n d t h e b o a r d s t h e m s e l v e s

h a v e b e e n i m p r o v e d .

increase in d e m a n d for solu-

t ion of p o w e r system p r o b l e m s

by a-c n e t w o r k ca l cu la to r s ,

n e w t e c h n i q u e s of p r o c e d -

u r e h a v e b e e n d e v e l o p e d a n d

a d d i t i o n a l fea tures h a v e b e e n

a d d e d — a l l of w h i c h increase

t h e efficiency of t h e b o a r d s .

A t e c h n i q u e of o b t a i n i n g

a p p r o x i m a t e self-regulat ion of g e n e r a t o r o u t p u t in b a l a n c i n g

load s tudies has b e e n deve loped . T h i s is d o n e b y us ing a r b i -

t r a r y va lues of r e a c t a n c e b e h i n d t h e g e n e r a t o r t e r m i n a l s .

T h e r e a c t a n c e va lues a r e inversely p r o p o r t i o n a l to t h e d e -

sired g e n e r a t o r o u t p u t a n d a r e set to va lues e q u a l to 30 to

40 t imes t he r a t i o of t he base m e g a v o l t - a m p e r e s to t he m e g a -

v o l t - a m p e r e s des i red o u t p u t . F o r e x a m p l e , t h e r e a c t a n c e

of a g e n e r a t o r w i t h a smal l o u t p u t , say 10 p e r cen t of base

O C T O B E R 1950 Bobo—Handling Power System Problems on an A-C Network Calculator 867