O

Ulllted States Patent [19] [11] Patent Number: 4,722,059 Engel et a]. [45] Date of Patent: Jan. 26, 1988

[54] PROGRAIVHVIED OVERCURRENT 4,623,967 11/1986 Naimer .............................. .. 364/483 PROTECTION CONTROL APPARATUS AND . . _ .

METHOD OF OPERATING THE SAME [75] Inventors: Joseph C. Engel, Monroeville Boro; Attorney, Agent’ 0" Fi'm-G- H- Telfef

Leonard C. Vercellotti, Oakmont; 57 ABSTRACT Richard A. Johnson; Seymour Salowe, [ 1 _ both of Mun-ysv?le; William R_ Programmed overcurrent protection control apparatus ‘rel-ballets’ Jr” Pittsburgh’ all of pa_ 311th selectatble tutne-overfuirrent Ioperation to govern

e in erru 1on o curren on at east one ower [73] Assignee: Westinghouse Electric Corp” line associz?ed with either a grofnd phase or a Ilgower

Pmsbufgh, Pa- - phase of a power system network is disclosed. A pro

[21] App]. No’: 725,195 grammedprocessor is included to derive an overcurrent . tlme-to-tnp in accordance with sampled measurement

[22] Flled: Apr. 19, 1985 _ current values of the power line and selected derivation 4 _ constants stored in a memory look-up table. The deriva

[51] Int. Cl. ...................... .. H02H 3/08, G(.)6F 15/46 tion constants are Selected from the lockup table based [52] US. Cl. .................................. .. 364/483, 364/481, . . .

361/94; 361/96 on derivation parameters wh1ch may be set and read by [58] Field of Search ..................... .. 364/481, 483, 492; ‘he Pmg’ammed Pm?“ fmm “me t° ‘mie- The Pm‘

361/79, 87 63’ 93_97_ 363/74 grammed processor utilizes the selected derivation con ’ ’ stants to denve the t1me-to-tr1p over a number of prede

[56] References Cited termined time intervals during which the overcurrent

Us PATENT DOCUMENTS i’é’li'iilliiier?iiiiiig §§§$€§i°§§i§3§éi$ 112133221‘; 115110“ et a1- ------------------------- - selected from the look-up table may be utilized for the

, , oran . . . . . . . . . . . . . . . . . .. ' ' - - ' - - - - _

ggggggg 513g; 34;!" a a1 333g; ?‘élii?mfmid‘ia‘lgé‘."in°l??fé‘iifi‘it?ifsé?til‘é‘i?il(iii 4:276:605 6/1981 01:; M81 vation relationships may be used concurrently to derive 4,402,028 8/1983 Udren ........... .. .. 361/87 the Newman‘ tune-t°-“1P 4,423,459 12/1983 Stich ct a1. .. 364/483 4,541,058 9/1985 Andow et a1. .................... .. 364/483 25 Claims, 22. Drawing Figures

PROBR

WITRULLER

AIIED OVERCIJRREIT PROTECTION

US. Patent Jan. 2691988 Sheet 1 of 18 4,722,059

38 \ jnqz (so _

44 32 Mi ( J 46 34 BREAKER

- in; ( MECHANISM

W 1.1”’ (36

402

502 522 542 562

IA [8 1C ‘ ‘ ID (58 PROGRAMMED TRIP

OVE'RCURRENT PROTECTION CDNTROLLER

11 (60 CONLROL

DISPLAY PANEL

FIG.|

4,722,059 F I6. 28

L/4_PR0CESS0R MIOROCOHPUTER

SYSTEM

DISPLAY a TRIP "42 DRIVER

76 1/0

TIME TRIP INST. TRIP PHASE 0

%

Sheet 3 0f 18 '

I02\ I04;

PHASE B OOOOOO

PHASE A

if 2 2 Y GROUND 1/! V. 2? Q11

RCL. "R

ml/

TRIP\ RESET\

DEADNAM READ\ WRITE\

SYSTEM BUS\.

Jan. 26, 1988

4 CHANNEL

0H3 CONVERTER

US. Patent

|4o\ I36 \

98

4,722,059

7

Jan. 26, 1988' Sheet 4 of 18 US. Patent

US. Patent Jan. 26, 1988 Sheet 5 0f18 4,722,059

48VDC

B‘ SENSE

A2

ééisv DRIVE (‘R84 UNDERVOLTAGE

JP" m

3%

PIC-3.4

US. Patent Jan. 26, 1988 Sheet 7 of 18 4,722,059

|.5' P.U. - ‘ mus CURRENT MEASUREMENT(RU.)——>

US. Patent Jan. 26, 1988 Sheet 8 0f18 4,722,059

220

222

' 224

22s ‘ |NTERRUPT—-l-@Ié-———‘ \

T~STATE 0

T-STATE I

US. Patent Jan. 26, 1988 Sheet 9 of 18

230 (232 INTERRUPT u NEXT

0 T- STATE Y

(216 CONTINUE PHASE OVERCURRENT

_ ALGOR ITHH

( 278 \ READ GROUND OVERCURRENT

SET PARAMETERS FROM PANEL

( IDLE )

Fl (5 . 9

4,722,059

US. Patent Jan. 26, 1988

( START )

(236 7

SELECT FIRST INPUT BY GENERATING PROPER CODES OVER 8! AND 52

Sheet 10 0f 18

(23B INITIALIZE GAIN

T0 | USING RI AND R2

( 24o CALL

RANCING SUBROUTINE

\ ( 252 CALL ' ,

CONVERSION SUBRCUTINE

v (264 (266 ALL CURRENT N

> , SELECT SIGNAL SAMPLES \ Qcouvgmo NEXT INPUT Y

C ( RETURN )

4,722,059

US. Patent Jan. 26, 1988 Sheet 11 0f18 4,722,059

( START ) 242

OVERRANGE N ACTIVE ’

Y

SET GA lN= USING RI

OVERRANGE ACTIVE

Y (248 SETGAIN'IM usmc RI & R2

OVERRANGE N ACTIVE

Y ( 25|

SET sAm-mé usmsmnz

( RETURN )

246

L6

_ US. Patent Jan. 26, 1988 ' Sheet 12 of 18 4,722,059

( START )

{254 GENERATE CONVERT

COMMAND T0 A/D CONVERTER OVER WRITE LINE

( 256

DELAY 45/18

, (25s READ A/D CONVERTER RESULTS OVER DATA LINES

(260 NULTIPLY RESULT

BY ( I/RANCE SETTING)

, (262 STORE DICITIZED

CURRENT SIGNAL SAMPLE IN PREDETERNINED MEMORY LOCATION

I

( RETURN I

FIG.I2

US. Patent Sheet 13 0f 18

2B0

INTERRUPT N ‘ NEXT | T-STATE

Y (282 CALL SAMPLING

a CONVERSION ROUTINE

(284 SQUARE DIGITIZED

CURRENT MEASUREMENT SIGNAL SAMPLES

, (286

Jan. 26, 1988 4,722,059

SUM- sun +12I

(Z88 COMMENCE cnouun' OVERCURRENT ALGORITHM

, v

( ID LE )

F l (5. l3

US. Patent Jan. 26, 1988 Sheet 14 of 18

290

< INTERRUPT > N 2

NEXT T-STATE

(294 SQUARE DIGITIZED

CURRENT MEASUREMENT SIGNAL SAMPLES

(300 ‘ CONTINUE

ALGORITHM

4,722,059

US. Patent Jan. 26, 1988 Sheet 15 0f 18

302

INTERRUPT N NEXT 3 T-STATE

Y (304 '

CALL ROUHNE, SQUARE &SUM

(30s GENERATE "DEADMAN" SIGNAL

I

< IDLE >

FIG. I5

308

INTERRUPT N NEXT 4 0R 5 ‘ T-STATE

,Y <3l0 CALL nourm?, SQUARE asun

( IDLE )

FIG. l6

4,722,059 _

US. Patent Jan. 26, 1988 Sheet 16 0f 18

3|2

INTERRUPT N‘ ‘ NEXT 6 T-STATE

3|8

INTEQIRUPT N Y

‘ (32o CALL ROUTINE SQUARE a sum

(32? COMHENCE PHASE OVERCURREHT ALGORITHM

( ID LE )

F l G. l 8

4,722,059

4,722,059 1

PROGRAMMED OVERCURRENT PROTECTION CONTROL APPARATUS AND METHOD OF

OPERATING THE SAME

COPENDING PATENT APPLICATIONS U.S. patent application with Ser. No. 725,050 filed on

Apr. 19, 1985 copending with the instant application is incorporated by reference herein for providing a de scription of a supervisory circuit suitable for use in the preferred embodiment; and US. Pat. No. 4,626,831 issued on Dec. 2, 1986 is

incorporated by reference herein for providing a de scription of an analog multiplexer and prescaler suitable for use in the preferred embodiment, both of the afore mentioned applications being assigned to the same as signee as the instant application.

BACKGROUND OF THE INVENTION

The present invention relates to overcurrent protec tion apparatus, in general, and more particularly to such apparatus under programmed control with selectable time-overcurrent operation to govern the interruption of current through at least one power line associated with either a ground phase or a power phase of a power system network. .

Examples of types of overcurrent protection appara tus which operate with trip time delay characteristics in response to a sensed overcurrent condition in a power line include protective relays, automatic reclosures, circuit breakers and the like. Apparatus of this type generally protect electrical transmission and distribu tion systems and their connected loads from damage due to overcurrents by governing the interruption of current through their associated power lines in accor dance with some time-to-tn'p vs. overcurrent coordi nated relationship or prede?ned family of curves. Typi cally, the characteristics of these time-overcurrent curve families have been implemented using electro mechanical, magnetic and thermal control circuits. Hence, once a particular time-overcurrent operation was characterized, it was intended to remain ?xed and if a change in characterization was required usually some mechanical adaptation was needed like physically inter changing or adding special elements, for example.

Recently, electronic overcurrent protection control apparatus, and more particularly, electronic apparatus including programmed digital signal processors have been developed to provide greater functional ?exibility in altering apparatus characterization with regard to time delayed current interruption control. Examples of programmed overcurrent protection control apparatus are found in the following US. Pat. Nos:

4,446,498; “Electronic Control System For Overload Relay Or The Like”; issued May 1, 1984 to F. A. Stitch and assigned to Siemens-Allis, Inc.;

4,432,031; “Method For Overcurrent Protection”; issued Feb. 14, 1984 to W. J. Premerlani and assigned to General Electric Company;

4,377,837; “Circuit Interrupter With Over Tempera ture Trip Devise”; issued Mar. 22, 1983 to J. J. Matsko et al. and assigned to Westinghouse Electric Corp.;

4,377,836; “Circuit Interrupter With Solid State Digi tal Trip Unit And Positive Power-Up Feature”; issued Mar. 22, 1983 to R. T. Elms et al. and assigned to Wes tinghouse Electric Corp.;

4,371,947; “ROM Controlled Protective Relay Sys tem For Power Transmission Network”; issued Feb. 1,

35

40

45

55

65

2 1983 to Norio Fujisawa and assigned to Tokyo Chirbara Denki Kabushiki Kaisha;

4,339,802; “Digital Protective Relaying Device”; issued July 13, 1982 to M. Yamaura et al. and assigned to Tokyo Chirbara Denki Kabushiki Kaisha;

4,328,551; “Apparatus And Method For Protection Of Electric Power Transmission Lines And The Like”; issued May 4, 1982 to M. Yamaura et al. and assigned to Tokyo Chirbara Denki Kabushiki Kaisha;

4,272,816; “Overcurrent Protecting Apparatus”; is sued June 9, 1981 to Y. Matsumato and assigned to Tokyo Chirbara Denki Kabushiki Kaisha. While the aforementioned exemplary references are

all directed to various novel methods and apparatus related to programmed digital signal processor control of overcurrent protection in power system networks, none of the above references appear to provide for both accurate characterization of the prede?ned time-to-trip vs. overcurrent curve families and the selectability of time overcurrent operation. The present invention is directed to programmed overcurrent protection control apparatus having aspects which are intended to fill these aforementioned gaps by providing accurate char acterization of prede?ned families of time-overcurrent curves with a common programmed relationship based on settable parameters and the convenient setability of the parameters to select the curve family characteriza tion suitable for the particular duty to which the over current protection apparatus is being applied using the common programmed relationship.

SUMMARY OF THE INVENTION

In accordance with the present invention, pro grammed overcurrent protection control apparatus is adapted for use in a power system including at least one power line to govern the interruption of current through the power line based on a derived overcurrent time-to-trip associated with an overcurrent condition of the power line. The control apparatus comprises a pro grammed digital signal processor and memory means, coupled to the programmed processor, for storing a plurality of digitally coded signals representative of predetermined derivation constants. Further provided is means governed by the program processor to sample a current signal, representative of measured current of the power line, at ?rst predetermined times and to digi tize the sampled current signals, a frequency cycle of the power line current including a plurality of first predetermined times. The programmed processor is operative over predetermined time intervals to derive for each predetermined time interval a digital signal, representative of a current value I", of a frequency cycle of the current contemporaneous with the corresponding predetermined time interval m, from the sampled cur rent signals digitized over the corresponding predeter mined time interval. The programmed processor is fur ther operative at second predetermined times corre sponding to the predetermined time intervals to read certain ones of a plurality of derivation parameter set tings. The program processor is operative to select, at other times, certain of the‘digitally coded derivation constants from the memory means corresponding to the read parameter settings associated with the other times. Still further, the programmed processor is operative, in response to a detection of an overcurrent condition, to derive an overcurrent time-to-trip based on the follow ing relationship: