Method and apparatus for monitoring instantaneous electrical

66 Pages·2013·4.14 MB·English

Ul'llted States Patent [19] [11] Patent Number: 4,612,617
Laplace, Jr. et al. [45] Date of Patent: Sep. 16, 1986
[54] METHOD AND APPARATUS FOR 4,396,986 8/1983 Salesky .............................. .. 364/483
EMLOENCITTROIRCIANLG P IANRSATMAENTTEARNSE OOUFS A POWER 44,,441093,,621992 192//11998833 JEjmjzdanltc ekt eatl. al. ............... .. 364/483 X
DISTRIBUTION SYSTEM
Primary Examiner-Edward J. Wise
[75] Inventors: Carl J. Laplace, Jr., Covington; Attorney, Agent, or Firm-F. W. Powers; J. L. James
Conrad F. Williams, New Orleans, [57] ABSTRACT
both of La.
A method and a device for monitoring instantaneous
[73] Assignee: Siemens-Allis, Inc., Atlanta, Ga.
electrical parameters of a power distribution system
[21] Appl. No.: 471,302 under load utilizing digital control means. An analog
signal equivalent to such a parameter is sensed and rated
[22] Filed: Mar. 2, 1983
down for processing by solid state components. This
[51] signal is converted into a binary coded digital signal
Int. Cl.4 ............................................ .. G06F 15/56
[52] having n digits. A plurality of digital signals is sampled
US. Cl. ................................... .. 364/483; 364/492
[58] Field of Search ............. .. 364/492, 493, 483, 481; and squared values with a format of Zn digits are de
323/256, 260; 324/76 R rived from each sample. The squared values of one
sampling period are accumulated to a sum value com
[56]
1 References Cited posed of 2n+m digits and the square root comprising
U.S. PATENT DOCUMENTS n+k digits of the sum is taken. This value is rescaled to
a true root mean square value by performing k left shifts
4,006,413 2/1977 Silberberg ..................... .. 364/483 X
as an accurate measurement result. The core of such
4,041,288 8/1977 Conway et al. .. ......... .. 364/483
device is represented by a microcomputer with built-in
4,298,939 11/1981 Fluegel ....... .. .. 364/492 X
4,346,346 8/1982 Silberberg 364/483 X analog-to-digital converter.
4,388,611 6/1983 Haferd .... .. .. 364/483 X
4,389,708 6/1983 Baldock .......... .. 364/483 X 23 Claims, 15 Drawing Figures
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U.S. Patent Sep. 16,1986
Sheet 1 of 12 4,612,617

US, Patent Sep. 16,1986 Sheet3 of12 ' 4,612,617
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U.S. Patent Sep. 16,1986 Sheet4of12 4,612,617
—.
FROM
POTENTIAL
TRANSFORMER
Fl? 5
R/o RIO IO
08
043
D6
_.
AND
FROM
+ R/Z
POTENTIAL L7 +Vcc
TRANSFORMER .
D7
5
' F I
F.
INT. SERVICE
ATH ‘A” PATH. ‘5"
EXECUTIVE
noun TIME
A A I
‘- a2 MSEC. —"| ZINTERRUPTQA
U.S. Patent
Sep. 16, 1986 Sheet 5 ofl2 4,612,617
DISABLE EXTERNAL’ 8'2
INTERRUPTS ’
INITIALIZE SYSTEM / 8l4
START INTERNAL TIMER
ENABLE TIMER INTERRUPTS
820
TIMER INT.
/ 822
TOGGLE HATCHDOG
SER CE SYSTEM FAULT
ECTION LOGIC
@
@
826
START
FIG. 8
US. Patent Sep. 16, 1986 Sheet6 of12 4,612,617
‘ START )
RE-ENABLE TIMER
INTERRUPT LOGIC
SELECT NEXT CONTROL
PATH ?qlz
SET "PATH" FLAG
JUMP TO SELECTED p1 ‘3'4
“ CONTROL PATH
P 7
SERVICE SERVICE SERVICE SERVICE
comma. CONTROL CONTROL CONTROL
QM @mw? @mw?
J J J \
0H6 qIB Q20
, Q22
CLEAR "PATH" FLAG / Q24
DEAD TIME
U.S. Patent Sep. 16,1986
Sheet 7 of 12 4,612,617
@
0 -(PATH, BIT 7) .1 I010
PERFORM BINARY-TO-BDC
CONVERSIONS
,-¢ IOIZ
PBCDl .
SERVICE DISPLAY 0mm
, I004
IOI6\
OVERCURRENT ? YES
ISAVG > 700 M (= 350%)? ‘
NO
|026\
‘NO
UNDERCURRENT 7
ISAVG< 2% THRESHOLD?
IIOIB
FREEZE FREQUENCY AND
PHASE COLNTS
ALERT SYSTEM
‘ EXIT )
FI6. lo
US. Patent Sep. 16,1986 ' Sheet8ofl2 4,612,617
SYNC TO (4-) P.T. ZERO
CROSS
/ "lo
@
DERIVE FREQUENCY AND
PHASE COUNTS BASED / "'2
UPON P.T. & C.T. zERO
cROss INPUTS
DETERMINE POWER FLOw
DIRECTION (FPF/RPF) AND / (H4
COMPENSATE PHASE COUNT
BASED UPON REGULATOR
CONFIGURATION 1.0.
CDMPUTE SIN/COS OF
POWER FACTOR ANGLE:
, m6
214 * sing! P.F. —- SINPF
214 * cosy! P.F. —> COSPF
@
FIG. H
U.S. Patent Sep. 16,1986. Sheet9ofl2 4,612,617
@
o—> (PATH, BIT 6) P ‘2'0
1
SELECT P.T. A/D INPUT CHANNEL ,1 l2l2
"AND" AND STARTYCONVERSIONS
SAMPLE SELECTED A/D ‘CHANNEL ANO
DERIVE "RMS" VALUE OF INPUT HAVEFORM ‘
@
I
PERFORM OPERATOR "NULL"
CALIBRATION ADJUSTMENT
@
AVERAGE NEW "RMS" VALUE WITH
PREVIOUSLY SAVED AVERAGE AND
UPDATE RUNNING AVERAGE
~|2l3
24 * (Vs + VsAvc) —> VSAVG
2 '
l
TEST FOR P.T. I‘NPUT DVERFLOW I220
AND LIMIT "VSAVG" T0 180 v "T