Patent GB-1253809-A (GB)
Title: Method of and apparatus for indicating the possible approach of a dangerous or otherwise undesirable condition of a physical variable in an elongated article or installation
Inventor: GOSLING CYRIL HENRY
IPC: G06G7/52
Filed: 1967-12-27
Abstract: 1,253,809. Statistical analog computers. BRITISH INSULATED CALLENDER'S CABLES Ltd. 30 Dec., 1968 [27 Dec., 1967], No. 58689/67. Heading G4G. For determining the approach of dangerous or undesirable conditions in elongated installations, e.g. electric cables, pipelines, and the like in response to measurement of a variable or variables, e.g. temperature, pressure or the like, at a small number (n) of longitudinal disposed points on elemental lengths short compared with the distances of separation, automatic calculating means are applied to derive one or more primary parameters characteristic of the distribution of values in the measured set, and a secondary parameter function of the difference between a desired limit or limits of the variable and the primary parameter or a combination of primary parameters and to compare the secondary parameter with a standard value or a standard series of values, or a standard continuous function predetermined by statistical computation in accordance of the known properties of the installation, thus obtaining a resultant representing the probability that at any unmeasured point along the length of the installation, the variable is in excess or defect of a desired limiting condition or range, and indicating the resultant of the comparison. In a Gaussian distribution, the probability P of a measurement additional to a set of n measurements exceeding a limit c is given by x = arithmetic mean of the measurements of the set r = range of measurements of the set. P is probability of any ore of N additional measurements will exceed limit C k is a constant for the number (n) of set measurements substrate if the function is derived and compared with a standard value, a standard series of values, or a continuous standard function derived from the Gaussian distribution modified by N according to any dangerous conditions will be indicated by alarm when equality prevails between and the comparison. Other probability systems may be employed. For Gaussian distribution a digital or analog computer comprises unit 1 adding and averaging to x the n measurements of a set, unit 2 deriving a maximum or minimum value x m  for the n measurements, unit 3 evaluating (c-x), differencing unit 4 evaluating half range and quotent unit 5 evaluating the latter being applied to function store 6 of standard of values of the Gaussian distribution ; the constant k and factor 2 being introduced into the quotient or the standard values. Equality between an element of the standard value series and the quotient indicates that the variable condition reaches the preset limit at a point not represented by a measurement of the set, and may initiate protection, e.g. load reduction in a cable. Gate reset devices of the computing units enable primary and secondary parameters to be computed at timed intervals and the secondary parameter to be compared with standard value or function to obtain a required indication followed by reset for another cycle. For long installations where n is large, measurements may be grouped into subsets corresponding to contiguous sections; the successive probabilities P 1 , P 2  &c. being aggregated to an overall probability by the compulation P* = 1-(1-P 1 ) (1-P 2 ) (1-P 3 ) &c. Telemetered measurements may be accepted, and the functions of store 6 may be represented by plural potentiometers preset in accordance with standard values of probability series: modified by N and n to give direct indication of the probability of a temperature limit being reached or exceeded. The probability may be modified in response to ambient conditions; e.g. voltage or load of a cable, rate of flow in a pipe, nature of fluid therein, atmospheric temperature; by introducing corresponding parameters into the computer to modify c or N or the standard probability value compared with the second parameter.