US 4,731,688 A · Range limitation for a protection device in a power supply network

Abstract

A method and device for range limitation and direct tripping for protection in the event of a fault on an electrical power line extending between two stations (P, Q) involves employing a travelling wave model in one of the stations (P) which, with the aid of measured currents and voltages in that station, to calculate the voltage distribution at a number of control points along the line. The range of the protection device is indicated as the distance between the measuring station and that control point for which a voltage difference (.delta.u) becomes equal to zero. The voltage difference consists of the difference between the absolute value of a voltage differene between the absolute value of a voltage difference (.DELTA.u), formed as the sum of a voltage value (U") calculated with the travelling wave model for the control point at a certain time, and the corresponding voltage value (U') one half-period earlier and the absolute value of the latter voltage value. When the voltage difference becomes greater than zero, direct tripping can be initiated.

Claims3

Dependent claims

A method for range limitation and direct tripping in connection with the protection of a power line (PQ) included in a multi-phase electrical power transmission system, in which, in a measuring station (P) near the power line, measurement is performed in each phase of current and voltage, and the measured values are supplied to a travelling wave model, located in the station, by means of which the voltage distribution at a number of control points along the line can be obtained, comprising:

a voltage difference .DELTA.u is formed as the sum of a voltage value U", calculated for a control point at a certain time, and a corresponding voltage value U' one time period earlier,
a voltage difference .delta.u is formed as the difference between the absolute value of the voltage difference .DELTA.u and the absolute value of the voltage U' for the same control point, and
the range for a protection device in the measuring station (P) is determined as the distance from the measuring point to the control point for which .delta.u is equal to zero when a low resistance fault occurs at the corresponding point of the real transmission line.

A device for range limitation and direct tripping in connection with the protection of a power line included in a multiphase electrical power transmission system, and for a control point Q, whereby the distance between P and Q constitutes the range of the device, the device comprises:

a first summation member adapted to form a voltage difference .DELTA.u.sub.Rq equal to the difference between an R-phase voltage, calculated with the travelling wave model, and the corresponding voltage one time period earlier,
a second summation member adapted to form a voltage difference .DELTA.u.sub.Sq equal to the difference between an S-phase voltage, calculated with the travelling wave model, and the corresponding voltage one time period earlier,
a third summation member adapted to form a voltage difference .DELTA.u.sub.Tq equal to the difference between a T-phase voltage, calculated with the travelling wave model, and the corresponding voltage one time period earlier,
a fourth summation member adapted to form a voltage difference .delta.u.sub.Rq equal to the difference between the numerical value .vertline..DELTA.u.sub.Rq .vertline. and the numerical value .vertline.u.sub.Rq .vertline. one time period eariler,
a fifth summation member adapted to form a voltage difference .delta.u.sub.Sq equal to the differfence between the numerical value .vertline..DELTA.u.sub.SQ .vertline. and the numerical value .vertline.u.sub.SQ .vertline. one time period earlier,
a sixth summation member adapted to form a voltage difference .delta.u.sub.Tq equal to the difference between the numerical value .vertline..DELTA.u.sub.Tq .vertline. and the numerical value .vertline.u.sub.Tq .vertline. one time period earlier,
a seventh summation member adapted to form a mean value .delta.u.sub.Rq of the voltage difference .delta.u.sub.Rq,
an eighth summation member adapted to form a mean value .delta.u.sub.Sq of the voltage difference .delta.u.sub.Sq,
a ninth summation member adapted to form a mean value .delta.u.sub.Tq of the voltage differ .delta.u.sub.Tq,
a tenth summation member adapted to form a voltage difference .DELTA.u.sub.RSq equal to the difference between .DELTA.u.sub.Sq and .DELTA.u.sub.Rq,
an eleventh summation member adapted to form a voltage difference .DELTA.u.sub.STq equal to the difference between .DELTA.u.sub.Tq and .DELTA.u.sub.Sq,
a twelfth summation member adapted to form a voltage difference .DELTA.u.sub.TRq equal to the difference between .DELTA.u.sub.Rq and .DELTA.u.sub.Tq,
a thirteenth summation member adapted to form a voltage difference u.sub.RSq equal to the difference between values of u.sub.Sq and u.sub.Rq one time period before the respective .DELTA.u-values,
a fourteenth summation member adapted to form a voltage difference, u.sub.STq equal to the difference between values of u.sub.Tq and u.sub.Sq one time period before the respective .DELTA.u-values,
a fifteenth summation member adapted to form a voltage difference u.sub.TRq equal to the difference between values of u.sub.Rq and u.sub.Tq one time period before the respective .DELTA.u-values,
a sixteenth summation member adapted to form a voltage difference .delta.u.sub.RSq equal to the difference between the numerical value .vertline..delta.u.sub.RSq .vertline. and the numerical value .vertline.u.sub.RSq .vertline.,
a seventeenth summation member adapted to form a voltage difference .delta.u.sub.STq equal to the difference between the numerical value .vertline..DELTA.u.sub.STq .vertline. and the numerical value .vertline.u.sub.STq .vertline.,
an eighteenth summation member adapted to form a voltage difference .delta.u.sub.TRq as the difference between the numerical value .vertline..DELTA.u.sub.TRq .vertline. and the numerical value .vertline.u.sub.TRq.vertline.,
a nineteenth summation member adapted to form a mean value .delta.u.sub.RSq of the voltage difference .delta.u.sub.RSq,
a twentieth summation member adapted to form a mean value .delta.u.sub.STq of the voltage difference .delta.u.sub.STq,
a twenty-first summation member adapted to form a mean value .delta.u.sub.TRq of the voltage difference .delta.u.sub.TRq,
a respective comparison element to compare the produced mean values with the value zero,
and means to deliver a signal, via an "or"-element, indicating the occurrence of a fault within the range of the protection device when any of the mean value is greater than zero.

20 more elements

Dependencies are inferred from the claim text.

Range limitation for a protection device in a power supply network

Life of this patent

Range limitation for a protection device in a power supply network

Life of this patent

Abstract

Claims3