System for monitoring and measuring high voltage D.C. transmission line current

Claim 3

The method of claim 1 wherein the signal υ.sub.t = V.sub.t cos (2 π F(t)t + φ.sub.t) where V t is the peak value of the transmitted voltage, F.sub.(t) = F.sub.o + a (υ.sub.m + υ.sub.o) where F o is the free-running frequency of a voltage controlled oscillator a is the gain which determines the magnitude of the deviation in F (t) with respect to F o υ m is the instantaneous voltage obtained from a low frequency oscillator υ o is an instantaneous voltage component at the output of an intergrator, and φ t is the phase of transmitted signal υ t .

Claim 4

The method of claim 1 wherein the signal υ.sub.r = K.sub.rt (ΔF) cos 2π f.sub.m · t + φ.sub.r ( t) where K rt and φ r are the amplitude and phase of the reflected signal, ΔF = F.sub.o - F.sub.i where F i is the instantaneous YIG filter centre frequency f m is a modulation frequency.

Claim 5

The method of claim 1 wherein F.sub.o = γH = γ(ho + αI) where H is the net magnetic field acting on the YIG filter H o is the biasing magnetic field provided by permanent magnets I is the current through the HVDC transmission line α is the proportionality constant relating the current I and the resulting magnetic field due to the current I γ is the gyomagnetic ratio of the YIG filter.

Claim 6

The method of claim 1 wherein signals υ t and υ r are transmitted through space.

Claim 7

The method of claim 1 wherein signals υ t and υ r are transmitted through a dielectric waveguide.

Claim 8

Appartus for the remote monitoring and measuring of current in a high voltage direct current transmission line, said apparatus comprising: (i) a YIG-tuned reflection filter placed at a monitoring and measuring station on said line and influenced by a magnetic field H which is a function of said current, said YIG filter having a centre frequency F o , (ii) means for generating a microwave signal υ t at said station where υ.sub.t = V.sub.t cos(2πF(t)t + φ.sub.t) where V t is the peak value of said signal υ t F.sub.(t) = F.sub.o + a (υ.sub.m + υ.sub.o) F o is a free-running frequency of a voltage controlled oscillator a is a gain constant which determines the magnitude of the deviation in F (t) with respect to F o υ m is an instantaneous voltage obtained from a low frequency oscillator υ o is an instantaneous voltage component at the output of an integrator, and φ t is the phase of transmitted signal υ t , (iii) means for transmitting said microwave signal υ t from a remote site to said station, (iv) means for receiving said signal υ t at said station and applying the signal υ t to said YIG-tuned filter, (v) means for transmitting a microwave signal υ r from said station to said remote site where υ.sub.r = K.sub.rt (ΔF) cos 2πf.sub.m ·t + φ.sub.r (t) where K rt and φ r are the amplitude and phase of a reflected signal ΔF = F.sub.o - F.sub.i where F i is the instantaneous YIG filter centre frequency f m is a modulation frequency (vi) means for receiving said signal υ r at the remote site, (vii) means at said remote site for detecting the centre-frequency component F o of the YIG filter present in the signal υ t , and, (viii) means at said remote site for generating a voltage υ o which is a function ΔF where ΔF = F o - F i and F i = the instantaneous YIG centre frequency, and where ΔF and F i are both functions of the line current I.

Claim 9

Appartus for the remote monitoring and measuring of current in a high voltage direct current transmission line, said apparatus comprising: (i) a YIG-tuned reflection filter placed at a monitoring and measuring station on said line and influenced by a magnetic field H which is a function of said current, said YIG filter having a centre frequency F o , (ii) means for generating a microwave signal υ t at said station where υ.sub.t = V.sub.t cos(2πF(t)t + φ.sub.t) where V t is the peak value of said signal υ t F.sub.(t) = F.sub.o + a (υ.sub.m + υ.sub.o) F o is a free-running frequency of a voltage controlled oscillator a is a gain constant which determines the magnitude of the deviation in F (t) with respect to F o υ m is an instantaneous voltage obtained from a low frequency oscillator υ o is an instantaneous voltage component at the output of an integrator, and φ t is the phase of transmitted signal υ t , (iii) means for transmitting said microwave signal υ t from a remote site to said station, (iv) means for receiving said signal υ t at said station and applying the signal υ t to said YIG-tuned filter, (v) means for transmitting a microwave signal υ r from said station to said remote site where υ.sub.r = K.sub.rt (ΔF) cos 2πf.sub.m ·t + φ.sub.r (t) where K rt and φ r are the amplitude and phase of a reflected signal ΔF = F.sub.o - F.sub.i where F i is the instantaneous YIG filter centre frequency f m is a modulation frequency (vi) means for receiving said signal υ r at the remote site, (vii) means at said remote site for detecting the centre-frequency component F o of the YIG filter present in the signal υ t , and, (viii) means at said remote site for generating a voltage υ o which is a function ΔF where ΔF = F o - F i and F i = the instantaneous YIG centre frequency, and where ΔF and F i are both functions of the line current I.

Claim 10

Apparatus according to claim 7 wherein the magnetic field acting on the YIG filter is given by: H = (magnetic field developed by current in said transmission line plus biasing magnetic field provided by permanent magnets).