Means for detecting corona within high-voltage electrical apparatus

Claim 2

Means for detecting the presence of corona within electrical apparatus comprising: a housing; a high-voltage working part within said housing; and a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: a (i) bushing conductor having a first end inside said housing connected to said working part and a second end located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said ground sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location effectively between said conductive path and said second end of said bushing conductor for deriving a first signal substantially proportional to I1 - I2, where I1 is the total current in a predetermined high-frequency band flowing into said bushing conductor from said working part and is constituted by IS1 IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona therein and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end; and I2 is the total current in said predetermined high frequency band flowing between said bushing conductor and said shield through said body of insulation, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, c. and means for receiving said first and second signals and for developing a third signal substantially proportional to

Claim 3

The corona detecting means of claim 1 in which said means of (c) comprises: a. means for receiving said second signal and developing an intermediate signal substantially proportional to (1 + (Z2/Z1) ) I2, and b. summing means receiving said first and said intermediate signals for developing a signal constituting said third signal which is substantially proportional to the sum of said first and said intermediate signals.

Claim 4

Means for detecting the presence of corona within electrical apparatus comprising: a housing; a high-voltage working part within said housing; a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: (i) a bushing conductor having a first end located inside said housing connected to said working part and a second end located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said groove sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said first end of said bushing conductor for deriving a first signal substantially proportional to I1, where I1 is the total current in a predetermined high frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona therein and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, where I2 is the total current in said predetermined high frequency band flowing through said tap, c. and means for receiving said first and second signals and for developing a third signal of (Z2/Z1) I2, where Z1 is the impedance in said predetermined high frequency band of said working part and Z2 is the impedance in said predetermined high frequency band between said bushing conductor and ground presented to current flowing through said insulating body between said bushing conductor and said shield.

Claim 5

Means for detecting the presence of corona within electrical apparatus comprising: a housing; a high-voltage working part within said housing; a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: (i) a bushing conductor having a first end located inside said housing connected to said working part and a second end located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said groove sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said first end of said bushing conductor for deriving a first signal substantially proportional to I1, where I1 is the total current in a predetermined high frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona therein and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, where I2 is the total current in said predetermined high frequency band flowing through said tap, c. and means for receiving said first and second signals and for developing a third signal of (Z2/Z1) I2, where Z1 is the impedance in said predetermined high frequency band of said working part and Z2 is the impedance in said predetermined high frequency band between said bushing conductor and ground presented to current flowing through said insulating body between said bushing conductor and said shield.

Claim 6

The corona detecting means of claim 3 in which said means of (c) comprises: a. means for receiving said second signal and developing an intermediate signal substantially proportional to (Z2/Z1) I2, and b. summing means receiving said first and said intermediate signals for developing a signal constituting said third signal which is substantially proportional to the sum of said first and said intermediate signals.

Claim 7

Means for detecting the presence of corona within electrical apparatus comprising: a housing; a high-voltage working part within said housing; and a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: a (i) bushing conductor having a first end inside said housing connected to said working part and a second enD located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said ground sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said second end of said conductor for deriving a first signal substantially proportional to I1 - I2, where I1 is the total current in a predetermined high-frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona in said apparatus and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end; and I2 is the total current in said predetermined high frequency band flowing between said bushing conductor and said shield through said body of insulation, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, c. adjustable transfer-function circuit means for receiving said second signal and developing a third signal proportional by a predetermined factor to I2, d. summing means receiving said first and third signals for developing a fourth signal substantially proportional to the sum of said first and third signals, e. said predetermined factor of (c) being determined by adjusting the transfer function of said circuit means so that said fourth signal is substantially zero under conditions in which: (i) said electrical apparatus is developing no corona and (ii) noise in said predetermined high frequency band is present on said transmission line sufficient to cause said first and third signals to be developed.

Claim 8

Means for detecting the presence of corona within electrical apparatus comprising: a housing; a high-voltage working part within said housing; and a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: a (i) bushing conductor having a first end inside said housing connected to said working part and a second enD located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said ground sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said second end of said conductor for deriving a first signal substantially proportional to I1 - I2, where I1 is the total current in a predetermined high-frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona in said apparatus and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end; and I2 is the total current in said predetermined high frequency band flowing between said bushing conductor and said shield through said body of insulation, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, c. adjustable transfer-function circuit means for receiving said second signal and developing a third signal proportional by a predetermined factor to I2, d. summing means receiving said first and third signals for developing a fourth signal substantially proportional to the sum of said first and third signals, e. said predetermined factor of (c) being determined by adjusting the transfer function of said circuit means so that said fourth signal is substantially zero under conditions in which: (i) said electrical apparatus is developing no corona and (ii) noise in said predetermined high frequency band is present on said transmission line sufficient to cause said first and third signals to be developed.

Claim 9

Means for detecting the presence of corona within electrical apparatus comprising a housing; a high-voltage working part within said housing; and a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: (i) a bushing conductor having a first end located inside said housing connected to said working part and a second end located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said first end of said bushing conductor for deriving a first signal substantially proportional to I1, where I1 is the total current in a predetermined high frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona therein and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, where I2 is the total current in said predetermined high frequency band flowing through said tap, c. adjustable transfer-function circuit means for receiving said second signal and developing a third signal proportional by a predetermined factor to I2, d. summing means receiving said first and third signals for developing a fourth signal substantially proportional to the sum of said first and third signals, e. said predetermined factor of (c) being determined by adjusting the transfer function of said circuit means so that said fourth signal is substantially zero under conditions in which: (i) said electrical apparatus is developing no corona and (ii) noise in said predetermined high frequency band is present on said transmission line sufficient to cause said first and third signals to be developed.

Claim 10

Means for detecting the presence of corona within electrical apparatus comprising a housing; a high-voltage working part within said housing; and a terminal bushing extending through a wall of said housing for carrying current between a transmission line and said working part, said terminal bushing comprising: (i) a bushing conductor having a first end located inside said housing connected to said working part and a second end located outside said housing and adapted to be connected to said transmission line, (ii) a body of electrical insulation surrounding said bushing conductor, (iii) a ground sleeve around a portion of said body of insulation, (iv) a tubular shield embedded in said insulation, surrounding said bushing conductor, and surrounded by said sleeve, and (v) a tap extending between said shield and said ground sleeve; and means defining a conductive path between said ground sleeve and ground; said detecting means comprising: a. means including a first sensor surrounding said bushing conductor and said shield at a location between said conductive path and said first end of said bushing conductor for deriving a first signal substantially proportional to I1, where I1 is the total current in a predetermined high frequency band flowing into said bushing conductor from said working part and is constituted by IS1 - IN1, where IS1 is a signal current component originating within said apparatus and indicative of corona therein and IN1 is a noise current component originating outside said apparatus and flowing through said bushing conductor from said transmission line via said first end, b. means sensitive to current in said tap for deriving a second signal substantially proportional to I2, where I2 is the total current in said predetermined high frequency band flowing through said tap, c. adjustable transfer-function circuit means for receiving said second signal and developing a third signal proportional by a predetermined factor to I2, d. summing means receiving said first and third signals for developing a fourth signal substantially proportional to the sum of said first and third signals, e. said predetermined factor of (c) being determined by adjusting the transfer function of said circuit means so that said fourth signal is substantially zero under conditions in which: (i) said electrical apparatus is developing no corona and (ii) noise in said predetermined high frequency band is present on said transmission line sufficient to cause said first and third signals to be developed.