Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1982-01-28
1984-05-01
Krawczewicz, Stanley T.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 51, G01R 3108
Patent
active
044464207
ABSTRACT:
A device and a method for detecting and locating faults and/or partial discharges in a gas-insulated electrical equipment, such as gas-insulated bus or cable, a gas-insulated substation or a gas-insulated switchgear. The detecting device comprises a plurality of field coupled current sensors located at given intervals inside the housing of the equipment for detecting any variation of the current flowing through the conducting element extending inside this housing. Each sensor consists of a toroidal helix pick up coil, preferably a differentiating Rogowski coil, located in an annular cavity machined in the wall of the equipment housing and extending all around the conducting element. Each cavity is connected along its entire length to the inner surface of the housing wall by a slit having opposed side walls sufficiently spaced apart to be insulated from each other. Each sensor gives a signal which is proportional to the detected variation of the current. A control circuit is connected to each of the sensors for comparing their signals and measuring the time interval between all the signals given by the sensors of a given variation current, and thereby determining where is located the fault or partial discharge having caused this given variation of current. The main advantages of this device are that it is not electrically connected to the circuit carrying the main current and it is not influenced by the voltage drop associated with the flow of current on the inside surface of the annular cavities. Moreover, the sensitivity of the device is a function of the number of turns in the pick up coil, and therefore can be very high.
REFERENCES:
patent: 2219262 (1940-10-01), Maple et al.
Westinghouse's Descriptive Bulletin 33-650D WEA, Entitled "Type CGI Compressed Gas Insulated Bus", Apr. 1975.
C. A. Ekdahl, Rev. Sci. Instrument 51, vol. 12, 1645 (1980).
M. G. Drouet et al., IEEE Trans. PAS-100, No. 7, 3350, Jul. 1981.
S. A. Boggs et al., IEEE Trans., PAS-100, No. 8, 3969, Aug. 1981.
S. A. Boggs, IEEE Trans., PAS-101, 1935, Jul. 1982.
M. S. Di Capua, Article Entitled "Rogowski Coils, Fluxmeters and Resistors for Pulsed Current Measurements", Apparently not yet Published.
M. G. Drouet, "Comments on Voltage and Current Sensors for a High Density Z-Pinch Experiment", Rev. Sci. Instrum 53(s), 263, Feb. 1982.
Hydro - Quebec
Krawczewicz Stanley T.
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