Power line sensor

• US 20070136010A1
• Filed: 01/12/2007
• Published: 06/14/2007
• Est. Priority Date: 03/19/2003
• Status: Abandoned Application

• Current Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Original Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Inventors: Gunn, Colin, Lightbody, Simon, Forth, J., Hancock, Martin, Sheppard, Jason, Kingham, Brian
• Application Number:
  US11/652,968
• Publication Number:
  US 20070136010A1
• Time in Patent Office: Days
• US Class Current: 702/62
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• CPC Class Codes: G01R 15/185 with compensation or feedback windings or interacting coils, e.g. 0-flux sensors using galvano-magnetic field sensors G01R15/20; conversion of DC into AC using transductors G01R19/20
• CPC Class Codes: G01R 15/186 using current transformers with a core consisting of two or more parts, e.g. clamp-on type G01R15/142 - G01R15/16 take precedence; tong testers G01R1/22
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

An apparatus for sensing the current in a power line of a power system and systems incorporating the apparatus are disclosed. The apparatus may comprise an enclosure providing a window operable to permit the passage of the power line therethrough. The apparatus may further comprise an active current transformer set within the enclosure and operative to produce a scaled version of the current. The apparatus may further comprise an amplifier coupled with the active current transformer and operative to reduce the phase shift and ratio error between the current and the scaled version of the current. The apparatus may further comprise a powering current transformer set within the enclosure and operative to receive power from the power line on a primary winding and deliver power on a secondary winding. The apparatus may further comprise power supply circuitry set within the enclosure, the power supply circuitry powered through the secondary winding from the powering current transformer and operative to supply power to the amplifier. The apparatus may further comprise at least one of secondary leads and secondary terminals extending from the enclosure, coupled with the active current transformer and operative to deliver the scaled version of the current outside of the enclosure.

Claims

1-84. -84. (canceled)

85. An apparatus for sensing the current in a power line of a power system, the apparatus comprising:

an enclosure providing a window operable to permit passage of said power line therethrough;

an active current transformer set within said enclosure and operative to produce a scaled version of said current;

a compensation circuit coupled with said active current transformer and operative to compensate for magnetic losses in said active current transformer;

a powering current transformer set within said enclosure and operative to receive power from said power line on a primary winding and deliver power on a secondary winding; and

power supply circuitry set within said enclosure and coupled with said secondary winding, said power supply circuitry operative to supply regulated power to power said compensation circuit as a function of power received from said secondary winding.

86. The apparatus of claim 85, further comprising a burden set within said enclosure and at least one of secondary leads and secondary terminals extending from said enclosure, said at least one of secondary leads and secondary terminals coupled with said active current transformer and operative to deliver said scaled version of said current outside of said enclosure, and said burden is coupled across said at least one of secondary leads and secondary terminals and is operative to provide a voltage representative of said scaled version of said current.

87. The apparatus of claim 85, wherein said compensation circuit is operative to compensate for magnetic losses by being operative to reduce a phase shift and ratio error between said current and said scaled version of said current.

88. The apparatus of claim 87, wherein said compensation circuit is configured so that an absolute value of said phase shift is below 0.05 degrees when said apparatus is operated over a dynamic range of 50 to 1 of said current to said scaled version of said current.

89. The apparatus of claim 87, wherein said compensation circuit is configured so that said ratio error is below 0.1% when said apparatus is operated over a dynamic range of 50 to 1 of said current to said scaled version of said current.

90. The apparatus of claim 85, wherein said compensation circuit is configured to generate a compensation current which zeros a flux in a sense coil included in said active current transformer.

91. The apparatus of claim 90, further comprising:

a secondary coil included within said active current transformer;

a current divider coupled to said secondary coil;

wherein said current divider is configured to feed a portion of said compensation current into said secondary coil to compensate for losses of said active current transformer.

92. The apparatus of claim 85, wherein said power supply circuitry comprises:

a shunt coupled with said secondary winding and operative to carry at least a portion of an output current of said secondary winding.

93. The apparatus of claim 92, wherein said power supply circuitry further comprises:

a regulator coupled with said shunt and operative to regulate a flow of current through said shunt.

94. The apparatus of claim 92, further comprising:

a microcontroller operative to sense said output current, and operate said shunt in a linear regulation mode, or a switched regulation mode in response to a magnitude of said output current.

95. The apparatus of claim 86, further comprising a detector operative to detect when said compensation circuit is unable to reduce said phase shift and ratio error by an expected amount.

96. The apparatus of claim 85, wherein said power supply circuitry is operative to provide power to power a device external to said apparatus.

97. The apparatus of claim 85, further comprising a wireless transceiver set within said enclosure, said wireless transceiver operative to transmit at least one digital sample proportional to said scaled version of said current for receipt by a device external to said enclosure.

98. The apparatus of claim 97, further comprising a receiver set within said enclosure, said receiver operative to receive time synchronization information, said wireless transceiver operative to transmit at least one digital sample that is time synchronized based on said synchronization information.

99. The apparatus of claim 98, wherein said transceiver is operative to transmit said at least one digital sample over a first wireless channel, and said receiver is operative to receive time synchronization information over a second wireless channel.

100. The apparatus of claim 85, further comprising a microprocessor and a compensation overload detection circuit powered from said regulated power, wherein said compensation overload detection circuit is operative to provide said microprocessor with an indication in response to failure of said compensation circuit to compensate for all of said magnetic losses.

101. The apparatus of claim 85 wherein said active current transformer comprises a sense core and a secondary core;

said sense core mounted within a groove formed in said secondary core.

102. The apparatus of claim 85, wherein said active current transformer comprises said powering current transformer.

103. The apparatus of claim 85, wherein said power supply circuitry comprises:

a bridge rectifier coupled with said secondary winding, said bridge rectifier operative to provide a rectified output current from an output current of said secondary winding;

a shunt coupled with said bridge rectifier and operative to selectively shunt said rectified output current from said secondary winding;

an energy storage device operative to receive a portion of said rectified output current that is not shunted by said shunt; and

a regulator operative to sense a voltage of said energy storage device and turn said shunt off in response to said voltage being below a first threshold, and turn said shunt on in response to said voltage being above a second threshold.

104. The apparatus of claim 103, further comprising a switched capacitor circuit coupled with said energy storage device, said switched capacitor circuit operative to generate a predetermined magnitude of negative supply voltage and a predetermined magnitude of positive voltage from said determined voltage of said energy storage device.

105. The apparatus of claim 103, wherein said regulator comprises a microcontroller, said apparatus further comprising:

a sense current transformer coupled to said secondary winding, said sense current transformer operative to provide a sense signal to a current monitoring circuit included in said compensation circuit;

wherein an output of said current monitoring circuit is coupled to an input of said microcontroller and said microcontroller is operative to sense zero crossings in said output and turn said shunt off near said zero crossings.

106. The apparatus of claim 105, wherein said voltage powers said microcontroller.

107. The apparatus of claim 85, wherein said power supply circuitry comprises a shunt switch coupled between a ground connection and said regulated power, said shunt switch selectable to be one of open or closed during a switched regulation mode, and a conductivity of said shunt switch operable to be dynamically modulated during a linear regulation mode.

108. The apparatus of claim 85, wherein said power supply circuitry comprises a first switch and a second switch coupled with a supply rail, said first switch selectively enabled to provide a conductive path to ground and said second switch selectively enabled to conduct when a voltage at said first switch is greater than a voltage of said supply rail.

109. An apparatus for sensing the current in a power line of a power system, the apparatus comprising:

an enclosure providing a window operable to permit passage of said power line therethrough;

an active current transformer set within said enclosure and operative to produce a scaled version of said current;

said current containing frequency components substantially within a first range of frequencies;

a compensation circuit coupled with said active current transformer and operative to reduce a phase shift and ratio error between said current and said scaled version of said current;

a powering current transformer set within said enclosure and operative to receive power from said power line on a primary winding and deliver power on a secondary winding; and

power supply circuitry set within said enclosure, said power supply circuitry operative to extract power from a power source within a second range of frequencies, said power supply circuitry further operative to supply regulated power to power said compensation circuit.

110. The apparatus of claim 109, further comprising a high frequency bypass coupled with said power supply circuitry and said power source, said high frequency bypass operative to pass said power at said second range of frequencies.

111. The apparatus of claim 109, further comprising filtering circuitry coupled with said active current transformer and said power source, said filtering circuitry operative to pass said first range of frequencies for receipt by said active current transformer.

112. The apparatus of claim 109 wherein said first range of frequencies is 4 kHz and below and said second range of frequencies is 400 kHz and above.

113. The apparatus of claim 109, wherein said first range of frequencies covers a frequency range at lower frequencies than said second range of frequencies.

114. The apparatus of claim 109, further comprising at least one of secondary leads and secondary terminals extending from said enclosure, said at least one of secondary leads and secondary terminals coupled with said active current transformer and operative to deliver said scaled version of said current in a form of digital data.

115. The apparatus of claim 109, further comprising at least one of secondary leads and secondary terminals extending from said enclosure, said at least one of secondary leads and secondary terminals coupled with said active current transformer and operative to deliver said scaled version of said current in a form of a scaled current signal.

116. A method of sensing current in a power line of a power system, the method comprising:

receiving a primary current from a power line on a primary winding of a powering current transformer;

delivering power on a secondary winding of said power current transformer, said delivered power comprising a supply voltage and a supply current;

producing a scaled version of said primary current with an active current transformer;

compensating for magnetic losses in said active current transformer with a compensation circuit; and

supplying regulated power with a power supply circuit to power said compensation circuit, said power supply circuit coupled with said secondary winding and supplied said supply voltage and said supply current therefrom.

117. The method of claim 116, wherein said regulated power comprises a supply rail voltage and an output current, and supplying regulated power with a power supply circuit to power said compensation circuit comprises sensing said output current, and operating a shunt in one of a linear regulation mode, or a switched regulation mode in response to a magnitude of said output current.

118. The method of claim 117, wherein operating said shunt in said switched regulation mode comprises selectively switching said shunt switch between opened and closed to regulate said supply rail voltage in response to said output current being one of at or above a determined threshold, said shunt switch coupled between said supply rail voltage and ground.

119. The method of claim 117, wherein operating said shunt in said linear regulation mode comprises modulating a conductivity of said shunt switch to regulate said supply rail voltage when said output current is below a determined threshold.

120. The method of claim 116, wherein producing a scaled version of said primary current with an active current transformer comprises:

magnetizing a secondary core of said active current transformer with said power line to supply a secondary current to a burden; and

compensating for magnetization losses in said secondary core with a compensation circuit that is powered with said supply rail voltage.

121. The method of claim 116, further comprising dividing a compensation current generated by said compensation circuit between said supply current and a divider resistor.

122. The method of claim 116, further comprising monitoring said compensation circuit to detect when compensation for magnetization losses is insufficient.

123. The method of claim 122, further comprising indicating to a user when said compensation for magnetization loses is insufficient.

124. The method of claim 116, further comprising providing an external device with power from said supply voltage.

125. The method of claim 116, wherein compensating for magnetization losses in said active current transformer with a compensation circuit further comprises reducing a phase shift and ratio error between said primary current and said scaled version of said primary current.