High-impedance bus differential protection
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsMarcos A. Donolo, Anushka M. Dissanayake, Pallavi Kulkarni, Jay Hartshorn
Life of this patent
Estimating the term…
Abstract
A system for high impedance bus protection that includes a safety module to divert excess current away from a protective element of an intelligent electronic device. The safety module may include a variable resistor and a bypass relay in parallel across secondaries of one or more current transformers. The bypass relay may be configured to close upon detection of excess current through the secondaries to divert the excess current away from the variable resistor and the protective element.
Claims18
A protective device configured for use in an electric power system, comprising:
- an overvoltage element configured to monitor a voltage and to initiate a protective action when the voltage exceeds a first threshold;
- a variable resistor disposed in parallel with the overvoltage element and to generate substantially all of an electrical resistance across the overvoltage element when the voltage is less than the first threshold;
- and
- a bypass device disposed in parallel with the overvoltage element and the variable resistor and configured to transition from a first state to a second state in response to a signal generated by the protective device;
- wherein the signal to transition the bypass device from the first state to the second state is generated a length of time after the voltage exceeds the first threshold, and after the bypass device provides a low-resistance path to dissipate the voltage across the overvoltage element and the variable resistor in the second state, and
- wherein the signal to transition the bypass device from the first state to the second state is generated when a DC offset is minimized.
A method of operating a protective device in an electric power system, the method comprising:
- monitoring, using an overvoltage element, a voltage and initiating a protective action when the voltage exceeds a first threshold;
- generating, using a variable resistor disposed in parallel with the overvoltage element, substantially all of an electrical resistance across the overvoltage element when the voltage is less than the first threshold;
- transitioning a bypass device disposed in parallel with the overvoltage element and the variable resistor from a first state to a second state in response to a signal generated by the protective device;
- and
- generating the signal to transition the bypass device from the first state to the second state when a DC offset is minimized;
- wherein the signal to transition the bypass device from the first state to the second state is generated a length of time after the voltage exceeds the first threshold, and after the bypass device provides a low-resistance path to dissipate the voltage across the overvoltage element and the variable resistor in the second state.
A protective device configured for use in an electric power system, comprising:
- an overvoltage element configured to monitor a voltage and to initiate a protective action when the voltage exceeds a first threshold;
- a variable resistor disposed in parallel with the overvoltage element and to generate substantially all of an electrical resistance across the overvoltage element when the voltage is less than the first threshold;
- and
- a bypass device disposed in parallel with the overvoltage element and the variable resistor and configured to transition from a first state to a second state in response to a signal;
- a plurality of current transformers in electrical communication with protected equipment in the electric power system and the overvoltage element;
- a series resistor disposed in series between the plurality of current transformers and the overvoltage element, the variable resistor, and the bypass device;
- wherein the signal to transition the bypass device from the first state to the second state is generated when the voltage exceeds the first threshold.
Dependencies are inferred from the claim text.