Abstract: The system for synchronous sampling uses an encoded time signal, such as an IRIG-B signal. The IRIG-B signal is applied to an edge detector, which produces pulses based on the edges of the encoded time signal. These signals are applied to a phase-locked-loop assembly which is arranged to produce an output sampling synchronization signal which is locked to the transitions in the encoded time signal, providing a synchronous control signal for data sampling of input signals to a plurality of electronic instruments, in addition to the use of the IRIG-B signal as time-of-day clock synchronization for the plurality of instruments.

Abstract: A system for checking synchronization of AC voltage sources before closing a power circuit breaker is provided comprising two power circuit breakers connected by a power transmission line, such as by using remote voltage via fiber channel. Each circuit breaker is respectively connected to a bus and a protective relay. The circuit also comprises voltage transformers between the bus and the protective relay. The protective relays monitor the voltages on the bus side of the circuit breakers and current flowing through the circuit breakers in order to detect short circuits on the line. A bidirectional communications link is further provided for connecting protective relays together.

Abstract: A power system bus total overcurrent system is used with a part of a power system which includes two buses and first and second power line portions which extend between them. A protective relay system includes protective relays for each of the first and second power line portions, located near the two buses, wherein the relays determine the total current into and out of each bus. The bus total overcurrent system includes first and second communication lines between each pair of relays and another communication line which extends between the first and second communication lines. In a current balance arrangement, the relays measure difference current using the same communication line arrangement between the two pairs of relays to determine a fault condition. Fault determinations are made in each case by the protection algorithms from total and difference currents.

Abstract: A protective relay system for a power system having protective relays at specific locations in the system. Each location has specific setting information for the relay for operation of the relay at that location. Each relay in the protective relay system includes in memory all of the setting information for all of the locations in the power system. Connection of the relay to a key identifier member at a desired location, in one embodiment, provides an identification of that location to the relay. The identification may also be provided by a system computer to which the relay is connected at the desired location. The relay uses the information to obtain the correct setting information for the desired location from its memory for proper protection operation at the desired location, eliminating programming of replacement relays.

Abstract: An architectural system for a protective relay used in an electric power system and responsive to analog signals from the electric power line includes a main circuit board which contains a processor for processing digital input signals to carry out specified protection functions. The system further includes an input signal board which includes current transformers (CTs) and potential transformers (PTs) for all three phases and low-pass filters associated therewith. Those components have correction factors associated therewith to correct errors produced by the components. The correction factors are stored on the boards having the components. The signals from the input signal board are applied to the main board for use by the processor, along with the correction factor(s) stored on the input signal board.

Abstract: The fault detection system includes at least one valid zero sequence voltage source, either from a local relay or a remote relay on a protected line. Zero sequence current is selected between total (vector sum from both ends of the protected line) measured zero sequence current or calculated zero sequence current. A zero sequence impedance-based calculation is then made and the result is compared against a threshold value to produce a trip decision. The trip decision is then applied through a normal tripping circuit or a slow tripping circuit, depending upon selected circuit conditions, involving the local and remote ends of the line.

Abstract: A protective relay system for a power system having protective relays at specific locations in the system. Each location has specific setting information for the relay for operation of the relay at that location. Each relay in the protective relay system includes in memory all of the setting information for all of the locations in the power system. Connection of the relay to a key identifier member at a desired location, in one embodiment, provides an identification of that location to the relay. The identification may also be provided by a system computer to which the relay is connected at the desired location. The relay uses the information to obtain the correct setting information for the desired location from its memory for proper protection operation at the desired location, eliminating programming of replacement relays.

Abstract: A power system bus total overcurrent system is used with a part of a power system which includes two buses and first and second power line portions which extend between them. A protective relay system includes protective relays for each of the first and second power line portions, located near the two buses, wherein the relays determine the total current into and out of each bus. The bus total overcurrent system includes first and second communication lines between each pair of relays and another communication line which extends between the first and second communication lines. In a current balance arrangement, the relays measure difference current using the same communication line arrangement between the two pairs of relays to determine a fault condition. Fault determinations are made in each case by the protection algorithms from total and difference currents.

Abstract: The fault detection system includes at least one valid zero sequence voltage source, either from a local relay or a remote relay on a protected line. Zero sequence current is selected between total (vector sum from both ends of the protected line) measured zero sequence current or calculated zero sequence current. A zero sequence impedance-based calculation is then made and the result is compared against a threshold value to produce a trip decision. The trip decision is then applied through a normal tripping circuit or a slow tripping circuit, depending upon selected circuit conditions, involving the local and remote ends of the line.

Abstract: The error compensating system and method is used in electric power monitoring systems, e.g. protective relays, and includes a test unit for applying a test signal to the front end of a data acquisition section of the power monitoring system and a phase reference module which converts the test signal to a square wave having falling and rising edges corresponding to transitions between the positive and negative portions of the test signal. A programmable logic device determines the zero crossings of the sampled digital signal from the data acquisition system and then determines the time difference between a falling edge of the module output signal and the zero crossing of the sampled digital signal. The time difference is representative of the phase shift produced by the data acquisition components. A compensation circuit adjusts the digitally sampled signals with the amount of the determined phase shift.

Abstract: The error compensating system and method is used in electric power monitoring systems, e.g. protective relays, and includes a test unit for applying a test signal to the front end of a data acquisition section of the power monitoring system and a phase reference module which converts the test signal to a square wave having falling and rising edges corresponding to transitions between the positive and negative portions of the test signal. A programmable logic device determines the zero crossings of the sampled digital signal from the data acquisition system and then determines the time difference between a falling edge of the module output signal and the zero crossing of the sampled digital signal. The time difference is representative of the phase shift produced by the data acquisition components. A compensation circuit adjusts the digitally sampled signals with the amount of the determined phase shift.

Abstract: The data compression system is used for communication between at least two protective relays on a power transmission line. The system is responsive to a linear digital output from an analog to digital converter to which is applied successive analog quantities. At the transmitting protective relay, a logarithmic compression element reduces the number of digital bits to be transmitted while maintaining any errors in the encoding/decoding process to a level acceptable for the existing protection scheme for the power system. The compressed data is transmitted over a communication line to the receiving relay, where it is decoded (expanded) and then used in the relay's protection algorithm.

Abstract: A DC monitoring system is provided in each protective relay in an electric power substation to detect DC grounds on the DC supply system. The DC monitoring system includes a first portion which indicates the presence of a DC ground. In a second portion of the system, the voltages at the contact inputs of the relay are recognized and compared against a standard voltage value range. An indication is provided when the recognized voltage is within said range. The combination of the indications from the first and second portions is useful in determining the location of DC grounds in the substation DC supply system.

Abstract: The apparatus detects subsidence current from unfiltered as well as filtered secondary current values in the current transformer. A lack of zero crossings during a predetermined period is a reliable indication of the presence of subsidence current. If subsidence current is detected, then a signal is generated which indicates that the circuit breaker for the power system has opened, providing an accelerated indication thereof relative to an indication produced by an overcurrent element dropping out.