Abstract: A computer workstation-based interactive tool for assessing the reliability of power systems is disclosed. This tool can be used to determine the effect on the reliability of both substations and bulk generation and transmission systems of system additions, design alternatives, maintenance practices, substation configurations, and spare part policies. Each utility using the present invention is modeled analytically. The model includes load characteristics, demand projections, voltage profiles, energy and operating constraints, operator and automatic responses to the occurrence of contingent events, generating unit dispatch, contingency remedial actions, load shedding practices, demand-side management, and equipment failure modes including planned and unplanned maintenance.

Abstract: Apparatus and methods for detecting the direction of a fault in relation to a switch connected between a source and a load are shown to include a voltage sampler for generating samples of the voltage during first and second power cycles. A current sampler generates samples of the current during first and second cycles. A first comparator compares the current samples from the first cycle to the current samples from the second cycle and determines the sign of the difference between the samples. A second comparator compares the sign of the voltage from the first cycle to the sign of the current difference determined by the first comparator and provides an indication of fault direction in relation to such comparison. The apparatus also includes a fault inception determiner, for providing a fault inception indication in relation to the voltage samples from the first and second cycles.

Abstract: A quadrilateral characteristic relay system for determining a fault associated with a multiple-phase electric power transmission system is disclosed. The system dynamically adapts one line of the quadrilateral trip region to account for the interaction of load current and fault resistance. As a result of the adaptation, the system exhibits better overreach and underreach performance characteristics. The system employs impedance and voltage plane quadrilateral characteristics using negative sequence current as a proxy for fault current. In the voltage plane, the fault determination is made through a series of comparisons, avoiding computationally inefficient mathematical divisions.

Abstract: Disclosed is a protective relaying system that trips a local circuit breaker (BL) connected to a transmission line by providing a trip signal ("TRIP.sub.-- BL") to the circuit breaker. The system comprises a local filter operatively coupled to the transmission line, and a local relay operatively coupled to the filter. The local filter receives inputs indicative of phase currents on the transmission line and provides an output ("VFL.sub.k ") derived from the inputs. The local relay (1) receives the output (VFL.sub.k) of the local filter, (2) receives an output ("VFR1.sub.k ", "VFR2.sub.k ") of at least one remote filter, and (3) generates the trip signal. The local filter and relay preferably employ substantially all digital electronic circuitry to generate the trip signal.

Abstract: A solid state voltage regulator and methods therefore are shown to include a transformer having a secondary coil, the secondary coil having a plurality of taps. A first solid state switch is connected between the regulator output and a first tap. The first switch need only have the capability of being turned on in response to a gate signal. A second solid state switch is connected between the regulator output and a second tap. The second switch has the capability of being turned on and turned off in response to gating signals. The output voltage resulting from the second tap is greater than the first tap. A controller, connected to the input, the output, the first switch and the second switch, senses the voltage present at the regulator input and output and generates gating signals in response to the sensed voltage. The voltage regulator may include several switches similar in construction and operation to the first switch.

Abstract: A process for identifying the type of fault detected by a protective relay includes measuring pre-fault and post-fault samples of current waveforms on the phase-A, phase-B and phase-C conductors of a transmission line. Next, increment currents DELIA1, DELIB1, and DELIC1 are calculated, whereDELIA1=(I.sub.ar -I.sub.apr).sup.2 +(I.sub.ai -I.sub.api).sup.2DELIB1=(I.sub.br -I.sub.bpr).sup.2 +(I.sub.bi -I.sub.bpi).sup.2DELIC1=(I.sub.cr -I.sub.cpr).sup.2 +(I.sub.ci -I.sub.cpi).sup.2.The increment currents are then employed to identify a two-phase to ground fault. In calculating the increment currents, I.sub.ar represents a post-fault value of the real part of the phase-A current, I.sub.apr represents a pre-fault value of the real part of the phase-A current, I.sub.ai represents a post-fault value of the imaginary part of the phase-A current, and I.sub.api represents a pre-fault value of the real part of the phase-A current. The phase-B and phase-C values are denoted accordingly.

Abstract: A reclosing relay in accordance with the disclosed invention comprises a reclose initiate (RI) input and a drive to last reclosure (DTLR) input, and an output at which a close signal is provided to effect the reclosure of a circuit breaker associated with the reclosing relay. The reclosing relay is operative when it receives a first RI signal at its RI input to provide the close signal to the associated circuit breaker substantially immediately or with time delay as programmed by settings. The reclosing relay is operative when it receives a signal from a second RI contact at its DTLR input to provide the close signal to the circuit breaker only after synchronism is identified between the line voltages on either side of the associated circuit breaker.

Abstract: A method for generating a computer model for use in system component design as well as overall system evaluation is disclosed. The method includes the steps of generating an equation model of the system component, modifying the equation model by integrating according to the trapezoidal rule, wherein an integrated model is formed having a plurality of parameter values. Certain of such parameter values define historical parameter values accounting for historical parameter information. the parameter values are arranged in matrix form and reordered. The reorder matrix equation is reduced by eliminating certain of the parameter values, thereby forming a reduced model. When the reduced model is incorporated is a system model it is necessary to modify the system model to account to the component model current parameter information. Such information is used by the component model to update the historical information.

Abstract: A one-terminal process for locating a fault associated with a multi-phase electric power transmission system is disclosed. The process is based on the principle that the impedance in a fault can be determined by correcting errors due to the interaction of fault resistance and load current. The fault may be a phase-to-ground fault or a multiple-phase fault.

Abstract: Methods and apparatus for switching a load between first and second sources is shown to include first and second solid state switches connected to the load. First and second mechanical breakers are connected between the switches and the sources so that each source is connected to the load through a circuit breaker and solid state switch. A controller is connected to sense the voltage from the first and second sources. The controller is connected to the first and second switches and the first and second mechanical breakers. The controller senses the phase difference between the voltages from the first and second sources. The controller causes the first and second mechanical breakers to open and close in response to sensing the phase difference between the sources. The first and second mechanical breakers can include medium voltage vacuum breakers.

Abstract: A numerical comparator employs numerical techniques based upon the behavior of the cylinder unit to compare phasors in real time. In one application, the torque signal generated by the numerical comparator, M.sub.k+1, is employed to determine whether a fault has occurred in a transmission line. Another application involves employing the output M.sub.k+1 to determine the direction of power flow in the transmission line. In yet another application, the output M.sub.k+1 is used to determine whether a voltage or current has exceeded a predetermined threshold. In yet another application, time dependent waveforms of positive and negative symmetrical sequence components are digitally produced.

Abstract: A materials characterization test cell is disclosed. The test cell includes a housing including spacers for supporting sample insulation materials, and a channel disposed in the housing to permit the passage of oil through the housing. A pair of electrodes is provided to provide a mechanism for making polarization spectrum and/or streaming electrification measurements.

Abstract: A system and method for automatically testing the operation of a protective relay system is disclosed. The system and method provide for continuous testing to ensure proper operation of the protective relay system while the relay remains in service and without interrupting the normal operation of the relay. This testing is performed by storing reference data corresponding to test signals, generating test signals, sampling a specific test signal, processing that test signal through the relay and comparing the processed test signal with the corresponding reference data. Upon detection of an error in the relay, the system and method further provide for isolation of the relay from the electric power system and automatic testing of individual electrical components within the protective relay system to determine the identity of the malfunctioning component.

Abstract: An enclosure and latching structure for the cable compartment of a tank for a padmounted distribution transformer. The enclosure is of non-conductive fire resistant material. A curved latch arm of non-conductive material is pivotally connected to support structure mounted on the front tank panel of the transformer above the midpoint thereof. The enclosure is shaped to conceal the cable compartment of the tank and is open at the back for engaging the periphery of the tank panel. The enclosure has an opening in the front adjacent the top thereof through which extends a locking device secured to the enclosure for mating with locking structure carried at the free end of the latch arm.

Abstract: A switchgear enclosure which permits closed door operation during the opening and closing of the primary contacts of electrical apparatus housed in the enclosure with the use of an arc-suppressor-type contact.

Abstract: A method and system for estimating phasors and tracking the frequency of a signal is provided. The method uses a variable N-point DFT to compute one or more phasors based on data acquired from one or more sampled signals. At each sampling interval the change in phasor angle between the current sampling interval and the previous sampling interval is determined and used to estimate the instantaneous frequency of the signal. Instantaneous frequencies are averaged over a cycle of the signal. In addition, a number of discrete frequencies and corresponding DFT windows based on a fixed sampling rate and a predetermined fundamental frequency of the signal are defined and used in estimating the instantaneous frequency. Once the average cycle frequency is determined the DFT window is adjusted by setting it equal to the DFT window corresponding to the discrete frequency closest to the average cycle frequency.

Abstract: A coil for an electrical apparatus such as a transformer is disclosed which includes an electric field control means to minimize flashover or arching at a lead of the coil.

Abstract: An arc resistant enclosure including two compartments having a toggle flap which permits the two compartments to share a single exit path from the enclosure for any pressure and gases produced in either compartment.

Abstract: A high voltage open-air switch has a movable disconnect switch blade which contains a circuit interrupter therein having interrupter contacts in series with the open air disconnect switch contacts. The circuit interrupter has a lower BIL rating than the switch. An operating mechanism causes the independent operation of the interrupter and disconnect switch such that there is a high speed opening of the interrupter contacts, followed by the low speed opening of the disconnect switch contacts, and a slow speed closing of the disconnect switch contacts followed by the high speed closing of the interrupter contacts. The switch can be adapted to numerous switch configurations and permits substantial savings in space by the reduced mounting space requirements for the interrupter assembly.

Abstract: A load tap changer (LTC) comprising in part a diverter switch is disclosed. The diverter switch includes a movable main contact (38); first and second fixed main contacts (40a, 40b); a pantograph system (30) for translating a rotational motion of a shaft (22) to a substantially linear motion of the movable main contact; and a link system (10) comprising a gear (12) adapted to be rotated by a motor, a spring battery (26) for storing energy of the motor, link means (14, 16, 18) for coupling the gear to the spring battery, and the shaft (22) coupled to the link means, wherein the spring battery is operable to rotate the shaft and to thereby effect the movement of the movable main contact. A predetermined amount of rotation of the shaft effects a movement of the movable main contact from a contacting relation with the first fixed main contact to a contacting relation with the second fixed main contact.