Pilot Wire Research Articles

A Novel Centralized Wide Area Protection “CWAP” in Phase Portrait Based on Pilot Wire Including Phase Comparison

A new centralized wide area protection (CWAP) to protect large scale complex grid is presented. The principle of protection depends on a combination of two types of pilot wire relays (current differential scheme and phase comparison scheme) . The phase comparison scheme is mainly used for error cancellation between two corresponding areas. The new idea depends on data collected from different phasor measurement units (PMUs) deployed on a real interconnected 500/200 kV grid. The current signals and phase angles measured by PMUs are used for identifying the faults between two different areas. The CWAP processes the data collected from a phasor data concentrator. The phase portrait as a geometric solution for solving the dynamic equations is used for identifying the faulted areas. The CWAP scheme is reliable and stable for long transmission lines with wide area grid. The simulation of the interconnected system 500/200 kV network using MATLAB/Simulink is used.

Production and further application of cored wire with ferroniobium filling for steel alloying at steelmaking shop of PAO NLMK

Taking into account market status of ferroniobium filled cored wires as well as necessity to decrease metal products cost in PAO NLMK, a production technology of cored wire with ferroniobium filling developed. For the wire shell manufacturing a steel cold-rolled band was used, having thickness of 0.4 mm, width of 59.2 mm made of domestic production 08Ю grade steel. The tensile strength was from 26 till 37 kg/mm 2 , specific elongation >30 %. A sample was taken from every bundle to check the wire shell lock closing tightness and to determine the coefficient of its filling by the powder-filler. To decrease the risk of the wire first layers deformation while coiling into bundle and the wire rupture during uncoiling in BOF shops, the bundle internal diameter was increased from 560 mm till 730 mm. The cored wire bundles packing was made by a polyester band. The test of pilot cored wire with ferroniobium filling was done at steel ladle treatment areas according to existing technology instructions. For the pilot wire application parameters analysis the indices of heats array were selected, for which other niobium- containing materials were not used. For comparison the heats indices were selected of similar assortment groups, for which only wires of outside manufactures were used (lump ferroniobium was not used). Based on pilot wire test results it was noted, that at production of low-silicon assortment the average pilot wire consumption on 0,001 % [Nb] growth was equal to 3.27 kg, regular wire consumption 3.19 kg. At production of 08Ю steel of low-silicon low-sulphur assortment, low-alloyed assortment with mass suphur portion less 0.002%, the wire consumption for 0.001 % [Nb] growth was 7.5 kg at test heats and at comparative — 7.6 kg.

Enhanced real time coordination of distance and user defined over current relays

Faults on the transmission lines are primarily cleared by pilot wire differential protection as well as from zone-1 and zone-2 of distance relays, depending upon their location on the lines. If the main distance relays fails to operate, then standard time inverse directional over current (DOCR) relays are set as backup protection in coordination with main distance relays. The desired coordination time margins between main distance relays and backup standard time inverse over current relays should be maintained at start of zone-1 and zone-2 of distance relays. Coordination of fixed zone-2 setting of distance relays with standard time inverse relays results in poor tripping time of backup DOCR.In this research article, zone -2 setting of distance relays are made adaptive, so that minimum coordination time margin is maintained for complete reach of distance relays. User defined time inverse over current relays are proposed in conjugation with flexible feature of zone-2 setting of distance for improving the operating time of backup DOCRs. The performance of the proposed algorithm is validated in real time simulation with hardware in loop testing of numerical distance and user defined DOCR. From hardware in loop simulation results, it is observed that the performance of the proposed combined distance &DOCR coordination algorithm is in close concurrence with simulated results. The sensitivity of proposed algorithm is checked for different phase as well as ground faults with different fault resistance and it is also observed that the proposed algorithm is highly robust for different fault conditions.

The study of directional overcurrent relay and directional earth-fault protection application for 33 kV underground cable system in Malaysia

Differential protection scheme is based on comparison of measured variables such as current and voltage at the two ends of a line via a communication channel such as pilot wire. This scheme is preferred and extensively used in distribution feeder protection system in Malaysia due to its fast operation. However pilot-wire differential scheme has its own drawbacks especially on the maintenance of the pilot-wire. Once the plot-wire is out of service, the feeder protection is jeopardised. One of the options to overcome such maintenance issue is to adopt directional relay as the feeder protection. This paper investigates a suitable relay connection and the maximum torque angle for the directional relay for 33kV underground network. In this study, a section of 33kV underground network in Kuala Lumpur (KL) city has been analysed. All faults types have been simulated at all possible location in the network. The obtained voltage and current were then used to determine the operation of directional overcurrent and earth-fault relay. The simulation results indicate that 30° relay connection with 0° maximum torque angle (30°/0°) is the most suitable setting to be applied for 33kV underground network in KL, as against the best general and most versatile setting, 45°/90°.

Effect of coating material and lubricant on forming force and surface defects in wire drawing process

A pilot wire drawing machine as well as wire end-pointing roller was developed. Using these machines, a wire drawing test for four different coating materials and two different lubricants was performed as the reduction ratio increased from 10% to 30%. Materials used for a substrate in this study are plain carbon steel (AISI1045) and ultra low carbon bainite steel. To compute the friction coefficient between the coating layer of wire and the surface of die for a specific lubricant, a series of finite element analyses were carried out. SEM observations were also conducted to investigate the surface defects of wire deformed. Results show that the behavior of drawing force varies with the lubricant-type at the initial stage of drawing. The powder-typed lubricant with a large particle causes the retardation of full lubrication on the entire contact surface and the local delamination of coating layer on the wire surface. As the flow stress of a substrate increases, the delamination becomes severe.

Laboratory Investigation of Using Wi-Fi Protocol for Transmission Line Differential Protection

Pilot wire differential protection is one of the most common methods for protecting short transmission lines. The conventional protection scheme has drawbacks, such as malfunction due to line disconnection and limited line length. A laboratory investigation of transmission line protection using Wireless Fidelity (Wi-Fi) communication protocol for data sharing between the relays located at the two ends of the transmission line is presented in this paper. The protection algorithm is based on current signals measured at both ends of the transmission line. The data is exchanged through the wireless communication network. The relay decision is based on data sharing obtained through wireless communication network. The suggested technique satisfies high degree of reliability and stability.

Effects of wind and oxygen concentration on a laminar diffusion flame established over a horizontal flat plate in micro-gravity environment

An experimental and numerical investigation of a laminar diffusion flame established over a horizontal flat plate in micro-gravity environment is described. Fuel is injected through the burner and the oxidiser (air) is provided by a forced flow parallel to the surface. The experiments were conducted in a range of oxygen concentration from 23% to 30% at two different wind velocities of 2.6 and 4 cm/s in a 5 s drop tower. The flame experiments make use of a pilot wire to ignite the sample in normal-gravity environment. It is observed that after the imposition of the micro-gravity, a pool-like flame is maintained momentarily due to the relaxation of the initial movement of the natural convection. The transition time is about 2.5 s for reducing an oscillated reacting flow to a forced boundary layer one. Two- and three-dimensional, time-dependent numerical solutions to the Navier–Stokes equations are used to simulate the experiments. Combustion process is described by a global one-step, finite-rate reaction given by the Arrhenius expression. Direct numerical simulation is used to provide a detailed description of the transition process of the flame in micro-gravity environment. The model results reflect the qualitative features of the experiments.

Communications systems for protective relaying

In normal power system operation, a variety of communications links are used to provide this information transfer, including: pilot wire channels operated by the power utility; pilot circuits rented from national communications utilities; power line carrier over the transmission lines; radio channels operating either at very high frequencies or over microwave; and optical fiber communications systems. These schemes were originally intended for electromechanical and static analog relays but have subsequently been applied to digital relays. Following a description of the ISO communications model, these communication links are discussed. Modulation techniques, asynchronous and synchronous communication, error detection, and protocols and profiles are also discussed.

Effects of magnetic field induction and ground potential rise on pilot wire relay system operations

In the paper, magnetic field induction and ground potential rise (GPR) problems have been evaluated to investigate false responses of pilot wire relays, causing the blackout of a 2100 MVA 161/69 kV substation in a major Taiwanese electric power utility. Based on available field information, the EMTP was applied to determine the magnetic field induced voltage (MFIV), and a simple model was used for GPR calculations. Those results and an analysis of the false responses are presented. Also, methods for protecting against the MFIV and GPR for the pilot wire relay system are discussed.

A new approach to digital current differential protection for low and medium voltage feeder circuits using a digital voice-frequency grade communications channel

A new approach to digital current differential protection is described which provides the capabilities of conventional pilot wire differential protection while using the limited data transfer capabilities of a digital data voice-frequency grade communications channel. This approach compares polyphase polarised current measurements taken at the feeder's terminals to detect faults and can trip in under two power system cycles. The algorithms decouple the measurements from the power system frequency and its waveform, and thereby have a high inherent tolerance to the complications introduced by communication channel delays and their fluctuations. For this project, the communications requirements have been limited to a full duplex 2400 bits/sec system suitable for operation over a voice-frequency grade channel.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Tests of 34.5-kV expulsion fuses at the Los Angeles Department of Water and Power

In the Los Angeles basin, the Department of Water and Power (DWP) of the City of Los Angeles operates a 34.5 kV, three-phase, three-wire, 60-cycle, subtransmission system as a distribution system. Large customer loads are served by nominal 6-percent impedance transformers located on customer property which transform the 34.5 kV volts to the customer utilization voltage. DWP will serve 120/240, 120/208, 277/480, 2400/4160, and 4800 volt services. Transformers are fused using pole-mounted and metal-enclosed cabinet-mounted fuses. Fuses are selected to coordinate with directional overcurrent relays and pilot wire relays at the substations. A switch and fuses are installed adjacent to each customer transformer. In order to characterize the 34.5 kV system parameters which are necessary for proper operation of fuses, the fuse performance and application reevaluation (FUSEPAR) program was conducted during June 1987 and October 1988. The results of the tests are presented. >

Innovations in power distribution in cement plants

A few of the many new product applications and protection methods first used in the decade between 1971 and 1981 for cement plant power distribution systems are surveyed. References noted in each brief discussion contain application details as well as equipment descriptions, ratings, and application advantages of the innovations discussed. Transformers: Transformer designs, transformer through fault protection. Motors: Thermal tracking motor protection wound rotor motor protection, dual drive protection, high efficiency 460 V motor design, large horsepower SCR-DC fan drives, medium voltage load commutated inverter drives. System: Medium voltage vacuum circuit breakers, pilot wire tie line protection, transformer ground differential protection, zinc oxide station class surge arresters.

Pilot Wire Relay Applications in Industrial Plants Utilizing a New Static Pilot Wire Relay

Pilot wire relaying is an extremely effective way to provide fast, selective protection for industrial plant cable tie circuits. The operating principles of popular pilot wire relay schemes will be reviewed, and special attention will be given to a new static pilot wire relay which offers an improvement in ground fault sensitivity, an especially significant consideration on resistance grounded industrial systems. A discussion of pilot wire overvoltages and overvoltage protective devices is also presented.

Communication System Design, Construction and Main-Enance Practces for Reliable Pilot Wire Relay Operation

Pilot wire relays offer an ideal form of high speed protection for urban transmission and subtransmission circuits.

Solid-State, High-Speed Phase-Comparison Relay Based on Zero Crossings: II - Design

The design of a comparison type of relay system for three-phase transmission lines based on the instantaneous position of zero crossings of the current waveforms is discussed. A composite signal based on these zero crossings is generated at both ends of a protected section and compared continuously by carrier current microwave or pilot wire means. It is extremely fast and can give as many as five clear indications of abnormal operation in the first cycle after a disturbance. Solid-state and magnetic devices are used exclusively for reliability, long life, and minimum power requirements.

Generalized Circle Diagrams and Their Application to Protective Gear

The common underlying theory of generally used systems of protection involving comparison of two vector quantities is derived by coaxial (bipolar) circles in the complex plane, where amplitude or phase comparison can be used interchangeably to produce any desired circle or straight line characteristic. Practical departure from ideal comparison, resulting from relay power consumption, is considered, and the relationship between this analysis and two currently used methods of distance relaying is pointed out. The basic circuit of a commonly used pilot wire scheme is analyzed and its characteristic considered, and the effect of long pilots with distributed constants is indicated.

Pilot-wire protection of transmission lines

THE PRESENT pilot-wire protective systems for transmission lines employing leased pilot-wire circuits are an outgrowth of conventional differential protective systems for other types of electric apparatus. Thus, these line-protective systems are characterized by the fact that the pilot wires are part of the differential connection between the current transformers at the line ends. The pilot wire has distributed shunt capacitance as well as series resistance, with the result that when these parameters reach sufficient magnitude, attenuation and undesirable phase shifts occur in the pilot-wire circuit. Thus, the system may be prevented from functioning correctly under certain operating conditions.

Multiunit neutralizing transformers

IN RECENT YEARS there has been a large increase in the number of communication, telemetering, pilot wire relay, and other control circuits required by power utilities in Canada. Service continuity on these circuits is of prime importance, and neutralizing transformers are required in many cases to maintain this continuity and to prevent damage to the circuits or terminal apparatus as the result of ground potential rise.

A Rapid Method for Preparing Powder Camera Specimens with Cellulose Acetate Capillary Tubes

Several details are described in the preparation of capillary tubes for x-ray power specimens which greatly facilitate the synthesis of such tubes and their subsequent removal from the pilot wire. The over-all method employed is essentially that of Fricke et al. Wires of 22-gauge copper, after annealing in an atmosphere of helium, are cleaned and dipped into the cellulose acetate solution by means of a crank-driven rack. The rate of withdrawal determines the wall thickness. A method is given for centering the filled specimen tubes precisely in the powder camera by the use of a centering jig.

The Application and Performance of Carrier-Current Relaying

THE GENERAL idea of pilot relaying is quite old. It has been employed for several decades in the Mertz Price system where pilot wires are employed for balancing the currents at the two ends of the line and has met with considerable success in Europe, and particularly in England. A simpler pilot scheme in which the pilot wire is used merely to conduct an impulse, and the conditions of the line at the two ends of the section are indicated by the relative positions of a series of power directional relays, has been employed and has been described elsewhere.1 Neither of the above schemes, however, has ever met with any great favor in the United States on account of the prohibitive cost of pilot wire circuits, and particularly on long lines, and because in the long run the scheme itself is no more reliable than the pilot wire. Experience has shown that the reliability of the latter is not quite at the 100 per cent level desired and mandatory for proper service.