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POWER SYSTEM PROTECTION LEARNING OBJECTIVES
TABLE OF CONTENT
2101: Elements of System Protection
2102: Types of Protective Relays
2103: Monitoring System Conditions
2111: Protection for System Stability
2112: Testing and Commissioning of Protective Schemes
2114: Fault Investigation and Analysis
2115: Introduction to Static Relaying
2116: Coordination of Protection Devices
2117: Power Supply for Protection & Control Systems
2118: Energy Centre Operations
2119: Telecommunications Protection I – HVSP Devices
2120: Telecommunications Protection II – Installation & Configuration
2121: Supervisory Control System (SCADA)
2122: Inadvertent Trips – Causes and Prevention
2123: Fault Calculations and Relay Settings
2125: Programmable Logic Controllers
2101: Elements of System Protection
The objective of this module is to overview the function of protection schemes, including general protection philosophy and its impact on the operation of the system. After study of this tape and the associated workbook, the participant should be able to understand the following overall concepts and apply them to his day-to-day work activities.
- Why protection is necessary?
- The philosophy and objectives of protection.
- Zones of protection - local and backup.
- Causes and consequences of faults.
- Tolerable and intolerable fault conditions.
- Relay and circuit breaker combinations.
- Elementary tripping circuit.
- IEEE Standard device numbers.
- Control circuit schematics.
- Monitoring relay performance.
- Factors affecting relay application.
- The need for coordination.
2102: Types of Protective Relays
The objectives of this module is to demonstrate the operation of the most common types of protective relay. This in turn will prepare the participant for succeeding modules which deal with protective schemes often using a combination of these relays. After study of this module, the participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Components of the differential relay.
- Where differential protection is applied.
- The differential principle - bus protection.
- Transformer differential protection.
- Restraint and harmonic restraint.
- Components of the overcurrent relay.
- Instantaneous overcurrent protection.
- Time-overcurrent protection.
- Adjustment of pick-up and time dial.
- Construction of directional relays.
- The need for directional elements.
- Operation of directional relays.
- The induction cylinder relay.
- Operation of distance relays - balanced beam and MHO type.
- Circle diagrams.
- Effect of load impedance.
- Three-zone elements; back-up protection.
2103: Monitoring System Conditions
The objective of this tape is to present concepts which are vital tools in the interpretation of system operating conditions. After study of this tape and the associated workbook, the participant should be able to understand the following overall concepts and apply them to his day-to-day work activities. He will also be able to answer test questions on the following subjects:
- Function of current and voltage transformers
- Effect of burden and saturation
- CT performance ratings
- VT connections
- The coupling capacitor VT
- Polarity, polarity test
- Three phase circuit diagrams
- Directional sensing for ground faults
- Phasor diagrams, construction and interpretation
- Phase rotation - sequence
- Per unit calculations
- Base voltage and base MVA
- OHMIC impedance and per unit impedance
- MVA fault capacity
2104: Fault Characteristics
The objective of this tape is to discuss the characteristics of different types of faults, and their effects on the power system. Knowledge of this material is vital to understanding the protective schemes that are presented in future videotapes. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Effect of load impedance on current flow.
- Effect of short circuit impedance on fault current.
- Voltage drop through the system under fault conditions.
- Impedance phase angle.
- Safety grounding: the ground mat.
- Neutral grounding: generator or transformer.
- Delta system grounding transformer.
- Aerial ground wires on transmission lines.
- Limitation of ground fault current through impedance grounding.
- Ungrounded systems - Hazards & ground fault detection.
- Phasor diagrams for different types of faults.
- Resonance.
- Ferroresonance.
- Distortion of balanced conditions under the various types of faults.
- Transposition of balanced conditions at generator to unbalanced conditions at the fault.
- Production of positive, negative, and zero sequence components.
- Effect of negative and zero sequence components.
- Zero and negative sequence relays.
- Rules for study of symmetrical components.
2105: Generator Protection
The objective of this tape is to review the types of fault that can occur on generators and discuss the various protection schemes that are used on both small and large generators. After studying this tape and the associated workbook, the participant should be able to understand the following overall concepts and apply them to his day-to-day work activities. He will also be able to answer related test questions on these subjects:
- Types of prime movers.
- Generator terminal connections.
- Generator bus connections.
- Unit and station service transformers.
- Generator mechanical problems.
- General electrical faults.
- Generator and prime mover tripping arrangements.
- Phase fault primary protection.
- Ground fault primary protection.
- Backup protection.
- Negative phase sequence protection.
- Generator capability curve.
- Loss of field protection.
- Effect of system disturbances.
- Generator off-line protection.
2106: Transformer Protection
The objective of this videotape is to review the types of faults that can occur in transformers and to present the different protection schemes that are installed on large and small transformers. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects.
- Transformer features.
- Types of faults.
- Overcurrent protection.
- Backup coordination.
- Primary fuses.
- Differential protection.
- In-rush current: harmonic filter.
- Phasing of differential CTs.
- Selecting CT taps.
- Calculation of mismatch.
- Differential protection for multi-winding transformers.
- Connection of multiple restraint coils.
- Limitations due to parallel CTs.
- Single-phase transformer CT connections.
- Ground (zero-sequence) protection.
- Directional ground protection.
- Remote transfer tripping.
- Thermal relays.
- Gas pressure relays.
- Transformer overall protection schemes.
- Protection of transformers in parallel.
- Reactor protection.
- Shunt capacitor protection.
2107: Bus Protection
The objective of this module is to review the different bus layouts that are used in power systems and to present the different protection schemes that are installed to protect against bus faults. After study of this tape and the associated workbook the participant should be able to understand the following overall concepts and apply them to his day-to-day work activities. He will also be able to answer related test questions on these subjects:
- Features of different bus arrangements.
- Single breaker - single bus.
- Single buses connected with bus tie breaker.
- Main and transfer buses with single breaker.
- Single breaker - double bus.
- Double breaker - double bus.
- Ring bus.
- Breaker-and-a-half bus.
- Special problems of bus protection.
- The ground fault bus.
- Partial differential protection with overcurrent relays.
- Directional comparison schemes.
- Residual current differential schemes.
- CT saturation problems.
- Multi-restraint relays.
- Linear coupler.
- High impedance relays.
2108: Motor Protection
The purpose of this videotape is to familiarize the participant with the features of motor operation and the most common types of protective devices that are installed. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Motor application: voltage levels.
- Induction motor characteristics.
- Torque curves: speed, slip, stall.
- Potential motor hazards.
- Starting arrangements.
- Current - time curves.
- Thermal limits for overload and start-up.
- Thermal and time overcurrent protection.
- Locked rotor protection.
- Phase fault protection.
- Ground fault protection.
- Differential protection.
- Protection against unbalanced conditions.
- Undervoltage protection.
- Synchronous motor protection.
2109: Line Protection
The objective of this videotape is to present the broad categories of line configuration and discuss the various types of protection schemes that are employed. Particular attention is paid to coordination for selective tripping and isolation of faulty circuits. After study of this tape and the associated workbook, the participant should be able to understand and apply the following overall concepts:
- Classification of lines and feeders.
- Typical system configuration.
- Faults on radial and loop systems.
- Reclosing arrangements.
- Breaker failure protection.
- Application of overcurrent relays.
- Setting of relay pickup and time dial.
- Coordination with downstream fuses and reclosers.
- Coordination procedure for loop systems.
- Maximum and minimum fault levels.
- Application of instantaneous overcurrent relays.
- Voltage control (restraint) overcurrent relays.
- Ground fault protection with directional overcurrent relays.
- Polarizing sources; current, voltage.
- Polarizing by negative sequence voltage.
- Effects of mutual induction.
- Limitations of overcurrent relays.
- Characteristics of distance relays.
- RX diagram.
- Protection zones; primary and backup.
- Multiple lines and power sources.
- Tapped lines; multi-terminal lines.
- Ground fault protection by distance relays.
- Backup protection.
2110: Pilot Protection
The purpose of this videotape is to familiarize the participant with the application of pilot protection, the various schemes installed, and the different types of communication channels employed. After study of this tape and the associated workbook, the participant should be able to understand and apply the following overall concepts:
- Pilot wire differential protection - 60 Hz signal.
- Twisted pair - solid conductors.
- Distance limitations.
- D.C. polar units.
- Effect of pilot wire open circuit or short circuit.
- Monitoring the pilot wire.
- Drainage reactor
- Effect of ground potential rise.
- Neutralizing transformer.
- Communication channels.
- Power line carrier; on/off mode.
- PLC, frequency shift keying (FSK).
- Audio tones.
- Microwave.
- Fiber optics.
- Direct transfer tripping.
- Directional comparison under reach.
- Directional comparison overreach.
- Phase comparison.
- Tripping, blocking, permissive commands.
2111: Protection For System Stability
The purpose of this videotape is to present protection schemes that are used to assist in maintaining system stability. The concept of steady-state operation and dynamic response is demonstrated with particular reference to the power angle curve. The physical consequences of instability are also discussed. After study of this tape and associated workbook, the participant should be able to understand and apply the following overall concepts:
- Power transmission.
- Steady-state Operation.
- Function of turbine governor and voltage regulator.
- Power Transfer Equation.
- Effect of change in V, XL and power angle.
- Critical power angle 900.
- Dynamic Response - Rotor Inertia.
- Power Angle Curve - Equal Area Concept.
- Loss of transmission line.
- Effect of initial loading.
- Phase-to-phase faults.
- Automatic reclosing of transmission lines.
- Automatic reclosing of distribution lines.
- Limitations of automatic reclosing.
- Synchrocheck relays.
- Single pole tripping and reclosing.
- Instability Out-of-step Operation.
- Load swings.
- Voltage profile - effect on distance relays.
- Out-of-step relays, blocking and tripping.
- Load shedding.
- Frequency relays.
2112: Testing and Commissioning of Protective Schemes
The objective of this videotape is to present and discuss the many factors involved in commissioning new power installations, placing particular emphasis on the testing of protective schemes. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their work activities. They will also be able to answer test questions on these subjects:
- Objectives of commissioning tests.
- Coordination of commissioning activities.
- Safety requirements.
- The need for documentation.
- Reviewing of block diagrams.
- Inspection of primary installation.
- Reviewing of protection schematics and wiring diagrams.
- Checking secondary wiring, insulation resistance and continuity.
- Checking control wiring, energizing the D.C. system.
- Checking circuit breaker operation.
- Testing VTs for insulation, ratio, polarity.
- Testing CTs for insulation, ratio, polarity, and excitation.
- Testing and calibration of relays.
- Secondary injection tests.
- Functional testing of protection schemes.
- Primary injection tests.
- Testing differential relays for stability.
- Requirements prior to energization.
- Tests for phasing.
- In-service tests with load applied.
- Company test procedures and records.
2113: Power Line Carrier
The objective of this videotape is to present a more detailed examination of power line carrier (PLC) systems. Earlier tapes looked at the protection schemes that employ PLC as the communication medium. This tape focuses upon the PLC equipment itself. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to his day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Principle of line traps.
- Inductors, series resonance with bus.
- LC line traps, parallel resonance.
- High Q and low Q traps.
- Two frequency traps.
- Wide band traps.
- Tuning line traps.
- Coupling-capacitor grounding equipment.
- Carrier signal injection.
- Line tuning equipment.
- Impedance matching.
- Reflectivity.
- Standing wave test.
- Coaxial cable.
- Signal loss attenuation.
- Expression for loss in dB.
- Table: dB loss versus power ratio and voltage ratio.
- Examples of dB loss.
- dBm - examples.
- Loss between adjacent transmitter and receiver.
- Hybrid units.
- Transmitter basic components.
- Transmitter tests and adjustments.
- Receiver basic components.
- Receiver tests and adjustments.
- Line and coupling equipment tests.
- Special test equipment.
- Overall trip tests.
- Audio signals, frequency band.
- Modulation and demodulation.
- Upper and lower sidebands.
- SSB carrier equipment and features.
2114: Fault Investigation and Analysis
The objective of this videotape is to demonstrate the various methods that are used to investigate equipment performance during fault conditions. While various types of fault recorders are considered, particular emphasis is placed upon the interpretation of oscillograms. After study of this tape and the associated workbook participants should be able to understand the following overall concepts and be able to apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Objectives of fault investigation and analysis.
- Disturbances, faults, power swings.
- Gathering of fault data (after the fact).
- Operational reports, relay targets.
- Sequence of event recorders (SER).
- Features of oscillograph machines:
- 1.quick start;
- 2.pre-fault;
- 3.continuous;
- 4.digital transient recorders.
- Starting sensors:
- Location of oscillographs on the power system.
- Selection of data to be monitored.
- Information available from oscillograms.
- The need to monitor carrier signals.
- Coordination of data from all sources for analysis, i.e. relay targets, operational
- Reports, system one-line diagrams, oscillograms, and SERs.
- Interpretation of data.
- 1.neutral overcurrent;
- 2.zero sequence voltage;
- 3.negative sequence voltage.
2115: Introduction to Static Relaying
The objective of this module is to introduce and present the major features of static relaying, including analog-type solid-state relays and digital microprocessor relays. At this stage in the program, it is assumed that all participants are thoroughly familiar with the functions and characteristics of the different types of relays. This module focuses upon the differences between solid state and electromechanical relays. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them in their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- Advantages and disadvantages of static relays.
- Static relay components: diode, transistor.
- Transistor circuits.
- Integrated circuits, thyristor, operating amplifier.
- FETs and MOSFETs.
- Basic relay circuits.
- Signal level detector, timer.
- Polarity detector, square wave generator.
- Phase comparison circuits.
- Amplitude comparison.
- Logic circuits.
- Switching circuits.
- Relay power supplies, voltage regulation.
- Examples of analog solid-state relays.
- Overcurrent relays, directional relays.
- Differential relays, distance relays.
- Digital microprocessor relaying.
- Signal sampling, analog-digital conversion.
- Reference algorithms.
- Printed circuit board modules.
- Main processor and logic processor.
- Monitoring, remote and local.
- Relay programming, remote and local.
- Substation control systems.
2116: Coordination of Protection Devices
The objective of this tape is to present a more detailed study of the subject of "coordination" of protective devices, particularly in the area of distribution systems. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- The coordination problem.
- Sensitivity and selectivity.
- Inverse time characteristic of protection devices.
- Expulsion fuses.
- Current limiting fuses - High Rupturing Capacity (HRC).
- Fuse curves.
- Minimum melt and damage curves.
- Fuse coordination procedure.
- Coordination of fuse with overcurrent relays.
- Coordination of capacitor bank fuses.
- Recloser application.
- Recloser characteristics.
- Fast and slow recloser curves.
- Function of sectionalizers.
- Voltage restraint sectionalizers.
- Coordination of reclosers, sectionalizers, and fuses.
- Conductor damage curve.
- Industrial consumer protection devices.
- Low voltage circuit breakers.
2117: Power Supply For Protection and Control Systems
The objective of this videotape is to stress the importance of uninterruptible power supplies for protection and control circuits, and to look at different means of achieving this. The provision of both continuous AC and continuous DC power supply is discussed and attention is paid to individual power supplies for electronic equipment. Some time is devoted to studying operation and maintenance of the common storage battery. This area often seems to be neglected, even though it is after all, the heart of uninterruptible power supplies. After study of this tape and the associated workbook participants should be able to understand the following overall concepts, and apply them in their day-to-day work activities. They will also be able to answer related test questions on these subjects: The need for "reliable" continuous power supplies to operate protection and control relays and circuits.
- The need for "reliable" continuous power supplies to operate protection and control relays and circuits.
- Different voltage level requirements.
- The lead-acid cell; lead antimony; lead calcium.
- Connection of cells in series to form a storage battery.
- Ampere-hour rating.
- Battery charge rate, overcharging.
- Hydrogen release.
- Significance of specific gravity and output voltage per cell.
- Equalization procedure.
- Sulfation.
- Safety precautions against acid.
- The nickel-cadmium cell.
- Supply to the D.C. bus.
- The SCR battery charger.
- Control of SCR firing.
- D.C. output filter circuit.
- Charger adjustments: float voltage, equalization voltage, programmed equalization, output slope, and current limiter.
- The controlled ferroresonant battery charger.
- The need for uninterruptible A.C. power supply.
- The D.C. to A.C. inverter.
- Pulse generation and pulse width modulation.
- The off-line UPS system.
- The on-line UPS system.
2118: Energy Center Operations
The objective of this module is to review, for the benefit of relay personnel, the responsibilities of the power system operators and the activities that take place in the energy control center. The operation of protection schemes is of vital importance to the correct functioning of the power system. Complete cooperation between power system operators and relay personnel is essential, and communication must be maintained in both directions. After study of this tape and the associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:
- The overall objectives of the power system operator.
- Clearance procedures, i.e. isolation of equipment.
- Frequency control: economic load dispatch.
- Daily load forecast.
- Daily generation schedule, including spinning reserve.
- System overload, falling frequency, load shedding.
- Inter-ties to neighboring utilities, power interchange.
- Generation unit characteristics, i.e. type of prime mover.
- Incremental cost of generation.
- Rate of start-up and load change availability.
- Frequency control by AGC (automatic generation control).
- Turbine governor droop characteristic.
- Generator load angle.
- Control of excitation, reactive power.
- Transmission line impedance characteristics.
- Effect of conductor resistance, i.e. heating.
- Shunt capacitance, charging current, Ferranti effect.
- Special switching procedure on long lines.
- Inductive voltage drop along transmission line.
- Shunt capacitors and shunt reactors.
- Power angle across transmission line.
- Effect of transmission line voltage on power transfer.
- Power transfer distribution through a complex network.
- Power angle limit for stability.
- System operator actions to improve system stability.
- Effect of equipment outages on system operation.
- Planned outages, system operation precautions
- Forced outages, state of "alert" and "emergency"
- System separation, i.e. islanding
- Energy center communications
- Energy center information presentation
2119: Telecommunications Protection I (HVSP Devices)
The objective of this module is to draw attention to the high voltage hazards that can occur on telecommunication circuits entering substations and power stations, and to review the protection devices that are used to combat this problem. After study of the videotape and the associated workbook the participants should be able to understand the following overall concepts and apply them in their day-to-day activities. They will also be able to answer test related questions on these subjects:
- The usage of wire lines.
- Routing of telephone cables by Telco.
- Effect on telephone lines of power system faults.
- Longitudinal common mode induction.
- GPR - Ground Potential Rise.
- Remote ground and local ground.
- High voltage hazards to personnel and equipment.
- Location of demarcation interface.
- Standard telephone line protection.
- Air gap arresters.
- Carbon block protectors.
- Gas tube protectors.
- Solid-state protectors.
- Limitations of protectors.
- Disadvantage of voltage clamping (i.e. circuit shut down).
- Mutual drainage reactor.
- High voltage interface.
- Dedicated entrance cable; features.
- Grounding of dedicated cable.
- High voltage special protection.
- Neutralizing transformer.
- Neutralizing reactor.
- Isolation transformers.
- High voltage relay for D.C. signals.
- Safety precautions for personnel.
- Optical isolators: teleline isolator.
- Tucon Fiber Optic Link.
- Fiber optic cable and multiplexer.
2120-Telecommunications Protection II (Configuration & Installation)
The purpose of this videotape is to continue on from SPT 19 the discussion of telecommunications protection. While SPT 19 presented protection devices, this module focuses on specific installation practice and typical configurations. After study of the videotape and associated workbook, participants should be able to understand the following overall concepts and apply them to their day-to-day activities. They will also be able to answer related questions on these subjects.
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Definition of types of communication service.
- Definition of SPO classification; A, B, C.
- Level of voltage rise at station.
- Protection requirements for different SPO classification and voltage level rise.
- HVSP configurations for different circuits.
- Location of protection (TELCO, RDL, HVI, NI).
- Selection and limitation of protectors.
- Grounding arrangements at RDL, TELCO and HVI.
- Grounding of dedicated cable sheath.
- Isolating of dedicated cable sheath.
- Surge arrester connections.
- Centre tapped isolating transformer as MDR.
- Location and mounting of HVI cabinet.
- Grounding of HVI.
- Installation of neutralizing transformer (typical).
- Need for rubber gloves.
- Primary winding connections to station and RDL grounds.
- Use of spare conductors in dedicated cable.
- Protection of unassigned pairs in dedicated cable.
- Connection of secondary windings.
- Insulation of isolating transformer (typical).
- HVI layout, terminal strips, ground bus.
- Remote side wiring.
- Station side wiring.
- Cable connections.
- Connection of protectors and MDRs.
- Circuit identification and documentation.
- Modular HVI.
- Installation pitfalls.
- Maintenance and inspection items.
- Safety considerations.
2121: Supervisory Control System - SCADA
The objective of this videotape is to discuss the application of SCADA systems (EMS, and DISTRIBUTION AUTOMATION), and to present the main features of modern installations including equipment layout, communications, operations and maintenance. After completion of this videotape and associated workbook, the participant will be able to understand the following concepts, and apply them to his day to day work activities. He will also be able to answer related test questions:
- Typical applications of SCADA.
- Basic features of SCADA, i.e. remote data collection, transmission, processing,
- Display, remote control.
- Polling by RTU address.
- RTU reporting by exception.
- Control commands; select - check - operate sequence.
- RTU data collection.
- Analog points, transducers, analog digital conversion.
- RTU inputs; analog, status points, pulse accumulation.
- RTU outputs; control of switching, load shedding, generator load, etc..
- Review of binary numbering system.
- Modems, signal transmission.
- FSK, PSK, A.M.
- Rate of signal transmission, baud.
- Components of 32 bit signal.
- Communication line arrangements, i.e. party-line, or separate radial connections.
- Master station assembly and peripherals; memory, clock.
- Front-end communications controller: functions.
- Display computer, display stations, operator input.
- Standby (redundant) station, failover.
- Applications software, executive software.
- CPU priority tasking.
- On-line diagnostics.
- Operator interface, workstations.
- Operator input, display response.
- Power system equipment status, tagging.
- Alarm system.
- Logging, reports, trends, sequence-of-events.
- SCADA installations, power supply.
- Preventive maintenance activities
- Functional tests, test sets, test points vSoftware update, modification
- Maintenance records
2122: Inadvertent Trips – Cause & Prevention
The objective of this module is to draw attention to the problem of inadvertent trips and misoperation of protection equipment. Typical case studies are presented, with the conclusions leading to recommended procedures to help reduce inadvertent trips. After completion of this videotape and the associated workbook, participants will be able to understand the following concepts and apply them in their day-to-day work activities. They will also be able to answer test questions on these subjects:
- Definitions of "Inadvertent Trips" and "Misoperation".
- The main causes of inadvertent trips and misoperation.
- Effects of installation errors such as: mistakes in wiring, inaccurate drawings, faulty equipment from the manufacturer, incorrect relay setting.
- The necessity for testing new installations.
- Typical procedures for commissioning tests.
- The effect of protection equipment failure and subsequent misoperation.
- The need for routine tests at set periodic intervals.
- Precautions required when conducting routine tests.
- The need for thorough preparation before commencing routine tests.
- Co-operation with the operator, equipment isolation and clearance.
- Precautions against interference with live circuits.
- Typical procedures for routine testing.
- The objective of in-service testing.
- The potential for human error and resultant inadvertent trips.
- Requirements for active protection during in-service testing.
- System limitations on in-service testing.
- Preparation, and typical procedures for in-service testing.
- Responding to trouble calls.
- Investigation of protection equipment misoperation.
- Incident reports.
2123: Fault Calculations & Relay Settings
The objective of this module is to present the concepts on which fault calculations are made. Both balanced and non-balanced faults are discussed, including phase-to-phase and phase-to-ground faults. The use of "percent impedance" is shown and the use of symmetrical components is discussed. After completion of this videotape and associated workbook, participants will understand the following concepts and be able to apply them to their day-to-day activities. They will also be able to answer related questions on these subjects.
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Fault characteristics (introduced in module SPT 4).
- Phasor diagrams (introduced in module SPT 3).
- Classification of faults.
- Characteristics of the 3-phase balanced fault.
- Impedance between source and fault.
- Calculation of fault current (single phase).
- Per unit (percent) impedance, base MVA.
- Conversion of per unit values to a different base MVA.
- Calculation of fault MVA at different locations.
- Calculation of fault current.
- Conversion between OHMIC and PERCENT impedance.
- Vectorial addition of impedances; the "j" operator.
- Equivalent (substitute) circuits to aid analysis.
- Symmetrical components; positive, negative and zero sequence quantities.
- System phase rotation.
- Characteristics of positive, negative and zero sequence components.
- Phase-to-phase faults; study of sequence components.
- Addition of sequence components to find fault current.
- Single line-to-ground faults, study of sequence components.
- Magnitude of sequence components.
- Vectorial addition of sequence components; operator "a".
- Positive, negative and zero sequence impedances.
- Examples of fault calculations using sequence impedances.
- Relay settings, significance of relay location.
- CT ratio, VT ratio.
- Measuring zero sequence current.
2124: Testing Techniques
The objective of this module is to draw attention to the many factors that affect the accuracy of testing on protection circuits and equipment. Fundamental testing techniques are presented along with a discussion of the pitfalls to be avoided. A demonstration on the use of the oscilloscope is included. The need for specific safety precautions is also discussed. On completion of this video and associated workbook, the participant should be able to understand the following concepts and apply them to day-to-day work activities:
- Types of electrical measurement.
- Influence of instrument accuracy.
- Effect of waveform (i.e. harmonics) on accuracy.
- Effect of source impedance.
- Effect of magnetic fields on digital instruments.
- Current measurement, current probes.
- Resistance measurement, ohmmeters.
- Measuring D.C. resistance of inductive circuit.
- Frequency measurement, counters, spectrum analyzer.
- Selective voltmeter to measure signal strength.
- Frequency bandwidth, definition.
- vMeasuring dB signal strength.
- dB logarithmic scale versus volt linear scale.
- The dB meter, "Terminated" or "Bridged" selection.
- Operation of timers.
- Phase angle measurement.
- The oscilloscope, operating principles.
- Set-up and adjusting the scope.
- Practical applications using the scope.
- Precautions when using scope on ungrounded circuits.
- Storage oscilloscopes.
- Types of test set, traditional (analog) and advanced (digital).
- "Load box" (resistance), "Phantom load" (inductance).
- Three phase test set.
- Out of phase sources, phase shifting transformer.
- Solid state test set.
- Features and operation of modern digital test set.
- Need for safety when performing tests.
- Clearance procedures.
- Switchyard safety, isolation and grounding.
- Potential hazards
2125: Programmable Logic Controllers
This Video presents the main features and advantages of PLCs, including hardware arrangements, software, (i.e. programming), and typical applications. Extension of the PLC is discussed, noting features of a typical distributed control system. On completion of this Videotape and associated Workbook, the participant should be able to understand and apply the following concepts:
- Process logic, logic diagrams.
- Hard-wired relay panels; control devices.
- Advantages of PLCs.
- Compact PLCs, rack mounted PLCs.
- PLC elements.
- Types of memory, RAM, ROM, EPROM.
- Terminal connections, input-output image memory.
- Input-output point address.
- CPU operation, scanning time.
- Nature of input and output signals, digital, analog.
- Function of input and output interfaces.
- Conditioning input and output signals.
- Voltage sources for input and output signals.
- OPTO-Isolators.
- A/D and D/A conversion.
- Output relays.
- Transistor switching.
- Protection against signal noise.
- The external programming module.
- Coding instructions.
- Entering ladder logic.
- Programming functions, timer, counter, latches.
- Programming examples.
- Troubleshooting with the programming module.
- Extended PLC networks.
- Interconnecting communication bus.
- Distance limitations.
- Input-output racks, local and remote.
- Remote input-output blocks.
- Distributed control system, SCADA.
- Monitoring and programming the system.
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