Power System Protection ILAs


ILA #1

1.     State purpose of protective relaying & list & define important relaying terms

      State fundamental purpose of protective relaying & state & describe definition of relay & of protective relay

      Using NERCs Glossary of Terms as reference state NERCs defination of protective relay system

      Describe purpose & application of protective relays


2.     Describe types of relays

      Describe function of various types of relays including protective, regulating, monitoring, auxiliary & synchronizing


3.     Describe quantities & events monitored by protective relays

      List quantities monitored by relays & list abnormal events relays protect against


4.     Describe types of protective relays

      Describe & illustrate types of protective relays including electromechanical, solid-state & microprocessor

      Describe purpose & illustrate usage of relay targets

      Describe purpose of circuit breakers


5.     List & describe IEEE device numbers

      List & describe IEEE device numbering system

      Illustrate usage of IEEE numbers with 1-line diagrams & DC logic diagrams


6.     State goals of protective relaying

      List & describe goals of protective relaying - include description of reliability, selectivity, speed, simplicity & economics as terms apply to protective relaying


7.     Describe concept of zone of protection

      Illustrate & describe concept of zone of protection

      Use 1-line diagram of power system to describe how zone of protection concept applies to simulated power system


ILA #2

1.     Describe purpose & demonstrate usage of per-unit system

      Describe purpose of per-unit system

      Demonstrate usage of per-unit quantities & formulas

      Convert between per-unit & ohmic values

      Calculate transformer's actual ohms starting with nameplate % data


2.     Describe purpose & illustrate usage of vectors & phasors

      Describe purpose of vectors & phasors

      Illustrate phasors using 3-phase transformer connections

      Describe purpose & illustrate components of synchrophasor initiative


3.     Describe purpose & illustrate usage of transformer polarity

      Describe concept of transformer additive & subtractive polarity

      Demonstrate usage of polarity markings


4.     Describe purpose & illustrate usage of symmetrical components

      Describe concept of symmetrical components

      Describe positive, negative & zero sequence components

      Describe sequence component mathamatical relationships

      Create sequence component diagrams & calculate fault current using sequence component concepts


5.     Describe purpose & illustrate usage of polarizing quantity

      Illustrate how transformer neutrals can be zero sequence current sources & describe importance of  polarizing quantity for determining fault current direction


ILA #3

1.     Describe purpose & illustrate usage of instrument transformers

      Describe purpose & illustrate operation of instrument transformers including CTs, VTs, CCVTs, RPDs & CPDs

      State why PRC-005-6 requires periodic testing of instrument transformers

      Using circuit diagram of instrument transformer -  describe how instrument transformner operates

      Describe concept of saturation with respect to current transformer

      Describe concept of DC offset

      Describe & illustrate CT accuracy rating system

      Describe & illustrate harmonic content in transformer excitation current

      Describe how CT ratios are chosen using an overcurrent relay application


2.     Describe purpose & illustrate concept of differential relay

      Describe & illustrate differential relay concept

      Describe operation of % differential restraint function

      Use animation of differential relay operation to describe how relay responds to internal & external faults


3.     Describe purpose & illustrate concept of over-current & distance relays

      Describe & illustrate basic application of over-current & distance relays for equipment protection

      Describe  purpose & usage of R-X diagram

      Describe how relay coordination can be achieved via either time solution or communication solution

      Using PRC-027-1 as reference state NERCs goals for protective relay coordination


4.     Describe purpose & illustrate concept of backup protection

      Describe & illustrate protective relay backup concept

      Describe & illustrate difference between primary backup, local backup & remote backup

      Describe how PRC-23-4 restricts usage of certain types of backup protection


5.     Describe purpose & illustrate operation of electromechanical relay designs

      Describe & illustrate how electro-mechanical devices used to perform protective relay functions

      Illustrate & describe induction disk, clapper, plunger, balanced beam & directional sensing electro-mechanical designs


6.     List & describe advantages & disadvantages of microprocessor relays

      List & describe advantages of microprocessor relays

      List & describe disadvantages of microprocessor relays

      Using relay manufacturer manuals describe features in commonly applied microprocessor numerical relays


7.     Describe purpose & illustrate concept of power system grounding

      Describe purpose of power system grounding

      Describe differences between ungrounded, high impedance grounding, low impedance grounding & solid grounding

      Describe & illustrate neutral shift that occurs when ground fault occurs in otherwise ungrounded system

      Illustrate construction & describe operation of intentionally ungrounded system

      Describe & illustrate usage of Peterson coils

      Illustrate construction & describe purpose of zig-zag transformer

      Describe & illustrate concept of safety grounding


ILA #4

1.     Describe differences in protecting radial versus looped transmission lines

      Describe how phase angles that occur during faults tend to match line impedance angles

      Describe, & illustrate with calculations, difference between normal current flow & current flow during fault

      Describe differences in protection used in radial systems versus looped systems

      Illustrate & describe usage of non-directional inverse time overcurrent relays to protect radial distribution line

      Describe & illustrate coordination issues involved in looped line protection


2.     Describe & illustrate how distance relays applied for transmission line protection

      Describe & illustrate multi-zone distance protection system

      Describe how backup protection provided in stepped distance scheme

      Describe in-feed effect

      Describe how in-feed effect can compromise coordination required by PRC-027-1

      Describe & illustrate advantages of reverse zone 3

      Describe how tapping transmission line disrupts distance protection

      Describe complications with using distance relays to protect series compensated transmission lines

      Describe how Z3 applications limited by PRC-023-4

      Describe impact of loss of distance relay's voltage source

      Describe purpose & operation of switch-on-to-fault protection scheme


3.     Describe & illustrate transmission line backup protection

      State difference between backup function provided by redundant relays, local backup & remote backup

      Describe & illustrate usage of breaker failure DC logic diagram


4.     Describe & illustrate operation of most common types of pilot protection schemes

      Describe advantages & disadvantages of  various telecommunication methods used in pilot protection

      Describe & illustrate operation of following pilot protection schemes:

-       Direct Under-Reaching Transfer Trip (DUTT)

-       Permissive Over-Reaching Transfer Trip (POTT)

-       Permissive Under-Reaching Transfer Trip (PUTT)

-       Directional Comparison Blocking (DCB)

-       Directional Comparison Un-Blocking (DCU)

-       Line Current Differential (LCD)

-       Phase Comparison (including Pilot Wire)

-       Line Current Differential


ILA #5

1.     Describe different types of generators including different methods of connecting  generation to system

      Describe construction of generators & categorize generators into small MVA & large MVA sizes

      Describe how generators connected to power system

      State & describe hazards generators are typically protected against


2.     Illustrate & describe protection typically applied to generators

      Using photographs & manufacturers literature describe features of electromechanical & microprocessor based generator relays

      Describe how generators protected from occurrence of following hazards:

-       Phase/ground faults in stator

-       Ground faults in rotor

-       Loss of field excitation

-       Motoring

-       Over & under excitation

-       Synchronizing issues

-       Unbalanced currents

-       Abnormal frequency operation

-       Breaker pole flashover

-       Delayed clearing of system faults

-       Over-voltage

-       OOS operation

-       Field grounds

      Describe content of 1-line diagrams of actual protection of large steam & hydro generators

      Describe & illustrate how protective relays could limit MVar range of generators as stated in VAR-002-4

      Describe & illustrate how PRC-024-2 restricts voltage & frequency based generator protection settings to within allowable limits.

      Describe & illustrate how PRC-025-1 requires that generator protection not limit  loadability of generatorsit

      Describe & illustrate how PRC-026-1 could limit application of generator OOS protection


ILA #6

1.     Illustrate & describe issues associated with power transformer protection

      Illustrate how transformers connected in power system

      Describe & illustrate how following issues impact power transformer protection:

-       In-rush current

-       Excitation current

-       CT saturation

      Describe how intentional fault switches used in transformer protection


2.     Describe & illustrate how protective relays used to provide protection for power transformers

      Describe how transformers protected from occurrence of following hazards:

-       Over-excitation

-       Internal ground & phase faults

-       Dissolved gas in oil

-       Thermal damage

-       Primary protection failure

      Describe & llustrate application of differential relay using 3-line diagram

      Describe & illustrate typical transformer protection using 1-line diagrams

      Describe how PRC-023-4 limits  application of overload protection in transformers


3.     Describe how protective relays used to provide protection for phase shifting transformers (PSTs)

      Describe construction & operation of PST

      Describe & illustrate protection of PST


4.     Describe how protective relays used to protect shunt capacitors & shunt reactors

      Describe & illustrate protection used for shunt capacitor bank & including description of voltage imbalance protection

      Describe & illustrate protection used for shunt reactor bank


ILA #7

1.     Describe & illustrate out-of-step protection

      Utilize power angle curves to describe concept of angle stability

      Illustrate out-of-step swing using R-X diagram

      Describe how impedance relays used to detect out-of-step swings.

      Describe how synchophasor initiative could be used to enhance angle stability protection

      Describe how stable power swings appear to a generator & describe how PRC-026-1 affects generator OOS protection


2.     Describe advantages & disadvantages of automatic reclosing

      Describe purpose & state issues associated with automatic reclosing in high voltage transmission system

      Use power angle curves to demonstrate advantages & disadvantages of automatic reclosing


3.     Describe how under-voltage load shedding systems used to avoid voltage collapse

      Describe purpose & describe issues associated with use of under-voltage load shedding relays to avoid voltage collapse

      Describe how UVLS schemes designed as stated in PRC-010-2


4.     Describe how under-frequency load shedding systems used to avoid frequency collapse

      Describe purpose & state issues associated with underfrequency load shedding relays that are used to avoid frequency collapse

      Describe how UFLS schemes designed as stated in PRC-006-2 & state how generator frequency trip settings must be compatable with PRC-024-2


5.     Describe purpose & application of remedial action schemes (RAS)

      Describe & illustrate purpose of RAS

      Illustrate concept of RAS using WECC-1 RAS as example.

      List & describe NERC's concerns with RAS as stated in PRC-015-1, PRC-016-1 & PRC-017-1


ILA #8

1.     Describe & illustrate application, design & operations of low & high impedance bus differentials

      Describe how CT saturation impacts bus differential protection

      Describe features offered by differential relay manufacturers to avoid false differential operation from CT saturation

      Describe concept of end-zone fault detection

      Describe how differential operation impacted by open or shorted CTs

      Describe & illustrate operation & application of low impedance bus differential

      Describe & illustrate operation & application of high impedance bus differential


2.     Describe purpose & illustrate design of commonly applied substation bus configurations

      Describe & illustrate application & operation of following substation bus configurations:

-       Single Bus / Single CB

-       Single Bus / Single CB with Bus Sectionalizing CB

-       Main & Transfer

-       Ring

-       Breaker-&-a-Half

-       Double Bus / Double CB

      Describe & illustrate how differential relays applied to each of substation bus configurations listed above


3.     Describe & illustrate content of NERCs PRC series of Reliability Standards

      Describe content of NERCs PRC series of Reliability Standards including: