Fault Locating Systems

Question 1

Types of disturbances

Answer 1

▪︎transient
▪︎short term
▪︎long term
▪︎steady state

Question 2

Define: transient disturbance

Answer 2

Very short, typically fault clears immediately (recloses)

Question 3

Define: short term disturbance

Answer 3

Time delayed clearing and reclosing event, system stability not affected

Question 4

Define: long term disturbance

Answer 4

System stability is affected
▪︎power swings
▪︎frequency variations
▪︎abnormal voltage problemss

Question 5

Define: steady state disturbance

Answer 5

System stability is not affected but power quality is

▪︎ may include harmonics produced by load

Question 6

List types of fault locating equipment

Answer 6

▪︎Digital Fault Recorder (DFR)
▪︎some protective relays
▪︎Fault Location Acquisition Reporter (FLAR)
▪︎National Lightning Detector Network (NLDN)
▪︎Dynamic Disturbance Recorder (DDR)
▪︎Power Quality Monitor (PQM)
▪︎Sequential Events Recorder (SER)

Question 7

Purpose of fault locators

Answer 7

Quick location of faulted transmission lines for fast and cost-effective restoration of the power system as well as service to customers

Question 8

Causes of faults

Answer 8

▪︎lightning
▪︎insulator failure
▪︎equipment failure 
▪︎trees 
▪︎accident accidents with vehicles or machinery 
▪︎vandalism (gunshots)
▪︎forest fires
▪︎foreign materials (animals/mylar balloons) 
▪︎restrikes

Question 9

Types of faults

Answer 9

▪︎Single phase to ground
▪︎Phase to phase
▪︎phase to phase to ground or 3 phase to ground

Question 10

Benefits of fault locating systems

Answer 10

▪︎Minimize outage times
▪︎Saves manpower and money by focusing the search by air and ground patrols
▪︎Enhanced system security and reliability
▪︎Ability to locate intermittent faults

Question 11

What is some secondary info provided by fault locating Systems

Answer 11

▪︎Magnitude of fault current and voltage
▪︎Relay response times
▪︎Total fault clearing time
▪︎Type of fault
▪︎Status of important relays during the fault

Question 12

Applications of data collected by fault locating systems

Answer 12

▪︎This info can be used to verify proper operation of relays and PCBs
▪︎Verify short circuit and load flow calculations
▪︎Verify transmission line constants - line impedance
•Measure voltage and current imbalance
•Check relay input connections for proper phase rotation and polarity

Question 13

FLAR overveiw

Answer 13

▪︎Only one to cover entire BPA system
▪︎Monitors all 500kV and some 230kV
▪︎Wide in area coverage but shallow in depth
• No coverage of most 230kV and all 115kV and below

Question 14

DFR overview

Answer 14

▪︎Intermediate level of detection
▪︎Installed at most major substations
▪︎Essentially recording machines that record power system parameters as viewed from the substation
▪︎Faults are recorded if connected to the substation and recordings analyzed to determine location

Question 15

relays with fault locating capabilities

Answer 15

▪︎Complex relays can locate faults on individual lines

▪︎Very accurate

Question 16

Explain disturbance monitoring

Answer 16

▪︎DFRs are also used to analyze system disturbances and their affect on the sys5
▪︎Modern relays can give a sequence of events for their elements and can be programmed Tom record events in situations where they do not trip
▪︎the DDR is also used

Question 17

Explain the Dynamic Disturbance Recorder (DDR)

Answer 17

Useful for:
▪︎disturbance analysis
▪︎Investigating system oscillations
▪︎Quantifying sudden changes in power system parameters
▪︎Obtaining data for verifying stability models

Question 18

Power Quality Monitor

Answer 18

▪︎Designed to record power quality parameters like voltage, flicker and harmonic content
▪︎Often compute and record industry standard measures for power quality

Question 19

How do DFRs work

Answer 19

▪︎Uses digital technology to record and store electronic signals
▪︎Records instantaneous values of voltage and current
▪︎1-10,000 samples per second for 2 second time periods

Question 20

Why do we use DFRs

Answer 20

▪︎Developed for the purpose of analyzing System Protection Operations and PCB performance.
▪︎Info is also used by SPC to study system disturbances where protective ops were not initiated.

Question 21

BEN5000 DFRs

Answer 21

▪︎Records 64 channels simultaneously
▪︎Records no-fault data
▪︎Can monitor up to 192 analog and 576 digital channels
▪︎Remote acquisition units are connected to the control unit by fiber optics
▪︎Fault data can be sent over telephone lines, microwave, or fiber

Question 22

System overview of DFR

Answer 22

▪︎Small computer monitors system voltage, current, relay status, and other parameters and records it into RAM
•Normally that is as far as it goes
▪︎during an event, it records into RAM and to a disk drive, also transfers pre-fault data to the drive
▪︎Then data on the disk drive can be sent took the FIN &/or printed
▪︎Will alarm when a event is recorded or for equipment problems

Question 23

Function of DFR buffers

Answer 23

▪︎Protect micro electronics of the DFR from direct instrument transformer’s currents
▪︎Switches allow the isolation of unwanted inputs
▪︎Analog/ digital converters convert the analog I’s and V’s to digital signals

Question 24

Function of status delays for the DFR

Answer 24

Allows the DFR to show indications and trigger alarms

Question 25

Function of RAM for the DFR

Answer 25

▪︎Random Access Memory ▪︎Electronic memory ▪︎Only used for temporary storage ▪︎The DFR is constantly writing data to the RAM which results in writing over old data

Question 26

Spec's responsibility for the DRF

Answer 26

They have full responsibility for operation and maintenance

Question 27

What to look at when inspecting the DFR

Answer 27

Disk Almost Full Light ▪︎Should normally be off ▪︎If light is on, system memory is getting full • Contact SPC Armed light ▪︎Normally on ▪︎Confirms that the DFR is ready to record the next event Event Counter ▪︎Log this during each inspection ▪︎Changes after an event is recorded Printer ▪︎Check for adequate paper ▪︎Do not add paper call SCP if needed

Question 28

DFR uses in fault analysis

Answer 28

``` ▪︎Type of fault ▪︎Phases involved ▪︎How fast fault was cleared ▪︎How quickly reclosing occurred ▪︎When other lines opened or closed ▪︎Distance to fault ▪︎Fault magnitude ▪︎Presence of restrikes ▪︎Harmonics ```

Question 29

Explain relays with fault locating capabilities

Answer 29

▪︎Some complex, numerical, or microprocessor relays can calculate the location of faults on their lines • JM annunciator relays are elecro-mechanical relays that allow the operator to calculate distance to fault ▪︎Only look at fault on a single transmission line ▪︎Relays with this ability will be clearly marked ▪︎After a fault occurs the Sub Operator will read and interpret the data from the relay

Question 30

List relays with fault locating

Answer 30

``` SEL-121 SEL-221 SEL-321 SEL-421 RED-670 ```

Question 31

Capabilities of fault locating relays

Answer 31

``` ▪︎Provide info such as: • Fault current sensed by relay • Relay response time • Total fault clearing time • Distance to fault • Type of fault • State of relay units during fault ▪︎Accuracy is ~1%of line length ▪︎Distance to fault is reported in miles of impedance ```

Question 32

Internal memory of relays with fault locating

Answer 32

Stores power system data ▪︎Memory is constantly dumping old data and storing new ▪︎When a fault occurs, pre-fault data is already stored ▪︎After the event, the relay stores ~4 cycles of pre-fault data and ~7 cycles of fault and post-fault data ▪︎Event data is stored until the Sub Operator or SPC removes it ▪︎Relays can typically store 12 ▪︎Access to fault location data can be made remotely

Question 33

How relays with fault locating calculate location

Answer 33

▪︎Determines the current and voltage at the time of the fault and calculates impedance ▪︎Data about the line's impedance characteristics are programmed into the relay by SPC ▪︎The relay compares line characteristics to fault impedance and determines a fault location in miles

Question 34

FLAR capabilities

Answer 34

▪︎Uses precision clock at substations to time trash traveling voltage waves to determine fault location and auto report it to the dispatch center ▪︎Attempts to pinpoint the locations of faults on the bulk electric system • Monitors all 500kV and some 230kV ▪︎Provides dispatches at DCC with the ability to quickly locate faults ▪︎Automatically distinguishes between faults and switching transients

Question 35

Brief description of how FLAR works

Answer 35

Remote units record the exact time a fault transient is detected Central computer at DCC calculate location with info from remote units System operates automatically Pinpoints fault location to the nearest tower

Question 36

How FLAR works in detail

Answer 36

▪︎Faults create high frequency radio waves >70kHz that travel outward from the fault location at a known speed ▪︎By knowing the precise time a transient arrives at a various points on the power grid, it can calculate an approximate location ▪︎There are remotes units away various substations ▪︎Remote units are in constant communication with central computer at DCC ▪︎Remote units detect between 70-350kHz with transient detectors ▪︎Each transient detector is coupled to the power system with a CPT ▪︎The central computer polls the remote units over microwave one at a time every 100 seconds ▪︎Remote unit reports the precise time a fault was detected to central computer ▪︎Computer them calculates likely location and prints the results ▪︎Time signals from GPS goes to a popular generator that corrects the remote unit clocks every 100 seconds via microwave to ensure it is in sync

Question 37

FLAR principle of operation

Answer 37

▪︎Time delay between when the wave arrives at different ends of the line used to calculate the position of the waves point of origin •EX: if the wave hits both ends of the line at the same time it originates in the middle ▪︎By knowing the time a traveling wave arrives at certain points, the fault location can be pinpointed •Disturbances travel on the power system like ripples on a pond •Travel speed is ~186,000 miles/ second

Question 38

FLAR equipment functions: GPS recorder and pulse generator

Answer 38

▪︎DCC computer kept on standard time by GPS ▪︎Pulse generator sends out sync pulses to remote units every 100 seconds • Remote units adjust their clocks to that pulse

Question 39

FLAR equipment functions: remote units

Answer 39

▪︎Continously monitor the power system ▪︎Detect the traveling waves of a disturbance, now the time and store that info ▪︎Time is accurate due to sync pulses

Question 40

FLAR equipment functions: central computer

Answer 40

▪︎In DCC basement ▪︎Polls all remote units, one at a time, every 100 seconds ▪︎Uses remote unit inputs to calculate a fault location ▪︎Checks event records by SCADA to see if it could of been a switching transient ▪︎Automatically prints out likely fault location

Question 41

FLAR responsibilities

Answer 41

▪︎Remote units are maintained and operated by PSC ▪︎Operations has no responsibility of or inspection ▪︎No inspection necessary because there is no control or indication at the panel and the central computer polls every 100 seconds verifying proper operation ▪︎If a problem arises at a remote unit overall system will still function because of large number of units on the system ▪︎At critical locations. Where loss of a remote unit might affect operation, 2 remote units are installed

Question 42

Explain the NLDN (National Lightning Detector Network)

Answer 42

▪︎BPA is a subscriber ▪︎Monitors lightning strikes across entire country ▪︎All strikes in BPAs service area are displayed at DCC and MCC ▪︎Uses a network of 135 detectors • Each senses magnetic and electric disturbances created by lightning ▪︎Triangulates location ▪︎Plots location on the BPA system • The brighter the color the more recent the strike ▪︎Dispatcher cam track direction of storms • They can cancel work if a storm is coming, increasing the reliability of the system in case of forced outages

Question 43

Explain Dynamic Disturbance Recorder (DDR)

Answer 43

▪︎Provide longer term trending data with slower sampling then that of the DFR ▪︎Have a particular application with in power plants to capture cascading or tending events that might evolve, that otherwise would be lost until the fault actually occured

Question 44

Explain Phasor Measurement Unit (PMU)

Answer 44

Saves power system wavelengths in a positive sequence format

Question 45

Explain Portable Power System Monitor (PPSM)

Answer 45

▪︎Can save data from transducers, telemetering, or direct PT/CT secondary values ▪︎Sampling rate varies from 20 to 240 samples/sec with 30 samples/ sec being typical

Question 46

Explain: Field Integrated Network(FIN)

Answer 46

``` ▪︎Maintained by PSC ▪︎Provides a way to remotely access substation and radio equipment for data retrieval and equipment connectivity by; ▪︎PSC ▪︎SPC ▪︎Dispatch ▪︎Uses microwave and fiber to send info from substation to ethernet communication equipment ▪︎Saves time for craftsmen to not have to drive out remote substations for info ▪︎Included equipment: • Rochester • BEN5000 DFRs • RFL 9745 • SEL PRTU & 2020 • SERs • SCADA 8600 • FLAR ```