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GPS Time Backup for Power Industry
John LoweRadio Station ManagerNIST Time & FrequencyDivision
WWV Ft. Collins, CO.
WWVH Kauai, HA.
WWV/WWVHProvided Syntonization
Frequency Calibration
• Standard Carrier Frequencies • 2.5, 5, 10, 15, 20 & 25 MHz • @10 kW radiated power on 5, 10, and 15 MHz• @2.5 kW radiated on 2.5, 20 and 25 MHz
WWV/WWVH Reception
Transmit
Ground/surface
E
FMultiple-hop1FL
1FH
2FL1EL
Receive
WWV/WWVH Reception
Transmit
Ground/surface
E
FMultiple-hop1FL
1FH
2FL1EL
Receive
Frequency stability 1 x 10-9
Time Synchronization 1mS
WWVBProvided Syntonization
Frequency Calibration
• Standard Carrier Frequency • 60 KHz• @70 kW radiated power (upgraded in 99’)
WWVB
Electron Content Diurnal Maps
Sunset Greenbelt, MD Sunset Boulder, CO
SunriseBoulder, CO
Time (UTC)
Sunset Greenbelt, MD
Sunrise Boulder, CO Sunrise
Greenbelt, MD
Sunset Boulder, CO
12
00
Sunrise Greenbelt, MD 0
60
0
00
00
18
00
12
00
06
00
00
00
June
3
June
4
June
5
50 µsec
WWVB in terms of WWV Controlling
Oscillator June 3,4, & 5 Slope +1µsec/24 hrs. (1800-1800 UT)WWVB 10 10 x 10N pts above WWV
Frequency stability 1 x 10-11
Time Synchronization 100 uS (?)1 x 10-12 With averaging
Power Grid Application Timing Needs
Application Need
General Purpose < ±100 ms
Time-Stamping SCADA and Operational Data Logs < ±1 ms
Substation Monitoring e.g. phasor measurement units (PMUs)(IRIG-B Replacement Applications with a local PTP grandmaster )
< ±1 μs
Extended distance applications(fault detection, transient suppression)
< ±1 μs
Power Grid Application Timing Needs
Application Need
General Purpose < ±100 ms
Time-Stamping SCADA and Operational Data Logs < ±1 ms
Substation Monitoring e.g. phasor measurement units (PMUs)(IRIG-B Replacement Applications with a local PTP grandmaster )
< ±1 μs
Extended distance applications(fault detection, transient suppression)
< ±1 μs
What GPS gives you!
Proposed SolutionTo Backup GPS
Proposed Solution
Internet Connected“Radio Common View”
Radio KNITKnowledgeable Networked
Integrated Time
To Backup GPS
Proposed Solution
Internet Connected“Radio Common View”
Radio KNITKnowledgeable Networked
Integrated Time
To Backup GPS
Proposed Solution
Pinch Hitting for GPSRadio KNIT
Knowledgeable Networked Integrated Time
Backing up GPS “time” by knitting together:-NIST radio station signals-Common View algorithms-Smart Internet connectivity
Field Receiver
GPSAntenna
Local clock
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
KNITting
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
KNITting
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
FieldReceiver
FieldReceiver
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
New Type Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
AddBetterClock
New Type Receiver
GPSAntenna
NISTRadio Station
Antenna
Atomic clock InternetConnection
AnAtomicClock
New Type Receiver
Monitoring Station
GPSAntenna
NISTRadio Station
Antenna
Atomic clock InternetConnection
AnAtomicClock
Monitoring Station
GPSAntenna
NISTRadio Station
Antenna
Atomic clock InternetConnection
FieldReceiver
FieldReceiver
MonitorStation
MonitorStation
MonitorStation
MonitorStation
MonitorStation
MonitorStation
MonitorStation
FieldReceiver
MonitorStation
FieldReceiver
MonitorStation
Good Clock
Wants to beA Good ClockWithout GPS
FieldReceiver
MonitorStation
WWVB
WWVH
WWV
CHU
FieldReceiver
MonitorStation
WWVB
FieldReceiver
MonitorStation
WWVB
FieldReceiver
MonitorStation
WWVB
GPS
FieldReceiver
MonitorStation
WWVB InternetConnection
GPS
Monitoring Station
GPSAntenna
NISTRadio Station
Antenna
Atomic clock InternetConnection
Monitoring Station
GPSAntenna
NISTRadio Station
Antenna
Atomic clock InternetConnection
PostsPathDelay
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay=- ε
FieldReceiver
MonitorStation
WWVB ε
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay
_ =Corrects
Local ClockCommon View ε
Field Receiver
GPSAntenna
NISTRadio Station
Antenna
Local clock InternetConnection
ReadsMonitor’s
PathDelay
ComparesTo Field
Path Delay
_ =Corrects
Local ClockCommon View ε
Maintains Synch
Monitoring Station ClockWe want a clock that can hold <1 µs timing accuracy for >7 days…
A synchrophasor is defined as the magnitude and angle of a cosine signal as referenced to an absolute point in time.
FieldReceiver
MonitorStation
How Far?
10 100Distance of WWVB Receiver relative to Reference [Miles]
10.0
1.0
0.1
RM
S D
iffe
renti
al T
imin
g E
rro
r (U
nm
od
eled
) [u
s]Differential WWVB Error (over 24 hrs) as a function of Distance
from Reference Receiver (Maryland)
How Far?North/SouthEast/West
Joint Proposal
Assured Timing for Critical InfrastructureRequest for Proposal
Other thingsNIST is working on…
GPSAll in View
GPSAll in View
NISTDisciplinedOscillator
NISTDisciplinedOscillator
Frequency stability 5 x 10-14
Time Synchronization 10 nS
NISTDisciplinedOscillator
FMASFrequency Measure& Analysis Service
TMASTime Measure& Analysis Service
SIMSistema Interamericano de Metrologia(SIM). This time scale, known as the SIM timescale, or SIMT, was developed to complementthe official world time scale,
Coordinated Universal Time
Frequency stability 5 x 10-14
Time Synchronization 10 nS
NISTDisciplinedOscillator
AlsoPrecision Time Protocol
Setup
Setup
Precision Time Protocol
Average Time Offset
13.6 us
Specification forLTE 1.5 us
Ideally: < 1 us
Calibratethe Client
Specification forLTE 1.5 us
Ideally: < 1 us
Calibratethe Client
300 nS RMS
Average Time Offset
13.6 us
Chip-scale Atomic Clocks
Chip-scale Atomic Clocks
1 mm
Passively Pumped Design:
Actively Pumped Prototype:
MEMS Beam-Clock Design:
Monitoring Station Clock<1 µs timing error over a week and 1×10-12 fundamental accuracy
NIST-on-a-Chip
The End
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