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TIMING APPLICATIONS OF GPS High Energy Transmission with High Precision GPS Time. Gaurav Sharma John Hannah Vivekanand Sivaraman. ABOUT BPA. Bonneville Power Administration – Power Supplier in the Pacific North West. Serves Oregon, Washington, W Montana, and most of Idaho.
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TIMING APPLICATIONS OF GPSHigh Energy Transmission with High Precision GPS Time Gaurav Sharma John Hannah Vivekanand Sivaraman
ABOUT BPA • Bonneville Power Administration – Power Supplier in the Pacific North West. Serves Oregon, Washington, W Montana, and most of Idaho. • 390 switching stations • 16500 MW Power Capacity & 8600 MW annual delivery • 181 Customers including industries and public utilities
Timing Applications in Energy Transmission • Power generation and Power transfer • Power Outages • Disturbance Records • Fault Location • Real Time Phase Measurements
BPA: Timing Techniques and Problems • Central Time System • Not enough accuracy for Fault locators • signal subject to distortions • High frequency pulse over Microwave for Fault Locators • Used up a lot of available bandwidth • Local Time Code Generators for remote stations • Time code generator needs to be manually resynchronized every couple of months – no resetting at regular interval • Radio reception from GOES or WWV • GOES receivers off the correct time. • GOES signal subject to interference and eclipses. • GOES satellite system problems – repositioning - requires antenna repointing. GOES: Geostationary Orbit Earth Satellite WWV: Radio Station, Fort Collins, Colorado
BPA: Timing Techniques ProblemsPossible Solution: GPS • 1 microsecond accuracy • Multiple satellite redundancy • High Reliability • BPA Lab Testing – showed high accuracy, precision and reliability in timing.
GPS Implementation inCentral Time System • New system - 3 primary sources, 1 voting switchover unit + Monitoring Systems • Primary sources equipped with GPS receivers, each having an antenna and a power unit. 2 with battery back up. 1 has a rubidium oscillator in the event of GPS input failure. • Improved Switching Tolerance (1 Microsecond level) (What is switching?)
GPS Implementation in Fault Location and Rectification • When a fault occurs on a transmission line a high frequency wave propagates in both directions from the fault. Compare the arrival time at switching stations on the either side of fault for locating it. • Problems with Old System: • Synchronization pulse used a lot of bandwidth (expensive) over the analog microwave system • Available to major stations only • GPS Implementation: • Initially, for the synchronizing the pulse to UTC only - • Later, also as FLAR units • Available to even minor and remote stations
GPS Implementation in Phasor Measurements • Phasor: a vector representation of a sinusoidal quantity that includes a magnitude and a phase angle. The power system in North America is a three-phase 60Hz sinusoid. • Phase angle between two stations determines the power transfer between stations. • Phasor observations used for monitoring. (Require 0.1 electrical degree accuracy for monitoring Or 5 micro-sec synchronization between monitoring units.) • GPS used as precise timing source.(The accuracy of time measurement ~1 micro-sec).
Conclusions • Expensive upgrades and redundancies were avoided. • GPS provided a comprehensive way for implementation of accurate timing system – no need for different timing system for every other system. • Stood the tests for accuracy, reliability, coverage and cost.